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Any Members Tried the Audio Interface CST-80 SUT?

My curiosity got the better of me and I just bought this SUT from Japan and wondered if anyone else had any experience with it. The very little I could find seemed to indicate it is a respectable unit and has even been likened to the highly acclaimed Cotter SUT.

It was made in the US around 1982 and came in two varieties. There was a 3 Ohm version with 30dB of gain and a 40 Ohm version with 20dB of gain.

I currently use a Fidelity Research FRT-4 which is excellent and has 4 different taps 100 Ohms, 30 Ohms, 10 Ohms and 3 Ohms + Pass Through for MM.  It will be interesting to see how it compares the FRT-4.

I will use it with my 1.0 mV / 60 Ohms Shinon Boron Red which currently uses the 100 Ohm tap on my FRT-4.

 

ateal
ateal OP
95 posts
 
Once again bimasta you have provided some excellent info. Thanks so much for the list of all those cart. 

I think your CST 80 H (high) is the 40 Ohm version like mine as I read elsewhere that the Low version is the 3 Ohm. It’s good to know that it appears very versatile. 

I won’t get mine for at least a week or two as they have not shipped it yet and it’s coming from Japan. But I’ll be sure to post my findings. 




lewm
6,770 posts
 
I've always wondered why manufacturers of SUTs use a resistance/impedance measurement (ohms) as a way of communicating the specifications of their products.  (Not all of them do it, but too many do.)  It's not very informative for the un-initiated.
intactaudio
84 posts
 
When it comes to transformers the two main factors to be designed around are the source and load impedances.  In the case of a SUT the source is a cartridge and the load is the phono stage.  This means that the cartridge impedance is the main factor that comes into play when mating it to a SUT. 

dave
ateal OP
95 posts
 
I agree Dave and it's one of the reasons I think the CST will not be ideal for my Spectral but it looks good for my Shinon.

As per my calculations if the CST has a turns ratio of 1:10 and my Shinon has an Output of 1.0mV and an internal impedance of 60 Ohms, then the output my MC Stage will see will be 8.87mV, but more importantly the SUT will give a reflected load of 470 Ohms or 7.8x the internal impedance of the cartridge.

The Spectral however, with its 0.2mV and 2 Ohms impedance will see 2mV at the MC Stage, which by itself is manageable, however the problem will be the reflected load of 470 Ohms which is 235x the internal impedance of the cartridge. Not ideal at all.

With the FRT-4 SUT I use the 3 Ohms tap which has a turns ratio of 35.8 and therefore the MC Stage sees 6.8mV and I get a reflective load of 36.6 Ohms or 18.3x the internal impedance of the cartridge.
   

 

roberjerman
2,086 posts
 
+1 for the Cotter P transformer! I used it with the GAS Sleeping Beauty and FR 1mk3F. Nicely designed with Jensen transformers and a captive silver Verion Triaxial cable in a well-shielded blue case. Wish I had kept it! 
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