2. amps-preamps
  3. 1292785967

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

Showing 4 responses by newbee

newbee
4,093 posts
 
I'm not sure the source of the hiss you hear is actually from your amp.

Consider that when turned on an amp is at full power all of the time. It's noise floor, to the extent it is evident, will be constant. It will not be affected by the position of the volume control if your preamp is off. What you hear with the pre-amp off probably represents the noise floor of your amp.

When you turn your preamp on it is also at full power as seen by your amp, even with the volume control minimized. The amplifying stage of a pre-amp is NOT affected by the volume control which preceeds it in the signal path. If you hear a hiss now, that wasn't there before, you are hearing the noise floor of the preamp.

If you have no noise until you turn on (and select) a source and you then note that the noise increases with rotation of the volume control, you are hearing the noise floor of the source (or the recording playing on the source). All your volume control affects is the level of the gain from the source before that signal reaches the amplification section of the preamp. It does not actually control the preamp's output gain which is constant.

That might explain why your hiss varies with movements of the volume control and exists even when you are using different preamps.

Something to think about..........
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.
newbee
4,093 posts
 
I agree with Ngjockey, I think your source of noise is external to your components. Sounds like your PC's/IC's are picking up some RFI.
newbee
4,093 posts
 
Maybe it is time to think about your source of electricity. What other things do you have on the same line? I have both dedicated lines as well as regular outlets in my audio room. While I do not have an RFI problem such as yours, the dedicated lines are definitely quieter than than the regular outlets. FWIW.
More to discover