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
    @chervokas I am not going to go through and answer because I am finding serious discrepancies in my observations on a daily basis :confused:. I have started fresh today and below are my findings while trying to isolate every variable as best as I can...

    Ok. I just ran an initial test. This is where things get wacky because it seems there has yet to be a constant set of parameters to reproduce the problem. What I can isolate it to one day changes when I revisit this problem on the next day. I feel like Clark Griswold chasing his tail in trying to trace the power interruption in his Christmas lights!

    So, my test this morning. I unplugged everything. My line conditioner, power strip and everything from the power strip. I then plugged my amp directly into the wall socket with nothing else. SILENCE on all inputs. Complete silence, no hum, nothing. Yesterday I was receiving hum on my two active inputs while everything was powered off except the amp, but all plugged in to the power strip with the line conditioner engaged. In fact, my DAC was unplugged while its input was picking up hum. This hum went away when the interconnects were pulled from the amp.

    Ok, back to today's test. Amp plugged directly into wall with everything else unplugged = no hum on all inputs. Then I plugged my phono pre into the other outlet (still powered "off"), and there is a very low-level hum/buzz present on both inputs with volume at max. I powered it on and...BZZZZZZZZZZZZZ! That hum/buzz gets magnified, as I would expect. Again, this is at high volumes only. My phono pre is set to 45dB gain, loaded at 47KΩ and opF. Also, this buzzy hum increases with volume when I touch the exposed tonearm wires arcing from the back of tonearm to junction box. This buzzy hum virtually disappears when I touch the metal connector connecting the tonearm wires to the junction box or when I touch either metal interconnect lead coming out of the junction box.

    Test #2
    Now I have plugged my power strip back in (Shunyata Venom PS8). I plugged only my amp into the strip and powered up. Silence on all channels (volume at max). I plugged my phono pre in, but not powered on, and I get the low-level buzz with volume at max (same as in test#1 above). This is on both engaged inputs (phono and DAC). Again, its not there when the phono pre is not plugged in. I unplugged the phono pre and the faint hum goes away. I power the phono pre "on" and, as expected, the buzzy hum is amplified considerably but only when the amp "phono" input is engaged. Buzz increases with volume when tonearm wire is touched and virtually disappears when tonearm wire connector or interconnect leads are touched. The other active input (DAC) stays the same with just the very very faint buzz.

    Note: When I pull the DAC interconnects from the amp, that very slight buzz mentioned in test#2 is replaced by a buzz of higher frequency, possibly even more faint, which is experienced on all disconnected inputs when amp is powered on, volume at max and my ear literally in the dish of the speaker's woofer. This is there whether phono pre is plugged in or not. However, this high freq buzz is not present on the phono input while the phono pre is unplugged and the interconnects are all plugged in. I am not sure if this amounts to anything, but it seems I need to note all observations. It sounds just like when a street light first fires up, but so very faint. I am not concerned with this particular buzz in my system because it seems like something that is inherent to the setup. Again, I thought it was worth mentioning if it helps diagnose the actual issue at hand.

    Thoughts? Ground issue with the phono pre?
     
  2. Preston

    Preston Forum Resident

    Location:
    KCMO Metro USA
    rob303 - these problems can be the most aggravating. I had the same issue when I recently bought a new phono preamp with much higher gain. I finally traced it to a video connection (cable), which I only use to navigate the idiotic menus on DVD-Audio and BR discs. It's unplugged now and no hum. I just unplug it when playing records. :) Good luck!
     
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  3. chervokas

    chervokas Forum Resident

    Haven't had a chance to read the whole thing but if you get the hum with things turned off but plugged into the wall and into the amp, there's probably a ground loop in the system. I'd buy a bunch of cheater plugs and start trying those out to see if in fact that's what's going on. The loop is great at picking up environmental sources of noise, which the cartridge may also be good at picking up. So I'd also look for all sources of potentially hum inducing radiation near any of the components or signal lines.
     
