Maestro Fuzztain

[lrgaraujo]

Are you guys (especially Chuck, since I had originally posted it on the Boneyard) familiar with the Maestro Fuzztain? It uses the N-channel mosfets of the 4007 in parallel as a variable resistor in the compressor part, if I understand it correctly.

Do you think there is a very solid reason for the the mosfets to be used in parallel or could we, for example, use one of them for compression and two for the dirty stage?

 

[Chuck D. Bones]

You can certainly use one N-ch MOSFET for gain control and the others for dirty gain stages. I suspect that Maestro used all three N-ch devices because a) they were there, b) putting them in parallel lowers the current in each one which reduces the distortion. Note how they biased the CD4007 GND pins at 1/2 Vcc. That will makes using the other MOSFETs for gain stages challenging, but not impossible. The peak detector circuit is interesting. I think this is the first time I've seen a common-base amplifier in a pedal. Very clever.

 

[lrgaraujo]

Nice, Chuck, thanks for the input! I hadn't noticed the source pins at 4V, if I was to use only one of them (say the one with source on pin 7) as gain control, would it be possible to connect pins 9 and 4 to 0V?

 

[Chuck D. Bones]

No. According to the datasheet, none of the IC pins should be allowed to go more negative than pin 7 or bad things happen. Remember I said it would be challenging? The gain stage(s) will all operate between +4V and +8V. Not a big deal since the inputs and outputs of each gain stage would be AC coupled. The Fuzztain has a buffer (IC4B) that provides a solid +4V reference which would serve as the negative rail for the gain stages.

 

[lrgaraujo]

You've probably saved me from frying an IC in the breadboard (which is not to say I won't fry others)