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previous: jon HiReading thru the recent t... -- 7/28/2000 1:34 AM

Re: Envelope Controlled Filter using tubes?

7/29/2000 9:16 AM
zachary vex	Re: Envelope Controlled Filter using tubes? there's a schematic for the doctor quack on this page at the amz site: http://www.muzique.com/schem/quack.gif the signal is buffered and sent two places... one is an envelope generator (lower) whose output is applied to the base of Q2, which serves as a variable resistor (you could do this with a tube too)in the filter circuit above, which also receives guitar signal from the buffer. the guitar strike triggers the env gen, which sends a changing dc level to Q2, which changes the center point of the filter, and it wahs once for every strike on the guitar. you could even build a simple wah circuit based on the crybaby, substitute tubes for the transistors, and use another tube or vactrol or lamp-driven photocell to act as the wah's control pot. you could make the envelope generator from a one-shot version of your multivibrator circuit you are using for the octave divider. as far as the octave, the groove tubes manual has a gibson tube bass amp schematic which has a compressor built-in. perhaps this circuit will work as your compressor. remember that you can use the "tube as a variable resistor" for this too. if you buffer and rectify the signal and store it on a cap, you can create a control voltage to drive the grid of a tube being used as a variable resistor, much like a fet, in a voltage-division scheme, or of course you could also drive an incandescent lamp-driven photocell and that would remain pretty old school. there's an amazing pitch-shifting vacuum tube circuit in the groove tubes book also, the magnatone vibrato, which uses those varistors you were talking about. might be some ideas there. the maestro octave box used a scheme where the octave portion of the signal only was "gated" using an envelope control and steering diodes... it only sounded the octave for a moment after you played a note. sounded like a tuned kick drum or an upright bass played pizzicato. when you defeat that envelope control, the octave becomes completely insane. it's wonderful that way, like a cloud of low end burbling around in and out of time with the music. zachary vex

7/29/2000 9:16 AM

zachary vex

Re: Envelope Controlled Filter using tubes?

there's a schematic for the doctor quack on this page at the amz site:

http://www.muzique.com/schem/quack.gif

the signal is buffered and sent two places... one is an envelope generator (lower) whose output is applied to the base of Q2, which serves as a variable resistor (you could do this with a tube too)in the filter circuit above, which also receives guitar signal from the buffer. the guitar strike triggers the env gen, which sends a changing dc level to Q2, which changes the center point of the filter, and it wahs once for every strike on the guitar. you could even build a simple wah circuit based on the crybaby, substitute tubes for the transistors, and use another tube or vactrol or lamp-driven photocell to act as the wah's control pot. you could make the envelope generator from a one-shot version of your multivibrator circuit you are using for the octave divider.

as far as the octave, the groove tubes manual has a gibson tube bass amp schematic which has a compressor built-in. perhaps this circuit will work as your compressor. remember that you can use the "tube as a variable resistor" for this too. if you buffer and rectify the signal and store it on a cap, you can create a control voltage to drive the grid of a tube being used as a variable resistor, much like a fet, in a voltage-division scheme, or of course you could also drive an incandescent lamp-driven photocell and that would remain pretty old school.

there's an amazing pitch-shifting vacuum tube circuit in the groove tubes book also, the magnatone vibrato, which uses those varistors you were talking about. might be some ideas there.

the maestro octave box used a scheme where the octave portion of the signal only was "gated" using an envelope control and steering diodes... it only sounded the octave for a moment after you played a note. sounded like a tuned kick drum or an upright bass played pizzicato. when you defeat that envelope control, the octave becomes completely insane. it's wonderful that way, like a cloud of low end burbling around in and out of time with the music.

zachary vex

Replies:

jon Hi Zachary,Looks like my we... -- 7/29/2000 2:31 PM