Turntable Hum - I know, I know, there's 1000 threads but...

Discussion in 'Audio Hardware' started by rob303, Oct 8, 2014.

  1. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    I've been reading thread after thread on "turntable hum" on this forum and others. However, a lot of the inquiries and recommendations are either vague or not specific to my situation. My "hum" is only at very loud volume (75% of max) and when I am not playing music. If I were playing a record, the music would be way louder than the hum. However, I want to make sure this is not simply a standard condition of turntables.

    Note:
    I run a ground between the TT ground nut and the phono preamp ground nut. As expected, without this ground there is a very loud hum at low volumes.

    In order to avoid confusion, I will list all of my observations below:

    "Hum" description:
    - TT motor on or off (I even tried unplugging it with no change)
    - Audible only when volume up past 50% and no music playing
    - "Hum" increases in volume when I touch tonearm wiring running from back of tonearm to junction box,
    - "Hum" virtually disappears when I touch either the metal tonearm wire connector at junction box, the metal connection ends on the RCA cables coming out of junction box or the ground nut on the back of the junction box. However, this loses efficacy when I take a step back, away from the TT and rack.

    What I have tried:

    - Unplugging the tonearm only creates a new, louder hiss/fuzz on top of the hum,
    - Based on advice in other threads, I used a multimeter to test resistance between the TT ground nut and the power outlet ground screw as well as the phono ground nut and the power outlet ground screw. Resulting measurement is zero (0).
    - I have tried running a wire from TT ground nut to amp ground nut with no change.
    - I tried running a wire from the TT ground nut to the ground screw in my power outlet with no change.

    Is this simply a characteristic of TTs? I understand the basic function of a cartridge, a phono preamp and a power amp is to amplify. By turning the TT off and turning the volume up, am I just amplifying low-level noise that is only audible under these conditions? Am I creating a problem that isn't actually a problem? Similar to, "if it hurts when I pull my arm behind my back while bending it like this, then I shouldn't pull my arm behind my back while bending it like this", am I unnecessarily stressing the system? Or is there a legitimate problem somewhere that I can fix to further reduce noise in my system?

    Thanks in advance for anyone's help!
     
  2. chervokas

    chervokas Forum Resident

    When you're touching these things are you touching anything else too -- like the rack? Are you wearing shoes and/or standing on a second floor or on something like a basement slab floor? When you say the hum is only audible with the volume turned up to a certain point, does the hum's volume increase and decrease as you turn the volume, or is it that it only becomes audible at a certain volume setting because it's low level hum?

    What arm and table are you using? These tonearm wires you're touching that's causing hum, are those just unshielded tonearm wires exposed between the arm tube and junction box? The phono cables from junction box to phono pre -- what's the shielding scheme on those?

    When you're touching those grounding points -- like the ground lug or the ground connected part of the the RCA plugs, you're grounding yourself and your body is acting as a shield. So whatever environmental EMF there is that your body is picking up is being drained to ground. You might want to try, if your equipment rack is metal, grounding it to the phono preamp ground lug. Just a couple of troubleshooting questions/steps.
     
    rob303 likes this.
  3. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    Not touching anything else. I am barefoot, standing on carpet atop a basement concrete slab.
    Hum volume increases as volume increases.
    VPI Classic 2 w/ 3D Tonearm. I believe these are unshielded. I am sure you've seen the standard VPI setup with the twisted wires arching from tonearm to junction box.
    I am using the Blue Jeans LC-1. This is what their website says about the shielding: "LC-1 Audio Cable uses a heavy double-braid shield, with one bare copper braid laid directly over another for extreme high coverage and high conductivity to ground"

    Link for Blue Jeans LC-1: http://www.bluejeanscable.com/store/audio/index.htm

    What about the fact that my touching these points does not cancel out sound if I step back and reach to touch them? It seems like my proximity directly correlates with the efficacy of my ability to cancel out the noise by touching those points.

    I tried that to no avail.

    Thanks a ton for taking the time @chervokas! I hope you have more insight for me.
     
  4. chervokas

    chervokas Forum Resident

    If the hum is going up and down with the volume knob, that hum might not be ground related but some hum being picked up in the signal chain itself and amplified. Those exposed VPI wires first of all are probably a design weak point, maybe there's a way to play around with some kind of half assed shielding for him to see. Maybe the hum going away when you're closer means that whatever source of EMF your body is functioning as a shield of is in that nearby space when you're standing close -- what's near the turntable that much be able to be switched off or moved away? Also, when you tried to connect the stand to ground are you sure you connected some raw, unfinished, uncoated part of the rack's metal to shield? Any finish on the rack will make for an ineffective connection to ground -- either scratch the finish off somewhere, or, if there are raw screws attaching to the rack, clamp a ground wire between that raw metal and the preamp ground lug. Yeah, those Blue Jeans cables are very well shielded.
     
    rob303 likes this.
  5. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    I just played around with it again and it does not change based on my proximity. I'm not sure how I came up with that initially, so sorry to add confusion.

