Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
Is this bad for my amp?
#151979 11/24/06 07:24 PM
Joined: Mar 2004
Posts: 340
Thasp Offline OP
devotee
OP Offline
devotee
Joined: Mar 2004
Posts: 340
I have an Adcom GFA-555 MKII.

When I had the Axiom M22ti speakers, I used a Harman Kardon 3480. The amp never got warm enough to heat the plastic.

Now I have the Thiel CS3.6 speakers with that new adcom, and my dad has the Axioms as a birthday present. He loves them of course. They're about 83 dB/1 watt/1 meter, and my multimeter measures them to be 3-3.5 ohms.

When I have music on at a louder volume and there's a loud bass riff, if the room is hot(goes up to 85-90F in the summer, is 80 now with all the computer stuff here), the heatsinks get burning to the touch.

It's not in a rack or a case, it's in the middle of the room. I read in the manual Adcom sold an active cooling piece for it, but this was almost 20 years ago. So they may not have them anymore.

Should I worry about this, or is this normal? The Thiels made the HK shut down at higher volumes, the timing was funny. I have a few songs with long bass transients that were made artificially that swoop down in frequency quickly and go up in amplitude, before it hit 35-40 hz the HK would blink off if I had it on too loud which was the reason to get this Adcom. When that swoop comes here the amp gets noticeably hotter, and stays like that until I turn it off for a while.

While playing music, it also stays on for about 20 seconds after I unplug it.. at the same volume. Is this normal for a large amp or does this mean the capacitors are in need of replacing?

Last edited by Thasp; 11/24/06 07:26 PM.
Re: Is this bad for my amp?
Thasp #151980 11/24/06 09:18 PM
Joined: Mar 2005
Posts: 7,463
Likes: 1
axiomite
Offline
axiomite
Joined: Mar 2005
Posts: 7,463
Likes: 1
Quote:

They're about 83 dB/1 watt/1 meter, and my multimeter measures them to be 3-3.5 ohms.




Holy mackerel.

So much for using the T-amp, huh?


***********
"Nothin' up my sleeve. . ." --Bullwinkle J. Moose
Re: Is this bad for my amp?
Thasp #151981 11/24/06 09:41 PM
Joined: Jun 2003
Posts: 6,833
W
Wid Offline
axiomite
Offline
axiomite
W
Joined: Jun 2003
Posts: 6,833
If the amp is getting so hot that it will burn you if you touch it then that certainly is not good. The Thiel CS3.6 do seem to be a pretty tough load for any amp but the 555 should be ok, it was a heck of an amp in its day. Maybe the Adcom is getting a little long in the tooth and you should start to think about a replacement. You could also think about something like this to help keep it cool.


Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud

Re: Is this bad for my amp?
Wid #151982 11/25/06 01:46 AM
Joined: Mar 2004
Posts: 340
Thasp Offline OP
devotee
OP Offline
devotee
Joined: Mar 2004
Posts: 340
I can take the decimal point off and have the same thing just without the parasound name. Maybe I will make my own.

I bought this amp in august, it was used. It ran as hot then as it does now, it depends on the room temp and what is playing. Music with heavy bass like some Iced Earth CDs really burn up the amp, but when the room is cooler and shostakovich is playing, it is much cooler.

Re: Is this bad for my amp?
Thasp #151983 11/25/06 02:27 AM
Joined: Jun 2003
Posts: 6,833
W
Wid Offline
axiomite
Offline
axiomite
W
Joined: Jun 2003
Posts: 6,833

Then maybe all you need to do is use the set up in a refrigerated room


Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud

Re: Is this bad for my amp?
Thasp #151984 11/25/06 03:25 AM
Joined: Dec 2003
Posts: 3,602
B
connoisseur
Offline
connoisseur
B
Joined: Dec 2003
Posts: 3,602
Quote:

They're about 83 dB/1 watt/1 meter, and my multimeter measures them to be 3-3.5 ohms.


A quick Google suggests that the Mk II gets hotter than the Mk I but I couldn't find any information on the amp circuit. DC measurement across the posts (and add a third because loudspeakers aren't a standard/passive load) confirms they are 4 ohm nominal. So no stray wires.

Looks like the Adcom just likes frying eggs when hooked up to speakers with low nominal resistance. And yes, it's hard on the transistors for them to get that hot (and other components, especially near the transformers & heat sinks)

Bren R.

