Solid State Guitar Amp Forum | DIY Guitar Amplifiers

HELLO,

I am currently drawing pcb for rod's project 27mk2. there are few capacitors in the diagram greater than 1uf in non polar which are hard to find in small voltage. so i would like to replace them with electrolytic capacitors. i have edited that image in paint...please verify if their polarity are ok.
Thanks in advance...
Subha

Non-polar electrolytics should not be hard to find.

I am assuming you want radial leads or could at least use them.

From Mouser:
647-UVP1H2R2MDD   2.2uf 50v NP  22 cents  5700 in stock.

647-UVP1H010MDD1TD   1uf 50v NP   12 cents   189 in stock

667-ECE-A1HN100UB   10uf  50v NP   19 cents   1934 in stock


Those are just ones I selected, there were a number of options at each value in terms of brand, voltage, etc.


Other large suppliers like Digikey ought to have similar selections.

Thanks enzo for your reply...I am from the other part of the world, India...where i have to rely on my local market. Sad but true...here larger value non polar capacitors are available in very higher voltage values like 300v,400v...which are not only costly but also huge to fit in boards...that's why i have asked here to substitute with polar electrolytic..

So can you please verify whether the polarity of those capacitor are correct or not??(please look at the second picture)....

Dear goshashuba.
I live in Argentina and have the same problems as you.

*Very* short answer: use standard (polarized) electrolytics.

C3/8/10 polarity is not important.

Just for consistency use C3/8 with negative to ground, and C10 with negative towards R13.
The general rule is "negative towards the point closest to ground and positive towards the IC".

I repeat it, if you have no DC voltage there, it will work the other way, but having a "rule" saves times lost thinking about it.

Symmetrical fed Op Amps have offsets measured in a few millivolts, that's why you can consider them "0".

Now, on the transistor, that's different:
The base needs to be fed some "positive" current (it's an NPN) through R15.
If one end of R15 is grounded, yet it has to be more positive than the other end, it means the other end (connected to base)  has to be "more negative than ground", so you need C15 negative connected to Q1 base.
As of C14 it's easy: Q1 emitter *has* to be 700mV more  negative than base .... which is already somewhat negative by itself, so C14 negative goes to emitter.

I detailed *why* I suggest such polarities so you can determine yourself what to choose in any other similar case.

Dear Fahey

Great explanation...Yes c14's negative should be connected to emitter..Similar to input buffer in microamp....

Thanks

Hello

I have just completed drawing p27 pcb (preamp board) on 1.75"*2.5" board area.
please check my attachments...(pre2.pdf)
I have used trimmer instead of real pot for checking purpose.

couple of questions to ask..
when drawing PCBs i sometimes find free spaces so that i can thicken certain tracks..Is it good to widen tracks unnecessarily (without wasting any extra board area of course! :)). Cause wide tracks are stronger..Which is beneficial for home PCB etching and soldering
For example I am uploading a PCB image from General_guitar_gadget_com. The tracks can be broken any time..  :)

Hello ghoshsubha444,

I'll assume you are going to hand drill this PCB?

If so,, word of advice;

Although wider tracks will be much easier to work with for DIY builders,, The Pads are the issue not so much the tracks.

Most software defaults to small pads which is fine for a million dollar factory but bound to frustrate those new to pcb building.

So try to find the Global editing menu, some call it DRC (design rule check).
You may find it possible to force larger pads on a lot of components.

Also print out a few track only copys *In actual size* to get a real world idea of how hard it will be to drill pads and leave enough copper to solder the components to cling to. 8|

On screen it might look big and easy to do but too late after you etch it all.

Also remember that for first time pcb makers there is a very good chance that you may want to change a component *After the build* and smaller pads will not like being tampered with more than once.

Re the GGG Dynacomp layout;
I'd steer well away from tracks like that.
Not only are the pads small the tracks are not consistent and go horribly close to other tracks.

Phil.

Fully agree with phatt, who is very experienced at homebuilding.
Yes, PCB software usually wants to outdo others by saying "*they* put 6 components and 15 tracks inside a stamp sized PCB, *we* put 12 components and 25 tracks there".
Crazy  :duh
And launch the software pre-set for that. :loco

Which is fine to design PC Video boards or Cellphones, but not for brute hairy cavemen (literally) like Rock Musicians.

Pads need to have enough copper around the hole, tracks must be wide enough so hairline cracks (very common in home etching) don't interrupt them, BUT, there's something you missed, they must not be too close either.

As an example, the power tracks you show "inside" the IC footprint are too thick and *will* touch the IC pads.

You'll need to halve most of your tracks, and avoid them getting closer than the free space you now have between IC pads.

To put it into numbers: I usually design with 40 mil tracks, whenever possible I widen them to 50/70 and up to 100 mils (*IF* I have a lot of free space, of course) and neck them down to 30 mils at certain critical points, and only for a short length, such as to pass between 2 components.
And never try to pass a track between IC pads.

Also if you have "free" space you can fill it with "Fills" or "Polygons", but avoid the cheesy "copper pour", so much abused.

Why?
I always see it very poorly used: skinny tracks (BAD) and a too tight *useless* copper pour, good only to save etchant but all that copper serves no useful purpose.

*You* apply "fills" attached to high current or ground tracks.

This is my general purpose 2xTDA2030/2050 amplifier and PSU, single supply to be able to use *any* 12 to 24VAC transformer I "rescue" from a dead amp. or find in a dumpster.

The top overlay and the bottom tracks, ready to laser print and thermal transfer:

Thanks Phatt and Fahey for your reply and great explanations..

I have some experience in etching PCB...

So the summery of the above discussion is too much thin tracks will cause terrible problem for home etching board.

Too wide tracks are not necessary either meaninglessly. The difference between tracks are also an important parameter must be in consideration.

I think ironing image on the copper board weaken the copper layer to stay attached to the board and too slim tracks often wore off..

Now my question is -
Is it bad to have ground plane (not closed:)) ??

please see my attachment of p27 pcb 100% sized image and rate it overall for spacing and widening only..(1 to 10).

Thanks

Just some general observations.

Hi @ghoshsubha444.  Having done many hundreds of board both professionally and at home I can only agree with @phatt and @JM.  There are a lot of things you can do with a professional PCB maker that you really can't get away with at home, such as tiny pads and running traces between IC pads.

There is no virtue in making traces thin (except where you really have to, and then it's a good idea to see if you can change the layout so you don't need to).  Home builders often get into trouble trying to imitate professional boards by hand, and I've seen home built amps with tiny boards mounted on a huge chassis.  Unless you are tight for space don't worry about making the board a bit bigger so it is more "comfortable" to etch, drill, and solder up.

As a general rule the available space should be reasonably evenly divided between trace width and spacing in between.  Very thin traces can get cuts from stress cracks, over-etch, imperfect resist coverage, dust, (and even once an eyelash on the photographic negative  ::) ).  So in general it is better to err on the side of large tracks than small.

