GGG ITS8: TroubleShoot

[WesMVaughan]

Problem: I have built two General Guitar Gadget ITS8(Tubescreamer Clones) identical and they do not sound the same.

Pedal A: (First build) I had fried this pedal by using a higher voltage adapter. I had to change out a capacitor and some transistors. It works fine now.

Pedal B: (Second Build) I had put some pots in the wrong place but they are in the right place now.

Both were built using the expensive boutique mod which meant putting a 1 meg pot for the gain control and changing out some resistors. The only difference between the two pedals is that I had to replace a capacitor on pedal A. I replaced a 10 farad 10v capacitor with a 10 farad 50v capacitor. I was told as long as they had the same farad rating it would be okay. The only other difference is that I used a non braided wire from the foot switch to the PCB in pedal A (which shouldn't matter).

Test 1: Pedal A & Pedal B settings = Level Max, Tone Max, Gain Max.                       Analysis = Pedal A has slightly more gain and treble.
Test 2: Pedal A & Pedal B Settings = Level Max, Tone Max, Gain all the way down.   Analysis = Pedal A is much louder and has more gain and treble.   

The difference can really be heard when the gain on both pedals are turned all the way down. The only thing I can think of is that when I fried Pedal A, I fried something else in the PCB. However, the pedal shouldn't be working if that is the case and pedal A sounds better than Pedal B. In addition, I did a much better solder job on pedal B yet it doesn't sound as loud as Pedal A.

Any help is greatly appreciated as this is driving me crazy!

[PRR]

> replace a capacitor on pedal A.

WHICH capacitor??

> I replaced a 10 farad 10v capacitor

10 microFarad..... 10 Farad would be the size of a trash-can.

> I was told as long as they had the same farad rating it would be okay.

Usually a good rule.

This particular plan has a sneak-path. Zero-volume depends on C7 (47uFd) being "zero!" impedance.

> heard when the gain on both pedals are turned all the way down

Why would you run a "screamer" all the way DOWN?

All electronics have some "faults". The wise designer shoves the faults into corners where they do NOT hurt the main uses. And also works within size/cost limits. If "all the way down" were an important operating condition, the designer would have arranged things differently; but "all the way down" probably is not an important condition.

I think you have the usual part tolerances, minor layout differences, etc.... simple hand-made electronics tend to vary.

[WesMVaughan]

I replaced Capacitor C11 which can be seen on the layout link below. Yes it is 10 micro farads.

The reason I run them with the gain all the way down is because I was told that is how Stevie Ray Vaughan ran his tube screamers. I use one for a dirty rhythm and the second for leads. However, I do usually have the gain turned up about 1/8 or more. I just figured that having two pedals built exactly the same, they should sound exactly the same. If a wire was poorly soldered to either the tone or gain pots, would that cause a loss in gain or treble, or would the pedal just not work at all? Thank You for your Help!

http://www.generalguitargadgets.com/pdf/ggg_its8_lo.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

[PRR]

> Gain all the way down

There's no "Gain" pot on GGG's plan.

All three pots have some effect on gain, notably what they call "Volume". Turning Volume full-down should give a useless signal.

Do you mean what they call "Drive"?

> I was told that is how Stevie Ray Vaughan

Yes, it makes sense that someone with SRV's hands and ears might use this circuit with R19 "Drive pot" set to zero.

In that condition, if two "identical" pedals are not the same, I would look at R6 R7 C3.

> If a wire was poorly soldered to either the tone or gain pots, would that cause a....

If you can't trust your solder joints, ANYthing can go wrong.

Maybe you can work-out what a specific bad joint did.

But a good solderer and a good inspector can turn-out joints that are 99.99% long-term perfect faster than you can think about a joint. Working alone (without a separate inspector) you may only do 99.9% perfect, but that's a lot of DIY.

If you doubt your joints, improve your soldering skills.

[WesMVaughan]

Yes I meant Drive.

I will check out those two resistors and c3 capacitor.
The funny thing is My solder job was much better on pedal B the second build however pedal A sounds better. Thanks for all your help so far!

