Audio Technica AT32 Query - UK Vintage Radio Repair and Restoration Discussion Forum

Bookman · 13th Nov 2018, 8:12 pm

It would seem the HiFi spirits were looking in my direction when I obtained through unsolicited purposes an AT32 with an AT630 step up txfr all with original boxes. Indeed, my amazement increased even further when I transferred the cartridge from its host head shell to my SME 3009 series III. The condition was as if had never been used.

I had intended it for my series II but it is boxed up in the attic.
A bit fiddly on set up as 1.7g tracking is recommended but not unexpected. However, upon start up I noticed an unpleasant hum and as such fiddled around with all of the connections which did have a significant impact but not enough.
I then removed the AT630 and ran the turntable direct into my Musical Fidelity M3Si which is apparently only suitable for MM inputs. However, it worked a dream with no feedback whatsoever albeit the volume was set at circa 60%/70%.
One would therefore assume that the feedback originates from the step up txfr but does it? In this I am referring to the host head shell which has a metal plate fitted that is soldered to the green pin connection; does this need to be mirrored somehow on the SME head shell?
Any feedback would be welcome.
Thanks
Joe

ajgriff · 13th Nov 2018, 9:12 pm

Sounds like an earth loop in the deck/arm wiring. I think that removing the transformer is simply masking the hum a little due to the reduced gain. Doubt if the headshell plate is relevant.

Alan

Bookman · 13th Nov 2018, 10:37 pm

Thanks Alan,
The txfr is a new item to my system in that my mix of cartridges and wands are all MM based. This is my first MC and there has been no hum previously?

ajgriff · 13th Nov 2018, 11:01 pm

I believe that the rated output of the AT32 is 0.4 mV whereas a typical moving magnet cartridge would be specified at around 5 mV thus the need for the step-up transformer or a head amplifier. Any induced hum at the deck/arm end of the system will, therefore, be magnified by a factor of ten or more. Hope this helps.

Great cartridge Joe and well worth the effort to get this right.

Alan

Bookman · 14th Nov 2018, 10:53 am

Thanks again Alan,
Your use of the term "induced" would give a reasoning for the problems at hand and how to rectify the situation. May I presume that the hum is power frequency based; i.e. 50Hz?
FYI my origins are just a few miles away and indeed I was employed at BSC Stocksbridge (formerly Samuel Fox) in my early days. I recall walking outside of the melting shop with a tong tester in my hand and I noticed it was reading 15 amps.
To put this in perspective I was approximately 40-50 metres away from one of the 80MVA transformers used for the arc furnaces. These had tapped secondaries where the lowest connection provided 220V therefore the secondary current was 210KA. Think of the magnetic field associated with that and the corresponding induced value I was able to read?
Joe

13th Nov 2018, 8:12 pm	#1
Bookman Hexode Join Date: Aug 2017 Location: Taunton, Somerset, UK. Posts: 318	Audio Technica AT32 Query It would seem the HiFi spirits were looking in my direction when I obtained through unsolicited purposes an AT32 with an AT630 step up txfr all with original boxes. Indeed, my amazement increased even further when I transferred the cartridge from its host head shell to my SME 3009 series III. The condition was as if had never been used. I had intended it for my series II but it is boxed up in the attic. A bit fiddly on set up as 1.7g tracking is recommended but not unexpected. However, upon start up I noticed an unpleasant hum and as such fiddled around with all of the connections which did have a significant impact but not enough. I then removed the AT630 and ran the turntable direct into my Musical Fidelity M3Si which is apparently only suitable for MM inputs. However, it worked a dream with no feedback whatsoever albeit the volume was set at circa 60%/70%. One would therefore assume that the feedback originates from the step up txfr but does it? In this I am referring to the host head shell which has a metal plate fitted that is soldered to the green pin connection; does this need to be mirrored somehow on the SME head shell? Any feedback would be welcome. Thanks Joe Attached Thumbnails

13th Nov 2018, 9:12 pm	#2
ajgriff Nonode Join Date: May 2004 Location: Halifax, West Yorkshire, UK. Posts: 2,587	Re: Audio Technica AT32 Query Sounds like an earth loop in the deck/arm wiring. I think that removing the transformer is simply masking the hum a little due to the reduced gain. Doubt if the headshell plate is relevant. Alan

13th Nov 2018, 10:37 pm	#3
Bookman Hexode Join Date: Aug 2017 Location: Taunton, Somerset, UK. Posts: 318	Re: Audio Technica AT32 Query Thanks Alan, The txfr is a new item to my system in that my mix of cartridges and wands are all MM based. This is my first MC and there has been no hum previously?

13th Nov 2018, 11:01 pm	#4
ajgriff Nonode Join Date: May 2004 Location: Halifax, West Yorkshire, UK. Posts: 2,587	Re: Audio Technica AT32 Query I believe that the rated output of the AT32 is 0.4 mV whereas a typical moving magnet cartridge would be specified at around 5 mV thus the need for the step-up transformer or a head amplifier. Any induced hum at the deck/arm end of the system will, therefore, be magnified by a factor of ten or more. Hope this helps. Great cartridge Joe and well worth the effort to get this right. Alan

14th Nov 2018, 10:53 am	#5
Bookman Hexode Join Date: Aug 2017 Location: Taunton, Somerset, UK. Posts: 318	Re: Audio Technica AT32 Query Thanks again Alan, Your use of the term "induced" would give a reasoning for the problems at hand and how to rectify the situation. May I presume that the hum is power frequency based; i.e. 50Hz? FYI my origins are just a few miles away and indeed I was employed at BSC Stocksbridge (formerly Samuel Fox) in my early days. I recall walking outside of the melting shop with a tong tester in my hand and I noticed it was reading 15 amps. To put this in perspective I was approximately 40-50 metres away from one of the 80MVA transformers used for the arc furnaces. These had tapped secondaries where the lowest connection provided 220V therefore the secondary current was 210KA. Think of the magnetic field associated with that and the corresponding induced value I was able to read? Joe