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Hum comes and goes with phono stage grounded and not grounded

Gurkov

Gurkov

Active Member
So, I got myself a used Musical Fidelity M1ViNL phono stage. Excellent sound and good capacitance options for the old MM’s (and also 68kOhm along with the usual 47k!) Run it with my Luxman R 1040 receiver.

Anyway, when first connecting it last night, I realised the hum was much lower in volume with the phono stage left ungrounded. The previous phono stage I always left grounded and likewise when I ran the TT straight to the Luxman’s phono connection.

But during the day today, the hum was suddenly terribly loud. So I tried grounding TT to M1, and voila - almost nu hum at all!

So now, evening again, and - you guessed it - hum is worse when it’s grounded then not grounded...

I know a hum issue can have a million different causes. I’ll work my way backwards and try with various other devices switched on and off.

But, one thing I couldn’t find an answer to when googling: can I try connecting the ground wire to the receiver’s phono ground screw, while still using the external phono stage (comnected to aux)? And also try maybe connecting it to one of radio antenna connections?

Not suggesting that will solve it all, just want to try it - but I want to be sure I don’t risk doing harm to the phono stage or receiver, or anything else...
 
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Gurkov said:
can I try connecting the ground wire to the receiver’s phono ground screw, while still using the external phono stage (comnected to aux)? And also try maybe connecting it to one of radio antenna connections?
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Try it. Shouldn’t hurt and it might help.
 
Thanks @audiocrzy ! Tried it this morning, hum was still pretty low with the pre ungrounded. Then tried grounding to receiver and it was no discernable difference. Will leave it like that and we’ll see. But good thing that I didn’t get more hum from it.

Tried grounding to the screws for AM and FM antennas too, hum was about the same but it introduced some (ever so slight) buzz. RF?

@gtv2000 I did swap carts during the day yesterday, but I think I ended up using the same one during grounded and ungrounded sessions. Will keep it in mind, though. Thanks!
 
I have a turntable with loud hum issues. I can usually (not always) solve the problem by unplugging and plugging the TT. I am plugging into the analog section of a line conditioner (similarly with phonostage and preamp) which in turn is plugged into a dedicated circuit breaker outlet. The amps are plugged into a different dedicated circuit breaker outlet but has not caused issues with ground loop elsewhere in the system. What is likeliest issue/solution ?
 
You may have an intermittent connection in the headshell. There are 8 connections in there. Or an intermittent cable. Try wiggling the output cables while playing, to see if the hum comes and goes.
 
lenjack said:
You may have an intermittent connection in the headshell. There are 8 connections in there. Or an intermittent cable. Try wiggling the output cables while playing, to see if the hum comes and goes.
Click to expand...

Thanks! Not sure if you're responding to me or the gentleman above here - whose problem I couldn't quite understand. Anyway, for me the problem is solved with grounding the TT to the receiver while still using the external phono stage. Might be other ways to deal with the phono stage itself, but since this works, I won't look into it more for now.
 
An update. With most carts, hum is inaudible, or nearly so, but some difficulties persist.

I have an Empire 4000D, discussed to some length in the epic Empire thread, that hums louder than others.

It got a little better when I noticed the blue and green wires were switched - thanks to @desertrat748 for pointing me to that. And even better when turning the TT’s power plug 180 degrees.

But hum is still there - AND what’s more, I now realize that it gets much louder with tonearm/cartridge close to centre of TT, i.e. the motor. It’s basically like that with all carts (even if it’s most obvious with the 4000D), I have checked with four others to verify,
 
I should add that I use a direct drive, but did try the cart on a belt drive in another room - with the same results. Louder as it moves closer to the centre of the record. Not sure where motor is located on the belt drive, though. It’s a Technics SL-20, will have to try and locate the motor on that one...
 
Gurkov said:
I should add that I use a direct drive, but did try the cart on a belt drive in another room - with the same results. Louder as it moves closer to the centre of the record. Not sure where motor is located on the belt drive, though. It’s a Technics SL-20, will have to try and locate the motor on that one...
Click to expand...
Most carts are shielded so for most carts it should not matter were the motor is. I am suspecting your headshell. Also what is the cart as some like Grado are not shielded? Some carts also need to be isolated from headshell ie need plastic screws or plastic washers or they hum.
Chris
 
cafe latte said:
Most carts are shielded so for most carts it should not matter were the motor is. I am suspecting your headshell. Also what is the cart as some like Grado are not shielded? Some carts also need to be isolated from headshell ie need plastic screws or plastic washers or they hum.
Chris
Click to expand...

Thanks for the reply @cafe latte ! I shoukd clarify, the Empire 4000D likely has an issue. But when I try the Empire 66 PE/X it has only the faintest, slightest hum at first - but with tonearm close to centre it gets just a little louder. And same thing with the Ortofon F15 and the Shure M75-6S.

The 66 PE/X has a plastic spacer between cart and headshell, the Shure has metallic srews and washers, so you may be on to something there. The Ortofon also has metallic screws and no spacer, but I believe that upper black part, like on most Ortofons, is non-metallic.

I also have a Pickering which is without hum and unaffected by closeness to centre. It has (like other Pickerings?) big fat plastic washers. :)

Has anyone tried a product like the Humbucker from Hagerman? Supposedly great with humming Grados and Regas...
 
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