Transformer for 600 ohm Japanese Ribbon Mic?

[Hot Vibrato]

Hey guys, I'm not an electronics expert, but I'm pretty good at soldering. My job for the last 21 years has been as a guitar repairman, and over the years I've installed thousands of pickups, pots, jacks, etc. so I've gotten plenty of hands-on with the soldering iron.

I just bought an Aiwa VM-13 ribbon mic on ebay. It's an RCA 77 lookalike without any pattern adjustment or voicing switch, I got it for cheap because the yoke mount is broken. I think this is otherwise a pretty solid mic, but the impedance is 600 ohms, which is quite different from an RCA 77D, which is switchable from 250 ohms to 150 or 30 ohms.

I have a 77D, which sounds fantastic, and I'm hoping that this mic will offer something similar tone-wise, but I wonder if the discrepancy in impedance will be an issue. I have a Cloudlifter I can dedicate to this mic, and I think the impedance will work just fine with it, but I may want to use it with a vintage tube preamp with no phantom power. For instance I believe my Gates preamp is wired for a load that's between 150 and 250 ohms, so I'm afraid a 600 ohm mic might be a poor match for it.

On a thread about the VM-13 on another forum, Mark Fouxman of Samar Audio said this:

"To do justice to this very fine ribbon microphone I would go the right way--change transformer for a high quality one, with right ratio.

If for some reason you'd like to use original transformer then I'd calculate (or measure, if you have right equipment) its impedance and make an active circuit (or custom adapt the loading on something like Cloudlifter to make it work right).

I'd consider going high Z and then lower it down with another transformer only in case of emergency. That would create way too much losses and noise for such a low signal device as ribbon microphone, and would be the least desirable way of doing it."

Dr. Fouxman has re-ribboned mics for me in the past, and I respect his opinion, so if he says a transformer replacement is an improvement, I'm all for it. I'm comfortable with the idea of soldering the wires, but at this point, it's simply beyond my knowledge base to select the appropriate transformer. I don't believe I have the right gear to take measurements from the mic, but could I remove the existing transformer, and somehow measure it, and use that information to help determine which transformer to use?

Please direct me to any info on the internet that can help me learn enough so that I can choose the right transformer for my mic. Any insight or direction would be truly appreciated

 

[shabtek]

Mark makes transformers

 

[emrr]

Yes, buy Mark's recommended transformer. 

 

[gridcurrent]

I think this is otherwise a pretty solid mic, but the impedance is 600 ohms, which is quite different from an RCA 77D, which is switchable from 250 ohms to 150 or 30 ohms.

it may not be in all actuality 600 ohms.

I believe my Gates preamp is wired for a load that's between 150 and 250 ohms, so I'm afraid a 600 ohm mic might be a poor match for it.

that Gates preamp might be a fine match the way it is presently wired.
in summary, take a listen before spending your money.