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
cmach
197 posts
 

I have used a CJ Premier 17LS and am now using the CJ CT-5.
Both worked without a problem.

Cmach
hiend2's avatar
hiend2
454 posts
 
Impedance Matching plays a large role in preamp/poweramp matching. More then i had any idea of. System is a Mini max tube preamp with a output impedance of 1200ohm. Amplifier is a rogue zeus input impediance of 100,000 ohms I think.
The zeus has 2 sets of RCA inputs. A normal high impedance input and A "low impedance input" Via A input transformer.
The Low Z input completely Blows the normal High impedance away in sound but there is a noticable Blur to the sound from the input transformer. After hearing the diffrence between the 2, Im making it a PRIORITY to match preamp/poweramp impedances very close as possible.
unsound
7,333 posts
 
Sonic Frontiers Line 3.
kwtoxman
25 posts
 
I have a Cary SLP 2002 tube preamp and would recommend it highly if you can be patient and find one used. It is a low impedance design from what I understand. It uses 6922 driver tubes and 12AU7 buffer stage tubes and is a fully balanced design, with a fully regulated power supply. The output impedance is 480 ohms, so it should mate well with 10K input impedance amps.

The sound slots nicely between typical warm tube preamps and very neutral preamps. The huge amount of tube rolling options allows one to further tune the sound to personal tastes.

Cary Audio are very helpful. Call them and speak to them about any questions.

I have found through experience that with the same speakers, a change in the preamp offers the the biggest change to the sound of my system.

Good luck

kw........
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