question regarding adcom amp

[mlastarza]

Bought an adcom GFA 555 amp on audiogon about a month ago. Hooked it up to a Yamaha RXV 661 av receiver and my RTA 11t speakers. Everything seems to work fine except after I turn off the amp, after about 15 seconds a noise is emitted from the speakers (like an electronic burp for lack of a more technical description). I've never had a seperate amp before and don't know if this is typical or of concern?

[venomclan]

Some Adcom amps and others do emit that electronic blurp. My Adcom does it also. They are missing a component in them that most modern amps have, I do not remember what it is exactly (relay?), but do not concern yourself with it as it is normal for that amp.
Venom

[tcrossma]

I'm kind of new to the external amp world myself, so i'm not sure exactly what should be expected from different amps. The documentation for mine recommends that the receiver be turned off first, then the amp. That's the way i'm doing it and i've never heard a "thump". I'm sure someone else here has experience with that particular amp and can chime in.

[nms]

I've read this is not a problem as long as it is not too loud. Judging by the time delay I'd guess you're hearing a capacitor discharging.

Most amps do not do this because they have a solenoid that physically opens the circuit when you turn it off, so those noises do not reach the speakers. This is the thing Venom mentions that your amp is "missing" ;)

[mlastarza]

Thanks for the replies. The owners manual for the amp states to turn the amp off first and wait for the red display light to go out before turning off the receiver. How much of a risk is it if it's not done in that order?

[venomclan]

The amp should be the first one off and the last one on. An amp will amplify any signal, or lack thereof through a speaker. If a receiver or preamp is turned off first, it can sometimes send a high pitched signal or other unwanted amplified signal to your speakers and potentially cause damage.

Turning on a preamp or receiver first will allow you to make any adjustments needed volume wise or input wise before or right when an amp is powered on.
Venom

[george daniel]

Adcoms,, particurlarly the 555's are notorius for the " thump"

[mlastarza]

Thanks folks. I shall resume my happy listening without worry.

[cfrizz]

How do you like having your speakers driven by a separate amp?

[mlastarza]

It sure sounds good. My son asked me "Does it sound BETTER?" I think it does but I look back on threads discussing cables and I wonder is my brain just hoping it sounds better? Between the amp and the new RD0-194 tweeters it seems I hear things I hadn't before versus my imagination? Redardless for a whopping $400 investment between the amp and the tweeters I'm pretty happy!

[ruf993turbo]

It is perfectly normal what's happening..