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Humming and static noise, Plinius SA 100 MkIII

Hello. I am currently using a pair of Plinius SA 100 MkIII's as mono blocks to power my B&W 802D's. First the amps have a slight hum when on and sometimes they are very quiet. More importantly, when I turn the volume up all the way without a signal from source, there is a very noticable high frequency hiss like radio signal distortation at the speakers. I have tried many things including changing preamps, cables, cords, etc but nothing worked. These amps generate 400 watts as mono so with the volume turned up all the way the noise may not be abnormal.

I would appreciate if any one with similar issue has an answer for me. I love the amps but the noise level is a bit too high. Note: in normal listening volume the noise is very low and not noticable at all only at vey high levels the noise is very noticable. Thank you.
espoverload
espoverload OP
14 posts
 
Thank you all for excellent advice although some of it just went over my head. I did one more experiment and changed amp on one side. A VAC tubed amp. The hissing noise was still there at high volumes without any input from source. So somewher, I am picking up the noise where than is amplified by the amps.

BTW, I am using a Richard Grey Power Station and RCA connectors since my preamps don't have XLR connection.
newbee
4,093 posts
 
OK. I'm going to assume that my comments were the confusing ones. Here is a simple method for locating your noise.

1) Turn on your amps only, but have them connected to the pre-amp. Any noise?

2) Assuming no, now turn on your pre-amp with volume minimized. Any noise now?

3) Assuming no, now with the source (like a CDP) turned on, but with Volume control minimized is there any noise now?

4)Assuming no, now with source turned on but not playing anything increase your volume control. You hear the noise now?

If the answer doesn't become obvious to you then, feed back with results and I'll tell you what I think might be involved.
espoverload OP
14 posts
 
I tried everything I could and it appears the noise is from amp or some signal it picks up. The noise is there even when the CD player and the preamp are off. I also tried stereo mode rather than mono with no luck. I even tried without biwiering and still the noise is there. Now even at listening volume levels the hiss is there and getting more anoying by the minute. Thanks
espoverload OP
14 posts
 
OK. It appears the amps have some noise (barely audible). The preamp, when turned on, picks up the noise and amplifies it even with the volume at zero. The higher the volume the higher the hissing noise. CD player has no effect on the noise. Thanks
ngjockey
1,042 posts
 
Suckered again.

Disconnect cable from TV. Any noise?
Turn off all dimmer switches ...
Try without RGPS ...
...
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