Chasing an Elusive Hum

[Rick Cornish]

Hi........
To any studio nerds who'd care to review this tome, I would gladly entertain your suggestions for reducing or eliminating hum in one set of studio monitors.

Here's the story…
= I'm working in my home studio, which is in a new building I built for this purpose last year. The building is located in an extremely remote area, miles from high-voltage power lines, welding shops, industrial parks or the like.
= I have three sets of monitors: Genelec 1032As (with or without a 1092 sub), Westlake BBSM-4s and a Berhitone.
= I’m experiencing 60Hz hum in ONLY my BBSM4s (my self-powered Genelecs are clean as a whistle). These are my only monitors that are not self-powered.
= I have a Alesis RA150 amp driving my Westlake BBSM-4s
= The amp is plugged into the output of my Apogee Quartet (balanced cables)
= The hum is present, even with no input plugged into the amp and does not change when inputs are present (hence, changing cables, adding a hum bucker, etc. are not relevant)
= I am running my entire system off a single, dedicated AC circuit. My building was purpose-built for my studio with a “home run” or “hospital ground” that goes back to building earth from the AC outlet where I power my audio gear. The power to the building was trenched in direct from the pole and not jumpered off my home. No other electrical items (lights, etc.) are powered from the circuit I use for my audio gear.
= I am running high-end speaker cables from the amp to the Westlakes in the bi-wire configuration recommended by the manufacturer (http://www.westlakeaudio.com/Speakers/M ... ction.html, http://en.wikipedia.org/wiki/Bi-wiring)

I have tried all the following with no effect…
= Lifting the ground on the amp
= Powering the amp direct from the wall (instead of from a power supply)—lifted or grounded
= Powering the amp direct a separate wall outlet from the rest of my system—lifted or grounded= Powering the amp from three different conditioning power supplies—lifted or grounded
= Changing speaker cables (non-bi-wire)
= Physically re-locating the amp in the room
= Re-routing the power cable to the amp (power and audio cables are running through separate raceways, speaker cables go direct from the amp to the speakers and only cross other cables at right angles)
= Tried different power cables to the amp
= Turning off the lights in the room
= Turning off the breakers for everything in my building except the line that powers my system (i.e. no power to anything else in the building—eliminating the possibility of interference from other electrical sources)
= I even sent the amp in to Alesis for service evaluation and it checked out fine

Again, the hum is present even with no input to the amp, so the usual suspects of ground loops, bad cables, etc. are ruled out… though I have checked all those issues, just the same.

Though I don't claim to be a studio designer or electrical engineer, I have built a few studios and worked in studios all over the country, so I'm not a complete idiot on this, but I've now tried everything I know. Given the above, the only variable that seems to be left (even though Alesis support gave my RA150 a clean bill of health) is to try out another amp.



I would love it if someone out there could point out something obvious (or less-obvious) I've missed.

Thanks!

[HCMarkus]

If the hum has been consistent across all of your testing, your Alesis amp is almost certainly the problem itself. Take the amp to your cousin's house and hook it up with any ol' passive speakers… Got Hum? Get New Amp.

[Michael Canavan]

If the hum has been consistent across all of your testing, your Alesis amp is almost certainly the problem itself. Take the amp to your cousin's house and hook it up with any ol' passive speakers… Got Hum? Get New Amp.

Agreed.
This is the kicker here:

the hum is present even with no input to the amp,

Not saying it's not possible, but I've never had that be the case if it was a grounding loop. Sounds like the amp is acting up and Alesis repair dropped the ball.

[Rick Cornish]

If the hum has been consistent across all of your testing, your Alesis amp is almost certainly the problem itself. Take the amp to your cousin's house and hook it up with any ol' passive speakers… Got Hum? Get New Amp.

Agreed.

Thanks, and agree. Methinks it's time to try out a new amp.

[mikehalloran]

Dirty power or defective amp.

If the amp is not the problem, you may need to go to a true balanced power supply. These have -60V on one line and +60V on the other. This is not "power conditioning". Furman and others make these. Not cheap ($1500-$4,000)nor are they energy efficient (26W just plugged it) but sometimes, that's the only fix. A single coil Fender running into a vintage tube amp plugged into one of these has zero hum.

http://www.furmansound.com/product.php? ... d=P-2400IT

Try a different amp first.

