RuudNL

"U67"-ish microphone
« on: May 22, 2020, 10:55:53 AM »
Just for fun, I recently put together a "U67"-ish microphone.
It is a kind of mix between a U67 and a U87.
The microphone works as expected, sounds good and I don't hear any difference between this microphone and a U87ai.
Measured self noise is 2 dB higher than a U87ai. Not too bad, but maybe a better EF86/EF806 could improve this.
I used an original Neumann capsule that I had as a spare.
The microphone is powered from an existing tube power supply, delivering +120 V for HT.
De-emphasis is through feedback from the output. (15 KHz is 5.5 dB down referred to 1 KHz.)

For those who are interested: the schematic is in the attachment.
There is a solution for every problem!

http://www.vansteenisaudio.nl


OneRoomStudios

Re: "U67"-ish microphone
« Reply #1 on: May 22, 2020, 01:05:25 PM »
Very nice. Which output transformer did you use?

RuudNL

Re: "U67"-ish microphone
« Reply #2 on: May 22, 2020, 01:47:21 PM »
This one (3U Audio):

https://www.ebay.nl/itm/3U-Audio-GZT-87-Output-Transformer-for-Condenser-Microphone/111683319855?hash=item1a00d8382f:g:f6kAAOSwiCRUg89Z

Although is has a small core, the frequency response is excellent.
(Measured from 'test input' to output, 20 Hz is only 1 dB down.)
There is a solution for every problem!

http://www.vansteenisaudio.nl

Re: "U67"-ish microphone
« Reply #3 on: May 22, 2020, 02:04:07 PM »
This is phenomenal. Thank you for sharing!

RuudNL

Re: "U67"-ish microphone
« Reply #4 on: May 23, 2020, 06:47:22 AM »
Picture of the prototype.


There is a solution for every problem!

http://www.vansteenisaudio.nl


 

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