Turntable Hum, Can't Solve It

[bar72]

had another look, looks like they've used 3 core wiring to extend to new switch, no earth point on switch so left it hanging although it does have 2 x earth wires connected to earth pole in original socket? i've probed at the wires though and the rest of the lights in the house are flickering? Defo something not right.

 

[toxcrusadr]

Ooh yikes. Loose wires causing flickering lights are not good.

But I'm not sure a switch without a ground wire is going to cause your problem. In the USA, even cheap wall switches do have a ground screw these days. Which is useless information to you, I know.

Do you have any power cords near the phono preamp? I assume the pre has some shielding over the tubes. Hopefully.

 

[woofmytweets]

What is a directional interconnect? The signal is AC. Alternating current. It has no "direction" per se - it has both back and forward


Or did you mean "shield connected on one side only?"

yes, that's what i meant - they're branded with arrows usually

 

[trinhsman]

RB300 had a full rewire due to failing. Seperate Earth lead was installed and ran everything ran fine through my old Pro-Ject Phono Box SE II. Started getting a problem with hum and thought it was the tonearm so I sent back to J at Audio Origami and he's returned arm with no fault found. Everything within tolerance. While the arm was away, I decided to upgrade to a Budgie Phono Pre Amp. Anyway, arm is back, runs through Van Damme Interconnects from tonearm to either Budgie or Cambridge Amplifiers Phono Stage. No matter what phono stage I try, both humming away that is noticeable when I turn up the volume. Tried moving Budgie to other side of room, different interconnects, still no difference. I'm going to shunt the lot to another property tomorrow and see if the issue is to do with the house wiring as I had a periodic electrical inspection from one of the landlord's electricians and unsure if it's a coincidence but everything was good when I used it prior to his visit.

I tried wiring an earth wire to the ground lug on the wall socket, from the Budgie and hum got worse? Same with the Cambridge Audio Amplifier, took a wire from the amps earth pole and wired to earth on wall socket, it also got worse?

Only other thing that I can think of is the sparky decided to move the kitchen light switch from the kitchen to the living room wall behind the original switch and did a "pull back" on the wires. I have noticed that the earth on the old & new socket has been left disconnected? would this cause a hum?

Cheater plug not an option, got young kids in the house. While unlikely, I'd rather have my kids than a Stereo System that has Earth Bypassed ;

I get it, but you could try it and if it stops the hum you have found your problem. Then deal with it another way.

 

[noisefreq]

I had a situation where the TV cable line was causing a hum in my phono chain.
If you have cable hooked up, disconnect it from the wall with the phono section on and see if the hum goes away.
Easy and worth a try.

 

[Bob]

couple things to try.

use a power strip with all components using this strip. then reverse any plugs that are 2-prongs.
then try cheaters on the strip with any three-prong plugs. repeat the tests reversing all.

My Bet: get another turntable in (cheap is OK as long as it is original and unmodded). then
test the rest of the food chain to validate the other components and reduce the list
of suspects.

You may also have several problems. also try adding a ground fault device in the power chain.
it could save your life. unplug the monsters (fridge, beer cooler, beer dispenser, AC, wife's
shoe coolers, etc)

 

[bar72]

Ooh yikes. Loose wires causing flickering lights are not good.

Do you have any power cords near the phono preamp? I assume the pre has some shielding over the tubes. Hopefully.

Power cords are on floor and pre is on 2nd shelve of a TV unit (about 1/2 meter from floor). Tubes don't appear to be shielded as I can just roll them out with my fingers and install new ones?

 

[bar72]

I had a situation where the TV cable line was causing a hum in my phono chain.
If you have cable hooked up, disconnect it from the wall with the phono section on and see if the hum goes away.
Easy and worth a try.

Thanks for the suggestion but I'm pure IPTV so only a CAT5 LAN cable from router supplies my box.

 

[bar72]

couple things to try.

use a power strip with all components using this strip. then reverse any plugs that are 2-prongs.
then try cheaters on the strip with any three-prong plugs. repeat the tests reversing all.