    This is probably obvious, but running the wire from the turntable ground nut to my hand also cuts the noise completely.

    I'll mess with it more tonight. I have the barebones Archetype rack but I think the metal rods have a black coating on them. I will experiment further with that and brainstorm on tonearm wire shielding. Hell, maybe I can ask VPI directly for some tips while they are in town this weekend for RMAF!

    Thanks again!
     
  6. chervokas

    chervokas Forum Resident

    Well, just guess of course, but it sounds like you're on a slab floor, your body I acting as a shield and when the wire is touching your hand and you're on the slab (even with the carpet between), you're grounding the arm tube which is acting as a shield for the tonearm wires in the tube.

    I'd try a couple of things. First I might try grounding the tonearm to something other than the phono stage lug, maybe the preamp itself -- back one of the chassis screws out of the preamp partially -- that aught to give you a raw metal connection to the preamp chassis. See if that may be a better ground. I'd also try, like I said, to ground the rack but I don't know how much continuity that racks metal parts have with one another so that whole thing may or may not work (unless your grounding all the metal parts that aren't otherwise in contact with a metal part that is grounded). Grounding an aluminum frame rack with MDF shelves but with all the aluminum continuously connect, definitely removed a persistent low level hum for me. Third, I'd definitely talk to someone at the show!
     
    rob303 likes this.
  7. Burning Tires

    Burning Tires Forum Resident

    Location:
    Atlanta, GA
    I have a very similar thing going on, and I'm also not even sure it's a problem per se, as it would be impossible to hear at normal levels or when there is any music playing. Just a low level hum that is only annoying if the volume is turned past the point of "too loud" while nothing's playing. If I stand there and squeeze the grounding lug on the TT, it cancels out the hum, and if I remove the grounding wire, the hum gets very loud. So it's not like the grounding isn't working. This is with a Music Hall mmf-5.1se, stock interconnects, on a carpeted basement slab as well. I was thinking maybe I need to upgrade the cables and/or use a separate ground wire? The ground wire is part of the stock cables supplied with the TT. Or maybe I just live with it. That's fine too. Also, I'm using no power conditioning products.
     
  8. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    Sounds good! I'll report back later.

    On another note, after powering down my phono preamp and listening for changes, I noticed a very low level buzz. You have to get within a foot of the speakers to really hear it and it is not affected by the volume knob. This was with only my tube amp on. Any advice here? Just typical tube noise? All tubes in the amp are relatively new (6 mos old).

    Thanks again!
     
  9. chervokas

    chervokas Forum Resident

    Again, really hard to troubleshoot from afar. Not going up and down with volume know so it could be ground loop noise and you can try cheater plugs on all but one of the components. It could be noise injected into the single line at the tubes from any number of different sources -- filament noise, proximity of some kind of transformer or something in the chassis, problems with the tubes themselves, etc Some of that would go up and down with volume changes. Heck, could be leaky caps. Lots of possible sources. Easiest thing to check as just an end user is a chassis ground loop by installing cheater pulls on everything but a single component to see if the buzz goes away.
     
    rob303 likes this.
  10. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    Yeah it sounds like you are experiencing the same exact thing as I am. I'll let you know if any of the suggestions above work. Please let me know if you find a solution as well.
     
  11. Burning Tires

    Burning Tires Forum Resident

    Location:
    Atlanta, GA
    Thanks! Will do. I'll keep an eye on this thread and post if I happen to find a solution. At least it's an issue that doesn't cause major heartburn. :)
     
  12. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    No kidding! Yeah, I'm tweaked out when it comes to those you need to buy. Now im focusing on DIY stuff.
     
  13. chervokas

    chervokas Forum Resident

    I should also say there could be other sources of hum outside the electronics -- like power cables running too close and in parallel with interconnects, even shielded ones, etc.

    The best thing to do to troubleshoot at least the source of the hum is start to strip down the set up. Unplugged all the components from the wall and from each other. Then, starting with the amp just loaded by the speakers and only it plugged into the wall, turn it on and see if there's hum. No? Then the source is not there. Add the next component, and so on.
     
  14. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    Good idea! My rig definitely has tight quarters in the rear with respect to power cords.
     
