Flabulanche compressor question

[HKimball]

I was contemplating the use of this circuit for a different pedal and I was curious about the role the schottky diode plays, and whether or not it has to be a schottky... I imagine the answer is yes but I thought I'd ask anyway.

I wanted to make a single jfet distortion with 2 red LEDs soft clipping but I highly doubt having 2 negative feedback loops would be a good idea for a single transistor so I wanted to make it a distortion loop that nominally adds some compression. I found a schematic online that shows a compression control potentiometer in the NFB loop of a bluesbreaker circuit but I can't find it now that I actually need it haha.

Thanks for any help in advance and I will continue to try and crack this in the meantime.

[HKimball]

Never mind I just found what I need on the aquataur article on the compressor circuit which inspired the one in the snow day OD. My bad you guys - I'll delete this thread as soon as I get to my computer (tapatalk won't let me delete for some reason)

[midwayfair]

The diode is to rectify the signal. The compression is created by producing a DC voltage at the FET's gate. FETs work by wiggling the voltage negative at the gate; if you cancel the signal some there, the input signal gets smaller and it compresses. Aquataur specifically talks about why you want to use a Scottky, but as a reminder, it's because you have a VERY limited amount of voltage available once you run the rectified signal through a gate resistor. You want the resistor there to prevent too much treble loss from the decay capacitor. It's a balancing act.

You can probably put the LEDs after the output cap just like the diode. It should be fine. You probably want a resistor between the diode and where the LEDs. That brings up your output impedance, but it should be fine and it'll make the LEDs conduct better. It's hard clipping, but the compression does the same thing as softclipping anyway, so it's 6 of one and a half dozen of the other.

[HKimball]

The diode is to rectify the signal. The compression is created by producing a DC voltage at the FET's gate. FETs work by wiggling the voltage negative at the gate; if you cancel the signal some there, the input signal gets smaller and it compresses. Aquataur specifically talks about why you want to use a Scottky, but as a reminder, it's because you have a VERY limited amount of voltage available once you run the rectified signal through a gate resistor. You want the resistor there to prevent too much treble loss from the decay capacitor. It's a balancing act.

You can probably put the LEDs after the output cap just like the diode. It should be fine. You probably want a resistor between the diode and where the LEDs. That brings up your output impedance, but it should be fine and it'll make the LEDs conduct better. It's hard clipping, but the compression does the same thing as softclipping anyway, so it's 6 of one and a half dozen of the other.

Jon,

As always thank you so much for the information - I hadn't even thought that due to the compression hard clipping the LEDs would sound different vs. Without the compression.

I'm planning on using a 2n3904 as an output buffer because it sounds great on your snow day OD as well as the EA trem and the xotic EP booster... I don't know if it's because it's a bjt or what but every circuit I've played through that has one sounds awesome.