C414 EB P48 build

[Migs 31]

i have used a trimmer in R5 (25k) and R8 (10k), i apply 48v and measure R7 (2.2k) with volt meter.
I tiddle R8 until i have 4.8v at R7 and then check voltage of both T1 (4.69v) and T3 (3.11v) source.
i now have semetrical waveform

Interesting.
So you “tiddle” (I guess trim) R8 ?
And you have 4.8V at R7 ?!? I’m getting 40,9V at R7-C7-T4 junction.
But what about R5, did you have to adjust it too, or left it at 13.3k ?

Well done anyway.
M

 

[Spencerleehorton]

I just wanted to report that i have succesfully biased my C414's correctly now.
i have used a trimmer in R5 (25k) and R8 (10k), i apply 48v and measure R7 (2.2k) with volt meter.
I turn (twiddle) R8 until i have 4.8v at R7 and then check voltage of both T1 (4.69v) and T3 (3.11v) source.
i now have symmetrical waveform, where as before waveform was mostly all above.
i then replace each trimmer for the amount it is trimmed too.

I just thought i'd make this clear again.
To measure at R7 (2.2k) and have 4.8v at this point, you measure either side of R7, i was confused when i looked back at this.
i also think its best to put a sinewave in and look at waveform then set trimmers acordingly so waveform is symmertrical.

R8 = 10k trimmer
R5 = 25k trimmer

ive also wound my own 6:1 step down transformer which all fits into one of these bodies which sounds pretty fantastic!!

to

 

[Spencerleehorton]

also just tried to bias with sinewave inputed into the capsule and cant seem to get waveform symmetrical?
Ive changed the trimmers to both 100k and waveform doesnt look right, still more waveform above the line than below, which ushally means its biased to less bottom end and sounds harsh?

 

[Spencerleehorton]

right, my problem is the transformer, ive wound a 6:1 version like the u54, but ive wound the CT the wrong side!!
will rewind!!

 

[Spencerleehorton]

All wound and sounds great and waveform looks perfect, loads of output, for vocals just needs a little pop filter.
Will make a few more of these as it sounds about as good as the U87i I have and much smaller.
Great on guitar cabs, acoustic guitars, vocals (although is a little light on the bottom end but perfect for vlogging or podcasting) , will also try as a room mic.