First breadboard build a success!! Now a question...

[Surfcaster]

I'm excited to report that my first breadboard build of the General Guitar Gadget MGV (Guv'nor clone) was a success!!  I had to do a bit of trouble shooting, found a few errors in my layout, but overall I feel really good about it.  And I have to say its a prett decent sounding pedal!  The only issue is I'm finding it too trebly for my rig, at least when using the LEDs, which I like otherwise.  It's workable with the treble turned all the way down, but I'd love to be able to lower the treble in the circuit so the treble pot is more useful.

Here is the link to the schematic:  http://www.generalguitargadgets.com/pdf/ggg_mgv_sc.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

I tried a couple of things.  I tried larger values for C2...270pf and 310pf...both reduced treble, but by the time I compensated by dialing up treble and mids to where they needed to be it sounded buzzy and compressed.

I tried a couple different values for C13, but those only affected the pot's range, it didn't lower the floor like I want.

I tried putting caps across the LEDs, but couldn't hear any difference.

Is there a resistor in the tone stack I could change to get me there?  I'm not familiar with that tone stack, so I'm not sure what does what.

Any suggestions would be greatly appreciated!

Thanks!

[LucifersTrip]

I think the Duncan calculator might help

http://www.duncanamps.com/tsc/

[amptramp]

I wonder why you need two capacitors in series (C3 and C4).  It seems like C4 should be deleted and C3 should be its 0.1µF value or maybe the existing 0.22µF value would work better.  I prefer to have the resistor next to the inverting input of the op amp because it would have less stray capacitance to ground that would affect stability.

Increasing C2 will cut some treble, but notice what happens at low gain: C2 is effectively shorted out, so its cutoff frequency varies with gain.  So does the rolloff frequency as set by C3, C4, R2 and the portion of the gain control to the right of the slider, so there is some (undesirable) interaction between the gain control and the tone controls.

The clipping action of the diodes will add harmonics which are always at higher frequencies, so you may need to cut the high frequencies after the diodes.  I would try a capacitor from the top of the level control to ground in your breadboard.

The combination of C1 and R1 gives you a turnover of 723.8 Hz which is much higher than you want.  I would increase the value of C1 so it will pass lower frequencies.  That combination definitely kills the bass, so when you turn up the level, you get a lot of treble.  By contrast, your input turnover is 15.9 Hz as set by C5 and R3.  To counteract this, C8 and R6 set the rolloff at 1064.4 Hz so that highs will decline at 6 db / octave with this corner frequency.  I would increase C9 as well - when the silicon diodes pass 1 mA, they act like 26 ohm resistors, so you get the effect of C9 in series with 1026 ohms giving you 705.5Hz for the turnover when clipping.

Note that the db losses from turnovers (high pass) and rolloffs (low pass) add through the entire pedal chain, so you should maintain as much fidelity as possible in each effect.  You can get 1µF capacitors in small film packages and you might want to try this for C1, C3 and C9 with C4 removed and shorted out.

I don't see a problem with the tone stack values.  Other than a cap across the level control, I would leave it alone until I tried the other things I have suggested.

[Buzz]

Hi Surfcaster.

A couple of years ago I built the GGG Guvnor kit version.

Same schematic and values, but I just did the 'paint by numbers'  ( lazy ) version offered by the kit option.

Well done on breadboarding it, especially as a first project, it's a big circuit.

I have to say, mine isn't too trebley or thin. It's my go-to distortion pedal, haven't found one better.

On guitar, I use a strat, and have the bass pot around 12 o'clock, the mid around four o'clock and the high at about 12. Distortion Knob at about 11 o'clock and gain that puts me roughly at unity, usually about 11 o'c. That gets me the sound I want on a 100W tube head.

Here's the biggie though... I also find it great on a Jazz Bass. Doesn't suck out the bottom. Bass pot maxed... mid about 2o'c, high about 9. Then I just turn the gain to a little over unity, and turn the distortion clockwise til I just get a little bit of dirt. Really pushes the amp ( 150w SS ) and gives me a great growling bass sound.

