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.
I appreciate all the input. Plugging the amplifier directly into the wall socket helped alleviate some of the buzz I was experiencing through the speakers. You now have to hold your ear close to the midrange to hear any hiss or low buzz. I do still want to replace the caps, as they are now around 35 years old. I did not know if anyone had a recommendation for these screw top caps. It also seems that most folks also replace the rectifiers when they replace the caps. Any suggestions for power filtering capacitors brands or models for the Threshold S550e?
Let's start with some pix of the original. Can you post a few pix, please?
What caps are in there now? Capacitance? Voltage rating? Temperature rating? Dimensions of the cans + lead spacing? Post a good closeup of the caps.
You may find that you can get modern replacements with more capacitance that will fit the physical dimensions of the existing caps. Once you know the size of the current ones then it's a matter of going to Digikey, Mouser, or any other reputable parts supplier to find a suitable replacement part. I wouldn't get hung up on the brand, the caps sold at those suppliers go into industrial, computer, and consumer applications and they'll certainly be up to the task.
Why replace the rectifiers? Ain't broke, don't fix.
What caps are in there now? Capacitance? Voltage rating? Temperature rating? Dimensions of the cans + lead spacing? Post a good closeup of the caps.
You may find that you can get modern replacements with more capacitance that will fit the physical dimensions of the existing caps. Once you know the size of the current ones then it's a matter of going to Digikey, Mouser, or any other reputable parts supplier to find a suitable replacement part. I wouldn't get hung up on the brand, the caps sold at those suppliers go into industrial, computer, and consumer applications and they'll certainly be up to the task.
Why replace the rectifiers? Ain't broke, don't fix.
Hi Chucker1,
Much of what you read is wishful thinking, or simply applies to a different situation. The higher quality filter capacitors tend to last longer. They are made and sealed better. I wouldn't touch them until you actually begin to see a problem. Same for the rectifiers, although I would yank the high speed stuff and install the original, proper rectifiers. That may reduce buzz a bit more. Yes, not what you have read.
Do you need filter capacitors? The absolute answer can be had simply by hanging a scope across them and looking at the ripple waveform. It is exactly that simple. Do that, take a picture of the ripple on the caps and post. Let us know the scale and probe, hopefully a x10 probe.
People can talk about things for pages. Why not just look and get the facts? What you put in may not be as good as what the factory installed anyway.
Oh, and yeah ... DO NOT GREATLY INCREASE CAPACITANCE !!!
Much of what you read is wishful thinking, or simply applies to a different situation. The higher quality filter capacitors tend to last longer. They are made and sealed better. I wouldn't touch them until you actually begin to see a problem. Same for the rectifiers, although I would yank the high speed stuff and install the original, proper rectifiers. That may reduce buzz a bit more. Yes, not what you have read.
Do you need filter capacitors? The absolute answer can be had simply by hanging a scope across them and looking at the ripple waveform. It is exactly that simple. Do that, take a picture of the ripple on the caps and post. Let us know the scale and probe, hopefully a x10 probe.
People can talk about things for pages. Why not just look and get the facts? What you put in may not be as good as what the factory installed anyway.
Oh, and yeah ... DO NOT GREATLY INCREASE CAPACITANCE !!!
How was it plugged in before the wall socket? Where is the rest of the system plugged in? Could there be a ground loop?
Here is some info to check out:
https://hifisonix.com/wp-content/uploads/2019/02/Ground-Loops.pdf
https://www.hifisonix.com/articles/ground-loops/
Hi rhthatcher,
Read the thread. It was suggested to try the amp unconnected to RCAs (eliminating ground loops) to allow troubleshooting between n amplifier fault and ground loops. A isolation transformer was also suggested to eliminate the common ground connections as well.
Take a breath, one step at a time.
Read the thread. It was suggested to try the amp unconnected to RCAs (eliminating ground loops) to allow troubleshooting between n amplifier fault and ground loops. A isolation transformer was also suggested to eliminate the common ground connections as well.
Take a breath, one step at a time.