Hi all,
I bought used ADCOM GFA 5500 and I've never had a powerful amp like this before. My previous amp is rated 120watt@8Ohm. What surprised me is that adcom's transformer emits much more pronounced noise, I'd say it's twice as loud as my other amp's transformer. It's not too bad, ie with music playing I can not hear it, but this is the first time I've noticed amp noise at all.
Most people here and on other forums experience speaker noise, especially when preamp is connected which is not the case with me, mine has a noisy transformer. Nothing is connected to the unit when I hear the noise.
So for those of you who have the adcom or other big power amp, is it normal to hear it's internal noise from 2 meters away from the unit in a silent room? If not, then is there anything I can do with it without sacrificing sound quality?
Thanks!
I bought used ADCOM GFA 5500 and I've never had a powerful amp like this before. My previous amp is rated 120watt@8Ohm. What surprised me is that adcom's transformer emits much more pronounced noise, I'd say it's twice as loud as my other amp's transformer. It's not too bad, ie with music playing I can not hear it, but this is the first time I've noticed amp noise at all.
Most people here and on other forums experience speaker noise, especially when preamp is connected which is not the case with me, mine has a noisy transformer. Nothing is connected to the unit when I hear the noise.
So for those of you who have the adcom or other big power amp, is it normal to hear it's internal noise from 2 meters away from the unit in a silent room? If not, then is there anything I can do with it without sacrificing sound quality?
Thanks!
I would check and make sure the transformer bolt is tight. If not, it can vibrate which gets magnified by the case vibrating, which can sound like humming.
Edit - no that hum is not normal. I have heard it before on a good working amp, but NOT from 2m away, maybe 1m, but usually much less distance.
Edit - no that hum is not normal. I have heard it before on a good working amp, but NOT from 2m away, maybe 1m, but usually much less distance.
Does it hum when you just switch it on and fade away quickly ??? If so, I would think its normal, I have 2-3 that did that. if it hums all the time, some of the transformer laminations have corrosion in between and have got themselves to where they can vibrate. Either way, cant be fixed easily and not much of an issue.
Cool.
Srinath.
Cool.
Srinath.
Refresh my memory.
Is this is a larger toriod type trannie? Toriods are prone to humming if DC is present on AC pwr line. If it is an IE trannie this will not be the case. So if it is a toroid:
(I am assuming the vibration pad for the trannie is in good condition?)
Does it hum, the same everyday or sometimes less sometimes more?
If it comes and goes it could be from the DC on the AC line and a filter will help.
I have some you can try.
Other option is an imbalance in the rectification. If you have individual rectification
diodes you can move positions and reduce or eliminate the hum buzz. If it is a rectification block (bridge) try switching it out with another or replacing with individual
Hexfred type diodes.
If all this fails you may have to try another trannie.
Is this is a larger toriod type trannie? Toriods are prone to humming if DC is present on AC pwr line. If it is an IE trannie this will not be the case. So if it is a toroid:
(I am assuming the vibration pad for the trannie is in good condition?)
Does it hum, the same everyday or sometimes less sometimes more?
If it comes and goes it could be from the DC on the AC line and a filter will help.
I have some you can try.
Other option is an imbalance in the rectification. If you have individual rectification
diodes you can move positions and reduce or eliminate the hum buzz. If it is a rectification block (bridge) try switching it out with another or replacing with individual
Hexfred type diodes.
If all this fails you may have to try another trannie.
It's a large and heavy thoroid. I've only had it for a few hours so I can't tell if the hum changes day to day. Not sure what rectification diodes are - I don't have much knowledge in electricity. I have another amp with thoroidal amp which is two-three times more silent, from what I can tell, but maybe it's got a filter in it - I can't tell. I owned about 5 different amps and was never concerned with transformer hum, thow mine were not as powerful as the adcom's one.
Do you hear white noise from the speakers when not playing music? What distance is it audible from?
Today I had a chance to connect a pair of speakers and I can tell that white noise from the speakers on the adcom is also about 2-3 times louder than on my old Cambridge Audio amp.
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So, we assembled a DC filter according to this layout:
with that applied, the low level component of the hum - the low rumble - was reduced by at least 50%. So now the transformer still hums, but I can't hear it from 2 meters away, however hard I try, whereas without the filter I could hear the hum from the distance of 4 meters.
Bottomline: I find the solution satisfactory.
with that applied, the low level component of the hum - the low rumble - was reduced by at least 50%. So now the transformer still hums, but I can't hear it from 2 meters away, however hard I try, whereas without the filter I could hear the hum from the distance of 4 meters.
Bottomline: I find the solution satisfactory.
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