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Adcom 5503 not producing Bass

Hey,

Having trouble with Adcom GFA 5503 I purchased off eBay. The amp it not producing any low frequencies. The sound is brittle and very hot sounding. When I switch back to an Adcom GFA 5400 (that I also own), the sound is rich and full. I'm driving a pair of Klipsch RF-3 II speakers. Also, when I hook up the 5503, there is a light hum coming through the speakers. The hum is not present when I hook up the 5400. So, did I get ripped off buying from eBay? I'm thinking about taking the amp to a local repair shop to see if they can help me. Any ideas? What would be causing the amp to not produce any bass/low frequencies?

Thanks so much to anyone taking the time to read this and respond.
schuman
willland's avatar
willland
846 posts
 
Shuman,

If you want "warmish" SS to mate with your RF-3II's, check out this B&K(no affliliation). Plenty of power(more than enough) to drive them and a warm signature to tame the top end.

Not a 3-channel amp like your Adcom but a very good price for a 5-channel.

Bill

http://app.audiogon.com/listings/multi-ch-b-k-reference-7250-multi-channel-power-amplifier-2012-10-07-amplifiers-85028
mechans
3,048 posts
 
If you want warm I agree with the Conrad Johnson amp suggestion. I can't think of anything that is nearly as warm as most of their gear. There are some "fixes" for warmth like cables and such but the cost is higher than you would want to spend.
junior77blue
1 posts
 
The hum could be from filter caps (12 of them) need to be replaced. Supposedly, over time they do age. I've been quoted....~$25/each to replace them plus labor.
jbellissimo
1 posts
 
I have just repaired a Adcom 5503 for a friend of mine. There are three electrolytic capacitors on the amplifier boards that go bad once replaced the gain stays flat well beyond the normal 20-20khz range. Be fore I replaced them it would drop off as the frequency dropped. 
georgehifi's avatar
georgehifi
10,312 posts
 
Also, when I hook up the 5503 there is a light hum coming through the speakers.
It’s old enough 25 years, sounds like to me it’s in need of some dried out electrolytic capacitors to be renewed, maybe even the power supply ones also. And there’s lot of them ($$$) All blue things top and bottom, plus there's some on the driver boards. 
https://img.canuckaudiomart.com/uploads/large/946706-adcom-gfa-5503-200x-3-amp.jpg

Cheers George
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