AR-51 PSU question

I am cloning the Telefunken AR-51 and have read its power supply is 140 volts instead of the more common 120 volts most classics liked to see. I intend to change the 1N47__ diodes to ones closer to the Telefunken's voltage. I have 2-68V 1N4760's and 2-75V 1N4761's. That leaves a supply voltage of 136 volts or 143 volts.  If 140 volts is my intended goal, should I go with 136 or 143 volts? Thanks.

-James-

James,

I can't help with the supply voltage, but I'm interested to hear how this project comes out. Are you using a K67 type capsule, as per the original? This circuit seems like it might be a useful way to use up the Chinese capsules that are being left unused from the U 67 body kit, etc.

I have not spent any more time reverse engineering the Copperhead, though I may try in a few months and post my results.

Dylan

My intent is to use one of the Chinese 32mm K-67 capsules I have laying around. If I find the sound lacking, and circuit mods don't/won't fix the problem, I will replace it with a decent-to-excellent K-67 clone. I'm also using a Cinemag CM-2480 in place of the pricier Haufe T14/1 transformer.

On another note, I'm almost done designing the final component, the headbasket. This is a homemade design borrowing from bottle mics and the old spring-shockmounted carbon mics. An interesting look with improved shock protection (hopefully).

Here are some early, dry-fit pics:

https://www.dropbox.com/s/8wv5h1h4d7w4kkm/Photo%20Dec%2004%2C%204%2030%2004%20PM.jpg

https://www.dropbox.com/s/qsxqgu3bv7zvb08/Photo%20Dec%2004%2C%204%2030%2048%20PM.jpg

HellfireStudios said:

I am cloning the Telefunken AR-51 and have read its power supply is 140 volts instead of the more common 120 volts most classics liked to see. I intend to change the 1N47__ diodes to ones closer to the Telefunken's voltage. I have 2-68V 1N4760's and 2-75V 1N4761's. That leaves a supply voltage of 136 volts or 143 volts.  If 140 volts is my intended goal, should I go with 136 or 143 volts? Thanks.

-James-

Click to expand...

Nice Mic  8),    You could strap some lower voltage zener in series to get what you want.

or build a complete passive solution  with drops resistor calculation. or .....

but at this difference level  in voltage you would approximatively get in the range of +- 0.05 ma plate current difference or/and about 1.5V capsule polarisation
if you expect a tube  with a little more plate current sweet spot you might a stick to the 143 as it will probably go down a tad .
Hope this helps,

Best,
Dan,

I thank you for the kudos. Building this mic from scratch has given me the greatest appreciation for mic designers. There is SO much more to making a mic than meets the eye.

As for your suggestion, I think I'll stick with 143 volts. Your thought on cable loss seems logical. Thank you.

BTW, I'm using a standard Alctron HST-11A PSU as that is what Telefunken includes with their mic (supposedly running at 140 volts).

-James-