  15. chervokas

    chervokas Forum Resident

    My experience is that usually with well-shielded interconnects, if there's audible hum it's not the proximity of interconnects and power cords, but it certainly can be. Best to keep those away from one another, and, if they have to cross, to have them cross at right angles, etc...all the standard best-practice stuff.
     
    rob303 likes this.
  16. KT88

    KT88 Forum Resident

    It's not an induced hum from power cables or other components as you can eliminate the hum when touching the ground lug on the table. Since you have proven continuity through that ground lug to the wall outlet ground, there are only two possibilities. One is a broken or poor ground in the tonearm wiring. The other is a broken or poor ground from your wall outlet to the home's fuse / circuit breaker, power distribution panel. Possibly even from that panel to earth. In either case, it sounds like the tonearm or the house wiring.

    The only other possibility that comes to mind is a misdiagnosed ground loop. That would be where you actually have a good ground from tonearm to the circuit breaker but there is an additional ground on that circuit somewhere, probably at the preamp or phonostage. The reason that seems unlikely is that you can cure it when grounding the arm to yourself, which would cause the loop if it were properly grounded to begin with. If it is not a grounding but rather a shielding issue, then you need to look at sources that could induce hum directly into either the phono cartridge or the tonearm wiring or even the phonostage, such as strong magnetic fields (by a power amp for instance) or lighting. Still, these sorts of induced hum are not typically resolved by touching ground, so I am really thinking it is the first two items that I pointed pout.
    -Bill
     
    SandAndGlass likes this.
  17. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    @KT88 Bill - the house wiring is another likely culprit. It is 1950s construction and still has the original cloth-wrapped thick copper wiring. All of the outlets were updated by a previous owner to the 3-prong outlets, but I am not certain of their ground-worthiness. The outlet for the stereo is one I upgraded and installed. The ground wire is attached to a screw on the inside of the outlet box. I have tested with a multimeter and, as far as I can tell, it tests as grounded (I am in no way an electrician and 100% youtube-schooled). Are there varying states of being "grounded"?

    Also, sorry to confuse you. The power cable and interconnect issues were recommended because I veered off-course in post #8 where I identified another unrelated noise - a buzz - when my phono stage is off and only the amplifier and speakers are activated.

    See below:
    Thanks for the input! Hopefully you can offer further insight.
     
    Last edited: Oct 8, 2014
  18. chervokas

    chervokas Forum Resident

    The second hum he describes, which is with the phono preamp powered down and doesn't change with changes in the volume pot, could have any number of causes. But it's still possible that induced hum in the turntable set up could be reduced by a person standing near the deck and touching the system ground in something like the way the induced hum in a single coil electric guitar pickup is reduced when the player touched the strings. In that case our body is functioning as a giant antenna for hum producing radiation which we're grounding when we touch the grounded strings or the grounded phono cable parts, etc. Better explained on the Seymour Duncan website than by me: http://www.seymourduncan.com/blog/the-tone-garage/background-noise-closing-the-loop/ If there's something inducing the hum near the table that's shielded by a person standing w/in arms length and grounding him or herself, it could definitely reduce induced hum (and it sounds like we're talking about pretty low level hum here but hum that does go up and down with the volume knob so something being amplified by the signal chain).
     
  19. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    Well, I found the culprit for my initial and worst problem. I took the advice of @chervokas in post #13 and started with the amp powered on and began unplugging things to see the effect. After almost completely giving up, I started messing with the tonearm (picking it up, moving it on its pivot, touching cart connection, etc.) and noticed the buzz/hum would vary in intensity as I moved the 'arm. Then I clicked my little LED work-light off to focus back onto the amp and...drumroll...the buzz dropped in intensity (!). I clicked the light back on and the buzz kicked back up in intensity. This LED and some non-essential devices are plugged into a cheap power strip that is plugged into my Shunyata Venom PS8. So, I bend down and turn the cheap power strip off and - boom - no more hum/buzz sound! Nada! Just the sound of nothing cranked to 11!

    Jeebus, the most obvious things need to smack you square in the nose for you to notice them. I have yet to see if the faint buzz when the phono pre is off is still there. Once I am finished rocking out the new Ryan Adams LP knowing the big hum is no longer creeping somewhere in the background, I'll kill the phono pre and see what happens.

    Thank you again to @chervokas for jumping on this issue with me and @KT88 for your valuable insight.
     
  20. chervokas

    chervokas Forum Resident


    Glad you found the problem. A phono cartridge is a lot like an electric guitar pickup and both are really good at humming in response to all kinds of stuff, like the switch mode power supplies that are not only common these days with appliances and electronics but also probably powering that LED lamp, etc. It's the kind of stuff you need to keep physically away from things like those unshielded tonearm wires, the cartridge itself...and keep electrically apart too on a different circuit or maybe using an isolation transformer or something, or just turn 'em off when you're listening.
     
