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I posted this issue in the preamp forum & was required to cross-post it here. I recently started to get a "buzz" coming from my speakers. In the past, I resolved this symptom by replacing the tubes in my Audio Research SP-16 preamp. However, when I replaced the tubes the other day, the buzz persisted.
I unplugged all of the audio components (one by one). The buzz stopped only when the preamp or the power amp were unplugged.
Does anyone have any thoughts what might be the culprit? Thank you kindly.
Follow Ups:
Michael: I ran the test that you suggested. The buzz still continues from both speakers equally. Increasing the volume on the preamp causes the buzz to increase as well.
You mentioned that this might suggest a filter cap issue? Any other possible causes? Thank you.
coming from one channel or both.
At least you can narrow it down to the section of the preamp.
both channels - generally speaking it means the problem is in the power supply.
Typically preamps need to a going over with a tech and a scope.
charles
You'd have to do a lot more experiments to understand where the buzz might be coming from.
This could be as simple as dirty tube sockets or sockets with loose pins (a possibility based on your statement that replacing the tubes before solved the problem), or a flaky component in the preamp that needs to be replaced.
One would have to go through the preamp with a scope, meter, and signal generator to figure out where things are going wrong.
At this point it seems like I should rule out either the power amp or the preamp as the culprit. If I plug one of the components (e.g. the CD player) directly into the power amp & the buzz goes away, it would seem like the problem is in the preamp. Does that make sense?
If I plug one of the components (e.g. the CD player) directly into the power amp & the buzz goes away, it would seem like the problem is in the preamp. Does that make sense?
Not necessarily..Lets try this..Lets determine whether your preamp is in fact the problem...Plug the preamp back into the amp and turn it on along with the amp..Put the unit on aux and plug in a pair of shielded cables or a single cable and turn the volume down before you do this..Short the end of the cable like this that would plug into your dvd or cd player and turn up the volume and see if the hum disappears..If it doesn't,you have preamp issues most likely a filter cap in the power supply..Is it humming in both channels?
Honest amplification is better than excessive 2nd order distortion anytime.
Michael, let me make sure I am getting this correct. (You have me treading in unfamiliar territory). After turning on the preamp & the power amp,& setting the preamp to "AUX", take a pair of shielded cables (I assume that RCA cables would do?) & plug them into the "AUX" plugs in the preamp. By "shorting the ends of the cables", are you suggesting that I short each of the cables to ground by running a wire between the pin on each cable & ground (e.g. the preamp or power amp enclosure)?
Thanks, Michael.
Kit
Yes
That is what I'm suggesting and it will tell if it;s a filter cap or signal issue with cables.
Honest amplification is better than excessive 2nd order distortion anytime.
Yes.
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