Quote from: joecool85 on January 05, 2011, 03:57:55 PM

Quote from: J M Fahey on January 05, 2011, 03:41:24 PM
Remember that your problem is not only having no ripple there, but being an *audio ground* reference for many gain circuits. In fact some people use an "as large as possible" electrolytic, paralleled with a .1 ceramic or similar.

Could you elaborate on this "audio ground"?  Also, why would having a small .1 or so ceramic cap help?  I've seen it a lot in pedal board PSU designs but never knew why.

Thanks for the excellent explanations.  I've been doing this hobby for 5 years now and know how to do stuff, but not always why.

Hi Joe,
In a nut shell, you are lifting your AC signal *Common* above the DC Ground. you are Floating it at a bias point higher than ground,,  it's biased at a different quisient point.

The really tecky part (Why Capacitor on the bias voltage) I'll leave for the experts to explain but what helped me big time was *Simulation* as you get to see stuff that, done in real time would cost a small fortune in scopes, sig gens and half a dozen DMMs just to take all the readings.

For a hobbist it really opens up a whole new world that you would not see outside of working in a repair shop.

Sims will show you just how the AC signal is moved up and down on the DC line (the Q point).
Quite frankly I would still be messing around with 2 or 3 transistor circuits and wondering why it does not work if it was not for Sims.

Heck the MaxiVerb, the PhAbbTone, The DDC circuit. None of these would not have been possible without the help of simulation software.

I use Circuitmaker (student edition) which is free up to 50 commponents.
I now have 100's of sim files I can call up if I need to reference something.

Now sims are not perfect and Absolutely nothing beats years of experience from qualified teck folk. (You know,,those smarty guys that brag about building 10,000 Amplifiers and make there own speakers) :loco
We  hobby types will never be able to reach such dizzying heights,,  
But as a hobby tool sims will save you 100's of hours of building waste of time circuits.
Just think of the solder you will save. LOL.
----
Ed,,, whoops Did I  mention Circuitmaker student is *FREE* ?
http://my.ece.ucsb.edu/bobsclass/2C/Simulation/circuit_maker.htm

I think this still works if not just google it I'm quite sure it's floating about just waiting to save you from hard labour.  Oh yes it even has some Valves to play around with. :tu:
Cheers, Phil.

To Clampup,
I Strongly suggest you seek professional advice because the way you are going you will land yourself in the ER.

Put it down and read up until you grasp what the hell you are playing around with. :grr

The green wire is for safety backup it goes to the metal chassis,,, which you do not have :duh

I'm sorry chum but that is flaunting death and stupid. :loco

Yes I can't stop you from flying a *non air worthy* plane without a parachute but at least
you get a warning when the engine conks out,,, but with electricity it's instant,, and often fatal.
Sure you might say but it's only You that gets hurt.  But what if you accidently kill someone you love because you thought you knew what you where doing?
How smart would you look then? 8|

learn the basics (And safety issues) then you will be able to understand the answers you are getting.
Just Google any word you don't grasp and spend some time absorbing how things work.
Magnitisium, Transformers, DC circuits, AC circuits. there's some for you already:)
How stuff works will even be able to help with this.
Good luck. Phil.

Quote from: clamup1 on January 02, 2011, 04:52:19 PM
hey i got the led to light up but i cant get anything but hum.
http://www.shedradios.com/images/crate_cr-112_04.jpg

at the vcc+ im getting 44 v. almost double the 24 thats supposed to be coming to the IC 2. the only thing before the IC 2 is a 5% 1w R and a led.
ive got 44v going to IC1 also. IC 1 and 2 are supplied by the same trace. could this be a grounding issue? help

Check you have 24VDC at C37.
If you get 40 VDC there then Zener D4 is likely futt, Replace.
Phil.

Hi forgot to mention;
Go to the index at Amptone and trawl through the masses of ideas.
http://www.amptone.com/index.html
Sorry no flash stuff just mainly text,, So You will be there for a long time

Although it focuses on tube amps and attenuation most of it is still just as relivant for an all SS rig.
Phil.

Hi THChrist,
           Well if all you really want to do is play the guitar then you can waste so many years trying to perfect an amp (Glass or Sand) you may forget how to play the instrument by the time you finish.

I make a personal point of not bothering very much with *One Off* builds/sites that claim or even imply they found the holy grail circuit.
Unless they have evidence of there inventions being used by live working musicians or have built quite a few.

The amount of times I've got excited over circuits at home only to find in real world working situations they never deliver.  

Want to see my shed full of land fill circuits (spare parts bin now)

In close to 30 years of messing with circuits only 3 or 4 of my inventions are worth a mention. (All posted here I should Add, check under schematics) I would not be so cruel as to post circuits that I knew had possible shortcomings.

You mentioned power tube sound so here is a little trick I did many years ago you might wish to try which will open your eyes about powertube sound.

I simply took a small little 20 watt SS Amp and wired a series lamp limiter into the Mains power cord which produces quite convincing power amp compression.

Caveat; The Amp circuit needs to be very simplistic for this to work.
i.e no onboard digital FX and fancy switching circuitry.

