2. amps-preamps
  3. 1140406847

Preamp impedance mismatch with McCormack DNA2

I recently purchased a McCormack DNA-2 with an SMC Rev.A mod. The amp currently has a 100K input impedance, however I am sending it back to Steve for some additional mods including the Jenson balanced transformer upgrade, which would change the input impedance to 10K. I am currently running direct out of my Reolution Audio Opus 21 cd player, but would really like to add a tube preamp. I am finding that alot of tube preamps are typically ( on paper ) not suited for driving a lower input impedance. However, what is on paper and what is reality are often two different scenarios. I would appreciate some suggestions on some balanced tube preamps that may work well with this amplifier. I don't live in an area where there are dealers so trying several at home is not possible. At least with some suggestions it will help narrow my search and the amount of traveling I will have to do. Thank you for all the help.

Darrin
rhythmace4218
albertporter's avatar
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albertporter
4,949 posts
 
Steve McCormack would be an excellent source for the answer to your question. I have known Steve for nearly 30 years, a very bright guy who will answer without any bias.

This is a natural since he's doing work for you.
porziob
316 posts
 
Since convential wisdom dictates that tube pre amps prefer higher impedences, & you inhabit a dealer barren area, you`re in a lose lose position. YMMV.
benie
147 posts
 
Check out this preamp http://www.space-tech-lab.com/SP-QA-111-BAL-SP.html . Albert at Space Tech.Labs can custom design to meet your needs. Very Very nice preamps.
rhythmace4218 OP
53 posts
 
I have talked with Steve McCormack. He was very helpful,and advised to look at preamps with a 1000 ohms or less output impedance. I have read many reviews on several balanced preamps and even though they may may have an output impedance substantially lower than 1000 ohms at 1khz. However, the output impedance drastically rises as the frequency falls. I realize this is normal, but almost all the reviews make mention of mating the preamp with an amplifier with an input impedance of at a minimum of 20-30K. I noticed that the DNA-500 also has a low input impedance of 10k. Maybe I could get some useful feedback from some DNA-500 owners as well. Perhaps I should skip the Jenson upgrade. Does anyone have any experience with this particular Jenson transformer upgrade from SMC? Is it worth it? Thank you

Darrin
bgrazman
226 posts
 
I'm having great luck with a Supratek Syrah preamp and the SMC Platinum version of the DNA 0.5.

Before the Supratek was an ARC LS-7 (also tubes).

The amp came into the system unmodifed... I had the Rev. A work done and lived with it a few years and just a few months ago went for the full monty. Have only seen the results get better & better.

I would also second albertporter's comments--Steve has always steered me in the right direction.

happy listening,
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