AudioCircle
Industry Circles => Well Tempered Lab => Topic started by: mick wolfe on 22 Jul 2012, 01:13 am
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I'm getting a persistent "hum" mostly weighted in the left channel. With volume advanced to normal listening levels, the hum is only evident between cuts and at the end of each record.....but it's still there. Everything is properly set up and several different phono cables have been tried. Now here's the interesting part.....when I leave everything on with the volume advanced to the point where the hum is quite evident and unplug the walwart, all forms of hum disappear. What's a mother to do? If the outboard power supply is the answer, I'm all over it. If not. any ideas? Thx .........Mick
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What gear?
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Also, check to make sure the tonearm plug is well seated.
Then switch cartridge connections to see if it changes channels.
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Thx for your response. Yes, I've checked all the usual suspects. This is the only area (
"hum" )where my previous Nottingham set-up has the Amadeus beat. The hum in the case of the Nottingham was at a lower volume and equal in both left and right channels. I know from dealing with phono playback thru the years that hum will be present somewhere ( as I've always used vintage CJ or A.I. single chassis pre-amps ).....just a matter of where and at what volume. Another area that's working against me is my vintage CJ Prem. 3 pre-amp which of course has the phono section/ line section in the same chassis. I'll hasten to add that even though the hum is a bit louder, ( and left handed) it's not nearly disturbing enough to start making wholesale system changes. Just in the end wondering if the walwart is the culprit and if the WT outboard PS would cure the problem.
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You should not be having hum of any sort, regardless of gear. Tube rush yes, not hum...
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What cartridge?
Since the hum is greater as your cartridge approaches the center of the record then it would appear it is caused by an interaction between your cartridge and something stationery.
I was once advised not to use a Grado on my Technics SL-10 due to their susceptibility to hum, especially near the middle of the record on a DD deck. In that case the motor was located in the centre so the potential cause was obvious. In your case the last tracks are still when the cartridge is closest to the motor but you would have thought it would be too far away to be a big issue.
Does the hum keep going irrespective of whether the motor is running?
Do you have access to another wall wart of the same voltage?
Are there any transformers directly below the centre/left rear of your turntable? You can get interactions between components due to magnetic fields and microphonics. I imagine that in the worst cases they might show up as hum.
Steve
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The position of the arm/cart. has no effect on the hum level. Hum is only noticeable when the music stops between cuts or at the record's end. As I've said, with the system full on, the hum is eliminated completely by unplugging the walwart. At this point you can still hear the slight tube rush of the phono section,but no hum whatsoever.
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I missed the 'and'.
Looks like you are going to need to do a bit more experimentation with earthing and trying a different wall wart so you can at least isolate that as a source.
Has it been there for as long as you have had the TT?
Did you make any changes prior to the hum appearing?
Have you experimented to see what the hum does if you move the turntable?
Steve
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Thx Steeva. Yes, the earthing experiments continue. The table sits in the exact spot that was occupied by my Nottingham about 2 months ago.
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I am having the exact same issue using my Soundsmith Aida. I would like to play around with some different grounding options but thats just something that I am pretty unfamiliar with.
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I am having the exact same issue using my Soundsmith Aida. I would like to play around with some different grounding options but thats just something that I am pretty unfamiliar with.
I've tried every grounding trick I can think of. My best guess points to the supplied wall wart as the culprit. The issue was not as prominent with my Nottingham,
but the Amadeus is sonically well worth that small bit of left channel hum. I've used the same Soundsmith SMMC2 with both tables. Not sure if the separate PS
offered would cure the problem either. May try it down the line.
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Wonder if you could get an audition of the Well Tempered DPS to see if that solves the problem.
And I imagine you have tried this (don't have time to check the whole thread), but if not, try running the grounding wire from the phono pre to your preamp, and maybe even your amp. Worked for me, though it was likely due to the P75 not the cart, table etc.
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Mick,
I too suspect the wall wart. I'll assume that it's a DC output with a voltage of somewhere between 12 and 24 volts? In any case, I think the bridge rectifier in the wall wart has an issue or two and is letting in some pulsating DC, or even some AC into the circuit. I suspect the wall wart may not be "technically defective", but is on the boarder of being out of electrical specifications.
I'm not that familiar with that table or the wall wart, but can I ask if the wall wart has polarized plugs, and if not, have you tried turning the wall wart 180° so the other plug side goes to the hot. If the plug is polarized, then there is nothing you can do except, replace it.