At home I often do boards by hand using a waterproof felt tip pen and the second layout would be much easier to do like that than the first.  You can do things like splay the legs of a transistor so they form a little tripod.  This not only gives you more space to work with when soldering it also supports the transistor better.

One problem with very tight spacing is when you are soldering you get blobs jumping across to other pads where it shouldn't.

PCB layouts are called "artworks" and there really is an art to producing a good layout, but the important thing to keep in mind is what sort of production process the final board will go through; there are a lot of differences between a board intended for one-off home etching and hand soldering, and one that will be reproduced thousands of times and be wave soldered in an automated bath, and you need to be aware of where you will end up right from the beginning of the process, the initial layout.

When you are using artworks from web sites you are often dealing with the output of amateurs who haven't given enough thought to how people, who are perhaps not as skilled in building, are actually going to put their creations together.  If you look at the boards that Heathkit supplied you can see that they assumed the typical builder would be ham-fisted and using a 100W plumbers soldering iron (or maybe a blowlamp  ;) ) and they were big with very generous tracks, pads, and spacings.

So when you are home-brewing, make everything, track width, track spacing, pad size, case size, human scale so it is comfortable for you to build, and later service/modify.  When you want to build your own digital wrist watch using SMD, or transmitters for tracking small animals (as I have), then it is worth the struggle, but otherwise you are only making a rod for your own back.


Specifically, it is more important with a ground plane that it is thick enough to carry the currents demanded of it, than it go right around, and that you don't end up with ground return currents in common with different stages sharing the same track, in fact there may be some benefit in not creating a full loop.  If you look at PCB's from ghetto blasters and home stereos you often find that the grounds from various stages are brought back to the power supply in parallel and connected there, just to avoid this "ground resistance in common" problem.  Home builders in particular tend to underestimate the currents flowing around power supply rectifier circuits, and in output stages, and make the tracks too thin.

I also must say to you that checking a PCB layout is quite a bit more difficult than checking a circuit drawing, and in reality you can't expect that anybody on a web site will check anything but the very simplest of layouts for you - you just have to go over the layout with the circuit next to you and check that every line goes where it should, and nowhere else (or perhaps you have a good friend locally who is also into electronics).  That's one reason why we still call the first power up the "smoke test".  :cheesy:  One trick is to try and re-draw your circuit working only from your layout.

I hope your build goes well for you.   :tu:

 :) :) :) :) :) :) :) :)

Quote from: ghoshsubha444@gmail.com on February 28, 2013, 02:26:08 PM
Thanks Phatt and Fahey for your reply and great explanations..

I have some experience in etching PCB...

So the summery of the above discussion is too much thin tracks will cause terrible problem for home etching board.

Too wide tracks are not necessary either meaninglessly. The difference between tracks are also an important parameter must be in consideration.

I think ironing image on the copper board weaken the copper layer to stay attached to the board and too slim tracks often wore off..

Now my question is -
Is it bad to have ground plane (not closed:)) ??

please see my attachment of p27 pcb 100% sized image and rate it overall for spacing and widening only..(1 to 10).

Thanks

I assume you mean a loop around the outside? NO steer well away from ground loops.

Go to *Valve Wizard* site and find the pdf on Grounding problems.

http://www.valvewizard.co.uk/Grounding.html

It is all still relevant with SS design.
It's all Valve stuff but actually much easier to grasp the problem when looking at Valve gear.

The issue is power supply current getting into/onto Signal path.

Just hold an electric guitar next to a big transformer and listen to the HUUUM. That should give you an idea of what you want to avoid in PCB layout.

i.e. Don't run the High current power rail next door (parallel) to a sensitive audio input.
If you must, cross them at right angle .

Re heat from iron;
No! If your iron De-laminates the copper from the board then you have purchased crap PCB.

I hold the iron on for 1~2 minutes and I press hard.
I use glossy magazine paper which comes off in warm water in around 5 minutes of soaking.

Don't forget to set your laser printer to max ink density so you get max ink onto the board other wise it won't work well. 
Phil.

Having etched quite a few boards in my time, I have never delaminated the copper from the board, and like Phil, I use a lot of pressure for a couple of minutes. The heat from the iron has a lot to do with how easily the image transfers. When I used photo paper, I cranked the iron to the max. With PNP blue, a lower temperature makes excellent transfers. Too high a temp with the PNP will make it smear. Then after transferring the artwork, I compare every track to a copy of the drawing I print out on transparency so it can be overlaid with the board and any necessary corrections made. And like Roly, those corrections are made with a permanent marker, in my case a Sharpie very fine point industrial waterproof marker.

Of course, after etching comes the inspection with magnifying glass, and meter check for shorts between traces. Then drilling with bench top drill press, compare to the transparency for missed holes, go drill that last one I missed, populate and solder away.

The only thing I can see from scaling up from pedals to amps is to have a very good idea of your current flow through the different circuit building blocks. Power and ground traces need to handle everything you throw at them, so size them accordingly for the main power busses. Pre amp components draw in the mv range (and micro amps of current) so those traces can be smaller. Power amps deliver a lot of voltage and current, and in a lot of SS amps I have seen, the traces will be accordingly larger.

Have fun, just don't get so lost in the project you forget why you are doing it.

GOT YOUR POINTS :)

Why Yes,  We do carry on a lot don't we?  :lmao:

Tiss all good because others read this as well and often some gems of advice are hidden in details,,, as I have found myself.  :dbtu:
Phil.

hello,

I have finished p27 preamp(exactly like the picture) and played a couple of songs with delay and compressor..

nice clean sound... but overdrive is not that good and noisy..So i am not playing with drive.

1.if we only concern about the clean..the clean is little noisy(very little noisy). since we have achieved such low noise in clean, is there any way to cure it completely?? 

2. I am not satisfies with the amount of treble and upper mids... rough :( bass side string's sound are not defined.. they are kind of boomy..What to do in this situation??

i have checked the tonestack with duncun software. compared with fender..bass and mid are in the middle position and treble is full..

I am using OPA2107pa as opamp that i had sampled from Texas.. But BC549 is not available so i had to solder cheap bc547 $0.0009/piece in indian currency(dont know A/B/C?). is this creating the noise?
I have found a pdf from diyaudio_com mostly like modified p27 with input and output buffer..
Can i implement it??(attached)from:
http://www_diyaudio_com/forums/attachments/instruments-amps/142195d1254079176-guitar-amp-design-build-guitar-preamp-1.pdf

looking for your input.

subha

1) congratulations, you built it well.
2) ***what speaker are you using?***
This amp expects a guitar speaker.
3) you can use the Fender tone stack instead of the P27 one.
Be sure to use also the proper 1M volume control.
If you want tho use your current pots, you must "scale" the values to keep the response.
Since you use 50K tone pots, 1/5 the impedance of the originals, you need to use 5X the original caps, as in .1uF>.47uF and so on.
Obviously use the closest standard value.
As in: if math says .23 to .25 uF, use .22uF and so on (within 20%, higher or lower is acceptable).
4) anyway I suspect your speaker.
4) does the bright switch have any effect?

