Jump to content

Recommended Posts

Hello all,

 

You may have seen my recent posts about obtaining an upgrade from my Pioneer PL15 R.

Well, a couple of days ago I did buy a used Technics SL 10 with AT 81 CP cart. Unfortunately it has hum which I can't figure out how to eliminate.

I've just been through all the usual suspects : changing power points, connecting and disconnecting TT leads ( incl. ground ) from various components, but still no change. My usual set up for phono is : TT - Denon AU 320 step up transformer - Cambridge phono stage ( 640 P )- line input on pre amp.

This worked fine with my old Pioneer, but the Technics doesn't like it. I've connected the Technics straight to the Cambridge, then straight to MM phono on pre amp, without any change.

 

Could some knowledgeable person ( s ) give me advice please ?

 

Thanks,

Dennis

Link to post
Share on other sites

This is just a stab in the dark, and other members might have better solutions to trial first - but have tried a different cartridge?

 

I recently had a weird issue where it was the cart itself causing the issue (despite being properly connected). 

Link to post
Share on other sites

Dennis, looking up the AT 81 CP cart ... it is a MM (with an output of 3.5mV).

 

So you certainly don't use a Denon SUT between it and your 640P phono stage.

 

Am I correct ... you did run the AT 81CP straight into your 640P ... and have also run the cart into the MM input of your preamp?  With no reduction in the hum?

 

If so ... does the hum come from both channels ... or just one?

 

Andy

 

Link to post
Share on other sites
1 minute ago, andyr said:

Dennis, looking up the AT 81 CP cart ... it is a MM (with an output of 3.5mV).

 

So you certainly don't use a Denon SUT between it and your 640P phono stage.

 

Am I correct ... you did run the AT 81CP straight into your 640P ... and have also run the cart into the MM input of your preamp?  With no reduction in the hum?

 

If so ... does the hum come from both channels ... or just one?

 

Andy

 

Thanks Andy ; OK I won't use the Denon SUT. I don't think it had any effect anyway, as it was set for " through ".

However, yes I ran the cart into the 640P ... no change, and I then ran it straight into the MM phono stage of the Rotel pre amp ..... also no change. The hum comes from both channels.

Cheers,

Dennis

Link to post
Share on other sites


Check that there isn't a missing/broken/disconnected ground wire within the chassis of the turntable.

Tonearm, chassis, sub-chassis, motor mount, etc.

 

Check that there isn't an un-shielded portion of tonearm cable close to AC wiring or other PSU circuitry within the turntable chassis.

Link to post
Share on other sites
9 minutes ago, jack_b said:

This is just a stab in the dark, and other members might have better solutions to trial first - but have tried a different cartridge?

 

I recently had a weird issue where it was the cart itself causing the issue (despite being properly connected). 

Thanks for your suggestion, but I don't have another cart to fit. It's a P mount and brand new.

When I auditioned the TT at the seller's place, I had to use headphones, as there were no speakers.

Sounded perfectly OK, but maybe the phones don't pick up 60Hz, which I've read is the frequency of this type of hum.

 

Dennis

Link to post
Share on other sites
1 minute ago, pwstereo said:

Check that there isn't a missing/broken/disconnected ground wire within the chassis of the turntable.

Tonearm, chassis, sub-chassis, motor mount, etc.

 

Check that there isn't an un-shielded portion of tonearm cable close to AC wiring or other PSU circuitry within the turntable chassis.

Thanks Peter. I'd have to take it to a technician for this, as I don't have the knowledge or skills.

 

Dennis

Link to post
Share on other sites
9 minutes ago, Berkel said:

Thanks Andy ; OK I won't use the Denon SUT. I don't think it had any effect anyway, as it was set for " through ".

 

Aah, that's a new piece of information, Dennis.  :)  Sure, if it was set to 'through' then it shouldn't have much effect ... apart from a slight signal degradation from the extra switch contacts and RCA contacts.

 

Quote

However, yes I ran the cart into the 640P ... no change, and I then ran it straight into the MM phono stage of the Rotel pre amp ..... also no change. The hum comes from both channels.

Cheers,

Dennis

 

Sounds like a wiring problem - as Peter suggested.  :(

 

Does the hum decrease if you clamp your finger & thumb on the base of the arm?

 

Andy

 

Edited by andyr
Link to post
Share on other sites


Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    No registered users viewing this page.




×
×
  • Create New...