let's talk ribbon mic transformers

[brad347]

So is one pretty much like the other in terms of turns ratio and resistance?

Is the Lundahl LL2911/2912 pretty much the only game in town?

I have an old RCA varacoustic sk-50. It is my understanding that the ribbon motor in these is identical to the 77DX model, but the varacoustic is an earlier design and has a more primitive (read:inferior) transformer. And a different acoustical labyrinth. And it's uglier.

Anyway, I'm getting in touch with Clarence Kane to get this old beast re-ribboned. I'm thinking of getting a better transformer to put in there to hopefully get me even more in the ballpark of a 77DX (I can't justify spending the money for a real one). I'm wondering if the LL2911 should do the trick or if there's something specific about the iron in the 77DX.

Thanks for any info!

[rodabod]

Ask Clarence, but also look at:

Sowter, Edcor and Cinemag. I'm not convinced the Lundahl would be suitable - I have a vague recollection that it might not spec well for a ribbon mic.

You'd be looking for one with a suitable turns ratio for your particular mic (probably somewhere in the region of 1:25).

Roddy

[fum]

The Lundahl 2911 is a higher turns transformer, 1:37 is normally how it's wired.

I believe that Cinemag sells an RCA replacement transformer (9887), which may be more the direction your looking.

For my $$, I'd have it re-ribboned first, and see what you think of it. If the previous ribbon was of questionable state, you may find that once the microphone is in working order, you may like the sound just fine.

And there's always something specific in the iron, whether it be core material or winding structure, different transformers sound, well.... different =)

Regards

ju

[Martin Kantola]

You should have a look at this if you want even higher ratio: (for making an active output version or so...)

http://www.lundahl.se/pdfs/datash/1927A.pdf

Martin

[brad347]

thanks guys.

[Velvetfreddy]

Just wondering how this turned out. I have 2 old varacoustics. I like them as they are, but hey....

[nosebleedaudio]

if you want a premo go Jensen..

[Crowley]

As you might expect, we've done a ton of work on transformers.

The "best" transformer needs to be matched to the specific ribbon motor, ribbon type and there are other factors as well.

You can't just spec a brand without considering things such as efficiency, noise, frequency response (especially at the low end), hum aperture, and turns ratio. What is the source Z of the ribbon? That matters very much. Do you want a very low noise floor? If so, then you don't want a high ratio, which many have.

In general, a more efficient transformer will sound "better", and have lower noise. Size is an important factor, and bigger is more efficient as that usually means lower Ohmic loss because larger conductors can be used. There are also several types of transformers to choose from. Some EI types, toroids (not a favorite here), multi tap, etc.

Here is a link to some stuff about ribbon mic transformers.

Latest News from Crowley and Tripp's Lab: Search results for ribbon microphone transformers