As of noise, grounding is difficult for the baginner; but practice makes perfect.
You already started te right way.

mobile update:when dialing volume pot the treble is getting even lower. So missing the crunch..

http://www_diyaudio_com/forums/attachments/instruments-amps/142195d1254079176-guitar-amp-design-build-guitar-preamp-1.pdf

Bad link, repost.

http://www.diyaudio.com/forums/attachments/instruments-amps/142195d1254079176-guitar-amp-design-build-guitar-preamp-1.pdf

thanks fahey for your reply

I am using Eminence Governor speaker with open Cab.

Yea, enabling the bypass switch, i am getting some treble boost
(1k).... (with some low cut)but the lower  strings (E-A-D-G) lack definition 

I do not know the math..can u calculate it for me with the same pot..since 250k,1M pot are totally unavailable here.

But the crunch is completely missing and with higher gain there so much noise and tone is so Fat ??? :-\...
Thanks

Quote from: ghoshsubha444@gmail.com on March 09, 2013, 11:33:25 AM
http://www.diyaudio.com/forums/attachments/instruments-amps/142195d1254079176-guitar-amp-design-build-guitar-preamp-1.pdf

Non-members cannot download link.  You will have to download PDF then upload here.

Quote from: Roly on March 09, 2013, 10:15:59 PM

Quote from: ghoshsubha444@gmail.com on March 09, 2013, 11:33:25 AM
http://www.diyaudio.com/forums/attachments/instruments-amps/142195d1254079176-guitar-amp-design-build-guitar-preamp-1.pdf

Non-members cannot download link.  You will have to download PDF then upload here.

hello Roly.Thank you for your interest.

I have already uploaded it named GUITAR PREAMP 1.pdf above the graph picture in my earlier post.

I am uploading it again for your convenience..

1) the "improved" P27 preamp published in DIY audio is wrong, like most of the stuff published there.
Tons of would-be "designers" which have no clue.
In this case, both buffers won't work, because their inputs are floating unbiased.
Besides, the first buffer is unnecessary because Rod's design *already* has 1M input impedance, and the second one, although not bad if you have a unused spare Op Amp, does not justify adding one when the simple transistor one is quite adequate .... and already tested as working ;)
Please post the link where that "improvement" is published, so I warn them about the errors.
2) here you have the corrected Fender values for 50K tone pots.
You'll need a 250K volume pot , don't tell me they are not available at an Electronics shop.
They might be called "220K" to follow modern conventions, but it's the same.
*Try* to get a Logarithmic or Audio one.
3) to increase the effect of original P27 bright switch, change values to 470 ohms and 0.1uF
In all caps I mention, ceramics and electrolytics (depending on value) are fine, also 25 or 50V types, don't need more.
4) you mention "noise" .... what kind?
5) what power amplifier are you driving with this preamp?

Maybe he was trying to buffer his one microvolt input signal.   :lmao:

Yeah, one missing input ground reference resistor could be a drafting error, but two looks deliberate.  If I had a spare op-amp I'd be thinking of providing a balanced output before adding noise to the input (not to mention being cautious about second-guessing Rod).

Quote from: J M Fahey on March 10, 2013, 11:06:13 AM

Please post the link where that "improvement" is published, so I warn them about the errors.

I was surfing randomly, so i can't recollect where it exactly was..

I have modified according to your value (tonestack) and please check the attachment
[picure a111].White=Fender,RED= modified according to you.. 

I dont know how to define the noise i am encountering but to be precise it is that noise you can hear when your amp is in high gain distortion setting and you are not playing anything.. :(

I am using LM3875 poweramp[National sample]. Power amp has been tested using computer and there is very low noise even in the maximum volume settings...


Questions:

1. I am using some of my pedals phaser and delay which are controlled by digital switching 7414 and 7476..
When i am connecting power to the control board, noise is being increased.. How to avoid that??

2. I am uploading a picture about my planning on the overall setup. please verify it...

Description:

I am building a pedal board using aluminium chassis where i will have three boards..1.phaser 2.copressor 3.delay so that i can on/off them with foot press. Guitar connection will be first to pedal board-->phaser-->compressor-->to amp(p27/distortion i will build later)-->back to pedal board for DELAY-->to amp-->noise gate(manual on/off)-->power amp-->>speaker.[picure a333]

3.A line out will be great for recording. how to do that??

4. Is it better to use Zener instead of regulator 317or 7809 7805 ,if noise is the concern??

5.Wha are the good alternative of bc549 since it is unavailable?
Thanks

Well, noise is to be expected the way everything is built and mounted (should I say unmounted? ;) ) now.
You have everything "on the table" (literally) and with some long, unshielded wires to boot.
And you add tons of stuff before even reaching the preamp input, then zig zag back and forth, so you definitely can't blame Ron for this.
Who, by the way, knows his stuff very well.
Just as an experiment, solder a jack to the preamp input with 1/2" max wires, and plug your guitar straight into it; and send its output straight to the power amp.
I bet it works as intended.
Congratulations on building all that stuff :dbtu: :dbtu:, now you need to get a metallic chassis, or an U or al least L shaped piece of aluminum, 1 mm thick is fine, and mount everything there.
Properly grounded of course.

By the way, getting a good layout and grounding is as difficult as the "electronics" design.

But as with everything else, practice makes perfect  :dbtu:

EDIT: and as you see my "5 X corrected" tone control schematic matches very well (center frequency and response) the original Fender one.
You just don't get the same boost value because the pot value is not optimum, but, hey!!, we have what we have. ;)

Quote from: J M Fahey on March 11, 2013, 06:35:46 AM
Well, noise is to be expected the way everything is built and mounted (should I say unmounted? ;) ) now.
You have everything "on the table" (literally) and with some long, unshielded wires to boot.
And you add tons of stuff before even reaching the preamp input, then zig zag back and forth, so you definitely can't blame Ron for this.
Who, by the way, knows his stuff very well.
Just as an experiment, solder a jack to the preamp input with 1/2" max wires, and plug your guitar straight into it; and send its output straight to the power amp.
I bet it works as intended.

I knew looking at the picture you will definitely remark :) :). But to assure you i had test it something like this-

Guitar cable directly soldered to p27-->>p27-->>power amp-->>speaker. May be layout and grounding problems are the issue..Let me observe them carefully :loco..

Quote from: J M Fahey on March 11, 2013, 06:35:46 AM
You just don't get the same boost value because the pot value is not optimum, but, hey!!, we have what we have.

