Stepped Attenuator to replace Potentiometer.

Hello Mr. Porter:

It is good hearing from you. I spoke with you some time ago from up here in New Hampshire. We are using the original CA-250 monos from 1972 -- pretty much renovated throughout -- that was listed as MR-250 (for Marine Research). As for the controls on the front of the monos, they are gain controls. We have a Threshold Stasis R5 controlling the main volume. I was just wondering if it be worth an upgrade on the MR-250s to upgrade the gain controls to something like DACT attenuators, known for their precise management of signal levels; however, given the 25 meg ohm impedance on the gain control pots, I am at a loss as to how to get around this without having a tech do some surgery on the innards. Any ideas? Thanks and hope all's well in TX.

Now I understand, that's why I ask how old. I knew anything in the last 20 years had no volume pot.

Good call on the impedance issue, that's mandatory to maintain. I'm not qualified to tell you what to change to make it right. Have you tried to contact Wolcott audio for advice? Hank is very bright.

Try Shallco.. http://www.shallco.com/attenuators.html

Thanks for the responses. I have not contacted Henry Wolcott as of yet; he and Mr. Lomax are quite busy (great, knowledgeable gentlemen by the way!), so I might first try the technician who knows these amps well enough to wrestle with their intricacies and quirks. Eldartford, I went to the DACT website and they offer the reknown CT-2 Attenuator, with the greatest resistance rating at 500kOhm. Given the gain pot on these monos indicates 25 meg Ohm -- and if my calculations are on track -- do you mean I would need to increase resistance by 50 Ohm were I to get the 500kOhm Attenuator? I'm not an engineer, so I just want to clarify.

I called Shallco and await response on an attenuator with a closer if not equal impedance match. You guys sure seem to know your stuff: Thank you for your informative suggestions, and long live audio engineering in advancing the Arts & Sciences.

Somut...You better check on the resistance of that pot. 25 megohms is far higher than any audio gain pot I have seen. I could believe 25 Kohms, although that would be a bit low.