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IC's and Humm

I hooked up another amplifier that I added to my system. My preamp has two pair of outputs. Before my system is dead quiet. The new amplifier runs quiet as I tried it running my main speakers. But when I try it with a secondary small speakers I get humm....so I tried switching the IC's from my monoblocks(NBS) to this stereo amp which was connected using some ($100) Monster IC's. The NBS are dead quiet and the Monsters produce a low audible hum. When using the monsters the humm also increases slightly when I turn the lights on. I think the problem is that I have run out of dedicated ports for this amp....so I use a nearby regular port. Sorry for the long description but I'm wondering is it just the IC or should I have a couple more dedicated ports installed. I run 2 pairs of monoblocks,preamp,dac,transport....and to get it dead quiet is like a combination to a safe....it must have a certain layout or I get humm and my tube amps are realy finicky about it.
wavetrader
wavetrader OP
260 posts
 
My preamp and amps do not support a balanced mode....just single ended....I tried a while ago running my preamp and dac on the same line with a conditioner....the sound was degraded. NBS advises their PC's direct to port.

Al....I will try running my subwoofer mono blocks thru one port and see what happens.....I plan to upgrade the Monster IC anyway as that is what's available now....If I get a quality shield IC and that fixes the Humm....is that ok or do I run the risk of some problems....

There must be many that run multiple dedicated ports....this problem can't be uncommon I would think. Is there a better configuration as to matching particular componets to ports....Amp-preamp....DAC-amp or amp-amp and so forth.

Roger
almarg's avatar
almarg
9,670 posts
 
Hi Roger,

I would think that if you install a different ic that fixes the problem, you should be all set. Probably what would be happening is that the different ic would have a lower shield resistance, which would essentially short out the ground offset between the components it is connected to, and thereby reduce the extraneous ground currents.

My own philosophy about power distribution is to connect everything in the system to the same dedicated ac outlet, that is isolated from everything else in the house (refrigerators, air conditioners, etc.). I do that to avoid the very type of problem that you are describing.

But I'm probably in the minority among those who focus seriously on power distribution. Most people put purely digital components on separate dedicated runs, to prevent cross-coupling of digital noise into analog signals. It's probably debatable as to whether a dac is a digital or an analog component. I would consider it to be analog, to prevent its outputs from being contaminated by noise from digital transports and other purely digital things.

Many people also put their power amps on separate dedicated runs, because of their large and fluctuating current requirements. But as you appear to have found, that creates the risk of ground offsets relative to the preamp.

I guess the bottom line is that some experimentation and trial and error tends to be necessary.

Regards,
-- Al
wavetrader OP
260 posts
 
Al thanks for all your help....I think I have a better understanding now...appreciated greatly.

Roger
wavetrader OP
260 posts
 
Just thought I would post this for reference

http://www.jensentransformers.com/an/an004.pdf
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