Ancient Sony ECM-50; new lease on life!

[k brown]

Digging around in my old notebooks, I found a reference to tests I made decades ago trying out ECM-50s without their stock phantom power supply, which besides the phantom reg zener and voltage filtering, consisted entirely of a teensy little transformer; it biased the FET, supplied the balanced output and fed phantom from a center tap. I'd never seen a mic FET biased only by the primary of a transformer.

My notes indicated it sounded best with a source resistor of about 20k. I happened to have a transformerless power module out of another mic that had just that value of source resistor, and voltage close to that supplied by the Sony phantom module.

Everything I've never liked about the sound of these mics vanished!
-- Considerably higher output.
-- A lot quieter. Simply amazed how quiet a 50 year old, tiny electret can be (granted these were the quietest pair of capsules I'd culled from a half dozen).
-- Much smoother top response and fuller on the bottom.

If you've only ever heard ECM-50s with their stock mini transformers, you ain't heard nuthin'.

I would assume even better with the source resistor properly selected by scope measurement (FETs are the same grey color Sony made almost everything out of in those days). The 'large' grey object beneath the contact spring is the FET. Obviously manufactured just for these mics; the contact spring is soldered to a short pin protruding from the top of the FET.

Suddenly these are very useful arrows in the quiver!

 

[k brown]

My fav ECM-50 anecdote (Tchad Blake sticking them in his ears to make binaural recordings):

https://www.soundonsound.com/people/tchad-blake-binaural-excitement

 

[Icantthinkofaname]

Are vintage Sony electrets good, or are they the ones that lose charge over time? I might grab a couple used ones since they're cheap, if they're good.

 

[k brown]

This diagram from the first ECM-50 manual shows it to not be a back-electret, which were the first electrets that held their charge nearly permanently.

Whether Sony switched to back-electret by the time the phantom-powered model (ECM-50PS) came out, I don't know. I have eight capsules from various iterations, and they all have normally strong output; they do vary a bit in noise.

I've had other models of Sony electrets that were very weak and noisy. Their earliest models were not back-electret.

Their earliest back-electret models proudly boasted a dot with the letters "BE" in it, on the mic body.

 

[Icantthinkofaname]

I was looking at the ECM33F cause I'm seeing them for like under $50 used.

 

[k brown]

Original post updated with photos.

 

[iomegaman]

Short vid with interesting use:

 

[k brown]

Val Garay on James Taylor too:
https://jamesmeder.com/post/177705087878/never-underestimate-the-little-guys-the-sony