Ribbon mic transformers

[Mr. Alexcool]

I recently made a ribbon microphone which worked a little bit, but had very low output with quite a bit of noise on recording. I added a $2.98 audio transformer (8ohm to 1kohm) from radioshack, and tried recording again, and alot of the noise was cut out and it had much higher output. I think it could be better though, with the addition of some neodymuim magnets, thinner foil, and especially a better transformer. I've been looking into some ribbon mic transformers in my price range, such as the Edcor RMX-1, Lundahl LL2911, and Sowter 8074. Do you know how these (or others available from $0 to $70) compare or if they are worth investing in? Your input will be greatly appreciated.

[Matt Syson]

Hi
Interesting project!
The ribbon's impedance is very low, a fraction of an ohm and it needs magnifying significantly. This implies high turns ratio on the transformer with a low resistance primary (less than 8 ohms) and high resistance secondary. Looking at the Sowter or Lundahl offerings should give some idea of what is necessary.
These units are some investment but probably necesary if you want a satisfactory outcome. Maybe a miniature 'output ' transformer from a tranny radio would give you better step up ratio with lower resistance windings. These would be cheap and you can play.
Good luck with it.
Matt S

[Mr. Alexcool]

Thanks for the input. I just happen to have a host of little radios that my aunt gave me for no particular reason. Now I know I could put them to good use.

[Matt Syson]

Hi
The output transformers may approack a decent step up ratio byt the frequency response will be poorer than a 'proper' ribbon TX and you will need to put it into a steel or preferably MUmetal can otherwise it will hum BIG TIME.
Still, all cheap and a useful learning excercise.
Post a pic of the mic assembly and finished??
Matt S

[rodabod]

Definitely get a proper ribbon transformer. The ratio is only the first issue - ribbon transformers are designed specifically, and have very low DC resistance on the primary amongst other important features.

Sowter offer two ratios depending on the resistance of your foil.

The Edcors are cheap and may be worth a try.

[slyeee]

you'll get some informations at this adress
http://make_a_ribbon_mic.tripod.com/

[Axiomhead]

Originally Posted by slyeee

you'll get some informations at this adress
http://make_a_ribbon_mic.tripod.com/

I built a few of these with the Radio Shack transformer a few weeks ago... My 3rd try yielded something that sounded pretty nice, except there was nothing above 10K. I ordered the Lundahl to furthur experiment but its on back order till November.

[cody brown]

cool thread!