impedance match of preamp and main amp.


I am considering mating a Mcintosh Mc602 with a Bat Vk 51se. I noticed the input impedance on the Mc602 is 10K. While most Bat amps are much higher. Does anyone see a problem with this? It seems I remember a Stereophile I used to know told me about a ratio minimum of 1 to 25. I am not sure though.
cturnem

Showing 3 responses by georgehifi

I like big solid state, biased hard into class A with huge power supplies, and that has bi-polar output for great current delivery.

The Classe CA400 you have is no slouch either, I would be quite happy owning that even though they are Mosfet output.

Your Vk 51se should be happy into that 75kohm input impedance.

The B&W 800D's are a bit of a bitch to drive, if you can understand the test here.
http://www.stereophile.com/content/bampw-800-diamond-loudspeaker-measurements

I would be more likely to go the big class A bi-polars for these 800's like what I use. Things like the big high class A biased Krells, Mark Levinson's and such that use bi-polar output stages, for good current delivery for the 800's.

Cheers George
Cturnem, sounds like you want to keep your Bat preamp, and that Mac looks to be a nice amp, if your keen on owning it.

Your Bat preamp is a low 410ohms output impedance at most frequencies and into the Mac it has a good ratio of 1.24, the problem is in the bass, and as I said above this is an easy fix if you get a tech to change the Bat's output coupling capacitors to 4 x larger in uF. Then it will be a perfect 1:24 ratio at all frequencies.
This job to do should be around $100-$200 then your Bat will also be a match for any amp you purchase in the future as well.

Cheers George
Al's right Cturnem.

But a simple solution for you if you want to go this way and use the Mc602, is to get a technician to change the coupling cap in the output of the Vk 51se and replace it with one of the same quality but say 4 x larger in uF (microfarads).

This would then take the high 4700ohm impedance from the -3db at 20hz region down to -3db at 5hz, where it should have much less effect on the audible bass frequencies.

Cheers George