# MXR Dyna Comp... did you know?



## amagras (Apr 22, 2015)

I've had this compressor pedal for years and never stopped to think much about its capabilities, just dial whatever setting I needed and played but today messing around some cleans with headphones I realized that it compresses the direct signal even with the sensitivity knob at minimum, a nice amount of compression. With matched unity output it increases sustain and rounds the attack, just a bit not too much. Nice for those who like to engage it at all times. 
Maybe it's not fresh news for everyone but for me is a nice discover  a recent conversation with Stratin2traynor moved me to share this.


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## mhammer (Nov 30, 2007)

Although there were others at the time, the Dynacomp was kind of the "sperm donor" for a lot of other compressors during the 70's and early 80's. They pretty much all used the same sub-circuit for deriving the envelope signal that would control the "gain cell".

The Ross compressor, like many Ross pedals, was just a few components different from the MXR - probably what we might call a "mod" these days - but improved it a little.

One of the things that was characteristic of the Dynacomp was its gain-recovery time. This was set mostly by a single 150k resistor, seen in the upper right-hand corner here:








This resistor (brown-green-yellow) sets the time it takes for the 10uf capacitor to charge up again and restore full gain. Several other manufacturers replaced this 150k fixed resistor, with either a toggle/slide switch, or a variable control, to change the value of the resistance, and let the gain be restored faster than stock.

The stock Dynacomp has a slow-ish gain-recovery. This can be very helpful for holding notes a long time, since the gain keeps creeping up as the note slowly dies out. On the other hand, if a person wants to pick or strum quickly, they may be going too fast for the circuit, and the gain will not have recovered enough to catch up with them. One of the results of this is that the compressor seems to miss the "attack" of quickly picked/strummed notes. Consequently, when companies provide a way to adjust the value of that 150k, whether continuously or in steps, they tend to label it an "Attack" control. It actually does not technically adjust the attack of the compression, but "Catch-up" or "Gain Recovery" don't look as sexy on the chassis as "Attack".

Compressors with a fast gain-recovery were often preferred by studio musicians hoping to get a clean sound where all the notes could be easily heard (just not too loud). The Dan Armstrong Orange Squeezer is one example of that. But a person can easily convert an Orange Squeezer to have a slow recovery, and a Dynacomp to have a fast one. When I come over to your place, I'll bring an example of each.


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## amagras (Apr 22, 2015)

Thanks Mark, I'm looking forward to try those. I have an idea of the sound because of my work with plugins but I'm sure that will give me the impulse I need to finally mod my DC.


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