Gus

SPA picture u47
« on: February 21, 2021, 09:04:34 AM »
Found this looks like one half of the tube is not used. Looks like a wire shorting the grid plate and cathode on one triode in one of the pictures
Can it be traced from the pictures
Is the transformer wired 13:1?

https://reverb.com/item/26608792-stephen-paul-modded-neumann-u-47


bockaudio

Re: SPA picture u47
« Reply #1 on: March 24, 2021, 06:10:18 PM »
Unusual in many ways. I'm not even sure that's an SPA drilled capsule. Usually, they would take out the BV8 and put a Jensen DBE in.

bockaudio

Re: SPA picture u47
« Reply #2 on: March 31, 2021, 05:06:27 PM »
Looks like what became SOP for them a 5751 pins 1-4+9 wired as usual 6-8 grounded.


 

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