2. amps-preamps
  3. 130786-78412

Thinking of a new preamp and looking for advice...

So, I am currently running a BAT VK30 into a Parasound A21 to Golden Ear Triton 2 speakers.  Sources are a Sony Z1ES and a Linn LP12 to a Parasound JC3+ phono stage. Green Audioquest cables all around. Most of my listening is vinyl--lots of jazz and 70's-80's rock and female vocals. I love the sound of my system, but the BAT is very finicky about power, and I have a ground loop that I cannot find...It works fine at other locations, but has a hum in only the right channel in my listening room...It's driving me bananas!

I demoed a Sonic Frontiers LS1 and the ground loop was gone, but it didn't have the open airy sound that my BAT does.  I am looking into an Audio Research LS-27, and also a McIntosh C47.  My must haves for a new preamp are at least 2 balanced inputs and balanced outs, and a remote control.  I may like to stay with tubes, but I'm not opposed to SS either.  Price-wise my ceiling is around $4000.  I would love to here from anyone who has either of these preamps as to what they like or don't like about them.  I am also open to suggestions. 

Thanks for your input.

128x128jptenberg1
Ag insider logo xs@2x
cleeds
5,944 posts
 
jptenberg1
I have a ground loop that I cannot find...It works fine at other locations, but has a hum in only the right channel in my listening room...
What makes you certain that the cause of the hum is a ground loop? Typically, a ground loop causes hum in both channels. Have you tried swapping cables from left to right to ascertain the problem isn't in the cable itself?
jmcgrogan2's avatar
jmcgrogan2
6,346 posts
 
Typically, a ground loop causes hum in both channels.

I have had a ground loop hum in one channel before. It can be very frustrating. I tried changing cables, cords, etc. It came and went for no apparent reason. 
The only fix was when I unplugged my cable F Type connector from the cable box and plugged it back in again, the hum was gone for good. I was planning on trying a Jensen Isolator, but didn't need it.

I didn't suspect this because the TV and video system is on a different circuit altogether. Ground loop hums are strange animals.
fsonicsmith's avatar
fsonicsmith
948 posts
 
I too agree with jmcgrogan2. I recently upgraded my preamp from an old Audioprism Mantissa to an ARC Ref 6. I have a Manley Steelhead and as much as I love it, ever since getting the Steelhead I have a ground loop that goes away if I switch back to my Simaudio Moon LP5.3. The Ref 6 sounds amazing too but it did not make my ground loop go away. In fact, it is now slightly worse. You need to solve your ground loop issue first. 
jptenberg1's avatar
jptenberg1 OP
3 posts
 

Thanks for the replies so far...So let me go into more detail about my ground loop.

It is only in the right channel-the left is dead quiet. I have swapped all interconnects and speaker cables and is has no effect. (well when switching interconnects from right to left to the amp, the hum changes sides as one would expect) I have tried both balanced and SE outputs from pre to amp.

I have unplugged all sources from the preamp and it goes away. As soon as I connect a source cable to any of the right channel inputs (either balanced or SE) the hum reappears. As I connect more sources to the preamp, the hum gets louder, so it appears to be a cumulative effect. However, the hum is at a constant level and does not get louder or softer with changes in the volume.

I sent the unit back to BAT after talking to Victor on an extensive phonecall and many e-mails. He gave the unit a thourough going over and could not reproduce any hum and sent it back with a clean bill of health. I brought it into my local audio dealer and had their repair guru put it on the test bench and could not reproduce any hum.

I have tried ungrounding all source components as well as preamp and amp. I have tried running a ground wire to all components. I have tried the preamp on another circuit. I have tried plugging it straight into the wall both on the same and other circuits. I have tried the Jensen ground loop isloators--both on balanced and SE between the pre and amp. Currently, all gear is running from a Furman outlet strip on a dedicated 20 amp line. I have also tried with a Monster reference 7000 power conditioner.

I have also switched the tubes from right to left channel, and swapped in a whole different set of tubes.

When I demoed another preamp from my local dealer (the Sonic Frontiers SF1) the hum dissappeared.

So, any other advice on ground loops would be greatly appreciated.

Ag insider logo xs@2x
cleeds
5,944 posts
 
I am still not convinced that this is a ground loop, especially because you report that the Jensen xformers didn't resolve the problem.

Here's what I suggest: Connect to your preamp a battery operated source, such as an iPod or portable radio, using a cable you've already proven is not defective. If the result produces hum, your problem is something other than a ground loop.
More to discover