Speaker hum question?

[Jeff Mayer]

Hi guys,

I am getting speaker hum with my A51 hooked up to a Bel Canto PRe2 channel preamp through RCA. I'm not sure how to alleviate this problem. The hum is audible from 6 feet away. When I disconnect the preamp the hum disappears (except for a small hum which is audible with my ear very close to the speaker). Should I run balanced connectors?? Thanks a lot. :roll:

Jeff

[Peter Nielsen]

Try this: Disconnect everything from the Bel Canto, except for the A51 connections. Do you still hear a hum? If not, then connect all devices one by one to see which one it is that generates the hum.

Usually it's the Cable box that is the culprit. A simple isolation device on the cable will solve the problem.

Peter

[Jeff Mayer]

Thank you Peter..

Unfortunately the connection chain is very simple and I am still experiencing the problem. I have a Disc player connected RCA to the Bel Canto and the Bel Canto to the A51. (No cable box) What is strange is that when I unplug the Bel Canto the hum goes away. About 10 seconds after I pull the plug I hear a faint electrical pulse (discharge) through the speaker and the hum subsides. All units are connected to the same outlet. BTW - The hum is by no means overpowering, it's just noticeable when everything is quiet even from 8 feet away. I don't have this problem connecting a receiver to the amp. I am perplexed. Might it be an issue that the Pre is only connecting to the first 2 channels of the amp?? No other connections to the amp at the moment.

Jeff

[blownrx7]

Sounds like a classic ground loop. Try using a cheater plug (a two prong adapter on your three prong plug on the Bel Canto or the A51) OR, try running a simple wire from a bare spot (or ground lug if you have one) on the Bel Canto chassis to a bare spot on the A51 chassis (under one of the chassis screws is usually a good area that is unpainted/uncoated).

[Peter Nielsen]

Sounds like a classic ground loop.

No, it does not.

Note that he says it still hums AFTER he disconnects the preamp from the wall. The hum can be heard for 10 seconds until the Bel Canto runs out of juice (until its electrolytic capacitors are discharged).

It sounds like the A51 inputs are a little too sensitive for the Bel Canto, with the effect that the noise in Bel Canto's outputs can be heard. Some kind of attenuators (like this or this) between the A51 and the Bel Canto will probably alleviate the problem...

Oh, there is another possibility: How close to the A51 is the Bel Canto? Try to put some distance (1 foot or more) between the units to see if that helps.

Peter

[Jeff Mayer]

Thanks guys for your help!

Actually as it turns out you're both correct.
I suspected a ground loop and that appears to have been the problem (mostly). A cheater plug on the preamp has diminshed the hum to the point where it's not an issue. (The plug seems to have a little more effect on the Preamp end.) There is still a bit more hum with the Pre connected than not (only audible from 2 feet) and I think Peter is correct that the amp inputs are slightly too sensitive for the Bel Canto and may be picking up a bit of output noise. Thanks for the links, Peter. I might invest in oneof those attenuators anyway. Just one more question - even though I'll be using a short run (6 feet) - any advantage to balanced connectors? The Bel Canto outputs are fully balanced. Oh..BTW, I've got the A51 sitting on the floor and the Preamp in a shelf 10 inches away. Might try monkeying with that now...

[Peter Nielsen]

Jeff, balanced connections (XLR) may possibly make the problem worse, due to the +4dB gain. However, if you have a pair of XLR cables you could always give it a try. (Who knows, maybe the Bel Canto XLR outputs are quieter than its RCAs?)

Peter

[Jeff Mayer]

(Who knows, maybe the Bel Canto XLR outputs are quieter than its RCAs?)

I will find out soon since I ordered inexpensive XLR cables...
The Bel Canto's RCA output is definitely producing a little noise in the form of hiss (only noticeable within a few feet of the speaker). I am using good interconnects. Strange since every review/account of this product touts its dead quiet output stage. Maybe I'm being to finicky.
Jeff

[Vince Helm]

hum problems

Hello Jeff,

I had a hum problem with my Halo gear. Two things that worked for me were making sure the amp and preamp are plugged into the same A/C outlet (I have two dedicated lines) or power conditioner. The cheater plug works but a power cable from PS Audio works very well as it is better than the stock cord and includes a removeable ground pin. You can get great deals on PS Audio cables from Audio Advisor as several of their top of the line power cables are on closeout to make room for new models. Oh, one more thing... If your amp is on carpet you may be getting a static built-up in the amp or cables leading to the amp and speakers. Make sure amp and cables are not touching the carpet.

Best of luck.
Vince

[Chris D]

Hey, Vince, welcome to the Guide and Club Parasound! :banana:

[Jeff Mayer]

Thanks Vince for the heads up.
The A51 has been sitting on an oriental rug since I bought it almost a year ago. Every cable going in an out of it is making contact with the rug too. Interesting. I didn't know these things could be so sensitive..
Power cable upgrade... You think it makes a difference? Thanks,
Jeff

[Vince Helm]

You might be ok with the rug. Is it made from natural fibers or synthetic? Wool is usually OK while man made fibers will cause static to build up. That may or may not add to the reason for the hum. My relationship with power cords has become a love/hate thing. Mostly I love them. It can take a lot of time and effort.

Good Luck!!
Vince

[Peter Nielsen]

Vince,

What have you done to the rest of the power distribution system? The cable between the equipment and the wall is just a few feet. What about all that other distance to the power source? What wall outlets are you using? What type of wire are you running from the outlet to the main breaker panel? Do you have cryogenically treated breakers in the main panel? What wire runs from your house to the distribution transformer?... :B

BTW, I agree wholeheartedly about the PS Audio power cables. The removable ground pin is an awesome idea, and they are reasonably priced and VERY good looking. IMHO they are worth it for the looks, good quality, and knowing that the connection is well done. However, IMHO they won't give you better sound or anything like that unless something is flawed with the original cable...

Peter

[Jeff Mayer]

XLR, RCA...both sound fantastic to me. IMHO XLR sounds a bit more etched and detailed but also leaner. RCA sounds fuller and more involving somehow. Could just be a difference of new XLR's vs. broken in RCA cables. Who knows. I'm going to run balanced for a while and see what happens. The noise problem seems to have dissipated. Don't really know how or why that is either. XLR does put out a slight bit more hiss than XLR (only noticeable within a foot or two of the speaker with everything quiet.)

BTW - The A51 is a brilliant piece of gear. It's got it all - including musicality and warmth. Didn't know what it could do until I got a good preamp. (I had been using an onkyo receiver.) Gentlemen - I feel like I've made it to the top. Just wish I didn't know there was a JC-1 out there. :lol:

Jeff

[Chris D]

Good stuff, Jeff. :T