    SandAndGlass, The FRiNgE and rob303 like this.
  21. The FRiNgE

    The FRiNgE Forum Resident

    Just to look at your electrical wiring and ground continuity, partial grounding can exist. (tech term "floating ground") Your wiring is probably BX shielded cable, a good thing, but bad over time. Older BX cable has no separate ground conductor. The armor (shield) is the ground conductor. The ground continuity is entirely dependent upon intimate contact of the armor to the metal outlet box, and the steel electrical panel frame. The BX wire connectors develop a patina over time, and corrode in basement areas, so that resistance and capacitance develops in the grounding circuit.

    My only recommendation is to hire an electrician to check your ground continuity, at least to the outlet you have your high fidelity equipment plugged into. Please have the electrician check your ground bonding to your water pipes and/or grounding rod. Any compromise in the grounding will cause a partial ground. (floating ground or a ground fault)

    As you touch the grounding post on your pre-amp, you essentially ground yourself (as much as possible relative to the degree the outlet grounds true to Earth) so as you also touch the tone arm, you'll not hear any additional hum, or perhaps a slight reduction in hum. Grounding begins at the electrical panel, and external grounding rod to Earth. Once that is taken care of, any problem that persists will be
    1) poor shielding of the tone arm
    2) poor grounding bond to the headshell
    3) poor contact of the jumpers to cartridge pins (especially the ground pins)
    4) a ground loop, (always ground point to point as I believe you have done correctly)
    5) an AC conditioner helps filter out RF interference harmonically related to 60 Hz hum, also little bleeps and strange noises that can occur.

    Even when grounding is ideal, there still may be residual low level hum at high gain, no signal. Fluorescent lighting is a no no, and television sets on the same circuit can induce hum. The neighbor's house wiring and electrical appliances can induce hum in your house if on the same transformer.

    I hope this helps. Please let us know your progress?
    Steve VK
     
    Last edited: Oct 9, 2014
    rob303 likes this.
  22. chervokas

    chervokas Forum Resident

    One other note fwiw for potential future troubleshooting, when I'm doing this kind of troubleshooting, I find it's easier, instead of starting with everything plugged in and unplugging things, starting with everything unplugged -- just the amp plugged into the wall and the speakers connected first -- and one by one plugging other things in (and not just into each other but into the wall). If you start with the amp and speakers and there's no hum, you know the problem is not there, if you add the preamp and there's no hum, you know the problem's not there. Then I'd add sources one at a time: one source, then unplug it. After I tested each source separately I'd try sources in combination. I think it's a faster way to locate the stage at which the problem is occurring vs. unplugging. When you start with everything unplugged you can potentially immediately rule out one stage after another.
     
    The FRiNgE and rob303 like this.
  23. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    Sooo...

    After being sick for a few days not touching my system at all, I came back to it today and the hum is there again. I started unplugging everything and have isolated it to my interconnects coming from my amp. I have one set going up to my phono preamp and one set going to my DAC, thats it. The hum is only present when the amp is set to my phono input or my DAC input with the volume well past 50%. Once the interconnects from each are removed, the hum is gone.

    The interconnects from my amp to phono preamp are the Blue Jeans LC-1. The interconnects from my amp to DAC are some nice Canare cables. Could it be the cables? Or are the cables expressing a symptom from something bigger?

    Thanks!
     
  24. The FRiNgE

    The FRiNgE Forum Resident

    The only problem I can think of with the cables would be a faulty ground connection at your amp's RCA inputs. If that is so, then the hum in each channel should be different. I tend to think the problem is not in the cables nor your connections. Just to set aside a possible cause, make sure your cable plugs and amp jacks are clean and oxidation free. A Q tip swab of 3M Finesse it, part 05928, will remove any oxidation. Finesse it is available at many auto body supply houses, and online. Follow up with isopropyl alcohol to remove residue from the cleaning. You will need to strip the Q tip of most of its cotton for cleaning inside the RCA jack. I do not recommend deoxit, which removes the oxidation, however promotes recurrence of it. (avoid)

    Clean connections will at the very minimum ensure signal integrity without loss. But a hum problem would be a more exceptional issue with high quality cables (check them anyway)
     
  25. chervokas

    chervokas Forum Resident

    Doubt it's the cables, both are well shielded types.

    So, let me get this straight -- you have an integrated amp, yes? When the amp is on and connected to speakers, but nothing is plugged into its inputs there's no hum on any input at any volume, yes?

    Then, when you plug the DAC and phono preamp in, there's hum on each input channel? Is it only with both the DAC and phono pre plugged in, or either (you tested one at a time I assume)? And all input -- DAC, phono and any unused inputs? Is this with the DAC or phono pre powered up-- both on, either on, neither on? It's not clear -- trying to isolated the hum, it's not inside the amp, that seems to be the only conclusions. Also sounds like there could be more than one source. Have you tried putting everything put the amp on cheater plugs? Have you switched off and unplugged from the wall socks things like lights, computers, monitors, and any thing that has a switch mode power supply wall wart?
     

Share This Page