Chasing an Elusive Hum

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Rick Cornish
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Re: Chasing an Elusive Hum

Post by Rick Cornish »

Thanks, Mike O. I'm leaning towards finding a used audiophile-oriented amp. Bryston (as you suggested), Anthem, etc. 150w+ per channel into 4 ohms. Hello, eBay.
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Phil O
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Re: Chasing an Elusive Hum

Post by Phil O »

It bothers me that your RA-150 checked out fine at Alesis. I can't imagine they would knowingly send it back to you with a problem. Maybe it IS fine. I think the suggestion of taking it to your cousin's house was a good one. Perhaps there is a power line problem at your location and the Alesis amp is just more susceptible to it. Find out for sure if there's a problem with it before buying a new one. Just thinkin' out loud here. :?

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Re: Chasing an Elusive Hum

Post by mikehalloran »

I agree with Phil that you still want to eliminate the line as your source of noise.

Something to watch for is an old Lexicon NT 212. It's the Bryson 3Bst (120W @ 8 / 200W @ 4 Ohms). The Lexicon 225 is the Bryston 4Bst (250 @ 8 / 400W @ 4 Ohms).

The other Lexington NT/Bryston amps were the 312 (5Bst) and 412 (8Bst) 3 and 4 channel versions of the 212/3Bst The NT 501 is an 800W mono amp but I forget the Bryston model.

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Re: Chasing an Elusive Hum

Post by guitardood »

Phil O wrote:Perhaps there is a power line problem at your location and the Alesis amp is just more susceptible to it. Find out for sure if there's a problem with it before buying a new one. Just thinkin' out loud here. :?

Phil
I was going to suggest this as well. FWIW, my Yamaha S-80 keyboard had a bad hum problem and I tried everything, until finally, just for shits and giggles, I modded a power cord (atypical NEMA 5-15P to C13) and reversed the blade wires. Hum disappeared. None of my other gear had a problem and the outlets were definitely wired correctly. Something to try.
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Re: Chasing an Elusive Hum

Post by Rick Cornish »

Thanks, Phil and Guitardood. I agree with HCMarcus's test suggestion. Unfortunately, I'm in a very remote area......no "cousins" nearby. I'll find some other way to test it this week.

Called a hifi shop I know down in the Twin Cities and found a used Acurus A 250 for $500, which could be interesting. Would rather have a Bryston, Anthem, Carver or Hafler, if I could find the right one in my price range.
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Re: Chasing an Elusive Hum

Post by HCMarkus »

guitardood wrote:FWIW, my Yamaha S-80 keyboard had a bad hum problem and I tried everything, until finally, just for shits and giggles, I modded a power cord (atypical NEMA 5-15P to C13) and reversed the blade wires. Hum disappeared. None of my other gear had a problem and the outlets were definitely wired correctly. Something to try.
Yamaha keyboards connected via USB exhibit ground loop issues, such as you experienced. I have solved that problem by modifying a USB cable - cut the USB ground wire.

Modifying a polarized plug to allow reversal can be very dangerous. That ON OFF switch still turns off the device, but the device is still hot and hazardous, with 120 volt waiting to bite the unsuspecting. Reversal of polarity is way more dangerous than removing or lifting the ground (plug third prong).
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Re: Chasing an Elusive Hum

Post by guitardood »

HCMarkus wrote:
guitardood wrote:FWIW, my Yamaha S-80 keyboard had a bad hum problem and I tried everything, until finally, just for shits and giggles, I modded a power cord (atypical NEMA 5-15P to C13) and reversed the blade wires. Hum disappeared. None of my other gear had a problem and the outlets were definitely wired correctly. Something to try.
Yamaha keyboards connected via USB exhibit ground loop issues, such as you experienced. I have solved that problem by modifying a USB cable - cut the USB ground wire.

