Asymetric clipping mod in a Tube Screamer.

[RobB]

I'll be putting together a tube screamer clone soon and have been thinking of adding a pot in series with one of the diodes so I can dial in some asymetrical clipping.  This could be a nice little added axtra.  
The simple mods page suggests a 50k pot for a circuit which shunts to ground.  I suppose it will also work in a feed back loop.
Has anybody had any success with this mod/technique?  
I'd appreciate some feedback on this idea before I drill an extra hole in the box.

Rob.

[Mark Hammer]

I've done it two ways.  One way involved use of a 2+1 diode combo and a switch to shunt one of the diodes for conversion to 1+1 diode pair.  The other way involved use of a 1+1 pair and a 50k pot in series with one diode to vary the degree of clipping in one direction.

Overall, I find either one a useful mod, though the switch version takes up less chassis space, provdes an obvious change, and one can describe it as being an SD-1/TS9 switch.  The other provides more variation, though I found not all that much use for the middle settings, since the effect IS subtle.

In both instances, though, you will get less volume and a more compressed sound in the stiock 1+1 setting, and more volume and dynamics when you switch to 2+1 or insert more series resistance along one diode path.  Although the effect is subtle, it does provide a different feel and makes you think about pick attack a little differently, since the one yields more obvious dynamic changes than the other.

[Mike Nichting]

my 2 cents, i have 3 -1N34a's and a 1N4001 in series on one side of a switch and 1- 1N4001 on the other. This with one of the original silicons still on the board.

 Really dig the 1N34 tone. Keep in mind if you use one Germanium diode on one side it will spit and sputter.

good luck

[RobB]

Thanks Mark, a four knobber it will be then.  I'll try a 100k pot first.

Mike, I plan to use two 1N60Ps(germanium) on each side to begin with but will experiment with diodes and op amps. Thanks.