Who knows better than you? ;). But being ignorant i want to know whether it needs further boost to compensate on the second stage...

Please look on my questionnaire on my early post..
Thanks Fahey

Just sharing my newbish "experience".
I also had noise problem when first building my own amp.
But it was BEFORE I put it in a chassis. After putting the whole thing into a chassis and connecting input ground to chassis, it was noiseless.
As far as I know, you should connect only ONE ground point to chassis. Please correct me if I'm wrong.

Overall layout
(http://sound.westhost.com/p27-amp3.jpg)
Apart from a grounded full metal chassis you will notice that Rod has added a shield over the preamp board (which may be metal such as aluminium, or single-sided PCB laminate, but must also be grounded); and another shield around the input sockets.

Preamp
(http://sound.westhost.com/p27-amp4.jpg)

Power amp
(http://sound.westhost.com/p27-amp5.jpg)

I'd just like to reinforce the point that Rod Elliott is a very professional and capable designer and frankly a cut or two above the vast majority of people who post circuits to the web. I've had 40-something years in electronics design but I would be very careful about second-guessing Rod or trying to "improve" one of his designs.


Now part of your problem seems to be trying to do too much at once.  Particularly with a new build we try to take each stage a step at a time, identify and correct any problems with that stage before moving on to the next, and in audio amps this generally means starting with the power supply, then the power amp, and so on moving stage by stage back towards the input.

The difference between having boards scattered over the bench, and mounted in a metal chassis, can be very large where picking up external electrical hum and noise is concerned.  The grounded metal chassis makes a very effective electrostatic screen around the assembly.

Now this particular amp design is a little unusual in that it uses some current feedback, and Rod has some particular things to say about how the main amp section should be laid out and wired to avoid instability.  I suggest you read them again closely and mount your power supply, main amp, and output sockets in your chassis then test at that stage that it is working properly.  You can feed a test signal from an MP3 player or similar into the main amp input, and you should be able to get a clean and loud output from your speaker (which must also be properly mounted in its enclosure).

Once you have got to that point you can then add the next stage in front of that and test again, then the next and so on until you finally get to the input sockets.

Before you get too deeply into distributing DC power around your chassis you need to read this thread;

http://www.ssguitar.com/index.php?topic=288.0 (http://www.ssguitar.com/index.php?topic=288.0)

Poor distribution and incorrect grounding causes a lot of preventable problems with amp builds, so it's important to have a single chassis signal ground point, and to distribute your power and ground lines radially from there, not daisy-chain fashion as your assembly drawing shows.

It is also important with single point grounding that you use sockets that are fully insulated from the chassis.


Q.1 I suspect that grounding may be the cause of the problem.

You appear to have used hookup wire for the signal interconnects between boards.  Generally speaking it is better to use screened cable for signal interconnects with the screen only connected at the receiving end, the common grounds going around via the single ground point.

Q.3 a line output can be added later using a simple op-amp buffer taking its signal from the input of the main amp.

Q.4 Not really, three pin regulators generally have better noise performance than zeners, but in any case supply lines should be well bypassed with both large value electrolytic caps and some smaller ones such as 0.1uF close to each IC, and particularly right at the input and output of three-pin regulators.

Q.5 Just about any reasonably high gain audio transistor.  The BC549 is a member of  very old family that go back to the BC109, and the main difference in the BCxx9 family are the packages and lead order.  The suffixes A, B and C are the sorted gain ranges being "lowish", "medium" and "high to very high".  Similarly the original BCxx7, BCxx8, and BCxx9 where 'rough", "smooth", and "very smooth" in terms of noise and audio quality, however today even the BCxx9 family are surpassed by audio-specific op-amps that are better in every respect.

The main thing when looking at the data sheet for a possible substitute is that it will withstand the supply voltage and pass the required current, with a safety margin for both, then that it has a gain, h_fe, the same or higher.  Then you chose the one with the lowest noise figure, but with modern transistors the noise figure isn't generally an issue except in really demanding circuits such as microphone preamps.


So, start getting the initial parts into a chassis, mains wiring, transformer, power supply, and main amp, and testing each stage as it is completed, then as you add stages in front of the main amp we can deal with the problems as they arise.

HTH

Quote from: newbiediy on March 11, 2013, 10:51:14 AM
Just sharing my newbish "experience".
I also had noise problem when first building my own amp.
But it was BEFORE I put it in a chassis. After putting the whole thing into a chassis and connecting input ground to chassis, it was noiseless.
As far as I know, you should connect only ONE ground point to chassis. Please correct me if I'm wrong.

which amp you built?

It was Little Rebel. Only 2W amp, so I didn't expect much noise from it.
But surprisingly it was so noisy before mounting it in a chassis. And surprisingly quiet after chassis work. :)

Quote from: Roly on March 11, 2013, 11:01:12 AM
Overall layout
(http://sound.westhost.com/p27-amp3.jpg)
Apart from a grounded full metal chassis you will notice that Rod has added a shield over the preamp board (which may be metal such as aluminium, or single-sided PCB laminate, but must also be grounded); and another shield around the input sockets.

Preamp
(http://sound.westhost.com/p27-amp4.jpg)

Power amp
(http://sound.westhost.com/p27-amp5.jpg)

I'd just like to reinforce the point that Rod Elliott is a very professional and capable designer and frankly a cut or two above the vast majority of people who post circuits to the web. I've had 40-something years in electronics design but I would be very careful about second-guessing Rod or trying to "improve" one of his designs.


Now part of your problem seems to be trying to do too much at once.  Particularly with a new build we try to take each stage a step at a time, identify and correct any problems with that stage before moving on to the next, and in audio amps this generally means starting with the power supply, then the power amp, and so on moving stage by stage back towards the input.

The difference between having boards scattered over the bench, and mounted in a metal chassis, can be very large where picking up external electrical hum and noise is concerned.  The grounded metal chassis makes a very effective electrostatic screen around the assembly.

Now this particular amp design is a little unusual in that it uses some current feedback, and Rod has some particular things to say about how the main amp section should be laid out and wired to avoid instability.  I suggest you read them again closely and mount your power supply, main amp, and output sockets in your chassis then test at that stage that it is working properly.  You can feed a test signal from an MP3 player or similar into the main amp input, and you should be able to get a clean and loud output from your speaker (which must also be properly mounted in its enclosure).

Once you have got to that point you can then add the next stage in front of that and test again, then the next and so on until you finally get to the input sockets.

Before you get too deeply into distributing DC power around your chassis you need to read this thread;

http://www.ssguitar.com/index.php?topic=288.0 (http://www.ssguitar.com/index.php?topic=288.0)

Poor distribution and incorrect grounding causes a lot of preventable problems with amp builds, so it's important to have a single chassis signal ground point, and to distribute your power and ground lines radially from there, not daisy-chain fashion as your assembly drawing shows.

