[chumaj001]

Hello,

I have couple of questions about amplifier noise. I have old but high end class A Technics SE-A5 power amp and SU-A6 MK2 pre amp, connected with analog shielded cables to my HTPC Asus Xonar ST sound card. My speakers are quite good high end Quadral Wotan MkV.


My pre amp volume level is set to about 1/4 of its maximum scale all the time and I am controling the volume of music on the PC.


Thing is, that when I put my ear VERY CLOSE to the speakers, I hear some quiet noise in the high frequency range. Its not audible from 1m or more, so its very quiet, but its there. When I turn volume on the pre amp to the max while not playing music, the noise is louder and I also could hear some RFI/EMI interferences. They are very quiet, but audible. This is of course extreme situation, cause if I would try to play some music at this volume level, it would probably destroyed the building

But question is: is this normal with all the amplifiers? Is there allways some audible noise or interferences from up close when the volume is at high levels, or is it because something is wrong.


My sound card has S/N ratio over 125db and my power amp as well.


Its not a problem when listening to music, I am just curious if its normal even with todays high end power amps, or if some internal parts in my amp need replacement because they are very old.


Thanks to anyone for answers.

 

[Glimmie]

A computer is full of RFI internally. So any sound card inside the computer case will pick up this noise. This is quite normal.


If you want a quiet computer audio system you need to only have digital audio I/O from the computer and use an external A/D and D/A converter.

 

[chumaj001]

I meant, that i hear the very small (white?) noise even with PC turned off - its produced by the amplifier. It could be heard only from very close (1feet) or with volume to the max. I assume, that any amplifier will produce some kind of such noise, but question is, how much is "normal" or within the limit. The same goes for interferences it could be heard only when volume is turned to 3/4 of its maximum. An I repeat that my sound card and amplifier shoudl both have S/N ratio over 125 and very very low THD.

 

[duvetyne]



Quote:
But question is: is this normal with all the amplifiers?

Yes,

Submerge all of your electronics in liquid helium to reduce the noise

 

[jneutron]



Quote:
Originally Posted by duvetyne /forum/post/18197833


Yes,

Submerge all of your electronics in liquid helium to reduce the noise

Sheesh..


The diodes stop conducting at 4.5K and go into forward blocking...


C'mon, everybody knows that!..

Cheers, John

 

[duvetyne]

It's a good thing that its critical point is over 5K then...don't you think?

 

[Gizmologist]

What about the magical mystical uber expensive power cables? They are supposed to dispatch the noise to NeverNever Land.

 

[chumaj001]

So (translated to normal english) even most expensive high end amplifiers will have noise during silence at high volumes or at normal volumes with ear close to the speaker?

 

[A9X-308]



Quote:
Originally Posted by Glimmie /forum/post/18196985


A computer is full of RFI internally. So any sound card inside the computer case will pick up this noise. This is quite normal.


If you want a quiet computer audio system you need to only have digital audio I/O from the computer and use an external A/D and D/A converter.

I hear this all the time, and I don't agree in many cases; the measurements don't bear it out for decent cards.

From John Atwood's Clarisonus blog .


I have a test on the Xonar bookmarked somewhere, and I recall it was very good too. If I can find it I'll post it.

 

[Glimmie]



Quote:
Originally Posted by A9X-308 /forum/post/18201600


I hear this all the time, and I don't agree in many cases; the measurements don't bear it out for decent cards.

From John Atwood's Clarisonus blog .


I have a test on the Xonar bookmarked somewhere, and I recall it was very good too. If I can find it I'll post it.

Sure you can shield the card and some computers are better than others with internal RFI. This is just my opinion and advice. By going to digital I/O you avoid any issues. However this is a much more costly approach.

 

[A9X-308]



Quote:
Originally Posted by Glimmie /forum/post/18204141


Sure you can shield the card and some computers are better than others with internal RFI. This is just my opinion and advice. By going to digital I/O you avoid any issues. However this is a much more costly approach.

They are simply PCI cards plugged into the machine. No noise issues. I use my 24192 with a high eff system and it's silent. I also use it as my measurement card.


The whole 'it's in the PC so it must be noisy' is BS.

 

[Speedskater]

I think that this type of problem is often a stage-gain (or is it gain-stage) problem. That is, each and every stage in the system should run out of head-room at about the same level. Also just hooking a power amplifier with lots of signal gain to very efficient speaker can cause this problem.

 

[duvetyne]

All electronics produce thermal noise.