You loose some wattage but the saggy compressed sound is very reminicant of tube power stages.

At times I wish I'd kept that litte amp it was so much fun for small gigs,, as I
needed no pedals,, just a straight rock sound with nice rattle and comp when driven hard.
The draw back, just like early small valve amps they sound great but only at one Volume level.

IMO the difference between a good or bad amp (Any type) can be mostly put down to
tone shaping. i.e how and where in the circuit these tricks are implimented can make
a massive difference.
Just hanging the Marshall value resistors off a semi conductor wired up the same way
shows little understanding of how to make good amplification.

I won't mention names but a lot of fet preamp circuits have become so popular because they use close to exact values as those used on some famous Valve circuits and again they are far from ideal as good *Reliable* circuits.
Yes they work but often the SNR is horrendous because they just hang 1 meg resistors
off every gate like a valve Amp and high gain on high imp = massive noise.

Try reading some of this stuff before you travel down the complex path.
Humans have a habit of insisting that complex problems must have complex answers and
often even the experts can miss a really simple idea.

http://www.amptone.com/truesecretofamptone.htm

A bit dis-jointed in places and rather long winded but it covers a lot of questions
that folks like you ask.

I may not agree with all of it but I'm sure it won't take long to catch on.
anyway I'm just rambling on so time I went.
ps, I only speak 2 languages, English and Oztrayland
Phil.

Hi JMF,
A bit of trivia for you,
Did you know that 8Tracks never caught on in the land downunder whereas cassettes where a huge hit.

My LM3080 has died   so that brings all progress to a grinding halt.

For the time being I relented and purchased a cheap S/hand Marshall pedal.
The *Ed 1 compressor* as it's called.
Same chip and very similar circuit that I've posted which of course still has the inherint hiss problem if you up the sustain and level.
With the level held low it's useable,, so will see how long I can stop myself from tampering with it. :lmao:
Hum?? I wonder how a couple of leds would work in that circuit.

Did find some interesting circuits while searching the net.
As to your comment about *Control Voltage* being an issue,, well 2 stood out and looked rather interesting.
*Pearl* Make one and the *DOD 525* looked trick.

Also *DOD Attacker* I did partly test but that is about the time the chip lost its magic smoke. I have a feeling that the control pin5 is a problem if you short it,, but I'll never know exactly what happened :grr
Cheers Phil.

Quote from: kin0 on December 05, 2010, 06:13:19 AM
Hay,

I don't what will function better as a preamp (before a velleman kit). I have 2 ideas

1. Use buffer----> baxandall tone stack --------> preamp http://www.till.com/articles/GuitarPreamp/ -----> volume control -------> poweramp. Some people told me it will be very transprent

1. Use buffer----> baxandall tone stack --------> booster (lpb-1 ?) -----> volume control -------> poweramp. I am not sure how will it work but I think because the lpb-1 isn't transprent at all it will be less transprent then the first one.

any ideas what will work better?
oh and also any ideas for a good buffer?

The Tillman circuit is meant as a small (onboard) front end and is not intended as a preamp input stage of a guitar Amp. Its real purpose is to overcome leed losses associated with long guitar cords.
By itself it is only a buffer and has no gain.
Phil.

Ouch,, Murphy's law says if there is a wrong way to insert a part then that's usually what's wrong when it refuses to work.

Might be time to invest in a light bulb limiter before you waste money on another set of transistors. 8|
Phil.

Hello tchrist,
Not sure where your heading but I agree with JM Fahey's last post. 8|
That stuff is Way to complex for little benifit as a tube power stage will still be better.

I did have a listen to the clip, Turning the knobs did little to effect any real change in sound.
Also a servere lack of bass but that's a matter of taste.

A note on tube preamps ,, it's a dog chase tail thing as the real benifit of Valves is in the power stage not in the preamp stages.
So if you want to throw money at something then build a Valve power stage and leave all the tricky complex preamp stuff for SS. Cheaper and Easier to fault find for the hobby types.
These days anything with an AX7 inside a preamp will sell.
IME, Complex valve preamps are no better than what can be done with transistor/chip circuits.
Sure if money is no object then go nuts but the cost is significantly higher with Valves.
Phil.

Hi folks,
         Yep I've never been able to get my head around all these different formats so Time for me to look into it further.

Sadly coming from an industrial background I missed out on basic Computer skills so a lot of this technoligy goes over my head I'm afraid.
Floppin hang it all ,,I'm Sooo old school I've still got Cassette players and Turntables.
I doubt I could even switch on an iPud. HaHa.

My first few Schematic's from the net took up about 10 pages of an old dot printer for
one schematic which had to be joined together with sticky tape.  :grr
But I've been using IrfanView since some enlightened person put me onto it which
allows one to resize things to fit on normal A4 paper.
That was a big big help. <3)
I've been using IView ever since but now I'm *up-loading* files I obviously need to
look deeper into the finer points,,,So thanks those helpful tips there maybe some improvement in the new year.

