Gain adjust on an Adcom 545.

K-amps · 10th December 2005, 11:47 PM

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

10th December 2005, 11:47 PM	#1
K-amps diyAudio Member Join Date: Nov 2003 Location: Indiana	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

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
How To adjust Adcom 565 Bias	HiFiMonk	Solid State	1	25th November 2005 12:09 AM
adjust gain of Brian GT's 3875	moreismore	Chip Amps	0	23rd November 2005 04:33 PM
Krell PAM-5 gain adjust	JeroenDortmans	Solid State	0	11th August 2005 03:49 PM
Gain adjust? Where?	jimbo1968	Chip Amps	5	30th June 2005 04:56 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

11th December 2005, 12:39 AM	#2
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	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