It is also important with single point grounding that you use sockets that are fully insulated from the chassis.


Q.1 I suspect that grounding may be the cause of the problem.

You appear to have used hookup wire for the signal interconnects between boards.  Generally speaking it is better to use screened cable for signal interconnects with the screen only connected at the receiving end, the common grounds going around via the single ground point.

Q.3 a line output can be added later using a simple op-amp buffer taking its signal from the input of the main amp.

Q.4 Not really, three pin regulators generally have better noise performance than zeners, but in any case supply lines should be well bypassed with both large value electrolytic caps and some smaller ones such as 0.1uF close to each IC, and particularly right at the input and output of three-pin regulators.

Q.5 Just about any reasonably high gain audio transistor.  The BC549 is a member of  very old family that go back to the BC109, and the main difference in the BCxx9 family are the packages and lead order.  The suffixes A, B and C are the sorted gain ranges being "lowish", "medium" and "high to very high".  Similarly the original BCxx7, BCxx8, and BCxx9 where 'rough", "smooth", and "very smooth" in terms of noise and audio quality, however today even the BCxx9 family are surpassed by audio-specific op-amps that are better in every respect.

The main thing when looking at the data sheet for a possible substitute is that it will withstand the supply voltage and pass the required current, with a safety margin for both, then that it has a gain, h_fe, the same or higher.  Then you chose the one with the lowest noise figure, but with modern transistors the noise figure isn't generally an issue except in really demanding circuits such as microphone preamps.


So, start getting the initial parts into a chassis, mains wiring, transformer, power supply, and main amp, and testing each stage as it is completed, then as you add stages in front of the main amp we can deal with the problems as they arise.

HTH

Thoroughly Explained :) :) Thanks sir.
I must go along step by step and first thing first.....

I have already completed power supply,power amp and p27 (apart from some pedals).

Let me prepare some documents about the schematics and the layouts to verify here..

Let me tell you my desire. all that  I want is to build some beautiful tone. may be i have only clean sound! But that must be beautiful so that when playing i have feeling for it. And i have realized that incremental development is the only way to survive, otherwise you will be frustrated and soon will be out of DIY stuffs.

will be back soon....

Quote from: newbiediy on March 11, 2013, 11:24:32 AM
It was Little Rebel. Only 2W amp, so I didn't expect much noise from it.
But surprisingly it was so noisy before mounting it in a chassis. And surprisingly quiet after chassis work. :)

:dbtu: :dbtu: :dbtu: :dbtu: :dbtu: :dbtu:

FWIW, here's one of my SS (obviously ;)) High Gain Guitar Amps.

1) first from outside, to know what we are talking about:

(http://img109.imageshack.us/img109/9105/sdc12245y.jpg)

2) then the inside, showing PCB mounting, compact and simple wiring, internal Aluminum shields:

(http://img846.imageshack.us/img846/2139/sdc12234x.jpg)

(http://img266.imageshack.us/img266/3523/sdc12231i.jpg)

And yes, it does have an output transformer  ;)

Quote from: J M Fahey on March 11, 2013, 06:52:29 PM
FWIW, here's one of my SS (obviously ;)) High Gain Guitar Amps.

1) first from outside, to know what we are talking about:

(http://img109.imageshack.us/img109/9105/sdc12245y.jpg)

2) then the inside, showing PCB mounting, compact and simple wiring, internal Aluminum shields:

(http://img846.imageshack.us/img846/2139/sdc12234x.jpg)

(http://img266.imageshack.us/img266/3523/sdc12231i.jpg)

And yes, it does have an output transformer  ;)

Do you run production?  :) :)

Did you paint on the transformer??

This is the main regulator circuit i built.

Additionally it contains 1 lm317 for taking 9v output.

Please verify whether my idea is clear on 'grounding'. please ignore my badpainting :o

Nice one JM  :dbtu:  The kind of elegant simplicity it takes years to achieve.   ;)

Quote from: ghoshsubha444all that I want is to build some beautiful tone

Oh, is that all?  The hard stuff first eh?   :lmao:

Well first we get it all working, and then we take Berlin, okay?.


The power supply circuit looks fine, but the 0.1uF and 1r/2W in series aren't needed.

Yes, the grounds should distribute radially from a single point, so you've got that idea.  This also applies to the distribution of power on the +ve side.  Each section should have one ground connection, and only one, or you will get hum from the dreaded "earth loop".

The single ground point is normally a large bolt through the chassis with nut and lockwasher, then washer, the mains earth, washer & nut, washer then the other earths with another washer and nut.  It ends up being a bit of a tree.  It is very important to make sure the mains earth is very firmly attached, and common practice is to crimp a closed ring terminal on the end on the earth wire so even if the nuts should work loose it will hopefully still be making contact.  If you can't get such a terminal you can fake this by looping the earth wire around and twisting it around itself to form a closed loop around the bolt.

Mains earthing is vitally important with guitar amps because the chassis common is carried through to the guitar strings, and if it should become live, so do you (and you may not be live too much longer if that happens!).  There should also be a suitable fuse in a suitable mains-rated holder in the mains infeed as fire protection.

Quote from: Roly on March 12, 2013, 04:55:46 AM

Well first we get it all working, and then we take Berlin, okay?.

ok :) :)

Quote from: Roly on March 12, 2013, 04:55:46 AM

Yes, the grounds should distribute radially from a single point, so you've got that idea.  This also applies to the distribution of power on the +ve side.  Each section should have one ground connection, and only one, or you will get hum from the dreaded "earth loop".

I am trying to refine my image and understanding. Please check my attachments.

Quote from: Roly on March 12, 2013, 04:55:46 AM
The single ground point is normally a large bolt through the chassis with nut and lockwasher, then washer, the mains earth, washer & nut, washer then the other earths with another washer and nut. 

What is 'other earth'?

is Bus connection of +Ve // -Ve permissible?

Re Other Earth Q,
Some folks get confused with Earth, Ground and Common as these terms can all be referring to the same Node in a circuit,,,, but Not Always.

Not sure how your circuit is wired now but this pic might help.

If you look closely at Fahey Amp inside pic shows the mains EARTH wire bolted to chassis and then a white wire (Circuit Common) traveling from there to the centre of those two big filter caps of the power supply.

And a special thanks to Jaun for showing the inside pics. :dbtu:
And I like the white front panel,, something you can actually read in the dark and knobs that actually point.
Phil.

Thanks  :-[
And yes, the picture clearly shows the back panel main grounding point, which I pop rivet, so it's impossible to unbolt by mistake .
Eagle eyed Phil  8| correctly found that the green/yellow ground wire goes from the center of the IEC connector to ground, and a white wire goes to the center of the main filters which is the "Electrical ground".
All other Amp grounds are referred to that.
In fact, if you look closely, I also send the power amp input ground to the electrical ground with a separate white wire, I wanted a good straight path and a PCB track would have zigzagged more than what I wanted.
Also speaker ground returns straight to main electrical ground.

