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In Reply to: RE: Now and then posted by John Elison on January 27, 2015 at 17:02:58
It's more resolving and generally more satisfying than the ART7. However even with 76db gain from Pass XP-25(loaded at 20-50R) there is excessive noise through a tube line stage that puts a limit on volume and dynamics. I suppose I need to keep an eye open for that matching step-up trannie...
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The T-2000 has a turns ratio of 1:56 and it worked well with the MM phono stage in my Yamaha C-2x preamp, which had 35-dB gain. I got no audible noise that I can remember.The Bob's Devices CM-1131 SUT has a turns-ratio of 1:40. It might work equally well with the MC-2000. A turns-ratio of 1:40 is only 3-dB less than 1:56.
I'm kind of surprised you are getting excessive noise with your Pass Labs XP-25. I own the XOno, which supposedly has 75-dB maximum gain and I get no noise with my DL-S1. I know that my DL-S1 has 3-times the rated output as your MC-2000, but based on its 40-Ω DC coil resistance in conjunction with my 20-Ω loading configuration, the results should be about the same.
Phono Stage Output = (Phono Stage Gain) x (Rated Cartridge Output) x (Phono Stage Load) ÷ [(Phono Stage Load) + (Cartridge DC Coil Resistance)]
76-dB = 6310-gain
75-dB = 5623-gainMC-2000 / XP-25 Output = 6310 x 50-µV x 50-Ω ÷ (50-Ω + 3-Ω) = 298-mV
DL-S1 / XOno Output = 5623 x 150-µV x 20-Ω ÷ (20-Ω + 40-Ω) = 281-mV
I wonder if cartridge age might have reduced the MC-2000's output voltage or increased its coil resistance, or both? The only other option is that your XP-25 is rather noisy or else your tube line-stage is noisy. Anyway, I would think you should be getting excellent performance with your MC-2000 using 76-dB gain.
Best regards,
John ElisonPS. Something else just occurred to me. I wonder if the magnet in the MC-2000 has lost some of it magnetism over the years. If you have a test record with a 5-cm/s 1000-Hz test tone, you might want to measure the output from the MC-2000. You can measure it at the output of the XP-25.
Edits: 01/27/15 01/28/15
Thanks. The XP-25 is dead quiet at 76db. The noise is slight tube rush from the AtmaSphere MP-1 as the volume control is cranked up for the MC2000's miniscule output. It's fine at a normal listening levels. Allowing for this small issue, I wouldn't characterize the MC2000's performance as anything but excellent.
I guesstimated that I get ~80db phono gain with the modified hybrid cascode input. And I am looking eternally for an MC2000, with the notion that the modified MP1 phono stage can handle it with no SUT.
Yes. You should be fine with MC2000 into the hybrid cascode. I haven't tried it only because for XP-25 I've transitioned to RCA terminations on the straight-shot tonearm cable. One of these days I'm going to replace the MP-1 XLR phono inputs with RCA.
BTW, the L07D recently lost speed stability. Whew, replacing all electrolytics fixed it. It had taken nigh on a year for Allied to get stock from UK of Howard's recommended PS reservoir caps. While I was in there I replaced the germanium diodes with Schottky.
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