[WesMVaughan]

Is It possible that I burned out the other capacitors when I fried the pedal? I am not sure if I checked them before with a multi meter. Could those capacitors be burned out and the pedal still be working? I doubt I burned out the resistors. If I did the pedal should not be working should it?

[WesMVaughan]

How can i test the capacitors? My friend has a ESR meter but it only tests Electrolytic caps. If I test for a signal with a multimeter, I could still get a signal but the cap might not be functioning properly. Am I right?

[MikeH]

Due to tolerances in components it is pretty common for 2 pedals to vary in the way they sound.  Not just true for pedals but amps and guitars too.  Didn't you ever have a friend who swore that his twin reverb was the best sounding twin reverb that he or anyone else has ever heard? 

Now if they sound VASTLY different it's possible that a minor error in one build is changing the sound just slightly enough to be noticed, but not enough to affect functionality.

You stated one pedal has more output; if the one you had fried had a lower output I would say you might have a damaged IC or transistor, but it looks like the one you fried is actually louder.

[Projectile]

Why would you run a "screamer" all the way DOWN?

Because it sounds great? Many people run a tubescreamer with the gain all the way down. It's one of the sounds the pedal is famous for, if not most famous. I almost always run my tubescreamer with the drive set somewhere close to zero. It's fairly standard practice.

[WesMVaughan]

Thanks for all the input. Yes MikeH I understand what you are saying...even though I have never actually A/B two exact pieces of equipment before. Since I'm running the pedals together I can adjust to the differences in them by turning the gain control. I still can't help but wonder, that if they were to sound identical would it help with my tone? At this point, I think my best bet is to test all the caps and transistors. The resistors should be fine and I know the IC is fine on both pedals.  The confusing thing is, I don't know which one is supposed to sound right.

[BadIdeas]

The confusing thing is, I don't know which one is supposed to sound right.

Are you trying to make a counterfeit or bootleg or something?
SRV was a big fan of Hendrix, and I've always said that if you play anything exactly the way Hendrix did, you're playing it wrong. I think the same principle would apply to SRV.

Do you know enough about electronics/effects to know what R6, R7, & C3 do? Are you familiar with RG Keen's "Technology of the Tubescreamer" article on GEOfex?
R6 is minimum gain resistor. R7 & C3 work together to set the frequency response and affect the gain of the clipping stage. Tolerances here would make a slight difference, especially in the cap I believe.

My suspicion is the tone pot & related components. I have read that pots have about a 20% tolerance. Since both of your tests were with the tone at Max, and the value could be as much as 30k, that could be where the extra treble is coming from.

[WesMVaughan]

I am trying to get a SRV tone. I am using a Fender American strat with Texas specials into the 2 screamers into a Fender Deluxe Reverb Reissue. I use one screamer for rhythm and the other one for a lead boost. I do not know much about electronics at all. I was hoping to save money by building the pedals b/c the TS-808 reissues with the supposed "holy grail" JRC-4558 op amp go for $180 each. Also I have learned a lot and have been able to fix other pedals/ electronics I have in the process.  Currently my tubes are out on my Deluxe Reverb and I never got the chance to really crank the amp with the screamers engaged. I usually ran the volume at about 12 o'clock (5 of 10). While I was able to get some good tones (blues and country), it was still lacking for SRV tone. If I turned the gain up too much it would sound distorted and if the gain wasn't up enough it would have no sustain. Perhaps I didn't have the amp cranked enough.
Thanks again for all the advice and input. When I get my fender amp re-tubed I will post some sound clips.