Quote from: J M Fahey on March 12, 2013, 12:34:04 PM
Thanks  :-[
And yes, the picture clearly shows the back panel main grounding point, which I pop rivet, so it's impossible to unbolt by mistake .
Eagle eyed Phil  8| correctly found that the green/yellow ground wire goes from the center of the IEC connector to ground, and a white wire goes to the center of the main filters which is the "Electrical ground".
All other Amp grounds are referred to that.
In fact, if you look closely, I also send the power amp input ground to the electrical ground with a separate white wire, I wanted a good straight path and a PCB track would have zigzagged more than what I wanted.
Also speaker ground returns straight to main electrical ground.

I still want to buy one of your amps, Juan.  It doesn't seem commercial amps sold in the US are built to this level of quality.

OK, thanks.
We'll arrange something.
JM

Watch out Joe!!
If you notice an old dusty Argentinian Falcon Car in your street with a few bullet holes in the panels and being driven by a mysterious looking man wearing dark sunglasses and asking for Joe's place.

Invite him in,,,Use the password *SSguitar* and ask if there is a Fahey amplifier in the Boot,,,Underneath the bones of some long forgotten politician. :police:

Sorry Jaun,,, I could not resist the temptation ;D ;D

Phil.

@ ghoshsubha444,
I'm fairly certain that Rods pages explains some of the loop holes in layout on at least one of those Many pages.

You may just need to go a little deeper into that site,, yes it is vast and you can spend hours finding hidden gems of info on His site,, but maybe worthwhile.    ;).

Re the linking of power rails to many boards,,,
Depends on the setup,,,, so very hard to know as the setup you describe seems rather complex. (Headscratch?)

i personally would not want to run a circuit from split rails then run single rail and back to dual rail.
Same  reason why I avoid using pedals in the efx loops of Amplifiers,,, it just complicates an already complex issue.

I run all pedal type circuits *Before* main Amp circuit so no efx loops.
I do use a *Parrallel* efx loop which overcomes some of the issues when needed.

Phil.

Re: groundin2.jpg - well we are half way there.  The green earth/ground/common is radial as it should be, but you show the red and orange +/-25V daisy-chained.  These should also distribute radially like the green ground side.  Buss connection of +ve and -ve is not permissible (for exactly the same avoiding "resistance-in-common" reason).

The "other earths" are your green wires (the mains earth being your blue wire).

Um ... are you really running your effects boards at +/-25 volts?

Looking again at your a222.jpg it looks like you are using on-board regulators for each board (can't see all of the Phaser board but I assume it also has a 3-pin regulator out of frame).  If this is the case then you can simply daisy-chain the supply because each board will be isolated from unwanted supply signals by their respective regulators.

I have spotted one other thing; on your p27 board one of the zeners is cuddling up to an electrolytic cap, and this isn't a healthy relationship for either of them.  Zeners get hot and like free air around them to keep cool, and electro caps don't like getting hot.  In general I try to give components that are going to get a bit hot, zeners, their series resistors, 3-pin regulators, etc., a bit of "breathing space", and also mount them so that they are a few millimetres up off the board rather than hard down on it (because over time they will also bake the board).

There is another little trap with 3-pin regulators; they require a couple of small caps, 0.01uF-0.1uF, connected between their input pin and ground, and their output pin and ground, as close as possible to the IC, otherwise you might get mysterious oscillations on your "regulated" supply rails.  On your boards this may now be easiest on the copper side.

Thanks Roly..

Quote from: Roly on March 13, 2013, 08:58:28 AM
well we are half way there.  The green earth/ground/common is radial as it should be, but you show the red and orange +/-25V daisy-chained.  These should also distribute radially like the green ground side.  Buss connection of +ve and -ve is not permissible (for exactly the same avoiding "resistance-in-common" reason).

Understood.

Quote from: Roly on March 13, 2013, 08:58:28 AM
The "other earths" are your green wires (the mains earth being your blue wire).

ok.

Quote from: Roly on March 13, 2013, 08:58:28 AM
Looking again at your a222.jpg it looks like you are using on-board regulators for each board (can't see all of the Phaser board but I assume it also has a 3-pin regulator out of frame).  If this is the case then you can simply daisy-chain the supply because each board will be isolated from unwanted supply signals by their respective regulators.

yea for complexity i ignored drawing 9v line. i run effects boards @9v :)

Quote from: Roly on March 13, 2013, 08:58:28 AM
I have spotted one other thing; on your p27 board one of the zeners is cuddling up to an electrolytic cap, and this isn't a healthy relationship for either of them.  Zeners get hot and like free air around them to keep cool, and electro caps don't like getting hot.  In general I try to give components that are going to get a bit hot, zeners, their series resistors, 3-pin regulators, etc., a bit of "breathing space", and also mount them so that they are a few millimetres up off the board rather than hard down on it (because over time they will also bake the board).

Eagle eyed!! 8|
I am modifying my pcb drawing and will obviously allow more spaces between hot items.


I am again drawing my power supply pcb to rectify earlier error. Will post here as i am done.

1.I am encountering a problem something known as bouncing. whenever i am changing/twisting my ceiling fan regulator I am getting heavy popping sound. Start up popping is not possible since i have used relay delay in my power amp?

2.whenever i am disconnecting the mains earth from the ground the noise is increasing hugely. Is this usual or is this because of noise in power line? if this is usual then how amps like Roland cube 15 with 2 pin in the plug exist?(apart from they are well isolated).

My current psu picture is attached..

Quote from: ghoshsubha444Eagle eyed!! 8|

I have been playing this game for rather a long time now.   ;)

1 & 2 - it seems that your amp is still spread all over your bench, and until it is mounted in an earthed metal chassis it is wide open to anything that comes along.

When an appliance is turned on or off there is a small spark in the switch, and apart from conducting a mess of radio frequencies along the house wiring this also directly radiates signals. 

Once the amp is on a grounded/earthed metal chassis it will be much better shielded against direct radiation, but even when the lid is screwed down it is quite possible for "mains-borne" interference to enter the amp via the mains wiring and still cause pops and splats - fridge thermostats are a well known source of such pops, but electric drills, food processors, vacuume cleaners etc., all can produce pops and whines, and may not even be in your house.  This is why is is fairly common practice these days to use some form of mains filter where the power enters the amp.

A simple and safe way to bring the mains in is via an IEC connector, and these are available in various sorts including fused, and with mains filters.  A free source of these is to scrounge dead computer power supplies.  Not all have filtered IEC sockets, but if you collect a few you should be able to find one.  Computer repairers here are only too happy for you to take dead power supplies off their hands, and even blown up ones still contain a lot of perfectly working components for the tinkerer.  I use the main capacitors in valve amplifier builds, the cases make good project boxes, and of course all those coloured wires mean you will never have to buy hookup wire ever again.

