I doubt if this can ever be resolved. I had a S500 that had the same noise. Now I have a s550e which sounds amazing but has a slight buzz through speakers when idling just like the S500 had. NOTHING I do gets rid of it. Lifted gnd on power cord. Removed input cables. Switched to balanced input. Can’t hear when playing music but bothers me to hear noise. It was dead silent until the rectifiers were updated and bias pots replaced and adjusted. This must be common in these amps. I’ve read other posts on this. Has anyone ever resolved it?
Undo the update of the rectifiers. Why were they changed in the first place? Did the routing of the wiring change? Did you rotate the transformer? Are the ground connections as tight as before, and so on. In other words, revert to the original if all was good.
The new bias pots can hardly be a problem, I would think.
Hugo
always handy to have pics, before and after
at least for me, too old to remember all details
when I was younger, with better memory, then I didn't know what's important to remember
at least for me, too old to remember all details
when I was younger, with better memory, then I didn't know what's important to remember
I took it to a highly regarded tech for the work because bias went out on one channel. It was a bad pot. In the service the power input fuse assembly was replaced because it was burnt from loose power cord. The rectifiers were updated to high speed. The amp sounds amazing. But I’m a perfectionist and disappointed with this because of the newly introduced buzz/ hum that I was happy to get rid of on the S500 Just looking for possible causes. The S500 was never serviced or updated. Just bias adjustment.
I am having a similar issue with my Threshold S550e, but I believe mine may be in need of Caps and bridge rectifiers, as it is all original. I have that hum through the speakers. It’s not loud but like you, it annoys me. Curious is you know which caps I could use to replace the originals and the type of bridge rectifiers you used?
The high speed rectifiers may well be a problem here. Normal rectifiers are highly engineered for a reason, and they are only cheap because they sell box cars full of them every year.
Most amplifiers have a connection from audio common to chassis ground through a 10 ohm to 100 ohm resistor. They are easy to burn out. Measure between your RCA ground and chassis without the preamp plugged into it. Power off. Another trick you can try is an audio ground isolation transformer. I bought one from Amazon, a WisWinDA model RCA-2. I also picked up some others from AliExpress. Large transformers with shield, I installed them in a metal enclosure. The small, cheaper transformers will have much higher distortion.
Most amplifiers have a connection from audio common to chassis ground through a 10 ohm to 100 ohm resistor. They are easy to burn out. Measure between your RCA ground and chassis without the preamp plugged into it. Power off. Another trick you can try is an audio ground isolation transformer. I bought one from Amazon, a WisWinDA model RCA-2. I also picked up some others from AliExpress. Large transformers with shield, I installed them in a metal enclosure. The small, cheaper transformers will have much higher distortion.