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In Reply to: RE: Tube Pre Amp for McCormack DNA 0.5 - Covergent MKII? posted by Crescent on October 21, 2014 at 07:16:07
Steve's amps sound wonderful.
I had the pleasure to work on one. Of course I couldn't resist having a listen to the 125.
The DNA 0.5:
Input sensitivity: 0.85V will present an issue for any mid to high gain preamp.
Steve offers a step-down tranny to address this.
Cheers,
W
Follow Ups:
seems that the gain (30dB) and sensitivity (0.85V for full output) are higher than 'usual', and the gain of the CAT is pretty high also (26dB or something for line) ...
So, this might mean the volume would have to be set 'lower' than with other amps, and noise MAY be an issue with high sensitivity speakers?
What preamp is the OP using now? Does the CAT sound best with the volume controls mid-point or higher? I guess there are a couple of questions, but certainly doesn't mean the CAT won't sound wonderful with the 0.5.
Of course, YMMV, etc. ...!
As the CAT MKll has ten tubes!
Thank you all for your thoughts and experience. My system is Mccormack DNA 0.5 Amplifier - YamahaCX 600-U Pre Amplifier - KEF 104/2 speakers. The Mccormack just replaced a Carver TFM 15 amp and is a huge step up. With that in hand I am looking at the Pre Amp.
Ray
There are some pres that have gain settings. This may be an option.
Otherwise, you'll have to reduce the gain with series resistors on the RCA jacks and or shunt the volume pots.
Fairly easy to implement and will provide excellent results.
Is the DNA 0.5's input - cap coupled or servo?
The DNA-0.5, 1, 2, and HT-1 all use the same direct-coupled input with an overall DC servo to minimize output offset. The later DNA-125, 225, and HT-5 use a cap-coupled input and eliminate the DC servo. Only the DNA-500 and 750 monoblocks are fully differential with transformer-coupled inputs. All of the DNA amps have about 30dB of voltage gain for sound quality reasons (I like the gain even higher but I felt this began to cause compatibility issues). For comparison, most amps fall in the range of 24 – 27dB gain, so it is not a big difference. Still, it is noticeable when switching from a lower-gain amp, and any residual noise from the preamp will be slightly more audible.
Best regards,
Steve McCormack, designer
SMc Audio
Hey, I have the Yamaha A-700 integrated amp (ca. 1981), still in use in my garage. I like the Yamaha 'loudness' contour method, certainly the correct way to do this. It sounded good as my main amp for several years, but when I went to tubes (Dynaco SCA-35 integrated amp, ca. 1965) around 1995, I heard a lot that I was missing (space, depth, sense that real musicians were playing together ...).Another 'funny' coincidence, I knew a guy that had the KEF 104/2 speakers, and the (then new) Carver Receiver. He loved the combo (it did sound good to me as well), I think he may still have that setup.
I am totally guessing, but think certainly the CAT preamp is 'worth a try' with the DNA 0.5, and if you find you can't turn the volume up hardly at all from 'off' without it getting too loud, maybe look into the transformers that someone mentioned above. I am guessing that these would be some 'plug' looking things that would be inserted inline with the interconnects between the outputs of the preamp and the inputs of the amp. It's just a way to reduce the voltage coming out of the preamp by 2x or so. There certainly isn't any concern about 'hurting' anything. Just when you turn things on for the first time, don't have the volume turned way up! Start at 'zero' or very low and increase slowly.
It should be 'OMG' better sounding than the Yamaha ... and should be for several times the price!
I have read about the need to rebuild/replace the internal woofers in the 104/2s though ... if these have the original woofers, you may want to look into that. Certainly a classic excellent sounding pair of speakers.
Edits: 10/22/14 10/22/14
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