[EMRR]

The earliest Alesis power amps all had some obvious residual hum, I haven't heard that model.

The rest of the 'no input connected' test; does that volume control on the amp affect the hum? I'm going to bet not.

Another vote for the amp as problem. As said, take it elsewhere and try it with a different system.

Alesis customer service may be stonewalling, it seems to be a common tactic in general. There should be a published residual noise / hum spec, and it should be verifiable. If the spec sucks and it meets it, well....time for a different amp.

[Rick Cornish]

Thanks, Doug and Mike O. Hum persists with no input and volume potted down, so I'm saying it's the amp.

Now—for my Westlakes (http://www.westlakeaudio.com/Speakers/P ... bbsm4.html) do I go with something similarly priced to the Alesis (ART, for example) or wait until I can afford to spring for something like an Amphion Amp500? Big difference in price.

(Wish I would have held on to my old Anthem!)

What do you guys think would make a good amp to rive my BBSM4s?

[mikehalloran]

Well, Westlake users tend to favor Bryston.

The only negative I have ever heard about the brand is price and there are many of them used on eBay.

Treat yourself to something excellent.

[James Steele]

Treat yourself to something excellent.

I guess I'll withhold my lowly Hafler recommendation. I have an old school P3000 Trans Nova I originally got for my NS10Ms (which have been on PERPETUAL LOAN to a friend... *cough*... don't get me started!) and I'm using it now for some even older-school JBL 4410s and seems to do the job nicely.

[mikehalloran]

Treat yourself to something excellent.

I guess I'll withhold my lowly Hafler recommendation. I have an old school P3000 Trans Nova I originally got for my NS10Ms (which have been on PERPETUAL LOAN to a friend... *cough*... don't get me started!) and I'm using it now for some even older-school JBL 4410s and seems to do the job nicely.

The only reason I didn't bring up Hafler is that they are out of business ... except it seems that someone is resurrecting the brand. http://www.hafler.com. I can't believe what used ones are going for on eBay and Craigslist -- there are bargains to be had.

Speaking of Hafler, I have an old 180W side Dynaco in the basement where analog goes to die. I've the matching preamp, too.

[HCMarkus]

Comparing the distortion introduced by transducers with that produced by a reasonably modern audio amplifier (several orders of magnitude lower) makes one wonder if just about any amp of adequate power (that doesn't hum) might not do a fine job…

Buy-Wire: Must confess, I don't buy the bi-wire thing. Sorry. It has religious overtones (which are inaudible, btw). Totally different beast than bi-amping.

[James Steele]

Shame they (Hafler) went under. Those were decent for the money.

[Rick Cornish]

Understand the controversy on the bi-wire configuration. Doesn't make a lot of sense to me, logically, but if Glen Phoenix (Westlake) says to use bi-wire, that's what I'll do.

Yesterday, my guy at Sweetwater lamented the decline in options for studio monitor amplification. There's low-end stuff (like my humming Alesis) and then it jumps significantly (to $1800 for Amphion). And of course, there's the crazy high-end amps guys like Bruce Swedien use (Electrocompaniet monoblocks at $4800 each). What's the best option for $500-1k?

[mikehalloran]

The problem with older amps is that components deteriorate over time. An old Dynaco, Carver, Hafler etc. is a great amp but may need servicing -- not cheap but when done by a knowledgeable tech, can be made as new or even better than new.

See if these guys are still around and it's not some web site that won't die. http://carvermk2.com/default.htm

If so, find a used m500t on eBay -- there are a few in the $400-550 range -- and have them hot rod it. Should run just under a grand.

One reason I recommended finding a used Bryston is that, beginning 2006, they instituted their 20 year warranty. Although new are quite expensive now, they weren't so expensive back then. Ten year old units under a grand do show up and all reports are that they do hold up.

[mikehalloran]

There's always Carvin. If you don't like it, they have a no questions asked return policy. Like everyone else in the low price range they've gone Class D -- how that will work with your Westlakes is something I don't know but it doesn't cost that much to try and you might like the results.

http://www.carvinaudio.com/collections/power-amplifiers

I've been using their gear for over 35 years and everything still works but haven't tried their current line of power amplifiers.