(http://3.bp.blogspot.com/_f2TjoRrM27k/TBPZtUVgwGI/AAAAAAAAAdQ/J-vr5oykRHk/s1600/iec+2.jpg)

Since you are going to take care of putting hot things close to caps I'll just comment that heatsinks need surface area to be effective - just bolting a lump of ali to a regulator won't actually couple a lot of heat to the air; a heatsink is a coupler that couples the device to the surrounding air, not a magic heat vanisher.  Again, computer power supplies normally contain several.

Ok Sir. I will give a look into my old SMPS.

I have tried to draw a new PCB for power supply but it is quite a headache  :o

So, I have tried to draw an image to depict the order of components in my earlier homemade PCB.

Please check my attachment.. and suggest if my earlier arrangement was wrong..If something seiously wrong then have to redraw it :(

My Advice FWIW;
Loose those extra resistors across line and for Gods sakes Put the damn thing in a metal case of some sorts otherwise you WILL go in circles for a very long time.

All this PSU stuff is Clearly explained on ESP site if you care to note!

Phil.

Well, those extra .1uF and 2K2 resistors won't hurt  :)
BUT yes, put it in some kind of chassis or you'll never even start to fight noise.

A chassis can be as simple as a sheet of 1mm or 1.5mm aluminum, with one edge bent and perforated to act as a front panel and hold jacks, pots , switches, etc.

As of a simple PSU, no actual PCB is needed, for ages I just contact cement glued filter caps to the chassis, and soldered 4 rectifier tubes ti proper cap legs, go figure.
"Silastic" type (https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcRYurZzFxPjw8oLmzUf_mdfCEBZJxN5lc9FC1bbIVgILfnIpfC7) transparent silicone sealant also works very well.
In fact, works better, only it takes at least overnight to dry.
And .1 bypass and 2K2 discharge resistors (if you want to use them) can be soldered straight pin-to-pin .

Or get a dead amplifier, DVD player, PC case cover, etc. and turn it into a makeshift chassis.

A dead guitar amp would be perfect.

The reason @phatt deleted those components is because;

a) the supplies will always be connected to their load so bleeder resistors are not required.  These are only required in bench power supplies which may not have a load connected, and in valve/tube amps where the heaters cool on power down and may leave dangerous voltages on the supply capacitors.

b) the 0.1uF are high frequency bypasses.  The connection wires to the load have inductance so these should properly go right at the device that needs them to keep the high frequency (and radio frequency) bypass paths as short as possible.  They won't do any harm in the power supply, they just may not do any good.  These should go right at the IC, often mounted on the copper side, between +ve and -ve for op-amps, and between +ve supply and ground for logic IC's.  Anything from about 0.01uF up will suffice.

Without a metal chassis trying to fight noise pickup is like trying to bail out the ocean.  VCR's are now a throwout item here and many of the earlier ones had a large metal chassis which make an excellent testbed, or move forward into your final metal chassis ... now.

"Silastic" is wonderful stuff, but anywhere you want to use it in direct contact with copper (such as sticking down PCB's) make sure you use "neutral cure", the acetic acid stuff is fine for general gluing but will attack copper.

Quote from: Roly on March 16, 2013, 12:28:08 AM
The reason @phatt deleted those components is because;

He Did? :o
Well I'll be darned, I got something right.  :cheesy:

I kinda knew the bit about the bleed resistor but was not sure how to word it.
So I'm glad you cleared the air on that.
I think for me I learn a lot from example from chaps like you.

I now see the point about the hifreq caps being at the device.
So I learn *Why* which is all good.

For goshshuba,,
I think *Teemu's book* explains the ground path layout stuff fairly well,,Might make for some good reading while you are scrounging for a metal case.

http://www.ssguitar.com/index.php?topic=711.0

Judging by the amount of stuff you have already built I'd say the case will get plenty of use because if you are like me the last thing you build is just the prototype for the next brain wave idea and having all the case/knobs/sockets/psu stuff already setup up really speeds up the process of prototyping.

my proto cases are reused many times over and they end up full of holes for knobs.
Yes plus 1 on Old VCR stuff. they also often have a lot of shielded cable just perfect lengths for small audio wire ups.

Some years back I built a 6V6 Amp from old transformers that where given to me and that chassis had so many modifications during the build that I had more holes than metal on the front.
I had to make a new case before I finally mounted it all in an Amp head. :cheesy:

Keep at it chum, it will all become clear to you in the end. It took me a long time to get my head around circuit layout which is not as simple as it first looks.
Have fun, Phil.

Quote from: phatt on March 16, 2013, 09:45:06 AM

my proto cases are reused many times over and they end up full of holes for knobs.
Yes plus 1 on Old VCR stuff. they also often have a lot of shielded cable just perfect lengths for small audio wire ups.

Some years back I built a 6V6 Amp from old transformers that where given to me and that chassis had so many modifications during the build that I had more holes than metal on the front.
I had to make a new case before I finally mounted it all in an Amp head. :cheesy:

Keep at it chum, it will all become clear to you in the end. It took me a long time to get my head around circuit layout which is not as simple as it first looks.
Have fun, Phil.

I am 200% agree with you. Till date i have spent almost double money on this than I presume. With this money I could have purchased a decent amp for sure! But who cares.  Its my money and DIY spirit that I care.

BTW, according to your suggestion I have somehow managed to find a spare SMPS case[photo attached]. Where I put PSU circuit. Do I have to put entire circuit on the case. If so, then I have to look for some bigger case like OLD VCR. But as the noise is concern, no improvement yet. Even I have tried to connect a 0.1 cap between +ve and -ve pin of the opamp.

Today i did a connection from computer to Amp with master volume almost set to 0. Its awful. But as I already know that guitar amp dosen't sound like hi-fi speaker.

Made a connection with keyboard too. Sound not bad. But not so good like the inbuilt speaker of the keyboard.

OK good cheap metal case,,, But Why is that ground lug that (I assume) comes from Earth pin from the IEC socket floating in space? (The Green Yellow wire with eyelet) 8|

Yes I do see where the earth for psu and common for circuit all join up but You MUST have it all tied back to the ground plug as well otherwise you have a floating Zero volts that is not grounded to EARTH pin and it will likely hum like mad.
Phil.

Edit,, whoopsy. yes I now see that the Mains socket is not in use,, but still the mains EARTH must connect to the case otherwise hum.

Quote from: phatt on March 17, 2013, 06:58:58 AM
OK good cheap metal case,,, But Why is that ground lug that (I assume) comes from Earth pin from the IEC socket floating in space? (The Green Yellow wire with eyelet) 8|

Yes I do see where the earth for psu and common for circuit all join up but You MUST have it all tied back to the ground plug as well otherwise you have a floating Zero volts that is not grounded to EARTH pin and it will likely hum like mad.
Phil.

