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?
If it's a transformer hum, you need to check your voltage. My voltage ramps up to 129volts and made my balanced conditioners transformer humm. It doesn't sound like a ground issue.. Also sometimes in shipping the transformer mount loosens up inside and it might need to be tightened down, but if your sub is doing the same thing you have a problem in the power.

Thanksfully 10" away isn't bad though..

Panamax conditioners won't help.. you need a regenerator (PS Audio Powerplant, etc.) that might help if it's a voltage problem. Take the amp to a friends house and measure his voltage and see if the amp humms.
Thanks - this seems to be the consensus in the cross post as well. I am going to take the amp to another house and see what happens, and see if I can diagnose the voltage, as well.
I would second the hypothesis that the voltage ramp up causes the hum. I've had a Spectron Musician IIISE in my house for about a week and a half, and it sometimes hums (the unit, not through the speakers)...but it's always been around 5-5:30 in the morning...never in the afternoon or evening. Come to think of it, kind of fits the same scenario with some Blue Circle Noise Hounds I have.
Problem was completely solved with a Channel Islands Audio XDC-2 AC filter. definitely transformer hum from DC noise riding on the eAC line.
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?

When I spoke to the guys at CI, they confirmed that there is a maximum draw per plug on XDC-2. I don't know whether you can do what you propose, but the CI guys can tell you very quickly I am sure. I think in the traditional configuration the max draw per plug is 7 amps - but they can also build the XDC in parallel (??? forgive my lack of tech knowledge) which means as long as the total draw on both plugs does not exceed 14 amps then all is well. That's the way they built mine, at no extra charge, and I have a 500 watt/channel Musician amp and a 450 watt subwoofer amp drawing on the unit without trouble.

What is a Musician II Hybrid?
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!


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.
Thanks for the reply. I looked at the Spectron website, but would be interested to hear your long term impressions on the upgrade. Seems the price is right for 90%+ of MIII performance (if that is the case).

I noticed that you are using DH speakers cables. I am doing the same, except in the Remote Sense config. I am in the process of trying to acquire some Cardas Golden Cross b-wires as an experiment. My system balance is presently good to very good, but not great. It has a tendency to get a little hot and edgy in the high end which causes me to play at a lower volume than I would like sometimes. The good news is that even at low volume the system is very detailed and dynamic - probably the flip side of the forwardness.

The Golden Cross are known to be very warm cables which tend to tame glaring, edginess etc, but still with plenty of detail and resolution. I noticed in one of the Musician II reviews the reviewer preferred his usual cables to the Remote Sense. I hope to give them a try withint the next few weeks. . .
The DH Labs speaker cables are remote sense. I worked with DH to get the right configuration on the Neutrik connectors.
How do you guys feel about your Spectron upgrade? I have a Musician II and I am considering the upgrade path.