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Adcom GFA 535 Shutdown Noise

madtech

madtech

Well-Known Member
I have an Adcom GFA-535 paired with a GFP-555 preamp. When I shut down the power amp there's a zipping sound that hits the left speaker first and then the right speaker. Nothing too loud or terrible but should it be anything to worry about? tks
 
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Nope, nothing to worry about and it's totally normal. That is the sound of the power supply capacitors discharging and the amp powering down. You don't hear that on amps with speaker relays because the relay will disconnect the speakers immediately when the amp is switched off. When the amp design has no relay you hear the amp slowly discharging as the capacitors bleed off.
 
My MOSFET amps will continue playing music for about 30 seconds after power switch is turned off.While draining the 96,000µf PS filter caps.
 
from the GFA535 owner's manual:

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Thanks for the replies. This is my first Adcom setup and I thought I might be heading for trouble. It's a sweet sounding combo!
 
really like the 535. Just put it to use in a new system.

Did hate the fact there is no protect and that it does have that noise at power down. I always turn off the speakers by disengaging them on the face of the amp. Just makes me feel better. Your experience may differ.
 
My GFA555 , perhaps the first gen. (1990 ?) use to do the same thing. Now it produces a loud momentary crackling noise ( amber leds lights flicker) when turned off. I have not had the time to address this issue as yet and just about the only thing I dislike about my other Adcom amp..mk2 version of yours , is the turn on transient it produces evident by the woofer cones extending outwards . Another thing I learnt about my GFA 535 is that sometimes the fuses located on the circuit boards will blow. This happened to me once and I replaced the blown fuse with the recommended value , just like the one taken out...So far its been over a year now and no problems.
 
paulram said:
My GFA555 , perhaps the first gen. (1990 ?) use to do the same thing. Now it produces a loud momentary crackling noise ( amber leds lights flicker) when turned off.
Click to expand...

Try a new power switch, it's a common failure. You can get the exact replacement at Parts Express. I had the part # around here but I can't find it now. Email Adcom and they'll give you a link to the right part.
 
Sorry for the late follow up ....but I am happy to say its not the amp but an equalizer
that had a bad transistor in its power supply going bad. That I fixed and so far everything seems ok.
 
madtech said:
I have an Adcom GFA-535 paired with a GFP-555 preamp. When I shut down the power amp there's a zipping sound that hits the left speaker first and then the right speaker. Nothing too loud or terrible but should it be anything to worry about? tks
Click to expand...

My 545 does the same thing, but only on one channel...
 
Normally when I turn off the amp I would get a faint squealing noise that subsides gradually , but the noise I got was a loud pop/crackle , associated with the peak lights coming on. I knew something was wrong.
 
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