Edit,, whoopsy. yes I now see that the Mains socket is not in use,, but still the mains EARTH must connect to the case otherwise hum.

Thanks for examining...

The Blue color wire is the main earth which is first attached to the chassis with a screw and from there a short black wire goes to Com ground where several wires are tied together. Similarly all +25v -25v +9v are all tied together and connected to their respective position as a single point.. Please refer to  my earlier attachment.

If you're paying attention you can go a long way in electronics on intuition - I know I did.

Quote from: phattI had more holes than metal on the front.

I think I can just fit another hole ... there ...
{drilldrilldrill - clang}
Oh dear, the front panel just fell in half.

Quote from: ghoshsubha444Till date i have spent almost double money on this than I presume.

Murphy's Law of projects - anything worthwhile costs twice as much and takes twice as long -  except software where you double that.

Quote from: phattbut still the mains EARTH must connect to the case otherwise hum.

...and possibly otherwise dead.

ghoshsubha, repeat after me, "the strings on my guitar are connected to amplifier common, therefore it is vital that amplifier common is securely connected to mains safety earth, lest I become an unwilling part of the light show".

I know nothing about Indian power mains practice; please post pic of plug and outlet - what voltage and frequency?

(http://shivashetty.files.wordpress.com/2011/04/powertheft-070709.jpg)
{this gives me the leaping jeebies :crazy2:}

Quote from: ghoshsubhaThe Blue color wire is the main earth

I've just looked up the standard colours used in India and blue is for a phase active (as it is here).

Mains safety earth is green (or now green with a yellow stripe here) so it is unmistakable.

Mains safety earth must be equal or heavier conductor to the mains active, and it is good practice to use the proper colours for mains wiring within equipment.  Heavy duty green should be used for mains safety earth and for nothing else (and no other colour should be used for mains safety earth).  For the amplifier common runs black is fine.

hello..

I dont know about if I am doing any mistake on other things but I can 500% assure you that mains earth is first attached to the chassis and from there to the common ground.


I have really messed a lot with wires and colors but when I will be done with the experimentation I will definitely set up the whole thing with proper color wires with neat arrangement.

Mains Voltage:220V @ 50Hz
Thanks for the care <3) <3)

compressor

Quote from: ghoshsubhaThanks for the care <3) <3)

Getting killed can seriously cut into your guitar noodling time.   :-\

Why am I not surprised to see an older style English mains plug?

{when I lived there I had to change all the plugs every time we moved house because there were at least three different "standards" in use, small round pin, large round pin (like yours), and rectangular pin which now seems to be the dominant standard.  I've seen some English wiring and switchboards that date back to the Roman invasion and make the guy up the ladder look cutting edge.  :o }

Grab an old computer case, glue/bolt/BluTac boards inside.  Profit!   :dbtu:

Roly you do have a knak for finding funny pictures :lmao:

I doubt the house would need a bug zapper cause even the fly's would have trouble navigating all that wire.

Or maybe they worry about the Roman invasion. ;)

But Hey, give him credit he is using a bamboo ladder and he is wearing rubber thongs.

Yeah looking at ghoshsubha's pictures I'm a bit concerned about all that stuff just hanging off a make shift work area. :trouble

Now I do not wish to dampen the enthusiasm of those wanting to learn,,,But Yep Safety comes first So PLEASE guys think about where and how you setup stuff like this as you can land yourself in deep trouble in the blink of an eye.

I read one case (it may have been here?) where a kid was trying out his over the head Hendrix style picking and as he threw the guitar up over his head those new string ends which had not been cut flicked into the Empty light socket above him which had been left ON after bulb removed. This instantly destroyed the Amplifier circuit and the guitar internals. :duh

Lucky for him the amp made a better path to ground than he did but you may not be so lucky.
I've had live open transformers and wire fall off my bench and you learn to at least gaffa tape temporary stuff down hard Especially if you have free Mains wire.

Big wads of tape go across open switches and transformer taps as it is just to darn easy to slip up.

I work on a wooden bench and I stand on a 20mm thick rubber mat and I wear shoes. :dbtu:

Plug paks make fairly safe supplies for testing (join 2 for dual rails)
I did a lot of early experiments with 2 old printer supplies which delivered 37VDC open circuit.
Two of these powered my first venture into making power Amplifier circuits.

When I did get into serious prototype I built a separate PSU in metal case with switch/fuse and screw and banana terminals for output to drive the bigger Amp circuits.

Even if you have the wiring earth Stuff all sorted with all that hanging out like this WILL ONE DAY Cause grief.
As has already been implied,,, the short cut is often the longer path.

If you live anywhere near an industrial estate then go find sheet metal workshops they throw out heaps of parts/offcuts/seconds that often make good proto boxes.
Or scrap metal yards and like places.
Phil.

I couldn't find the one I was looking for, a guy on an aluminium extension ladder being held vertical by half a dozen blokes at the bottom, up in a Gordian knot of cables suspended in mid air.

(http://www.spiritofhealthcare.com/wp-content/uploads/2011/12/the-gordian-knot.jpg)

I don't think a wooden ladder and rubber thongs would help.  Gutsy or stupid; you wouldn't get me up in that lot for anything (and I've done some hairy stuff at times on live switchboards).

{I wish I had a pic of one English switchboard I saw that had fuses consisting of exposed clips holding glass tubes about 3 inches long and 1/2 inch in diameter with fuse wire threaded though them - and no cover.}

I don't recall the light socket incident, but Rod has a lurid warning on his site about changing guitar strings near a live amp (or live anything for that matter).  Vent holes are only designed to stop small fingers, not unruly guitar strings.

Yep, the best you can expect is FLASHBANG!!! and a smoking ruin.  At worst you "shake hands with beef".  Safety is only excessive until you don't have enough of it. 

(http://t1.gstatic.com/images?q=tbn:ANd9GcTwzJQvdYaUXp4tsfDBUuk0dw7SRiDyFY_mqIRf62Cl1uPIROhA)

(http://www.worktotallysucks.com/image/hatemyjob/small/1112/-hate-my-job-1323218404.jpg)

:lmao: :lmao: :lmao:
Ha ha!!

hello ssguitar users

I am little busy with my exam...will start the project as soon as my exam is over..

Have a nice day!

see you later.

Quote from: ghoshsubha444@gmail.com on April 11, 2013, 12:28:30 PM
I am little busy with my exam...will start the project as soon as my exam is over..

That's good, and that's good.  Best of luck.   :dbtu:

is this still project 27?
im confused because you have 6 pcb...

ghoshsubha444@gmail.com, can post your pcb layout with the components?

Quote from: yoyoy_kun on September 26, 2013, 03:42:07 AM
ghoshsubha444@gmail.com, can post your pcb layout with the components?

Rod has boards for sale.