Modifying a polarized plug to allow reversal can be very dangerous. That ON OFF switch still turns off the device, but the device is still hot and hazardous, with 120 volt waiting to bite the unsuspecting. Reversal of polarity is way more dangerous than removing or lifting the ground (plug third prong).
Wasn't connected via USB, just MIDI & audio. Ground lifts didn't work, only think that got rid of the hum was reverse polarity. I've got a friend with a Yamaha Motif with exactly same issue and same solution. The Motif Rack uses a wall-wart and doesn't have the problem. Haven't got shocked or fried anything yet (knocking on every piece of faux wood in my vicinity, LOL!)
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Re: Chasing an Elusive Hum

Post by mikehalloran »

My house is 2-wire, no ground. I've reversed polarity a few times to reduce hum. That opens a real can of worms when dealing with a power amp -- if that fixes it, I'd replace the amp.

That said, high end amplifiers are generally very good at diminishing noise that plagues lesser quality products.

In my case, I'd try to ascertain if line noise is the problem or if the amp is the problem. I still think a better amp is the solution based on a thorough description of the problem. I could be wrong...
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Re: Chasing an Elusive Hum

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mikehalloran wrote:I still think a better amp is the solution based on a thorough description of the problem. I could be wrong...
I'm inclined to agree. I knew I was taking a risk with the Alesis....they're not known for building high-end gear, but the published specs met my needs and the price was right.

I thought I'd crossed amp issues off the list when I sent it in. Subject to verification, I am inclined to say this is the problem. If so, either the Alesis tech missed the issue or their own spec is such that the hum I'm getting is considered to be within tolerance. I'll pull the amp this afternoon and plug one channel of my home theater speakers into in tonight. That should prove something.
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Re: Chasing an Elusive Hum

Post by monkey man »

EMRR wrote:The earliest Alesis power amps all had some obvious residual hum, I haven't heard that model.
Sorry I'm so late to the "party", Rick.

I ran an RA100 for several years into Alesis Monitor Ones via Monster cables and had the same issue.

Obvious question based upon my experience with the lower-powered model:
Does the hum stop when you touch the amp's chassis? Have you tried this?

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Re: Chasing an Elusive Hum

Post by Phil O »

Hmm. I've had an RA100 for many years. It currently powers the speakers connected to my TV. Quiet as a monkey...err mouse. It's been a great amp. No noticeable hum.

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Re: Chasing an Elusive Hum

Post by monkey man »

Maybe you got lucky, Phil?

We had a character called Lucky Phil in drink-driving ads here in Jungleville for some years.

Here he is:

https://www.youtube.com/watch?v=aoy7ChrynNw

Note that the policeman sounds like Crocodile Dundee. LOL

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Re: Chasing an Elusive Hum

Post by Phil O »

Could be. Or maybe you got unlucky. Dunno. But, I make it a point to never drive while I'm drinking. The driving part is too distracting.

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Re: Chasing an Elusive Hum

Post by Rick Cornish »

Amp tested outside my studio this morning: Plugged the center channel speaker from my home theater into one channel with no input and the pots all the way down: Same hum present. So the Alesis is guilty as charged and I'm officially shopping for a new amp. Given that the Westlakes are rated at IEC 80W short/200W long and 4 ohms nominal (2 ohms minimum), this is becoming a challenge.
http://www.westlakeaudio.com/Speakers/P ... bbsm4.html

The hifi stuff I've looked at isn't rated below 8 ohms and many don't have balanced inputs. Bruce Swedien drives his with Electrocompaniet monoblocks (which run $4800 a piece). That's about 10x my budget. So, the search continues....
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Re: Chasing an Elusive Hum

Post by mikehalloran »

http://www.ebay.com/itm/Bryston-Limited ... 2354cdfc18

See if he'll take a grand.

http://www.ebay.com/sch/i.html?_odkw=br ... 2&_sacat=0

3 channel version of the same amp might not get bids if no one understands what it is. You can use two channels.
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