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  4. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    If the cheater plug remedies the problem, is that the fix? Or is there a better way to kill the ground loop?

    Thanks!
     
  5. chervokas

    chervokas Forum Resident

    Well, people will say that defeating the chassis ground is a safety hazard -- and I suppose it is, if the chassis becomes energized and you have defeated the chassis ground you stand a good risk of getting a nasty shock instead of having the signal sent to ground and a fuse blowing. But I've often just left cheaters in place. You could use ground lift RC circuits on one of the chassis internal connections between signal and ground, I think people do that to lift the loop; and there are transformers you can insert between the pieces of gear creating the loop. I dunno. There are other possibilities for the source of hum/loop including ground path problems in the gear itself resulting in loops -- it does happen, sometimes designs aren't so great. But I'd start with the cheaters and see what you get.
     
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  6. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    If the cheaters prove to solve problem, thoughts on this thingy?

    http://www.ebtechaudio.com/humxdes.html
     
  7. The FRiNgE

    The FRiNgE Forum Resident

    I just had the thought that your phono pre AC plug needs the polarity reversed. If the AC plug is non-polarized (both prongs the same size) try reversing it.
     
  8. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    All my stuff is 3-prong.

    I did take it one step further and disconnected the TT from the phono pre and that proved to cut the noise. It looks like the true culprit is the TT. A friend in the HiFi biz even suggested he thinks this may be a trend with moving iron cartridges. Who knows. I'll keep effing with it, but glad it only occurs in extreme cases and doesnt affect music.
     
  9. chervokas

    chervokas Forum Resident

    Well, if it's just the table, it's probably the cart and or cable picking up induced hum from environmental sources but a ground loop does the same thing, functioning as an antenna. It's pretty hard to eliminate all hum from a turntable rig because we live in environments today were there are just so many sources of EMF radiation impinging on the cartridge that it's hard to get rid of all of it. As I said I recently discovered that I had to ground the stand my turntable and phono pre sit on -- even though there's no contact between the aluminum frame and any component chassis -- to eliminate the last of what I thought was unavoidable hum (it was only really noticeable as hum with no music playing and the volume cranked). Still try the cheater plugs. And go around the room and make sure all the usual sources of hum and noise are switched off and unplugged and if that's not possible are kept far away from the turntable. It's also true that some cartridges are better shielded than others. (This probably will have no impact, but do I remember correctly that you're running the phono imput at 0 pF capacitance? Usually the capacitance at the phono stage input is part of an RF rejecting circuit. Hum isn't RF, but just in case it might help you could try to increase the capacitance loading.)
     
    rob303 likes this.
  10. DavidFell

    DavidFell Forum Resident

    Location:
    Chicago
    I sometimes get hum when my cuing lever is lifted; goes away when the lever is released. I also, on occassion, pick up radio stations this way!
     
  11. Reid

    Reid New Member

    Location:
    Medina, Ohio
    Hi, I'm Reid. I created an account just so I could hopefully find a solution to this, because I'm having the exact same problem. To the original poster, did you ever find an exact solution to this problem? Thanks!
     
  12. The FRiNgE

    The FRiNgE Forum Resident

    Hi Reid,
    Wow! It's been a year plus since the original poster has messaged.
    Turntable hum is not easy to diagnose online, since there are so many causes for it. If you have read the previous posts, Chervokas offers very good common sense troubleshoot advice, mostly by disconnection of everything and starting with just your amplifier.

    Mentioned also, most magnetic cartridges behave exactly like guitar single coil pickups, which are sensitive to picking up stray AC magnetic fields.

    For hum to occur, we need two things:
    1) a source of hum, any AC device that produces a magnetic field, the most common devices are transformers and high voltage AC lines.
    2) poor defense against stray electro-magnetism, insufficient shielding and grounding, which can be in varying degrees.

