Preamp Hum

[dav305z]

Hi guys. I just hooked up my turntable, and the preamp is humming away. I know it must have something to do with the ground, but I can't seem to find a place to ground it that will stop the noise. I know with a cheapo preamp some hum is inevitable, but this is LOUD, almost as loud as whatever happens to be playing.

Any suggestions?

[royphil345]

Hmmmmmm.......

Oh sorry.... Know you're sick of that noise...


That's a tough one. Could be a bad connection just about anywhere. Carefully cleaning the cartridge clips / pins with contact cleaner may help. Clean the RCA connections... If there's a removable headshell or cartridge clip, clean the contacts on those... If the turntable has a separate ground wire, connecting it to the preamp should do the trick.

Could also be a defective preamp or a fault in the turntable wiring or cartridge. If you have a friend with a system, testing your turntable or preamp with other equipment would help narrow down the possibilities.

I recently had a problem with hum that was caused by placing my preamp on another component. Moving the preamp to it's own shelf solved the problem.

[jrhymeammo]

Sounds like the never ending process that I'm also going thru. I thought I had permantely eladicated the problem by placing the setup in a closet. But no.

I had moved my phono pre to a different shelf, then the problem had started again. So, I moved it down to the original position and played around with wires, problem solved. Have you recently moved to an area with a huge radio tower or electrical layout? Only thing I can tell you is to keep playing around, even after you've tried "every possible " combination.

My ground wire doesnt help me in my situation, but if I remove it and place it in different positions..... the results are astonishing. Just play around and hear what you can do.

Try lifting your IC off the floor about 12-15 inches, that helps me more than anything. Well right now anyways.

What pre do you have?
Best Wishes

[basite]

how do you mean 'you can't find a place to ground it'

if the ground wire is 'plugged in' then the hum should be gone,
if not, then your ground wire is broken...
that's pretty much the only option I guess...
which tt and which preamp are you using??

some tt's don't have a seperate ground wire, then ground it 'internally' by somehow connecting it to the 'earth' (?) on the powerplug...

Keep them spinning,
Bert.

[Resident Loser]

...what time is it?

It's process of elimination time!!!...

What's humming the TT?, the wires?, the pre?

Do you only get the hum with the selector set to TT?

If yes, it's either the TT or the wires...

If no, it's the pre...

In addition to the two RCA-type connectors, is there a third single strand wire coming from the TT?...If you connected it to the AC outlet cover screw, that may be the problem...If so, make sure your volume is low and touch it to any metal part of the pre...does hum go away? If your pre has facilities to support a phono cart (meaning a phono stage) there should be a thumbscrew or somesuch to connect that wire to...if not, find a screw, perhaps something that holds the preamp's cover to its base, back it off a bit and connect the wire there...

Of course, we are assuming that the cart was installed correctly, that the wires in the tone-arm and those wires that connect the TT to the phono inputs are not faulty...

jimHJJ(...and that the phono input circuitry is not faulty...)

[dav305z]

Okay, here's some more info from my explorations. The tt - a Marantz 6170 direct drive - has a third ground wire which is in fact clamped to the preamps metal base.

Here's the thing, when I touch any metal part of the tt or preamp, the hum quiets down a lot. Does that mean anything? The cartridge is a new Grado Black, so I don't think the problem is coming from there.

I'll keep hunting. Any advice would be terrific.

[jrhymeammo]

you touch the pre and hum decreases? You are grounding the unit by touching it... Me too. Just play around. My rememdy will not cure you, but I'll let you know as soon as I get everything control.

Try wedging in your wires. You might find one position that works. I did, but can't find that best position again after I moved it

[royphil345]

Sure you have the Grado hooked up right? The layout of the pins may not be the same as on your old cartridge. No damage to the connections between the cartridge clips and wires?

Grado cartridges have been known to cause some hum on some tables. For that reason, I've been recommending this cart instead of the Black. http://www.lpgear.com/Merchant2/merc...ct_Code=ATC95E The severity of the problem makes it seem like something's wrong though... Bad connection somewhere, bad turntable wiring, bad or improperly installed cartridge, bad preamp...

Exactly how cheapo is this preamp? Maybe a bad choice for teaming with a Grado cart that tends to hum. A cheapo phono preamp is always a bad choice... The least expensive preamp I would recommend is this. http://www.phonopreamps.com/tc750pp.html Quiet and very decent-sounding. Spending more will generally get you smoother sound and better dynamics.