The kit has a switching option for the clipping diodes. Red LEDS or 1n4148s.

I like the LEDs for guitar and the 4148s for bass.

Maybe double check your parts values and connections.

Of course if you're using different gear you will be getting different results, but from my experience I would not describe the GGG as an overly trebley pedal.

Good luck, I hope you get it sorted, this is a damn fine circuit.

[Surfcaster]

Thanks for the info.

LucifersTrip...I had looked at the Duncan Tone Stack Calc., but couldn't find a tone stack in it that looked like this??

AmpTramp...thanks!  That's some serious analysis...I really should take an electronics class!  I'll try replacing those caps and see what happens.  The only 1uF caps I have are aluminum electrolytic polarized...I assume I can use them as long as I get the polarity right??

Buzz...it IS a great pedal, I was very impressed with it.  Running it through my little homebrew amp side-by-side with my Marshall JVM, I was able to get very similar tones!  The issue might be my particular amp and guitars, but I've got a few commercially produced pedals that seem to work fine with it (Catalin Bread Dirty Little Secret, BBE Green Screamer, Visual Sound Jekyll & Hyde, MI Audio Crunchbox).  The Guv'nor is certainly not thin...I was quite pleased with the bass response, but the highs just seemed to get a little piercing.  

I will go through and check my values again...good advice.  Worst case scenrario, it does work seem to be fine with the Treble all the way down, so if nothing else seems to work, I can use it like that.

One question, you mention using 1N4148 diodes in your build.  The schematic calls for 1N914 diodes.  I saw somewhere else recommend 1N4148...is there a noticeable difference between these two diodes?  I'm not sure if I have enough 1N4148 diodes to see how they compare for myself.

[Buzz]

1n914 and 1N4148s are pretty interchangeable in my experience.

I don't think you would notice any difference between them.

[amptramp]

Aluminum electrolytic polarized capacitors should be OK for this use and it should be easy to determine what polarity to use.  Even going larger to 0.47 µF capacitors in place of the 0.1 µF and 0.22 µF capacitors will make some difference.

If you are breadboarding the circuit, there is one more possibility: small resistances added between the diodes and SW2 will make a change in sound and limit the creation of high-frequency harmonics.  This may give some of the effect of a Tube Screamer where clipping does not preclude having the input signal go through the clipping stage at unity gain rather than disappearing entirely once the diodes conduct.  Start with a value of 100 ohms or less just to see what happens.

[LucifersTrip]

...I had looked at the Duncan Tone Stack Calc., but couldn't find a tone stack in it that looked like this??

I honestly haven't check it out in a while, but it used to have something at least similar. Is there a Marshall tab?

"Tone stack types: Fender modern, Vox, Marshall, James (passive predecessor to Baxandall), Fender E series, Steve Bench tone stack, and now the Big Muff tone stack used in FX units.  Simply click on the appropriate tab to bring up a different schematic."

http://www.diystompboxes.com/smfforum/index.php?topic=83044.msg689618#msg689618

"It is free and easy to use...check out the Marshall tab, that is about what's going on with the Guv'nor."

[Surfcaster]

I honestly haven't check it out in a while, but it used to have something at least similar. Is there a Marshall tab?

"Tone stack types: Fender modern, Vox, Marshall, James (passive predecessor to Baxandall), Fender E series, Steve Bench tone stack, and now the Big Muff tone stack used in FX units.  Simply click on the appropriate tab to bring up a different schematic."

http://www.diystompboxes.com/smfforum/index.php?topic=83044.msg689618#msg689618

"It is free and easy to use...check out the Marshall tab, that is about what's going on with the Guv'nor."

I actually did look at all the tabs...starting with the Marshall...and none of them really looked like the Guv'nor.  I'm pretty familiar with the standard Fender and Marshall tone stacks, but the Guv'nor is laid out a little differently...the TMB controls don't connect the same way and there are extra caps and resistors in there.  I even tried subbing out component values as best I could and got a very strange curve...didn't seem right.   Anyway, I couldn't figure it out!