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previous: Jim S. I'm afraid this setup might not wor... -- 9/15/1998 1:18 PM

Re: Overdrive w/Dynamics

9/15/1998 2:12 PM
John Greene	Re: Overdrive w/Dynamics When guitar players refer to "dynamic overdrive", this usually means that the amount of clipping that occurs is easily controlled by the player's pick attack. Light picking results in a sound that is clean or nearly clean, and hard picking results in saturation and extra harmonics resulting from increased signal clipping. I've been experimenting with something that does this almost exactly. It's a modification to my clone pedal I made last year (tube-screamer based). I found that by using certain MOSFET devices as diodes, you get a progressive limiting effect. It compresses before it clips which allows you to go between a clean sounding signal to one that crunches nicely simply with pick dynamics. The reason for this has been discussed here before regarding how the MOSFETs conductance changes in proportion to the square-root of the current, similar to a tube. It sounds dangerously tube-like. I think the compressive aspect gives it much more bottom end. Too much actually, I'm going to try messing with the cap/res combo on the clipper to be more TS9 like and see if that doesn't help out. The MOSFET device I'm currently using (VN0300) I think is a little too 'soft' so I'm going to try some devices with more conductance to 'harden' the clip some more. The best part is that I was able to implement the changes using a 100K pot with a DPDT push-pull switch so you can switch between the Tube-screamer sound and the new 'crunch' mode by pulling the volume knob out. The two sounds are quite different and it's like having two effects in one. If I get the time to mark up a schematic and document the changes, I'll make them available to whoever wants to take a look. --johng

9/15/1998 2:12 PM

John Greene

Re: Overdrive w/Dynamics

When guitar players refer to "dynamic overdrive", this usually means that the amount of clipping that occurs is easily controlled by the player's pick attack. Light picking results in a sound that is clean or nearly clean, and hard picking results in saturation and extra harmonics resulting from increased signal clipping.

I've been experimenting with something that does this almost exactly. It's a modification to my clone pedal I made last year (tube-screamer based). I found that by using certain MOSFET devices as diodes, you get a progressive limiting effect. It compresses before it clips which allows you to go between a clean sounding signal to one that crunches nicely simply with pick dynamics. The reason for this has been discussed here before regarding how the MOSFETs conductance changes in proportion to the square-root of the current, similar to a tube.

It sounds dangerously tube-like. I think the compressive aspect gives it much more bottom end. Too much actually, I'm going to try messing with the cap/res combo on the clipper to be more TS9 like and see if that doesn't help out.

The MOSFET device I'm currently using (VN0300) I think is a little too 'soft' so I'm going to try some devices with more conductance to 'harden' the clip some more.

The best part is that I was able to implement the changes using a 100K pot with a DPDT push-pull switch so you can switch between the Tube-screamer sound and the new 'crunch' mode by pulling the volume knob out. The two sounds are quite different and it's like having two effects in one.

If I get the time to mark up a schematic and document the changes, I'll make them available to whoever wants to take a look.

--johng

Replies:

jason I'd like to see that schematic also... -- 9/16/1998 6:38 AM
cbs John Greene -- 9/23/1998 7:03 AM