[Resident Loser]

Okay, here's some more info from my explorations. The tt - a Marantz 6170 direct drive - has a third ground wire which is in fact clamped to the preamps metal base.

Here's the thing, when I touch any metal part of the tt or preamp, the hum quiets down a lot. Does that mean anything? The cartridge is a new Grado Black, so I don't think the problem is coming from there.

I'll keep hunting. Any advice would be terrific.

...is it's AC line cord three-conductor or only two...as jrhyme suggests, your body is providing sort of a ground, an atmospheric one...

If the cord is two conductor and the blades are non-keyed (both of equal size) you could try reversing them in the outlet...the outlet may be miswired, but read on...

If the cord is three-conductor, your AC outlet may not be grounded, but you would need either a multi-meter or test lamp to ascertain this...HOWEVER, if you are not comfortable or simply inexperieced working around the higher voltages involved, it's a job best left to a pro or at least someone who is aware of the risks involved...

Additionally, the pre may need to be grounded...once you find out if the outlet (and hence the plate screw) is a viable ground source, you could try to run a single conductor wire from it's chassis to said plate screw...conversely, you may need to disconnect your grounds...

And I realize this is going to sound redundant, but have have isolated the problem to the phono hardware/circuitry? I don't recall an affirmation of that fact...

jimHJJ(...apologies if you have already done any or all of this...)

[dav305z]

Okay, I grounded the preamp, that seemed to help to quiet the hum, but in no way eliminate it. I've further noticed that most of the hum comes from my subwoofer. There is a noticeable, but tolerable hum from the speakers when I turn on my receiver, then the subwoofer comes on and its ridiculous.

The tt plug was not keyed, I flipped it around to no avail. I'm not quite sure how to really isolate the hum to a specific component without having other components to sub in (I suppose that's the next step). I think I'm going to try replacing the wires I'm using to connect the cartridge as they're....old. Wish me luck, and any other bits of advice/ epiphanies would be appreciated.

One more thing...now that the preamp is grounded, no amount of touching it will help the hum.

[Resident Loser]

Okay, I grounded the preamp, that seemed to help to quiet the hum, but in no way eliminate it. I've further noticed that most of the hum comes from my subwoofer. There is a noticeable, but tolerable hum from the speakers when I turn on my receiver, then the subwoofer comes on and its ridiculous.

The tt plug was not keyed, I flipped it around to no avail. I'm not quite sure how to really isolate the hum to a specific component without having other components to sub in (I suppose that's the next step). I think I'm going to try replacing the wires I'm using to connect the cartridge as they're....old. Wish me luck, and any other bits of advice/ epiphanies would be appreciated.

One more thing...now that the preamp is grounded, no amount of touching it will help the hum.

...re: the above underlined, that's the way it should be as the earth ground supercedes your body and it's grounding potential...NOW...It's starting to sound like it may have something to do with the AC mains frequency 50/60 Hz depending on which part of the big, blue marble on which you reside...

Are all of your interconnects shielded? If they are directional, are they connected as indicated by any arrows they may be marked with? Are any of your signal wires running in proximity of and parallel to, AC cords? You don't have all your wiring bundled right? Signal and AC should be as far from each other as praticable and only cross each other @ 90deg. angles...Is any of your gear or wiring close to probably a non-audio device that may contain a transformer? Do you have a light dimmer?

jimHJJ(...just some more shots in the virtual darkness of cyberspace...)

[dav305z]

Well, first all admit that most of the technical speak in your post went a bit over my head. But I understood enough to say that this could be the source of my problem. I live in a college apartment, which is slightly bigger than the average shoebox. There are wires...everywhere. I've got the tt next to my TV, although in my defense, the first thing I did when I heard the hum was to unplug that and move it away.

Which wires are my interconnects? I will try and move my AC wires out of the way and see if that helps.

[basite]

interconnects are the connections between 2 different parts of your system, this could be optical, digital coax, analog cinch, xlr, DIN, ...

in this case it will be analog cinch cables (standard, their color is red and white)
tv's and tt's together, is asking for war with signals...

powercords should be kept away from interconnects.

you say you have alot of hum everywhere,
this also makes me think that there must be a grounding problem in the appartement...
is it only with the tt, or is it on every source?

Greetings,
Bert.

