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?

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

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:



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





And yes, it does have an output transformer 

Do you run production? 

Did you paint on the transformer??

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:

Quote from: Roly on March 11, 2013, 11:01:12 AM
Overall layout

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


Power amp


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

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, 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?

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

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

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..

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

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

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

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

GOT YOUR POINTS