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-   -   Gain adjust on an Adcom 545. (https://www.diyaudio.com/forums/solid-state/69499-gain-adjust-adcom-545-a.html)

K-amps 10th December 2005 11:47 PM

Gain adjust on an Adcom 545.
 
I just modded an old 545. I made it dual mono with extensive bypassing on the power caps. I also heavily "reduced" feedback and while I ensured equal voltage gain wrt the stock NFB, I feel there is a little more hiss than before at the output.

Using 111db Horns so need to tame the hiss.

I do not want to increase the FB back up because I LOVE the sound like this. It is much more detailed and punchy. The voicing is a tad thicker in the mids, which I like. But imaging and detils, much better.

Any ideas? Chris? Dennis?....Nelson?

Thanks,

K-amps

anatech 11th December 2005 12:39 AM

Hi Arif,
Less feedback = more gain. Now you need to try and reduce circuit induced noise. It won't be easy but may be possible. The circuit will have to be modified I feel.

You might want to try replacing the diff pair with FETs and clamping the drain voltage, cascode style. Just a suggestion. I haven't had a chance to try it myself yet.

-Chris


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