I just purchased a Threshold S550e in great condition but have noticed a couple of issues. The transformers vibrate pretty loudly on startup and then settle down after about 5 seconds or so. I am also noticing a very low humming through the speakers with no source material playing, and this also occurs without the preamp attached. I feel pretty confident that this amplifier is due some new PS filter caps and bridge diodes, but I cannot find any info on what I can or should be using as replacements for the existing 6 caps and the bridge rectifiers. Any help would be appreciated.
Relax. Don't jump to conclusions.
Is it a hum, or buzz? A hum will not be filter capacitors or rectifiers. A buzz may possibly be, not always.
Is it a hum, or buzz? A hum will not be filter capacitors or rectifiers. A buzz may possibly be, not always.
What background do you have? What test equipment?
First determine (not guess) the problem that is causing the symptoms. Then repair the problem.
First determine (not guess) the problem that is causing the symptoms. Then repair the problem.
Hi Chucker1,
What you can do is try to unplug the inputs and install RCA shorting plugs. If that solves the issue, you do not have filter cap problems. After that you can try an isolation transformer for the audio before even opening the cover.
What you can do is try to unplug the inputs and install RCA shorting plugs. If that solves the issue, you do not have filter cap problems. After that you can try an isolation transformer for the audio before even opening the cover.
I will give that a try. It makes me wonder if I have some sort of power issue. I am using a 20amp circuit and the APC power conditioner says I am only pulling about 5amps. Stangely, when I biamp my speakers with Threshold on the LF and using my mini tube amps on the HF, the Threshold Transformer will start to vibrate for about 5 seconds when I power off the tube amps first, as if taking some amperage off the ac line causes a surge in ac power to the Threshold. I have used s450e’s and several other amps in this room with no issue. It’s perplexing, but I will try the shorting plugs.
Hi Chucker1,
Troubleshoot logically. Do not guess, don't jump to conclusions. Prove each idea.
It might help keep you on track to write down on paper. Mark each test, observations only, no conclusions. This will keep you on track.
Personally, I feel power conditioners are two things. A massive waste of money, and they limit performance of larger power amps. Power amplifiers should always be plugged directly into an AC outlet, large amplifiers may use their own circuit on the same phase as the rest of the equipment. A power conditioner will always have higher impedance than a direct connection to the AC mains.
You can use a power line filter for your signal sources and preamp. Current draw is generally low and typically pretty constant. Not so with power amplifiers.
Troubleshoot logically. Do not guess, don't jump to conclusions. Prove each idea.
It might help keep you on track to write down on paper. Mark each test, observations only, no conclusions. This will keep you on track.
Personally, I feel power conditioners are two things. A massive waste of money, and they limit performance of larger power amps. Power amplifiers should always be plugged directly into an AC outlet, large amplifiers may use their own circuit on the same phase as the rest of the equipment. A power conditioner will always have higher impedance than a direct connection to the AC mains.
You can use a power line filter for your signal sources and preamp. Current draw is generally low and typically pretty constant. Not so with power amplifiers.