My Bet: get another turntable in (cheap is OK as long as it is original and unmodded). then
test the rest of the food chain to validate the other components and reduce the list
of suspects.

You may also have several problems. also try adding a ground fault device in the power chain.
it could save your life. unplug the monsters (fridge, beer cooler, beer dispenser, AC, wife's
shoe coolers, etc)

Thanks Bob. Tried everything except another TT. I'm in UK so everything 3 prong at wall outlet. I will try and borrow a replacement TT to try eliminate things.

 

[Bob]

one last thing: I used to have a 2 TT setup. TT1 had a combo cable (2 RCAs for left and right Plus ground wire)
and TT2 had 2 cables (one for Left and right and a completely separate ground wire).

occasionally, of course, one would fall off and HUM appeared. I went to a separate two screw ground
connection and made sure it (hard) connected to the preamp.

so, my last item to check is the connection on your preamp - ensure it's solid. some are
long bolted mounted from the inside and extended outside for your TT connection. crud
gets in there and a couple twists and unlocks and re-twists will kill the crud.

your next test with the TT will confirm whether the food chain past the TT is good
then if it is good, then it's the TT and it's either the tonearm re-wiring,
the cartridge, or the cable.

then you could swap the cartridge headshell from loaner to yours. problem stays
then its in the tonearm rewire or the cable, if not then (rewire and cable) are OK
and its the cart.

good luck. It will be a HUGE relief when you find and fix this.

cheers
Bob

 

[bar72]

thanks for more input Bob.

So far, amplifier on CD / DVD, No Hum.

Phono Pre to Aux on Amp hums with TT Earthed to Phono Pre. Removed TT earth lead from phono pre (just left hanging in the air) and wired Phono Pre earth lug to amplifier earth lug and hum greatly reduced (-75dB in Audition which would suggest that the Phono amp is good as SNR for phono pre is -75dB).

Then I've disconnecting the TT wiring from Phono Pre and got 2 RCA plugs, stripped back and shorted + / - then fitted shorted RCA's to phono pre. Audition still showing -75dB so assuming that somehow I've cured it by disconnecting TT Earth lead and grounding Phono Pre to Amplifier Earth.

I can only assume that by connecting TT earth it's causing a ground loop and hum?

When I drop needle I can't hear hum in run in / outs now

Thanks to all for your help & suggestions.

 

[Bob]

You have your solution! seems that under different circumstances the ground/earth wire
"equalizes/neutralizes" the different ground potentials and reduces hum. here it's the
cause. sounds like hum entering your system through the TT is entering the phone pre.

Now - enjoy the music!

 

[woodj]

sounds like hum entering your system through the TT is entering the phone pre.

Sounds like ground loop.

 

[Bob]

yes, but reversed. this probably a component in the food chain that doesn't properly
equalize the grounds - I would suspect something wasn't done with the ground
signal.

tracing it is tough. I always substitute to narrow it down. then the tough decision
of fix, avoid, replace.

 

[bar72]

thanks again Bob. I'm happy with it now as my volume on amplifier at -40dB, while listening to vinyl is loud. Cannot hear hum (sounds more like the sea sounds at the beach now) until -10dB which would wake the dead if listening to playback at these levels.

 

[woodj]

tracing it is tough. I always substitute to narrow it down. then the tough decision
of fix, avoid, replace.

Almost always.

 

[Bob]

@bar72

wake up the dead? dude we need to build a business, go IPO and become billionaires.
then next product is to spin them in the graves.

 

[nj pheonix]

I had ( probably still do someplace) a budgie phono pre. I'm not saying it's your problem but I seem to remember I had an issue and reflowed a solder joint which caused a hum. At the time , I didn't have time to dig into it so I set it aside. So if I found today it'd probably have the same hum. My point being it might not be the TT at all. I was thinking there's something ( I won't go as far as to say misdesigned) that might under easily repeatable conditions cause a hum in a budgie. I'd try a different phono pre ( which if I understood what you said before , plugging into sound card, kind of points that way.)