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Vintage threads from the first ten years

Whisper Compressor

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1/5/2000 12:47 AM
Mike	Whisper Compressor I pulled out some effects I've built and wasn't happy with. One more try before I scrap them. 1. Whisper Compressor: It seems to compress in waves. Not smooth at all. The notes increase volume in waves. 2. Tycho... Octave: Sound tails off, then increases in volume. Almost acts like the Whisper Compressor as above. Thanks, Mike

1/5/2000 1:42 AM
R.G.	Hmmmm... The whisper compressor probably suffers from too much gain in the compression/envelope side chain. The Tycho clone is almost certainly a biasing problem - not equal swings in each direction of signal, or too much DC in the transformer, driving it into saturation.

1/7/2000 1:35 AM
Mike	How do I measure "too much DC in the transformer"? Mike

1/5/2000 6:41 AM

>>Whisper Compressor: It seems to compress in waves. Not smooth at all. The notes increase volume in waves.

There are 2 possible problems. (1) Your clm6000 is defective. There are LOTS of them floating around that are sub-standard. (2) The detector section is only half-wave rectified so you are getting breathing caused by fluctuations in the dc control voltage. It should be more noticeable on low frequency notes.

When designing this device, I actually had a detector section that used a bias network that greatly reduced the breathing effects but got out-voted in which version to use, for several reasons, not the least of which was reducing parts count.

Even with the detector on the schematic, when using a good clm6000 the problem should not be very noticeable. I might suggest adding a series resistor then a capacitor to ground on the output of the detector opamp. Starting values 1k/1uF, and increase capacitance to 2.2uF if more smoothing is desired.

The Q&D Compressor 1 is a much smoother device.

regards, Jack

1/7/2000 1:32 AM
Mike	Is there a way to check the CLM6000 in ciruit, without having to swap it out? (Don't have anymore) Mike

1/7/2000 12:58 PM
AMZ	You can lift the opposite end of the current limit resistor before the CLM6000 and connect it to +9v. The resistance of the CLM6000 variable resistance on the feedback of the opamp should be very low... maybe 200 to 500 ohms. BTW, the Silonix NSL-32 and the EG&G Vactrol VTL5C2 are almost exact replacements for the CLM6000. regards, Jack

1/8/2000 4:54 PM
Mike	Re: Whisper Compressor-Solved The NSL-32 checked out fine. I had the filter caps backwards! Thanks, Mike

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