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Adcom GFA555 II Makes speakers pop on shutdown

Kencat

Kencat

Super Member
I'm posting here because this (problem?) is more amp related because a different amp does not make the pop,pop,pop,pop pop noises in the speaker, so I have ruled out the speaker. Thinking about it though, another speaker on the same amp doesn't do this either, but it does make one little tunk at the end of powerdown.

Combination 1 - Adcom GFA555 II + Infinity Quantum 2 - makes five or six pops after the amp has discharged the caps - the preamp is still on at this point. The pops aren't loud enough to cause great concern, at least I hope they aren't potentially damage inducing.

Combination 2 - Adcom GFA555 II + RS Mach 2 - one tunk

Combination 3 - Nikko Alpha II + Infinity Quantum 2 - dead silent on shutdown (can hear a relay click in on power up and down)

I checked DC offset on the Adcom with the preamp hooked up. maximum 1 mV observed. The Adcom does induce a very small tick in the speaker when clicking the switch on (preamp is already on first).

Is this normal for the Adcom ? I don't detect any relay clicks on power-up with this. The amp sounds superb, to me anyways.
 
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I had an old Sony CD player with PS caps that made my system pop a few times through the speakers before going into really nasty distortion. I thought it was the amp section of my reciever but the popping did not repeat after I changed music source. Is this happening with a variety of music sources, tuner, phono, Aux, etc? Does this happen with a different pre-amp? Or with your Adcom and speakers by themselves? Kind of a process of elimination approach.
 
My GFA-535 does it also. Not bad enough to bother me. I also have a bit of hiss through my speakers so it might be part of the same problem or not.
 
In a situation such as this where your getting distortion passed to the speakers, at what level do these supposedly harmless "POP'S" become damaging? Just a curiousity question as I have encountered with different amps from time to time myself but I have yet to ever have a speaker damaged and I am hoping it is not just luck.

Later,
 
I recently had an Adcom come through here I worked on, was suprised to find no
speaker relays in there. So what you get is when you turn the amp on and off it
emediatly sends a signal to the speakers and can make some very strange noises.

Also different speakers react differently depending on how there designed and the
arangement of caps in them. I was not to comfortable with this arangement even
if it was not that much on most speakers, but I knew it did it and it bugged me!

It seems to be normal for an Adcom amp and many people like them but I just did
not feel completely confident in how it was designed.
 
That's odd, I have a GFA-1 that does have relays. You'd think that it should be the other way around, the newer amp having them. (No noise out of this amp other than a little hiss BTW)

On another note along the same lines though, I have a Bose 1801 and 4401 amp/pre combo that has a 60hz hum issue when used together. If I use my PL pre it's not there and using the 4401 with a tube amp it's not there either. Why? Beats me.
 
My 555 II would have a light thump on turn off, however you must be sure when you turn off the amp first you wait for the caps to discharge before shutting down the preamp. This is usually a minute or two.

555 II is a good amp, I never had "multiple" pops when shutting mine down, just one per chnl and is was low in intensity.

Ron
 
Kegger said:
I recently had an Adcom come through here I worked on, was suprised to find no
speaker relays in there. So what you get is when you turn the amp on and off it
emediatly sends a signal to the speakers and can make some very strange noises.
Click to expand...

Mine makes an electronic 'boing' type noise on shutdown. It is strange and it is specific to Adcoms.
 
Thanks for the responses everyone,

So, the Adcoms don't have the relays, therefore they do these wierd things. OK, I can live with that :yes: .

The amp is very quiet once charged up and sounds great on the Quantums. The Q2 is a 4 driver system, 2 of which are wired out of phase. 3 of the driver systems have a cap and inductor in series, and the woofer has an 1100 mF and a 900 mF cap. With the slow discharge of the Adcom caps, perhaps there are some strange induced currents going on in the speaker (duh. obvious if there are unrequested noises happening) :dunno:

The Mach 2s don't do it, so proves Kegger's statement of depending on the speaker design.

It is a quirky thing to have on an expensive amplifier....wonder if Adcom thought the relay circuitry hampered the sound, sure hope they weren't just trying to save .50 $. That would be :thumbsdn:
 
I have an Adcom GFA-545 paired with an Adcom GFA-555 II preamp hooked to Vandersteen 2c's. I have never experienced the kind of popping that many of you described, so I wonder if it is "normal".
 
AlleyKat said:
I have an Adcom GFA-545 paired with an Adcom GFA-555 II preamp hooked to Vandersteen 2c's. I have never experienced the kind of popping that many of you described, so I wonder if it is "normal".
Click to expand...

Put a Sony preamp on that 545 and you will hear it. .

DC voltage. . . My 555s all did it with preamps other than Adcom. . Light pop when changing functions etc. different than turn on thump. . .much quieter and a sharper static sounding pop. .
 
I never noticed a 'pop' on shut down but when powering up their is a slight thump. This is with a Adcom 535.
 
Yes it is normal and do to the design of the amp with having no speaker relays just
like many of the vintage amps do the same type of thing.

Yur amount of issues you will hear from it will be quite a wide range depending on the
accossiated gear and may vary even more depending on your speakers/xover design.
 
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