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Buzz/hum from Spectron Musician II amplifier.

Cross posted in amp forum: Just purchased the unit from another 'Goner. It makes phenomenal music, but has an electrical buzz/hum upon power-up which comes up slowly and then reaches a steady state after about 3-5 seconds.

No noise through the speakers, thank goodness, but from inside the case itself. It is just loud enough to be barely audible from about 10" away. Incidentally, the amp in my subwoofer is doing the same thing and both are on the same circuit, so I suspect noise coming through the circuit. The seller confirms he had no such problem, which tends to reinforce this conclusion.

I tried to reverse the ground - using the 79 cent 3 prong to 2 prong adaptor. No luck there. Hum was also present when plugging into through a Panamax power condition on the same electrical circuit. I am out of ideas. Anyone?
jswarncke

Showing 3 responses by rhanson739

rhanson739
269 posts
 
Just the other day, I received my Musician II that has been recently upgraded to a Musician II Hybrid. There was a significant and new hum similar to what you've described... mostly heard about 10" away, but also noticeable from the seat during some quiet passages.

Based on what was said in this thread, I tried an experiment: Normally I plug my amp into the "Filtered AC" plug on my PS Audio P500 regenerator. This connection doesn't regenerate the AC, but presumably has some sort of filtering... clearly not enough to knock down the hum. I plugged the amp into the "regenerated" outlet, and the hum stopped.

I suppose that this supports the DC noise theory.

Problem is, as I understand it, one is not supposed to use regenerated AC ports for the amp, lest I restrict the power. Thoughts? (I'm planning to contact PS Audio for their opinion.)

My P500 also has a slight bit of hum. Do you suppose that the Channel Islands XDC-2 would work between the wall and the P500, knocking out hum for all the gear?

Rob
rhanson739
269 posts
 
Jswarncke -

I had to send my amp back to Spectron because both channels just rolled over and died one day. I don't know why, and I don't think they did an autopsy on it. To make matters worse, when I was debugging the problem over the phone with John Ulrick, we smoked one of the boards by turning the amp back on too quickly - so we think.

Rather than risk a repair on an aging unit, I asked them to upgrade it to the Musician II Hybrid. Basically, they take out the two amp modules and the power module, replacing them with the same modules that are used in the Musician III. They may do other mods, but I'm not sure what they are.

I couldn't afford to replace the II with a III or IIISE, so at $1,295, this was the best way to get a "clean" amp at an affordable price.

For what it's worth, the upgrade is nice. It's not even broken in, but I can tell that there's quite a difference. Or, possibly, it just sounds better after a month of no music!

Rob

PS: I'll contact CI about the draw. In talking with PS Audio today, they have an upcoming product that may help, but it's still in development. They also advised me not to continue using the Regen outlet on the P500, as it would eventually degrade the unit.
rhanson739
269 posts
 
The DH Labs speaker cables are remote sense. I worked with DH to get the right configuration on the Neutrik connectors.
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