2. amps-preamps
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1st setup failed, need advice for B&W N805 amp

Okay, so my current components are failing me. I have a Peachtree Decco and Emotiva UPA-2 (just received this, motive for my post).

I was previously using only the Decco to power the N805's... my source was my PC connected via USB. So the Decco functioned as a DAC/preamp/amp and all was fine... except two things. 1st, although the room is small, I could use a bit more power. 2nd, I noticed the left channel on the Decco was a bit louder than the right. At first I thought it was the speakers, but I tried another set and same thing. It also doesn't have good balance at low volumes.

So I bought the Emotiva UPA-2. Fast forward to today. I setup the UPA-2, turned the power on, and to my disgust - there was a very loud/audible humming which corresponded with the output level on the UPA-2. At first I thought it was my generic monoprice cable causing the problem. But then I tried connecting both my TV and iPod straight to the UPA-2 and... the humming was gone. Could it be possible that UPA-2 doesn't work well with a tube preamp? Either way, I disconnected the thing and I'm back to using the Decco only.

I really need some advice. First, is there anything I should try before giving up on the Decco + UPA-2? And second, if it came down to it, I'd rather keep the Decco and look for a new power amp. I'm trying to keep the price under $500 and used would be okay. I don't need anything crazy, the room is only about 12x12. Any suggestions would be greatly appreciated... thanks
koven
8 responses Add your response
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knownothing
1,543 posts
 
That is a bummer. I would contact Signal Path and ask them about potential compatibility issues with the Emotiva. http://signalpathint.com/index.php/Contact-Us/Contacts/ It may very well be an impedance mismatch between Pre (Output Impedance???) and amp (Input Impedance: 47K ohm).

I have had similar volume mismatching issues with an int. amp that does not have a quality volume pot and it can be frustrating. Another amp wont fix this, as it sounds like a problem inherent with your Decco. I would ask Signal Path about that too - but the ultimate solution may be a different preamp and DAC.

Something like a Benchmark DAC1 PRE ($).

Or in a more modest price range - preamps like these:

Antique Sound - Wave Line-One-Vacuum Tube Preamplifier
Parasound - Zpre2 Audio/Video Preamplifier
Emotiva - USP-1 Stereo Preamplifier

and DAC's like these:

Musical Fidelity - V-DAC Digital to Analog Converter
Cambridge - Dac Magic Digital to Analog Converter

Good luck!
blindjim
3,092 posts
 
Hum came after installing the emotiva amp... right?

first try using a cheater plug to lift the ground off the new amp... $0.75.

Second try plugging the amp into a ckt the preamp is not on. Same with other components.

Last thing I can think of is turning the EMotiva amp's plug over (if that's doable) and pluggin it in that way.

I'd try to keep my cable box off the same ckt as the amp.

Good luck.
rwwear
2,851 posts
 
Disconnect the coax/cable from your TV and see if the hum goes away. You may need an isolator for the cable TV.
stanwal's avatar
stanwal
3,147 posts
 
If all else fails NAD will drive the 805s. I have a 3140 driving a pair in the system I set up in my wife's craft room which is a little bigger. But try everything else first.
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knownothing
1,543 posts
 
I have been thinking about Blindjim's comments and I think he might be seeing something. I have heard about ground wires sometimes setting up current loops in audio systems that cause audible hum. PS Audio actually makes the ground pin removable on some/all of their power cables to address just this issue. His $0.75 hardware store and/or "move the plug" solutions could be very cost and sound quality effective.
realhifi
159 posts
 
Why why why? To think that a $500 amplifier tacked onto the back of a Decco should be able to do justice to a highly regarded $2,800 stand mounted monitor speaker seems a bit optimistic. In my experience a like priced or higher piece (or pieces) of electronics is what is needed for those wonderful little speakers to really shine. If you look at any Brit mag you can easily see when system recommendations are made that the budget for the source and electronics always exceeds the cost of the speakers.
The idea is simple....whatever you put into the speakers
will be what comes out. The better the source, the better the sound.

NAD....not your best choice.
jt3
33 posts
 
Maybe try a Cambridge Audio 650 integrated?

I am listening to a 550 currently, and wow this little amp is surprising me. Don't be fooled by the price.
lewinskih01
907 posts
 
Koven,

I'm with the first posters: don't assume it's how the electronics are. Follow their leads. Leave component changes for last.

On my upgrade path I've had B&W 804S connected to relatively cheap Rotel components and, while the sound wasn't the best the speakers could reproduce, the components didn't have issues like humm.

BTW, I was thinking about a Decco for my brother, so I'm interested in your experience.

Good luck!
Horacio
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