[Resident Loser]

Well, first all admit that most of the technical speak in your post went a bit over my head. But I understood enough to say that this could be the source of my problem. I live in a college apartment, which is slightly bigger than the average shoebox. There are wires...everywhere. I've got the tt next to my TV, although in my defense, the first thing I did when I heard the hum was to unplug that and move it away.

Which wires are my interconnects? I will try and move my AC wires out of the way and see if that helps.

...are the wires that generally connect sources phono, tuner, tape, CD player, MiniDisc, iPod, computer audio output to yout head unit, which can be a receiver or pre-amp or integrated amp...They also connect things like a pre-amp to a power amp (in the case of separates), equalizers and processors or subwoofers from "sub out" RCA-type jacks...They usually carry line-level audio signals and (a) should be shielded and (b) should be as short as possible as they can be susceptible to various forms of interference (RFI, EFI, EMI in audio jargon)...

BTW TT close to tee-vee? TVs spew all sorts of hash into the audio atmosphere...that may be a part of the problem...also PCs and their monitors, blackberries/PDAs and cell-phones and wireless phones and video game processors...and refrigerators and air conditioners and hair dryers and...and...if you share your electrical service with anyone else, anything they may have, capable of generating AC line-borne bleats and blats...

jimHJJ(...spring cleaning anyone?...)

[jrhymeammo]

I've got the tt next to my TV, although in my defense, the first thing I did when I heard the hum was to unplug that and move it away.

My Grado mounted TT used to do that. I used have my TT right next to my TV, and I would hear hum when it was on. Just turn your tv off (or unplug it). If it doesnt help, then move isolate your system from other wires(extention cords/power strips, etc.).

If your tonarm/wires have been yanked, then that might be it. If I raise my tonearm's VTA to the highest setting, it would hum for some reason.

[dav305z]

jimHJJ(...spring cleaning anyone?...)

Indeed. I fear that the room might just be too small and have too many electronics to really isolate the turntable. In this room I have the following electronic appliances:

Refridgerator
TV
Computer
Printer
Receiver (connected to 4 speakers)
subwoofer


That's my room. The other 3 guys in the apartment have similar setups.

[royphil345]

I live in a hi-rise and we all have that stuff.

This is getting crazy...

With a solid-state preamp, moving magnet cartridge, decent sheilded cables and turntable all in good working condition... There should be no need for any of this. No hum that loud (he said he couldn't hear the music over it) under any circumstances.

You still never told us what your preamp was. It could be a deadly combination of noisy Grado cartridge and noisy cheapo preamp. Could be a defective cart or preamp if they're both new and untested. It happens. Could be a problem with the turntable wiring. If the preamp doesn't hum when your turntable's not plugged into it, you might be able to rule the preamp out as the cause.

You could try plugging in one channel of the turntable at a time. If you find one channel doesn't hum, try it in the other input of the preamp... Maybe narrow down the possibilities some.

Red = Right signal (hot)

Green = Right ground (earth)

White = Left signal (hot)

Blue = Left ground (earth)

Never hurts to double check...

[dav305z]

When I unplug the tt input, the humming resides, but doesn't go away.

The preamp is a cheapo. I guess one of the problems with cutting corners is that you just end up completely disastisfied (the Marantz is a freeby I found in my uncle's basement). The thing is, I don't want to spend too much on a better one unless I can be quite certain that it is indeed the root of this problem. I'm afraid of digging further and further and spending more and more money. If I can possibly figure out exactly what the problem is from the start and know what I'm getting into, I'll be much happier.

[royphil345]

Yeah... I can understand that...

If a CD player doesn't hum when plugged into the input you're using on your receiver or preamp... I'd have to suspect the phono stage. I just experimented with mine and there's no hum when the turntable's not plugged into it (or when it is for that matter).

Teaming it up with the Grado might be making matters even worse because they are prone to hum problems. Any chance of returning the preamp? The one I recommended from phonopreamps.com is very nice for the money. Had one awhile back. Upgraded mostly because it was so inexpensive I didn't trust it. Thought I might be missing out on something. Not much difference between that and some pricier solid-state phono stages I've tried.

Could be the Grado just hums on your table... It happens with Grados and some tables. Usually not that loud though. Could be a combination effect with the preamp.

Sorry I can't be more help. It's hard to diagnose a problem when you have several pieces of untested gear and nothing to swap them out with.

Good luck!!!

[dav305z]

Just to update you guys on this, I tracked down a Radio Shack preamp, just plugged it in, and...PRESTO! No hum. Too bad Radio Shack discontinued this little guy.