Ross dist/Dist+ vol recovery works a treat !

[MartyMart]

From this thread : http://www.diystompboxes.com/smfforum/index.php?topic=19538.0

Just added it to a Ross board which was not much above unity when maxed and it helped
a lot - thanks MarkM BTW
It meant a few components "dangling" and leads covered in hookup wire covering, but could be easily
added to a PCB or vero version.
Thanks to those who put it together and Mr Tremblay for the schem.
MM.

[snoof]

nice idea fellas.  i scrapped my dist+ build because it didn't have enough vol on the low drive settings.  Maybe I'll revisit...

[MartyMart]

I needed it due to using vintage OA90 diodes ( Ge ) if 4148's or LED's are used then there's
probably going to be enough volume.
Adjust that FB resistor for more/less vol, perhaps socket here would be good or even an extra pot
say a 250k log would be good as a "boost" control !

[the_random_hero]

Question - are OA91 diodes good for clipping circuits? They are pretty much the only germaniums available to me without ordering from a few states away, even then I can only get 1N34A's. I've heard they have a really low forward voltage, so I'm guessing they wouldn't distort a hell of a lot.

[GibsonGM]

Let's take a look, Random...clipping occurs when a signal exceeds a threshold voltage, the Vf that 'turns on' the diode and makes it begin to conduct.  Any voltage above that threshold is clipped, resulting in whatever 'variety' of clipping we've set up.   That's why LEDs sound different than 1N4001 or 4148 - they're conducting at different portions of the wave cycle relative to each other.   Of course this is related to how much voltage output you have to play with from your opamp or transistor gain stage, etc.    Can't hurt to try an OA91, and see if you like it ) 

Since the Vf of Ge diodes is lower than those others, it follows that they will begin to conduct sooner in the wave cycle, and therefore you should get more clipping rather than less.    I took apart a DOD Heavy Metal pedal, and guess what?  1n34's inside!   They're also the original diodes in the Dist+.      I like assymetrical clipping, using a low Vf and one of a higher value - it seems more 'natural' to me. 

[petemoore]

  Imagine small waves traveling down a hallway as analagous to the Pos swing of your guitar pickups output.
These waves are travelling under wave peak limiters...walls you would have to duck under to get down the hallway...or would chop the tip of the wave off if it got that high.
  You want to see the waves get high enough to touch the partial walls coming down from the ceiling, so you make the waves become much larger amplitude [and add a booster to your guitars output signal].
  Now the waves are "just touching the bottoms of the walls, and this causes cool splashing and distortions of the original waveforms, you also notice the wave after touching the wall with it's tip is a touch smaller.
  That was cool, but you want to see the wave smash into the wall a little bit more..
  So...you lower the wall by lowering the diode threshold voltage, now when your boosted waves hit the walls, more splashing and serious distortion of the waveform happens, but the waves, after having most of their tops clipped off don't have much form or force, it's amplitude got seriously whacked.
  The distortions of the lower threshold looked cool, but now there's hardly any waveform left after that point.
  You decide you've moved the wall down too low for the boosted wave to have much form or amplitude after having 2/3's of it whacked off the top, that the wall should be somewhere between the low point ["Ge] you set it at and the high point [LED] where it barely touched the wavetips.
  You put in Si diodes and notice the wave smashes into the partial tip clipping walls pretty good, looks cool, and yet there is sufficient height of wave after the tops got whacked off to make post clipping wave watching also be interesting, as there is enough amplitude of wave to make ~pronounced shapes.
  Increase the wave amplitude by turning up guitar/gain/pre-clip boost volume, and by picking the strings harder, raising the PU's on your guitar etc. this'll make the wave clipping a more forceful affair.
  Or, decrease the threshold to more forcefully clip a signal which is a bit weaker in waveform amplitude to set an increased clipping amount.
  LEd or 2x seriesed Si's = high clipping threshold.
  Si or 2x seriesed Ge's = 'med' CT
  Ge = low clipping threshold.
  Only thing is, there's the other half of the waveform not mentioned yet...I typed only about an analogy of water being the positive swing of the signal, the bottom half...basicall the same as the top half, unless you boost that half harder...or set the clipping threshold higher or lower [see assymetric clipping] by using a different diode type to set the threshold voltage clipping threshold on the negative swing. ie I typed about what 1 diode is doing in what is usually a pair of back to back diodes [2 parallel opposite polarity diodes].
  builiding a DiST+ or OD 250 or Rat, anything with clipping elements have a leg to ground [or near ground..small variable resistor anyone?] reading up on the clipping element possibilities and diddling with diodes swaps demonstrates well how different diode configurations sound.
  'Simple mods and tweeks' and 'AMZ labs notebooks' have some nice diagrams etc. worth a look.

[the_random_hero]

Let's take a look, Random...clipping occurs when a signal exceeds a threshold voltage, the Vf that 'turns on' the diode and makes it begin to conduct.  Any voltage above that threshold is clipped, resulting in whatever 'variety' of clipping we've set up.   That's why LEDs sound different than 1N4001 or 4148 - they're conducting at different portions of the wave cycle relative to each other.   Of course this is related to how much voltage output you have to play with from your opamp or transistor gain stage, etc.    Can't hurt to try an OA91, and see if you like it ) 

Since the Vf of Ge diodes is lower than those others, it follows that they will begin to conduct sooner in the wave cycle, and therefore you should get more clipping rather than less.    I took apart a DOD Heavy Metal pedal, and guess what?  1n34's inside!   They're also the original diodes in the Dist+.      I like assymetrical clipping, using a low Vf and one of a higher value - it seems more 'natural' to me. 

*smacks himself on the head* You're absolutely right. For some unknown reason I was thinking about it in the opposite direction - the samller the threshold, the lower the clipping to signal ratio. It might become another option in my multi-OD that's eventually going to get built :p

[anti-idiot]

isn't this an easy way to recovery some volume?

http://dominocs.com/ToneWorks/DistPlusoutput.html

[MartyMart]

Ahem, that does seem an easier way to do it, but what will that do to the output impedance.... ?? 

[WGTP]

I have wondered about that.  Doesn't the Rat have a 1K rather than 10K at the op amp output?  100 may be too small, but what are the consequences?

[WGTP]

Messing with this value on the bread board didn't get the results I expected.  It didn't necessarily produce more distortion and seemed to make it thinner sounding and less smooth.  This is with a 1K resister rather than the stock 10K.  I didn't try a 100 ohm yet.  Good place to try a trim pot.   

[anti-idiot]

Messing with this value on the bread board didn't get the results I expected.  It didn't necessarily produce more distortion and seemed to make it thinner sounding and less smooth.  This is with a 1K resister rather than the stock 10K.  I didn't try a 100 ohm yet.  Good place to try a trim pot.   

this is not for more distortion, just for more volume. for more distortion, u should fool around with the resistor at the feedback loop (1M) and the resistor to ground (4K7)

http://dominocs.com/ToneWorks/DistPlusdist.html