    For example, a marginally shielded cable will not produce hum in the absence of an electromagnetic field. A well shielded cable and system will not produce hum under more severe conditions.

    The most common causes of cartridge hum... ground loops are often mentioned, but the ground loop is not the most common cause..
    1) poor ground connection of the RCA plug to the phono amp input
    2) Cheap cables, sometimes the original turntable cables are the cause
    3) disconnected turntable ground wire (some turntables do not have a separate ground wire, as the ground will be internally connected to the L Ch RCA plug)
    4) broken tone arm ground/ turntable chassis ground (if touching the arm increases hum, the arm is probably ungrounded, it needs to be chassis grounded)
    5) Poor ground connection at the cartridge, the pins and connections need to be cleaned
    6) Oxidized headshell to tone arm contacts (clean with jeweler's polish or automotive paint polish such as Meguire's Ultimate compound. Remove all remnants of the compound with isopropyl and you'll need a magnifier to make sure there is no lint or residual gunk on the contacts.
    7) Poor ground bonding at the electrical panel, and/or grounding rod/ water pipe.
    8) a ground loop can cause hum, but there must also be a source to produce it, a stray AC electro-magnetic field.

    Even under the best conditions, there may be a low level AC hum, perhaps barely audible at volume settings much higher than the normal listening level. For hum levels so low, I regard this as normal.

    Devices that emit electro-magnetism and cause hum:
    1) fluorescent lights
    2) CRT's in television sets
    3) Light dimmers in the house, and don't rule out the neighbor's house
    4) Low voltage halogen desk lamps, and LED lamps that contain a step down transformer (a "sneaky" cause for major hum problems)
    5) wall warts anywhere near the turntable, maybe as far as 10 feet away (wall warts transform AC to lower voltage and emit electro-magnetism)
    6) Refrigerator and furnace transformers and relays
    7) It is possible a step down transformer near the building will be a source of hum, although they are supposed to be shielded
    8) any high voltage line near the building, 1200 volts or greater emit very strong electro-magnetic energy. Many areas have 1200 high tension lines, and three phase service. If an AM radio hums loudly between stations (or worse on a local station) you are literally bathing in AC electro-magnetism. (depressing)
    9) AC motors, AC fans (DC fans are ok) air conditioners, attic fans, etc.
    10) A power amp too near the turntable.. too near would be one shelf below in a rack. Move the turntable away from the power amp.
    11) I'll add to this list as I think of more

    If hum still persists, a very good test is to connect the system at a friend's house. I once owned a Luxman L-11 that produced mechanical transformer hum in my house, but never produced any hum at any other location... and after I moved.

    The original poster owned a VPI turntable. A large loop of tone arm wire may be part of the problem as this loop isn't shielded. A cartridge of higher impedance will be more susceptible to hum, and/or less tolerant of exposed, unshielded segments of wire. Sometimes the turntable needs to be replaced.
    Steve VK
     
    Last edited: Dec 31, 2015
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  13. Reid

    Reid New Member

    Location:
    Medina, Ohio
    Wow, thank you so much for the detailed response! I'll try moving my setup to a more isolated location in the house, and away from any possible interferences. This is so frustrating, but I have high hopes.
     
  14. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    Reid - between the awesome reply from @The FRiNgE above and the older posts from @chervokas, all your bases should be covered. Also, its helpful for you to fill out your system info in your profile. Sometimes someone with the same TT, cart or phono pre etc. may be able to help you with hardware issues.

    Anyway, my system has almost 100% changed since then. I cannot recall if there was anything exactly that was a "silver bullet". My issue was a multitude of things. I think a majority of my issue had to do with my tonearm wiring and cartridge, similar to a single coil guitar pickup. That is no longer a source of noise for me now, but I have a different cart, ICs, phono pre and amp. So maybe the cart had minimal shielding? Maybe my phono pre had a ground loop? What I have learned since then is vinyl playback will always have some background noise but the music will trump it 10 fold in volume. If it doesn't, then you really have a major issue. I also run all tube amps, which have their own noise quirks but nothing that is a detriment to the music. These things are deep rabbit holes and we have to keep in mind this is a different animal than a total solid state system running CDs.

