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previous: Doug H I think you will need higher grid-t... -- 2/1/2001 3:58 PM

Re: Got my Tube driver going, got a couple questions

2/3/2001 1:49 AM
KB	Re: Got my Tube driver going, got a couple questions Most of these tube starving devices use a Cathode follower after the op-amps which means that using a higher voltage is not going to give you anything but more noise as unity gain is all you get from the tube. It's output is low impedance so it drives the input of the tube amp very well. However, if you rewire it and take the signal off the plate using a 100K plate resitor and a coupling cap to the output jack then change the probable 10K cathode resistor to 820 ohms and bypass it with whatever cap you want as the rolloff frequency then the voltage will give you something. IMHO I don't like the way op-amps go with tubes and some JCM model Marshalls use back to back zener diodes as clippers to square the wave a little then Cathode folowers to drive the high impedance inputs of the next gain stage. The sweet sustain and smooth distortion comes from cascading several gain stages and some Audioheads decouple the power nodes in between for good clean plate voltage. Dc standoffs for the heaters will reduce the hum reduction by several dB and eliminate noise. All of this in a little box ain't gonna happen. Either build a mean ass tube distortion box or stick to the stock pedal with Dougs mods as I would be willing to bet if you bypass the tube you will like it even more.

2/3/2001 1:49 AM

Re: Got my Tube driver going, got a couple questions

Most of these tube starving devices use a Cathode follower after the op-amps which means that using a higher voltage is not going to give you anything but more noise as unity gain is all you get from the tube. It's output is low impedance so it drives the input of the tube amp very well. However, if you rewire it and take the signal off the plate using a 100K plate resitor and a coupling cap to the output jack then change the probable 10K cathode resistor to 820 ohms and bypass it with whatever cap you want as the rolloff frequency then the voltage will give you something. IMHO I don't like the way op-amps go with tubes and some JCM model Marshalls use back to back zener diodes as clippers to square the wave a little then Cathode folowers to drive the high impedance inputs of the next gain stage. The sweet sustain and smooth distortion comes from cascading several gain stages and some Audioheads decouple the power nodes in between for good clean plate voltage. Dc standoffs for the heaters will reduce the hum reduction by several dB and eliminate noise. All of this in a little box ain't gonna happen. Either build a mean ass tube distortion box or stick to the stock pedal with Dougs mods as I would be willing to bet if you bypass the tube you will like it even more.

Replies:

Doug H The BKButler circuit uses a super-h... -- 2/4/2001 5:45 PM