BV08 copy transformer from AliExpress low end cut and hum?

[Spencerleehorton]

with a bit of testing there is audable distortion, not sure whether it the txf or something in the mic as i did see a resistor that looked a little cooked!!
bit frustrating really as before i fiddled, this mic sounded excellent!!!

update:

ive tried the original config with first working txf which is 5:1 and still getting distortion when i hit hard on a acoustic guitar or sing loud into the mic with a pop shield so i will check voltages inside as im pretty sure the cooked resistor is the culpret.
original config there wasnt any distortion.

update:

It works fine if i use lower gain on preamp and back off the mic, sounds good.
probably best i get some sleep and come back to this after my night shifts!!!

 

[kingkorg]

It's kinda difficult to follow your project as it's now scattered between at least two threads. You ditched the capsule as it sounds bad, but it's the circuit that is not performing as it should? How do you know the capsule is bad?

You re-wound the TX which wasn't broken because of bad ground connection. If I remember right from the other thread you had issues with plate voltage, if it's still the case no wonder it's distorting. You need to bias the tube right. I don't mean to sound condescending, I just think you should take the time and systematically troubleshoot the mic, otherwise you'll be chasing your tail and blame it on components that are perfectly fine.

In my own case at least 90% of the time it's my own error rather than a faulty component.

Good luck, and greetings from a fellow night shift worker.

 

[Spencerleehorton]

All voltages look good now, 1.1v on cathode and 49v plate

 

[MagnetoSound]

So you got a new tube, right?

 

[Spencerleehorton]

This is the EF800 I’m using in the proctop U47.
I’m waiting on another EF14 for this other version will then try the bv08 with the EF14.
I’ve built 3 x u47s now, two with EF800 and one with EF14.
Both EF800 sound pretty good now but will keep tinkering until I get something that’s really nice.