AMI 'Spirit of 76' (Median Compressor)

ninjagrips said:
Pretty sure it was Stompbox Parts, but it might have been Tayda.
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Check for proper FET orientation, if you have not already.

Then and if you have a signal generator, throw a 1kHz sinewave into the pedal and adjust by sight and sound. You will be looking for a linear (smooth, not jumpy) reduction in volume as the 'Compression' control is turned to the right. have the 'attack' and 'release' on fast (counterclockwise). If it really jumps in drops or visually begins to truncate a side of the sine wave, your FETs may be too out of tolerance for the trim to correct.
 
andrewsrea said:
Measure between pins 2 & 3 (Source and Gate), not gate to ground.
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Reviving this thread because I just finished building my Median. I also can't get to 1.875 measuring the drain of Q1, it gets up to something like 1.56 with the trimmer maxed.

Measuring source and gate and setting it to about 1.83, it gets pretty squashy at extreme compression settings.

Just clarifying because in another thread I saw someone referencing setting it just below the measurement of the transistor.
 
joelorigo said:
Reviving this thread because I just finished building my Median. I also can't get to 1.875 measuring the drain of Q1, it gets up to something like 1.56 with the trimmer maxed.

Measuring source and gate and setting it to about 1.83, it gets pretty squashy at extreme compression settings.

Just clarifying because in another thread I saw someone referencing setting it just below the measurement of the transistor.
Click to expand...

You want to measure the Vsd (voltage drop of the source referenced to the drain). I did that then adjusted to my ear and use, which is more like a limiter with gentile compression and some transients mixed in using the Blend function.
If you have it squishing, that means there is enough bias at the gate to actuate it like a switch. Using the trim pot clockwise (I believe - it has been a while) will leak more signal to ground (the method of compression) and change the bias of Q1. As long as Q1 is working like a switch, you are going to get compression.

Hope that helps!
 
andrewsrea said:
You want to measure the Vsd (voltage drop of the source referenced to the drain). I did that then adjusted to my ear and use, which is more like a limiter with gentile compression and some transients mixed in using the Blend function.
If you have it squishing, that means there is enough bias at the gate to actuate it like a switch. Using the trim pot clockwise (I believe - it has been a while) will leak more signal to ground (the method of compression) and change the bias of Q1. As long as Q1 is working like a switch, you are going to get compression.

Hope that helps!
Click to expand...
Thanks! I am definitely getting compression. I tried it all the way clockwise and all the way counter clockwise and points in between. I think I have it where I want it - for now anyway :)
I have only ever had the Xotic SP before so with all these knobs on the Median I have lots to play with.
 
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