It is really unacceptable - this means a signal to noise ratio of about 75 dB against the specification of 120dB! Even the tubed Audio Research REF150 I am using has less than .001V in any of the channels. Was this measured without speakers?
Considering the expense and trouble to ship it, I would try to carry it to another place with a good mains supply, and measure it there.
That was measured with speakers attached. I took the measurements on the set of binding posts that aren't being used.
I didn't know it was ok to turn on the amp with no load attached.
I thought that was only the case with most tube amplifiers. If it's an issue with SS, then I'd be a little surprised.I didn't know it was ok to turn on the amp with no load attached.
Can you repeat them with the speakers not connected? Just in case there is a grounding path between their negatives, creating a loop.
Interesting. My multimeter is nowhere of the quality of a Fluke, yet a figure of 0.007 is what I always get with shorted probes on AC -- is this a common figure?OK. No speakers connected: .007 left and .008 right. I shorted the probes together with the meter set to AC and it didn't null. It was .007 with the probes shorted. I also reconnected the speakers but unplugged the subs that are built into my speakers and powered the amp up andthere was no difference in the hum level.
Interesting. My multimeter is nowhere of the quality of a Fluke, yet a figure of 0.007 is what I always get with shorted probes on AC -- is this a common figure? (...)
Frank
Frank and Mep,
You have to scold your multimeters.
It is not possible to diagnose noise with such an high error in the multimeter.![]()
Hi mep,
I recognize that I'm a newbie on this site but have been involved with this hobby for some 30 years plus.
Perusing this thread and knowing what this can do to a music lover, is there a reason why you continue to try to resolve this issue versus selling and moving on?
At some point ................................?
GG
Mark,
Is there any physical damping (weight on top, etc.) that you can safely attempt to see if you can eliminate the hum?
Lee
Hi mep,
I recognize that I'm a newbie on this site but have been involved with this hobby for some 30 years plus.
Perusing this thread and knowing what this can do to a music lover, is there a reason why you continue to try to resolve this issue versus selling and moving on?
At some point ................................?
GG
I agree ...
This is crazy -- basically saying the engineers at Krell back then when designing the beast couldn't pick that the amp was generating a bit of hum! Well, duuuhh ...Lee-The answer is no. If I could get the schematic to this amp, I think the problem could be resolved. I have previously talked about a friend of mine who lives in WA and who is the most brilliant engineer I have ever met. I have been talking to him about this issue and here is one of the things he said: "I could easily believe that the magnetic field from that transformer is coupling into the input lines. Still though, if I had to bet it would be on the simpler problem of the supply filter caps, notably the ones associated with the front-end amps. We really need a schematic at this point."
The bottom line is that my friend is fairly certain (without seeing a schematic) that there is not enough filter caps on the front end of the amp.
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