[BadIdeas]

I guess if getting a specific tone is important to you, far be it from me to judge.
My Visual Sound Jekyll & Hyde has a JRC 4558 in it, so I would venture to guess their Route 808 would too. It's marketed as an "interpretation" rather than a clone, with a bass boost switch, more output, and of course the Pure Tone buffer. $100.
I'm not sure if the TS9 (also $100) uses the JRC4558, but apparently the only difference between a TS9 and an 808 is two resistors in the output buffer, as detailed in the aforementioned article. Of course, it may be worth noting that the author of that article currently works for Visual Sound.
As for your amp, I'm pretty sure SRV was the "everything on 10" kind of guy. I don't know if the same went for his guitar, but most great guitarists I am familiar with knew how to use it's volume knob and picking dynamics to control the amount of distortion.
There is also an interesting bit of mojo I have read, and I don't know how much truth is in it, but here it goes. He apparently needed an extension cord to power his amp in most venues, but one time it was not needed, so it was not used. Stevie started losing his temper about how bad his sound was, so his crew tried to figure out what was wrong, and came up with nothing. They finally figured out that the only thing that was different was that the extension cord was not being used. Apparently this cord became an extremely important piece of equipment, being repaired many times before finally being retired. I don't know much about tube amps, but I suppose it's possible that the impedance of the cord... well, I guess if someone more knowledgeable cares to speculate...

[WesMVaughan]

wow that is fascinating! It was just some random extension cord? Just another variable in the already complicated equation of guitar tone. I am not trying to sound just like SRV, however if I am to cover his songs I would like to have a similar tone. His tone also works well for the type of Country music I play. The tone he has on the song Texas Flood is what I am going for the most b/c of the long sustained bends. It sounds like a  high gain clean ( the best way I can describe it).
What tubes would you recommend I get for my DRRI? I have heard JJ are good tubes. I also use that amp to play jazz. I use an ES-335 straight into the amp.
I agree with you on the "everything to 10". I think that is paramount. It is just rare I get to play that loud especially when practicing with a band. Thanks again for all your input!

[WesMVaughan]

Do you know much about tubes?

[BadIdeas]

I do not know much about tubes, I'm afraid, and I couldn't tell you what SRV used. I really haven't been learning effects for very long, and I'm just barely getting my head around how tubes work in a circuit.

BTW, I found where I read about the cord. It was the November 2006 issue of Guitar World Magazine. The article was called "Testify", written by Cutter Brandenberg promoting his book, You Can't Stop a Comet. Stevie wanted his own power outlet for each show because there would be less noise, so they had a junction box with an extra long cord.
The article ends by discouraging people from dressing like him and trying to act like him. I have nothing against cover bands, though. I've seen a Pink Floyd cover band, The Floydian Slips, several times. They usually get all the sounds spot-on. One time, though, they had this new lead guitarist who would play the Gilmour solos, then go into some kind of pseudo-metal shred thing that was just awful. The next year he had a much better handle on the style and was able to improvise appropriately.
As for the sound, I would look for an opportunity to directly compare your screamers to what you hear on the record. I can't seem to find his pedal board in this video, so I don't know if one is even on for this song:
http://www.youtube.com/watch?v=tWLw7nozO_U

[WesMVaughan]

So the cord basically cut out noise? Or did it affect his tone in some way? And yea I agree with the whole dressing and acting like SRV. SRV is only about 15% of our set list but I really like his tone. It is very similar to the tone used in a lot of Texas country bands I listen to. Since I am from Texas, a lot of people know SRV and I just want to make him proud. Anyways I am getting my DRRI re-tubed and I will try and post some sound clips with the screamers ASAP! Thanks again for your input!

[BadIdeas]

So the cord basically cut out noise?

No, having his own power outlet supposedly reduced noise. I don't know how the cord affected his tone, but it probably had something to do with this thread:

http://www.diystompboxes.com/smfforum/index.php?topic=88318.0

[WesMVaughan]

I finally got my DRRI re-tubbed and it sounds better than ever, turns out the old tubes were biased cold. So I just tried out my pedals again, and still have the same problems as mentioned before. With either of them engaged by themselves with the gain turned all the way down and the volume maxed, the tone is grainy, basically I want the clean sound only with more sustain and compression. It just sounds crackly and distorted. I am starting to wonder if this is because the way I modded the pedal. I I did the expensive boutique mod which was suppose to have given the pedal more gain. Maybe I should revert it back to a regular un-modded tube screamer and it will be less grainy?

[WesMVaughan]

Anyone have any ideas about this?