I've posted what I hope is a better effort.
Please note a small booboo. ***R13 should be 5k***
I paralelled two 10k as 4k7 is not quite right. The offsets are obviously quite touchy and
without knowing exact DC offsets it's hard to know exactly where to set bias points
so a trial and error working up and down until you find it.

The input to the LM3080 is about as low as you go for SNR but the output may still
need work as the sustain knob still presents a fair amount of hiss when the Amp is
cranked up to live gig levels.
(not bad but enough to be annoying,,
I'll except a Compressor but I'll burn in hell before I use a noise gate)

I might throw it all in a make shift jiffy box and give it a test run at the next Club gig.
Phil.

Hi fellow tone tweakers,

It seems it's a love/hate thing with Compressors, some like some don't.

My main experiences are with the dreaded CS2. (hated it and sold it,, noisey as hell)
Also still own a Quadraverb GT. (poor me) It's preamp systems where also a horrabillas experience.

My CS2 was a long time ago and I have learnt a lot since those days so I thought I
should at least test some ideas and see what really goes on inside these circuits.
Heck why not,,I've got an LM3080 chip in the junk pile somewhere.

I've always found Compressors more trouble than they are worth but after hearing a neato trick using a CS2 in front of TS9,,,
Wow really did improve sustain and bingo it sounded a lot less like a compressor.
Well you learn something new everyday.
Obviously it got me thinking about Comp circuits again.

Now I'll cut to chase.
Needless to say out came the breadboard and after a few weeks of breadboarding many
ideas I've found a few things you might like to know. None of these tricks will fix the clean sound of these comps but may improve the OD sound if used *IN Front* of Distortion units,, Obviously after Distortion won't work as well.
If you are into a lot of funk rythums then I admit clean comp is a usefull tool
but Still Noise is usually the enemy.

The Pumping action.
After much headscratching it dawned on me that the clamping action is not a matter of speed but *DEPTH*, it's far too much.

I Fixed Pumping action by *Changing diodes to LEDs*.
A switch could be used here for standard (hard) and led (soft) comp.

This raises the comp point and although you loose a bit of clamping it still retains a fair amount of sustain which helps to overcome that dreaded humph mumph you get with most Comp circuits. (Very nice I like)

The switch on the caps changes the recovery time.
2u2= fast, 10uF= slow. Can't make up my mind about that part yet.

**NOISE**,, As said a huge issue. (on all but the rare expensive studio racks
systems)
It seems that everyone just copys the other's ideas with a few changes and throw it on the market. Even Bootweakers don't seem to try hard to solve some of the noise issues found in some classic circuits.
Heck,, maybe I'm alone in my quest to build quiter circuits.  :lmao:

So lower noise was the priority, the *must fix* otherwise it's just going to end up
landfill and I'm wasting my time.

Now being this unit plays around with a lot of gain I can't say I've made it *Noiseless* but I believe I've dramatically improved on the CS2 styled Compressor circuit.

Tokai made one similar to Boss CS2 unit and it apparently had a better S/N so I mixed up some ideas from a whole pile of schematics and then I just kept tweaking things.

So yes I'm very impressed,, With the Sustain full up and Attack slow it works well
with my distortion units.

With the Leds engaged it has already fooled me a couple of times so it would be hard to tell if it colours the sound. Obviously run clean it still retains the classic CS2 comp sound if that is your thing but I'll hazzad a guess and say it will NOT be as noisy and hissy.

Of course if you wind up the level it will still deliver some hiss but I'm assuming you all know not to use the Compressor output as a master volume,  :trouble.
I doubt you would need to turn up the level much as this unit still has heaps of headroom. (A 50k level pot may work just as well here)

So if you wish to get more from your distortion units this may be an improvement.
At the least I've created a working circuit that may give others with better insight some ideas to work with.

When time permits *I will* be building this circuit. The Danger is to keep on tweaking but I doubt I could improve it further without resorting to much more complex circuits.
Have fun with it, Chrissy Cheers from Phil.

Quote from: bry melvin on December 19, 2010, 12:01:05 PM
amp doesn't have a thermistor...just a cap

Thanks Chum, Something strange happening  :loco as only *now* that I've submited another post did I see you actually posted part of the schematic.
WAS not there before???  Oh well no matter, thankyou for the clarification.
Cheers Phil.

Hi,
Well that helps a bit but still I have no idea where the extra black wire went or should go.
Schematic should tell you.

I'd leave it off as (I assume) the amp will work without that cap connected.

As to the power transistors swapping
If you put them in the wrong side the amp will surely blow fuses.

one will be a "npn" device and the other a "pnp" They are polar devices and only work one way.
Make damn sure you get them the right way around.
Phil.

Quote from: Enzo on December 19, 2010, 12:57:02 AM
All TO3 bipolar transistors have the same pinout.   

All bipolar TO220, TO218, and TO247 transistors have the same pinout - ECB across the front.

I knew the TO3's where all the same but was not sure about the other tab types.
Arrh darn You Enzo you got me again  :grr,,, I must owe you a point then :tu:
Cheers Phil.

I'd fly over and have a better look at it for you,,, but my private Jet has a flat tyre. :lmao:
Phil.