Another FF Clone By Transmogrifox
9/8/03
Note 1: C4 may be 160 uF to about 470 uF without significantly changing the sound.
Note 2: C5 may be 53 uF or anything in between. I recommend 100 uF if any value other than what is shown is used.
Note 3: R11 and R12 may need to be adjusted to properly bias the M1 (see bias notes for details).
Note 4: R14 adjusts the brightness of the LED. Make R14 smaller to make the LED brighter, larger to make it more dim.
This combination of "Qbreak P", R14, R13, and D2 can be omitted if this is built without an "on" LED indicator. These have no effect on the signal.
Note 5: The value of C2 is actually 4.7 nF. I accidentally forgot to change it from the default when drawing the schematic in PSPICE...however, 1nF would probably just make it sound more "gritty". This is why I put the 4.7nF cap here, --was to soften the sound a bit.
Note 6: Feel free to experiment with Rf. I have tried the value shown, 100k and 150k. Increasing Rf will increase the amount of distortion on the lowest setting. I thought 150k and 100k weren't to my taste, but 47k is a little too small for me, so I think I'll try an 82k, which is what I recommend for Rf.
Bias Conditions:
Adjust R11 to set the DC voltage measured between the drain of M1 and ground to be 5.5 V. The drain of a MOSFET is essentially equivalent to the collector of a Bipolar Transistor.
Adjust R4 to ensure that the drain DC voltage of M3 is 6.5 V.
Other approximate DC voltages for bias:
Gate, M1: 2.3 V
Drain, M1: 5.5 V
Gate, M2: 2 to 2.4 V
Drain, M2: 4.6 V
Gate, M3: Same as drain, M2
Source, M3: Same as Gate, M2
Drain, M3: 6.5 V
A DC Bias variance from the listed conditions above of +/- .5 Volts will likely result in only a subtle audible difference, if at all.