Telefunken ELA V1140 - Knock down gain

[abbey road d enfer]

I think that´s not the right way.

Do you deny that using a 1:1 xfmr results in a noise factor that is about 20dB worse than with a 1:10?

 

[Michael Tibes]

3 x EF12 and an EZ11, doesn't that scream for a V41 circuit?? If I remember right there should be schematic around here or at Kubi's-

Michael

 

[Bo Deadly]

3 x EF12 and an EZ11, doesn't that scream for a V41 circuit?? If I remember right there should be schematic around here or at Kubi's-

Michael

Yeah, pretty close:

 

[amplexus]

Well damn, that might be an approach....

 

[Bo Deadly]

Looks like the main differences are that V1 is running a lot colder with the 15K+4K cathode resistance (and the transformer is "standing" on it to bias V1) and V3 is only partially bypassed.

 

[abbey road d enfer]

And that most of the gain is due to the first two tubes. The output stage has a gain of 1.33 only. Which compensates for the 1:18 input xfmr.

 

[abbey road d enfer]

Well damn, that might be an approach....

An expensive one, though. All this iron... 1:18 input (unobtainium), power xfmr with 3 separate heaters, two parafeed chokes and one output.
Also note the input EMI/RFI filter that has nothing to envy to the products. most recent
One can see it was a no-expense-spared project.

 

[Michael Tibes]

Could the chokes in the V41 circuit be replaced by constant current sources?

 

[abbey road d enfer]

Could the chokes in the V41 circuit be replaced by constant current sources?

They could, but it would imply increasing B+ significantly.
Then you would have to choose the topology:
Google The Optimised SRPP Amp: An article Martin Blencowe wrote for AudioXpress on the SRPP as an OTL amplifier
or The Tube CAD Journal,SRPP Decoded
or a solid-state CCS?