Adcom 5503 not producing Bass


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.
It sounds like you bought an amp in need of repair. As a side note, I would say that if you think that the 5503 sounds "rich and full", you should try a better amp. You are in for a pleasant surprise.
I was using an adcom 545 with a classe ssp 25 pre amp and paradigm studio 10's. It too lacked bass and sounded a bit thin on the higher frequencies. I purchased a used classe ca-150 ($800) and am really happy! Great bass, lots of detail and more power and the more I listen, the more I appreciate my new amp. Maybe you ought to consider selling both adcoms and looking at a used Conrad Johnson mfa 2200.
E-Bay didn't sell you the amp.
"E-Bay didn't sell you the amp."

Maybe. Ebay didn't make up the ad and take an active role in selling the product but they did take a commission when the sale was made.

"So, did I get ripped off buying from eBay?"

Its a combination. You bought the amp from Ebay and the seller. Since they both made a direct profit from the sale, both have an obligation to the buyer (Although not an equal obligation). Simply put; while Ebay may not take full responsibility for selling you the amp, they are responsible, at the least, for helping you recover the money you lost.

I would contact the seller first. If they have good feedback, they will probably do what ever is necessary to fix the issue. If that doesn't work, eBay should be willing to look into the matter. I don't see them offering to give you a refund (Unless you meet Paypal requirements), but they should try to do something. Its in their best interest to do so. Situations where people get ripped off are very bad for their business. Even if you have a broken amp and can't get your money back, they may give a partial refund (Possibly for things like commission, paypal fees, etc.)

I didn't say the 5503 sounded "rich and full", for if it did, I would not have written a post asking about why it sounded brittle. Staying on point, I agree the amp is in need of repair, but I'm wondering what it'll take to get this thing back to proper working condition. What is causing the amp to sound this way and what can be done to fix it? Lastly, I would be curious to hear you recommendations of alternate/better sounding amps in this price range. For what I paid for the 5503 ($500), what else is in that price range that would bring me a "pleasant surprise"? I'm looking for a warm sounding amp to match with my Klipsch speakers.


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.

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.
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.
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. 
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.

Cheers George