100H Inductor for V76

[tomas.borgstrom]

I just finished a pair of V72. They sound great and quite close to the original units. I decided to also build a REDD47 and a V76 in the same rack. I will remove most of the filters in the V76 but I will include a switchable 80Hz low cut filter. Since LC-filters are rare these days it would be fun to stay true to the original design. The problem is the 100H inductor (87 in the schematics) . After some searching I only found anode chokes with that high value, ex this one:

https://www.thermioniclab.com/en/anode-chokes/anode-choke-100h.html

How will it perform in a low cut LC filter?

Another question. I'm going to leave out the 0.85H inductor in the signal path (84 in the schematics). Should I remove one of the 100pF decoupling capacitors (C25, C26)?

 

[jensenmann]

Reach out for our member MrDude. He´s wound pretty much everything necessary for a V76: https://audiosohn.com

 

[tomas.borgstrom]

I contacted him. Unfortunately he's only remaking Bv. 514.

 

[Murdock]

Try Reinhöfer. They do custom stuff. I had some three chamber M42 bobbins which I wanted to use as plate chokes. They wound them for me with some pretty thin wire and a lot of turns. The same as V76 chokes. Pretty cheap too.
As the filter inductor don’t need to be gapped you can use high permeability cores with fewer windings. So it should be a pretty easy job for them.

 

[abbey road d enfer]

Another question. I'm going to leave out the 0.85H inductor in the signal path (84 in the schematics). Should I remove one of the 100pF decoupling capacitors (C25, C26)?

This inductor and the two capacitors constitute a 25kHz low pass filter. Leaving the inductor without the caps makes no sense.

 

[lukas]

Look at the pics, transformer with 87 number, probably the same dimmension as V72 choke three chamber bobins with different turns. I can try calculate and winding this things(EI48 lam's), if u want...

 

[tomas.borgstrom]

Look at the pics, transformer with 87 number, probably the same dimmension as V72 choke three chamber bobins with different turns. I can try calculate and winding this things(EI48 lam's), if u want...

Thank's for the support. I don't fully understand. Do you offer to wind a 100H inductor?

 

[lukas]

Yup. One EI60, and EI48 on the pics.

 

[Ilya]

Sowter can wind you a custom 100H inductor. I used their stuff in my build.
However, if you have a low voltage rail available, you can make a gyrator with an op-amp to simulate this inductor. This is much cheaper.