Posted by mark_ivan on April 24, 2007 at 19:59:39

Hi

Have been trying different cartridges on a Rega P25 with RB600 arm:
Ortophon OM20 Super, Rega Exact, Dynavector 10x5.

Was interested in LOMC and the Cinemags, and out of sheer paranoia that they (CineMags) would either go up in price or cease becoming available by the time I needed them, I bought a pair.

Very curious to know what step up ratio you used with your 2.5mV Dynavector 20xh and the Seduction?

Would like to try this with my 2.5mV 10x5, but the stepup ratios seemed better suited to cartridges with outputs below around 0.5mV (since I think the lowest ratio on the CM is 1:18 and the 40dB Seduction multiplies that by roughly 100).

Can you provide some detail?

Thanks,
Mark

• Re: Ping Rockpassion: Cinemag SUT with 2.5mV cart and seduction? what step up ratio? - rockpassion 13:24:01 04/25/07 (2)
  In Reply to: Ping Rockpassion: Cinemag SUT with 2.5mV cart and seduction? what step up ratio? posted by mark_ivan on April 24, 2007 at 19:59:39:

  Hello Mark,

  I am currently on the road and do not remember which load I tried. I do believe it was the 37.5 ohm connection but to be sure I will need to check. I can let you know this Friday or Saturday if you can wait.

  Regards

  Richard
  
  

  ---

  • That would be great... - mark_ivan 20:27:50 04/25/07 (1)
    In Reply to: Re: Ping Rockpassion: Cinemag SUT with 2.5mV cart and seduction? what step up ratio? posted by rockpassion on April 25, 2007 at 13:24:01:

    Since I also have a Dynavector (lower pedigree though) with similar output, I would be very interested in 'recreating' the setup you are using with your Seduction and Dynavector cartridge.

    There might be some difference though as my arm does not have a separate ground wire (Rega RB600).

    I had not considered using the SUTs with this cart because I assumed the resulting output would be too high (~ 18 * 2.5mV), but apparently there is more to it than the straight step up ratio.

    Recreating your set up would be an interesting reference to start from if I decide to explore other options like the JFET buffer that was suggested, or a Denon 103.

    Did you use the transformers as outlined on the Cinemag site (paralleling the two input coils), what type of connection between the transformer and the Seduction?

    Thanks,
    Mark
    
    

    ---

    • Re: That would be great... - rockpassion 15:59:24 04/30/07 (0)
      In Reply to: That would be great... posted by mark_ivan on April 25, 2007 at 20:27:50:

      Mark,

      I was using the 37.5 ohm connection which resulted in the best sound. The 150 ohm was way too shrill.

      I got my Shelter 501ii setup and have about 20 hours on it. It also sounds much better on the 37.5 ohm connection.

      As far as connection goes I setup two connections for the cables from the tonearm/cartridge, one for the 37.5 ohm and one for the 150 ohm. I then ran a couple with connectors directly to the Seduction box. That way I can change between the two loads by simply switching the cables. I could have put a switch in but I did not want to wait and I had all the stuff to just do the cables.

      I have a marked up schematic but went away for the weekend and I am away this week. If you would like a copy I can email it to you on Friday. I will say the biggest problem I had was hum but I fooled around with the grounding and have most of it taken care of. I can only really hear it when I turn my Foreplay II up really, really loud.

      Richard
      
      

      ---
• Re: Ping Rockpassion: Cinemag SUT with 2.5mV cart and seduction? what step up ratio? - Eli Duttman 22:32:08 04/24/07 (0)
  In Reply to: Ping Rockpassion: Cinemag SUT with 2.5mV cart and seduction? what step up ratio? posted by mark_ivan on April 24, 2007 at 19:59:39:

  Mark,

  As PJ indicated, there are interesting loading issues in combining HOMC carts. and SUTs.

  FWIW, I favor a brute force approach to the problem that WILL work. Microphone trafos require LOW impedance sources. HOMC carts. are intended to work into 47 KOhm loads. Buffering the cart. with JFET source followers matches the impedances perfectly. FETs are better than tubes for this job, simply because they are less noisy. A bipolar PSU eliminates caps. in the signal path on the I/P side.
  
  Eli D.
  
  

  ---
• Re: Ping Rockpassion: Cinemag SUT with 2.5mV cart and seduction? what step up ratio? - Paul Joppa 21:33:58 04/24/07 (0)
  In Reply to: Ping Rockpassion: Cinemag SUT with 2.5mV cart and seduction? what step up ratio? posted by mark_ivan on April 24, 2007 at 19:59:39:

  Your math is correct, you want a ratio of 2 to 4 for a good stepup ratio with a 2.5mV cartridge.

  However, you have not accounted for resistances and impedances. The SUT provides a low loading impedance to the cartridge, and if the cartridge has a high internal resistance that may cause a big drop in the actual level seen by the SUT.

  This is not widely done except by accident - usualy a matched impedance is the lowest recommended loading. It gives a 6dB reduction (half the voltage). A really tiny load will damp the cartridge more, up to twice as much, which may be audible. Cartridge reactance (inductance and capacitance) may become problems - I would not even think of this with a MM cart - but probably some high-output MC carts would work this way. The cart would be operating in current mode instead of the normal voltage mode. Ampex used a current-mode tape head in their last tube tape deck, the MR-70, and it's considered quite exotic. For phono carts, this is unexplored territory with intriguing potential...
  
  

  ---

Post a Followup: