Soul food diodes mod

[Coda-effects]

Hello all !
I recently finished to mod my Soul Food by adding a DPDT allowing to choose between stock diodes and germanium D9E.

I wrote a step by step guide for those who are interested in doing the mod:
http://codaeffects.blogspot.fr/2015/03/electro-harmonix-soul-food-diodes-mod.html

However, I am really surprised with this mod..
I cannot hear a real difference between the stock and germanium diodes! Maybe the germanium diodes sounds a bit better at higher gain setting, but it is really a "maybe". I do not know if anyone could tell in a blind test...
Surprisingly, when I remove the diodes (no clipping), there is still saturation! And the sound is really close to the stock version! I just do not get it... Why is there saturation whereas the clipping diodes had been removed?
Are the "real" clipping diodes somewhere else ? (IC?)
So what is the role of these diodes? Just for the look ? So why putting it on the top of the PCB where no one could see it?

I am a bit confused....
Why are there builders still doing it ?

Have I done something wrong along the way ?

Thank you all for your input!

Benoit

[juansolo]

The diodes will only really come into play with the gain wound up and different ones don't actually make a massive amount of difference considering they are 'essential'.

Welcome to the world of hype and marketing bullshit

[midwayfair]

However, I am really surprised with this mod..
I cannot hear a real difference between the stock and germanium diodes! Maybe the germanium diodes sounds a bit better at higher gain setting, but it is really a "maybe". I do not know if anyone could tell in a blind test...

This follows with what AnalogMan found when he got one of the first ones and immediately made the mod. Shocking, eh? 95% of the sound between two sets of clippin diodes is going to be their forward voltage, which is almost the same between the two diodes you used. You could use regular silicon diodes instead of the stock's schottkys and you should hear a bigger change at lower gain settings. At a certain point on the gain dial, the diodes will stop being the primary source of distortion as the op amp itself starts to noticeably overdrive.

Surprisingly, when I remove the diodes (no clipping), there is still saturation! And the sound is really close to the stock version! I just do not get it... Why is there saturation whereas the clipping diodes had been removed?

Calculate the gain of the op amp in the distortion side. It's multiple HUNDREDS. Of course it's going to distort! The diodes are just there to clip the signal after it's been amplified. They don't change the rules of op amp circuitry.

Are the "real" clipping diodes somewhere else ? (IC?)

No.

So what is the role of these diodes? Just for the look ? So why putting it on the top of the PCB where no one could see it?

They do clip the signal, it's just not as "essential" as people think. The location is likely because it was the easiest place to fit a through-hole component on a surface-mount pedal. They're added at the same time as the pots, by hand, so they probably didn't want someone accidentally desoldering a surface mount component while putting it in. It might also simply be a joke about the diodes, similar to how the KTR put them way off to the side and wrote "these are essential" next to them.

Why are there builders still doing it ?

Uhhh, because people who don't know any better will fork over cash for it?

Have I done something wrong along the way ?

Nope! You've done it correctly.

[Coda-effects]

Thanks for the answers! Everything is starting to make sense now!
So the main part of the saturation directly comes from the OP-Amp...

This follows with what AnalogMan found when he got one of the first ones and immediately made the mod. Shocking, eh? 95% of the sound between two sets of clippin diodes is going to be their forward voltage, which is almost the same between the two diodes you used. You could use regular silicon diodes instead of the stock's schottkys and you should hear a bigger change at lower gain settings. At a certain point on the gain dial, the diodes will stop being the primary source of distortion as the op amp itself starts to noticeably overdrive.

Actually I did tried to use classic 1n4148 diodes, but heard no difference... I also used 4 diodes (2 on each polarity) to see whether it changes anything... Could not hear anything different!
Maybe I am deaf after all 

It might also simply be a joke about the diodes, similar to how the KTR put them way off to the side and wrote "these are essential" next to them.

This actually could be quite a funny joke from EHX !

The diodes will only really come into play with the gain wound up

At a certain point on the gain dial, the diodes will stop being the primary source of distortion as the op amp itself starts to noticeably overdrive.

So the difference should be heard at low or high gain setting ?

[juansolo]

Bill specifically wanted op-amp clipping in the circuit if you believe the interviews. Hence that section runs at lower voltage to the buffer.

As Jon says, if you use diodes with similar forward voltage, there's going to be little audible difference between them.

Hunt down the "Klone science" thread. A huge amount of nonsense that's spouted about this OD is covered in there.

[Coda-effects]

OK thanks !
I am really glad I made it to DIY, I really learnt a lot of stuff that keeps me away from "hype" madness. It is sad that marketing prevails upon listening in the music market now...
Thank you for sharing your knowledge with me!

[selfdestroyer]

Just wanted to say, I love the spoon idea for removing those knobs. I use shoe strings to pull them currently.

Cody

[GrindCustoms]

Just wanted to say, I love the spoon idea for removing those knobs. I use shoe strings to pull them currently.

Cody

For tight plastic push on knobs, all you need is an hair dryer, heat up the knob for couple seconds and it will pop right off.

Tight knobs can if you force them to much pull on the pot shaft beyond it's actual tolerance and scrap the pot, don't ask me why i know that......

End of derail.

Rej

[HKimball]

I'm actually a little confused now - I have a mythical overdrive with oa126/1n34a diodes and there's a noticeable difference between them. Now if that's the forward voltage that's fine - I just don't understand all this talk about no difference between stock diodes and 1n4148 diodes which have a .65-ish fv.

That aside, I had no idea that op-amp distortion ever sounded good? I thought it was to be deliberately avoided?