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Re: Sunfire/Carver hum???

Posted by Zarathurstra on July 11, 2003 at 10:34:15:
I've owned the following Carver Amps:
M1.0T , which didn't hum an M 4.0T, which hummed and two
TFM-42's both of which hummed. If you take the covers off the last 3 amps it looks like the inputs run very close to the power supply
and output terminals so noise may be inductively or capacitively
being fed back to the inputs. I have fairly sensitive speakers
(92db spl at 1 meter) and with no music playing I can here a
power line frequency hum coming from the speakers within 2-3 feet of the speakers, but at my listenining position (about 8 feet)
It's not audible. Despite this "problem" the TFM-42's which
I currently have, and bought used on ebay on a Lark, are
(were) one of the unsung sonic bargains in audio, and I think
the Sunfire I listened to in 1995 when they first came out was
very similar in sound. Despite my impulse to buy something
newer whenever I listen to the TFM-42's I'm drawn into the
experience and really, yes really, am at a lose to say what
would need to change to make my system sound better.
The M1.0T however is another matter. Supposedly "TFMed"
to sound like a Conrad-Johnson Premier 5, I always found the
sounstage to be a bit flat, veiled and muddy with fat, sloppy
bass, but it was the best thing I had owned up to that point.
The thing is it was a very quiet amp with no hum from the speakers
but a slight amount from the "magnetic field coil" audible when within about a foot of the amp with no music playing. Anyway
one way to check to see if it's the amp itself, or a ground loop,
is to disconnect anything you have connected to the input,
leave your speakers connected and short the inputs of the amp.
(I guess you have a two conductor power cord on your units) Then turn it on. If the hum can still be heard the hum is in the amp and
there's not an easy solution to that in my experience. If there
is no hum then indeed some kind of ground loop or incompatibility
problem with the grounding schemes exists between your components.
PS. Shorting plugs can be had from various places but can be hard to find. I think Audio Advisor had some Cardas ones at a steep price.
If you have a friend who is into electronics they should be able to
rig some wires and connectors together in a minimal amount of time and expense.