how to set the trimmer in mxr dynacomp?

[swt]

I have a dynacomp clone. When i play 5th and 6 th strings, or bass notes, it sounds muddy, too much attack cut on the way even when set low. Is there any way to set it properly with the internal trimpot?. How's the correct way to do it?. Thanks for any help!

[Jay J]

I did this just this weekend. I wasn't quite sure if I had set the trimpot correctly when I first got DynaComp working, so I checked the Analog.man's website for that.

First I turned the pots all the way up, let the guitar be untouched so I could hear some static noise. Then started turning the trimmer from one end to another, trying to find the loudest point. That's were I left it.

Now someone can tell you how it should really be done...

[Jay Doyle]

Jay J,

You did it right, the loudest and therefore the noisiest, is the correst position that balances the OTA. Not scientific but still right.

[R.G.]

The theoretically correct position is dead center. In fact, most manufacturers will put in fixed equal-value resistors there instead of a pot to keep from having to make an adjustment in manufacturing.

The whole purpose of that being a pot is to adjust for the non-perfect balance of the OTA. It's to balance the bias currents of the input diffamp. Imbalances lead to higher feedthrough of gain-change signals, so it's really there to get rid of thump or breathing noises as the input signal changes level.

Realistically, I think 99% of all OTA's would be fine with two 1K resistors there.

The right way to set the thing is to put the pot dead center, and then listen for thump or breathing on notes. If you can't hear thrump or breathing, it's fine. Only change it from dead center to get rid of gain change oddities.

[Jay J]

After reading R.G's reply I decided to check the resistance of my DynaComp trimpot. Funny thing... 1104 ohm and 1109 ohm. And all that just doing it by ear!

Shows how accurate an instrument your ear can be. Or how lucky you are sometimes.

[swt]

Well thanks guys!!. I did what RG suggested, dead center, and all problems dissapeared!. Thanks again for the guidelines!