Re: Is this bad for my amp?
Thasp #151985 11/25/06 03:43 AM
Joined: May 2002
Posts: 10,654
shareholder in the making
Offline
shareholder in the making
Joined: May 2002
Posts: 10,654
T, sure it isn't as good for your amp as if it was just running warm. But with those speakers, playing that sort of program material and at those levels, apparently that's the way it's going to be. Keep in mind that from the numbers you give those speakers are drawing about five times as much power for a given sound level as, for example, the M80s, which are a relatively easy 4ohm load because of their higher sensitivity and flat impedance curve. So, it may not be good for the long term, but enjoy the moment.


-----------------------------------

Enjoy the music, not the equipment.


Re: Is this bad for my amp?
BrenR #151986 11/25/06 03:47 AM
Joined: Jun 2003
Posts: 6,833
W
Wid Offline
axiomite
Offline
axiomite
W
Joined: Jun 2003
Posts: 6,833
When I did a search for the Thiel 3.6s it stated its sensitivity rating @ 86dB/W/m (2.8V) which would be within what would be a normal sensitivity rating. Their impendence however does drop off to a low 2.3 ohm and 3 ohm through most of their range. I would suspect this would be a difficult load for any amp.

Does the thermal overload led come on when you play the music loud ? If not I wouldn't be to worried about it but running some sort of fan ( Parasound or not ) would be a good idea imo.


Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud

Re: Is this bad for my amp?
Wid #151987 11/25/06 04:02 AM
Joined: Mar 2004
Posts: 340
Thasp Offline OP
devotee
OP Offline
devotee
Joined: Mar 2004
Posts: 340
I don't get 86 at 1 watt 1 meter. Maybe I have a room null in the frequency range I used for testing when I got them. I don't trust specs, I like to measure myself. I only have the multimeter now, the mic is long gone so I can't retest.

I borrowed my dad's axioms and tried the amp. I put my earplug headphones on so I could play them at stupidly loud levels and it never got more than slightly warm.. I guess it's a speaker thing. Then again I also measured these to do a solid 28 hz in this room before they even began rolling off in 1 dB increments, so the amp does have that burden.

I also tried the old HK again on these. It didn't have a chance to get hot.. it got warm, warmer, then shut off. What a wussy.

I have also put those earplug headphones on and tried playing far above the levels I'd ever reach without them on just for testing purposes. The overload LEDs never went on. I guarantee I did my best.

I'm sure the M80s would have been easier to power, they don't dip as low in impedance and even if they did are far more sensitive. But I can't give these speakers up now.. they don't sound amazing, they sound normal, until I listen to any other speaker side by side. It's worth the trouble.

I think I'm going to run a molex extension cord from my computer which is near the amp, and use two 120mm computer fans I have. I can tape the corners of the fan to the two back corners of the amp and it'll blow cool air through the fins. If I hook it to the fan controller, I can even control the volume. If I keep them low it won't even be noticeable over general room noise.

Thanks for all the responses.

Last edited by Thasp; 11/25/06 04:05 AM.
Re: Is this bad for my amp?
St_PatGuy #151988 11/25/06 04:07 AM
Joined: Mar 2004
Posts: 340
Thasp Offline OP
devotee
OP Offline
devotee
Joined: Mar 2004
Posts: 340
Quote:

Quote:

They're about 83 dB/1 watt/1 meter, and my multimeter measures them to be 3-3.5 ohms.




Holy mackerel.

So much for using the T-amp, huh?




I had one of those actually. Can you believe it didn't agree with the speakers?!

Page 1 of 2 1 2

Moderated by  alan, Amie, Andrew, axiomadmin, Brent, Debbie, Ian, Jc 

Link Copied to Clipboard

Need Help Graphic

Forum Statistics
Forums16
Topics24,939
Posts442,452
Members15,615
Most Online2,082
Jan 22nd, 2020
Top Posters
Ken.C 18,044
pmbuko 16,441
SirQuack 13,840
CV 12,077
MarkSJohnson 11,458
Who's Online Now
0 members (), 221 guests, and 0 robots.
Key: Admin, Global Mod, Mod
Newsletter Signup
Powered by UBB.threads™ PHP Forum Software 7.7.4