To summarize, I do suspect some AC component getting passed, and no grounding scheme or technique will fix this problem. Perhaps a better power supply (not a wall wart) may be the answer.
Wayner
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Also, I hope your wall wart is away from your TT or phono/preamp as it has an AC stepdown transformer that likes to make big magnetic fields. The further away from TT and pre, the better.
But you've probably done this already?..........
W
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Mick,
Have you talked to Mike Pranka about this?
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Also, I hope your wall wart is away from your TT or phono/preamp as it has an AC stepdown transformer that likes to make big magnetic fields. The further away from TT and pre, the better.
But you've probably done this already?..........
W
Yes Wayner, I've tried just about everything that you've mentioned. I think the wall wart has to go ( at least in my case) for the problem to be resolved. The
big question is what to replace it with. Might eventually have to test drive the WT power supply before all is said and done.
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Mick,
Have you talked to Mike Pranka about this?
Mike seemed to agree that the wall wart could well be at the heart of the matter. He offered to send a power supply to try, but he really couldn't guarantee
it would cure the hum either. I wished he could have suggested better wall wart , but that was not to be. May eventually have to audition the PS. I hasten to add that
the hum is not hideous by any stretch, but it would be nice to eliminate it.
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I got rid of the walwart (for a dps) and got rid of my hum problem. Was that simple for me.
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You could test with just about any 12V power supply as long as it had the same polarity.
You are only interested in hum vs no hum for this test.
Steve
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I got rid of the walwart (for a dps) and got rid of my hum problem. Was that simple for me.
OK....thx, that's good to know.
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You could test with just about any 12V power supply as long as it had the same polarity.
You are only interested in hum vs no hum for this test.
Steve
Steve.....I'm working that angle too. Thx.....Mick
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Just throwing this out there, would one of these work? http://www.zzounds.com/item--TRXFTCHAMELEON
Its 12v 300ma, has bunch of different sized heads to fit just about any input size. Im a full time musician and im not really sure why I haven't thought of using one of these before. I have one of these permanently mounted on the bottom of my pedal board I tour with so removing it just to try this seems like a hassle unless I know it will power the table.
Do you guys think this would work? Ghetto DPS? ha
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Ok, the one problem with off the shelf wall warts is that they will almost never measure 12 volts. I'm making some more assumptions again, but I guessing your DC motor has a speed control, so varying voltage can be dealt with.
I was thinking of a true DC power supply like one of these:
(http://www.parts-express.com/images/products/standard/120-536_s.jpg)
http://www.parts-express.com/pe/showdetl.cfm?partnumber=120-536
Wayner
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Thx Wayner. That certainly fits the budget.......Mick
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Ok, the one problem with off the shelf wall warts is that they will almost never measure 12 volts. I'm making some more assumptions again, but I guessing your DC motor has a speed control, so varying voltage can be dealt with.
I doubt the one that comes with the table will measure exactly 12V either. Mosty likely, if you put a DMM on it, it will measure around 14V as you would be measuring it without load. Anyway, for an initial hum vs no hum test, having the correct speed speed does not matter.
If you decide to stay with a different (but not DPS) supply then getting close to the original voltage would matter a bit more. It is easy enough to measure the voltage of the supplied unit and then set an adjustable one to match then use the speed pot on the TT got do any fine tuning.
Steve
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For the record, the hum issue has been resolved by simply replacing the original wall wort. A fellow AC member and Amadeus owner sent me an Enercell ( Radio Shack) power
adapter to try. ( part # 273-316) No hum and even better sound from the Amadeus. Hope this helps anyone with a similar issue.
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Good to hear. When I switched to Naim gear we switched out the original wall wart for a Triad brand. Worked perfect. And now with the dps no problems either. At least it's fairly easy to sort if you do have a mismatch.
I was told, by crazy Pierre of Mapleshade, that one should split the wires of the wallwart and spread them apart 6". I tried it- hard to keep them apart.
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Good to hear. When I switched to Naim gear we switched out the original wall wart for a Triad brand. Worked perfect. And now with the dps no problems either. At least it's fairly easy to sort if you do have a mismatch.
I was told, by crazy Pierre of Mapleshade, that one should split the wires of the wallwart and spread them apart 6". I tried it- hard to keep them apart.
Pierre's OK, but that's one of his tips I think I'll pass on. He produces some of the sounds from a CD I've ever heard though.
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I had my maple board period.... :cry: