how to clip?

[foxfire]

i've been playing around with adding clipping diodes to pedals. i'm working on a pedal right now that is a lpb2 and a hogsfoot in one. i added 3 1n34a's for asymmetrical clipping to the end of the circuit right before the volume pot. i really like the sound of the ge's but the volume drop is a bit much. and yes i know i could use led's and or si's for more volume. so other than using led's or si's is there a way to get the ge fuzz with out the big volume cut?

some things i have been thinking about are...
i haven't played with using fet's for clipping. how do they compare to ge's? and could i put the clipping diodes somewhere else in the circuit? like right after the input cap?
i had read something somewhere once on where you can add diodes but i can't find it anymore so i have to ask? 

[wampcat1]

You just need to add a volume recovery stage after the diodes.
bw

[John Lyons]

FETs are sort of like softer sounding Silicon diodes. I like them...
Check out the articles at AMZ (above) about FETS and Mosfets as clipping devices.

John

[foxfire]

You just need to add a volume recovery stage after the diodes.
bw

i hate to have to ask but, after doing a search and reading however many posts i'm still not sure what a volume recovery stage is?
my best guess is that it is basically adding an other booster(lpb2) that would be activated when i switched the diodes into the circuit? if i'm correct or at least close would i want to leave off the input and output caps?

[Mark Hammer]

i hate to have to ask but, after doing a search and reading however many posts i'm still not sure what a volume recovery stage is?
my best guess is that it is basically adding an other booster(lpb2) that would be activated when i switched the diodes into the circuit? if i'm correct or at least close would i want to leave off the input and output caps?

Diodes clip by setting a hard ceiling on how much signal is permitted to pass unaffected (well, it's more than that but we'll turn a blind eye to the other details at the moment).  It may take a gain of x100 to get the signal level up to the point where the diodes do their magic, but whatever the boost those diodes will set an absolute ceiling on signal amplitude.  Unfortunately, any tone and or volume control after that point is going to further subtract signal, such that the only way to get any appreciable output level is to run the thing at full tilt, which means you can't get lightly distorted tones with audible boost in volume level.

The solution is to simply stick a gain stage AFTER the clipping diodes.  That stage is described as a "gain recovery" stage, though perhaps more precisely it is a level-recovery stage that does so by providing some additional gain to compensate for what the diodes took away.  How much gain needs to be provided will depend on what it is yu're trying to accomplish and how much compensation is needed.  For instance, a pair of germanium diodes will seriously restrict possible output levels, so more gain is needed for recovery in that instance than might be needed if it was a pair of silicon diodes or LEDs instead.  Similarly, if one had a pair of clipping LEDS (less restriction on max volume than silicon or Ge diodes) followed by a tonestack (significant passive loss), you'd probably want a recovery stage to compensate.

[Dragonfly]

You just need to add a volume recovery stage after the diodes.
bw

i hate to have to ask but, after doing a search and reading however many posts i'm still not sure what a volume recovery stage is?
my best guess is that it is basically adding an other booster(lpb2) that would be activated when i switched the diodes into the circuit? if i'm correct or at least close would i want to leave off the input and output caps?

after typing a nice big response, i see that Mark beat me to the punch

you can split the circuit at the diodes so that when you switch "on" the clipping diodes, the volume recovery stage is automatically engaged....

[foxfire]

i'm just not sure what a "gain recovery stage" looks like. i am unfortionantly a very visual guy. i'm sure it's "right in front of me" but, i'm not sure what it is?

[Dragonfly]

i'm just not sure what a "gain recovery stage" looks like. i am unfortionantly a very visual guy. i'm sure it's "right in front of me" but, i'm not sure what it is?

You could use any simple gain stage...LPB1, Jfet booster, etc...

[foxfire]

i'm just not sure what a "gain recovery stage" looks like. i am unfortionantly a very visual guy. i'm sure it's "right in front of me" but, i'm not sure what it is?

You could use any simple gain stage...LPB1, Jfet booster, etc...

ok thats what i was thinking it was. now do i just add the whole lpb1 for example or are there parts of the lpb1 that would be re dunant like the in/output caps?

[foxfire]

i just want to thank everyone for taking the time to spell this out for me. i promise to take this knowledge and pass it on whenever i can.

[Dragonfly]

i'm just not sure what a "gain recovery stage" looks like. i am unfortionantly a very visual guy. i'm sure it's "right in front of me" but, i'm not sure what it is?

You could use any simple gain stage...LPB1, Jfet booster, etc...

ok thats what i was thinking it was. now do i just add the whole lpb1 for example or are there parts of the lpb1 that would be re dunant like the in/output caps?

a LPB1 circuit would be just fine.

[foxfire]

just wanted to check, i'm gonna need a 3pdt switch to switch both the clipping diodes and gain recovery stage(lpb1) on right?

[boyersdad]

Foxfire, have a look at the Big Muff Pi schematic. It's really easy to understand what each stage (or section) are doing. Thefirst stage is a buffer, the second and third are the clipping stage, and the last transistor and surrounding components are the recovery stage. It boosts the week signal to a usable level, and sends it off to the amp.

[GibsonGM]

The way I do this is to have a gain recovery stage...can be the last stage of the BMP, an LPB, opamp, Mosfet Boost, what have you.   I rig in a gain control resistor for it (replace the 2.2K resistor with a 5K or 10K pot, in the BMP circuit, and include the master volume for trimming the levels down to something reasonable).  In fact, I rig 2 gain pots.  Then, I set up a DPDT switch to jumper one of the pots.  That way, the OTHER pot is the drive control.  Use an LED on one, a'la the Fulldrive, and you have an indicator light.

You could expand the switching so that you can switch in the new diodes, and the circuit will switch over to a pre-set volume level that you can set to compensate for the volume drop.  The possibilities are limitless  ;o)    To build a boost just for when other diodes are switched in wastes power, changes the sound an awful lot, and seems like a pain.  Using the boost all the time after the dist., just at different levels, is guaranteed to make you crack a grin and grab some strings...

[foxfire]

well i've got it. i can finally see the trees in the forest. thanks again for taking the time.