Tube microphone inspired by u67 on a soviet pentode 6j1p

[raywisby]

Hello everyone! I build a "u67 Clone" on the soviet pentode 6j1p (EF95). I used mic body and the rk67 capsule from aliexpres.
https://ko.aliexpress.com/item/4001...lo2kor&spm=a2g39.orderlist.0.0.6e0f4aa6bFD5Ox
The assembly is not very neat, but it was important for me to make sure that it was working

Transformer t13 with 9.5:1 ratio
C2 - I used a 250v polypropylene capacitor, it turned out to be very large, I had a hard time finding a place for it


Sounds good for me!

 

[RuudNL]

It seems the HF roll-off starts at a pretty low frequency.
Maybe 'fine tune' C6 a little?
The Neumann U67 first has a little bump around 10 K before the HF attenuations sets in.

 

[raywisby]

Кажется, что спад на ВЧ начинается на довольно низких частотах.
Может быть, немного «доработать» C6?
Neumann U67 сначала имеет небольшой скачок 10 K, прежде чем начинается затухания на ВЧ.

I've tried different capacities, 220pf with my capsule works better for me

 

[Drosselmeier]

It seems the HF roll-off starts at a pretty low frequency.
Maybe 'fine tune' C6 a little?
The Neumann U67 first has a little bump around 10 K before the HF attenuations sets in.

rise in high frequencies depends on the capsule, and this is a graph from the supply of white noise to the circuit I think

 

[RuudNL]

It doesn't say if it is an acoustical measurement (capsule + electronics) or a measurement of the electronics alone.
If it is a capsule+electronics measurement, the HF is too much attenuated, if it is an 'electronics only' measurement, -4 dB @ 15 KHz. could be about right.

 

[raywisby]

It doesn't say if it is an acoustical measurement (capsule + electronics) or a measurement of the electronics alone.
If it is a capsule+electronics measurement, the HF is too much attenuated, if it is an 'electronics only' measurement, -4 dB @ 15 KHz. could be about right.

This is SW RT input test, this is not an acoustic measurement, sorry for not explaining

 

[Stack]

Hello everyone! I build a "u67 Clone" on the soviet pentode 6j1p (EF95). I used mic body and the rk67 capsule from aliexpres.
https://ko.aliexpress.com/item/4001...lo2kor&spm=a2g39.orderlist.0.0.6e0f4aa6bFD5Ox
The assembly is not very neat, but it was important for me to make sure that it was working

Transformer t13 with 9.5:1 ratio
C2 - I used a 250v polypropylene capacitor, it turned out to be very large, I had a hard time finding a place for it


Sounds good for me!

View attachment 89064

First off, Congratulations ! Bet it does sound like a U67. It’s a great tube mic for all sorts of things. The costs ? These devices are fairly straight forward circuit wise. The magic’s in the combination of things like tubes, transformers and all the surrounding electronics. This inspires !

 

[Stack]

Acoustical properties do require an anechoic room for the acoustic analysis, to be completely fair about it.