Preamp Noise with High-Efficiency Speakers

As you know, the noise issue becomes hypercritical when you have very high efficiency speakers.

Make sure no power cables are touching each other or any other cables. Cross at right angles with a few inches of space in between.

Usually it would be the input interconnects from source to preamp. You could probably test that by switching to a shorted unused input and seeing if the noise persists. Also make sure the shielding in the cables is oriented in the right direction. When in doubt, reverse them. (Make sure your cables are shielded.)

Get the cables up off the carpet if you have carpeting.

While it probably is the very high efficiency of your speakers there are pre-amps with low enough noise levels to make them silent, especially SS ones. What I suspect your problem might be is that the pre-amp has too much gain for your amp which has a high sensitivity. Most pre-amps typically have gain from 10db to 26db which may be too much. A pre-amp with zero gain might be the answer. With digital sources you really do not need added gain from your pre-amp (but this does not negate the other values of using a pre-amp). Think Placette or Wyred active units. Or, if you can deal with a cheap add-on resolution, insert a Rothwell fixed attenuator between the amp and pre-amp.

A remote possibility, easily to check, is a 60 cycle hum. Simply terminate the PC from your pre-amp with a cheater plug and see if it goes away. If it does you have sourced your problem if not your solution.

Hope that helps a bit.

Newbee nailed it. Nice post Newbee.

I assume that you've tried all the different amps, preamps, and cables using your AMR dac as the source. If you are getting the exact same problem with all of that equipment, the dac may be the problem. I know the problem doesn’t happen when you run it straight into the amp but that doesn’t rule it out. Aside from the volume control on the dac, it may have global gain settings as well. The gain from your dac plus the gain from your preamp may be too much. I can have the same problem with my Wadia. When I use it with my Wilson speakers, I have to open it up and lower the global gain using a row of dip switches Wadia gives you just for this reason.

I'm not saying this is definitely the case, but its definitely worth looking at. If it turns out that you don't have any global gain settings, try going from the fixed out to the variable out on your dac and lower the volume manually.

Good comments by the others. One additional thought:

By any chance have the preamps you have tried been located close to the DAC or the source, perhaps just above or below it or them in a rack? While is the power amp located several feet or more away from those components?

If so, it could be that the DAC and/or source are radiating digital noise into the preamp. If that seems like a possibility, try locating the preamp a few feet away from the other components.

Regards,
-- Al