    Good luck!
     
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  15. Reid

    Reid New Member

    Location:
    Medina, Ohio
    Thank you all for your input! I truly appreciate it. So just a few additional things to mention: my turn table comes with a built in preamp that I have removed, so I am using an external preamp. It's a preamp that comes as a DIY kit, it's called "Muffsy Phono Preamp". Also included with the DIY kit is the AC/DC hifi power supply.

    So I had an idea the other day, and it was to eliminate the AC/DC power supply and just run the preamp off of two 9 volt batteries; therefore hopefully taking out any possible noise caused by the AC power. So I wired the two batteries to it, it worked just fine... But I still had the slight hiss/hum sound at a higher volume - the same volume level I would hear it at with the AC/DC power supply connected. So does this rule out the possibility of interference from AC current? Does this show that it's more likely a problem caused by a ground issue? Thanks again!
     
  16. Reid

    Reid New Member

    Location:
    Medina, Ohio
    Update: Problem Solved

    The RCA cables that I was using to connect the turntable to the preamp were pretty short, so I was limited to the amount of distance that I could place the preamp away from everything else that could potentially cause interference. I bought some longer, higher quality RCA cables which allowed me to place the preamp further away from my receiver and turntable, and I immediately noticed a difference! I now have a dead silent, clean sound. So all in all, it wasn't the fault of the preamp or turntable or ground, simply too short/poor quality RCA cables. Thank you all for your help, I truly appreciate it!
     
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  17. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    Glad you found the solution! These things are a real headache. As you can see there are so many variables. It almost requires another person visiting your home to help troubleshoot. Things like your issue are not always obvious Qs someone would ask via internet.
     
  18. Tullman

    Tullman I prefer analog

    Location:
    Boston MA
    Yes, there are many people on this forum that think poor quality ICs are all you need and the rest is in your head.
     
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  19. Dave Calarco

    Dave Calarco Well-Known Member

    I'm having a very similar problem but the hum is mostly isolated to my left speaker. I tried most everything on this list, but when my phono input is selected I still have a low end hum coming from my speaker when nothing is playing that fluctuates with the volume. In trying to isolate it, I believe it has to do with the RCA connectors b/w my preamp and receiver. However these are very, very nice connectors so I am fairly certain it is not the wires themselves. I just spent an hour trying to fix it but no avail. It's f'g frustrating.
     
  20. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    How loud is it?
     
  21. Dave Calarco

    Dave Calarco Well-Known Member

    it's not very loud. just present. I just don't understand why it's only coming out of the left channel. I would expect it to be even but its not. the right channel is silent
     
    Last edited: Apr 16, 2016
  22. Jrr

    Jrr Forum Resident

    I know this is a very old thread....I will read it thoroughly. I am having the exact symptoms you describe on a new VPI Prime. I wrote down eight things to try to resolve my issue. Really appreciate everyone who took the time to document them.
     
    Last edited: Aug 29, 2017
  23. rob303

    rob303 Forum Resident Thread Starter

    Location:
    Denver, CO
    I had to think long and hard. I believe the issue was a classic case of misguided fault. The entire time I had a bunch of the LED strips you get at IKEA in that room. I moved the lights and problem solved. :hide:
     
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  24. KT88

    KT88 Forum Resident

    Yep, that was EMI. Jrr found his trouble to be grounding and shielding faults due to poor finish or contamination of the pivot bearing. Now resolved.
    -Bill
     
  25. Jrr

    Jrr Forum Resident

    Yup! Just a quick sanding of the pivot point. The finish blocked the grounding of the arm. Only took three months to locate! Factory defect. So, lesson is usually it's the fault of something other than the mfg of the table, but don't rule it out as I had.
     

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