Mic pre input transformer. Can it be reversed for microphone output transformer?

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kato

Well-known member
Joined
Aug 16, 2004
Messages
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Location
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Supposing you have a 1:10 mic input transformer and a need for a 10:1 mic output transformer, and a busted checking account. Could you reverse that 1:10 into a 10:1?  Would it work?  And if so, would it be sub-optimal in an audible way?

I understand even if the impedances are correct, the inductance and DCR will be different as it's a longer wire around a larger core, and these specs factor into design considerations that could shift the frequency response if not compensated for.

That said, here's my specific example.
The D-U87 calls for a
            CM-2480 impedance: 16.5K : 150 (10.5 : 1) operating level: +18dBu - data sheet

I have a spare:
            CM-75101A    impedance: 150,600 : 15K        operating level: -2 dBu

What 'cha think? Worth trying? Or don't bother.
 
see the minus 2 db and the  plus 18 db?

that is a problem.

UTC A-26 as linbe input,

not a problem as the A 26 has the level capability to be used in reverse,


 
I say try it kato--in both cases -2 (~1.74vp-p) is on the low turns side and the +18 (~17.4vp-p) is the higher turns side 10 times difference;10 x winding ratio, over.
 
I agree with shabtek,

They're likely giving you the primary rating, which is now going to become your secondary. But you really won't know until you try.

 
Works in principle at least - probably worth trying. As the others say, you might get different noise performance or bass response if the inductance and DCR are different, but it should work to a degree.

I've made a few tube mics with reversed Sowter and Lundahl mic input transformers, which have worked well.

Stewart
 
zebra50 said:
I've made a few tube mics with reversed Sowter and Lundahl mic input transformers, which have worked well.

Stewart

Yeah, that's what gave me the idea. I believe the "royer mod" for the MXL2010 used a Jensen direct box transformer in reverse.

The grown up side of me says "dig up $60 and bite it." (buy the right tool for the job.) The kid side says "I wonder what would happen if..." But I dug deep in my couch cushions and only found some popcorn, a few honey nut cheerios, and some mouse droppings. Kid wins!

Anyway, I measured the resistance of the 150Ω side, what we'll call my "secondary" / faux secondary is at 13Ω.  and the faux primary measures 2k18. It's reported that
sredna said:
the AMI transformer has ~ 22 Ohms on the secondary and ~ 440 Ohms on the primary.

That's a big difference on the "primary."  I wonder if that's too much coil for that poor fet to kick up sufficient flux to squeak out a peep. Even if it does, I'll never really know if it's compromised unless I compare both transformers side-by-side.

Thanks for your thoughts guys. Pipe in if any other thoughts.  I'll be back when I find $60...
 
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