Hybrid P3A - Tube differential input stage - ECC88

[Ciro82]

Me and my friend we are thinkering about this:






What do you guys think?

 

[Ciro82]

 

[Ciro82]

 

[rongon]

Really nice work there!

Running a ECC88 LTP from a 35V B+ is pretty marginal, no? What is the voltage on pins 1 and 6 of the ECC88?

 

[Ciro82]

Second prototype:
+50 0 -50 V supply;
Current mirror on top of the ECC88;
All BJTs in VAS, VBE and Drivers stages swapped with more robust ones;
Bootstrap network;
Doubled power stage BJTs.
2nd proto schematic and PCB:


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Third prototype:
+50 0 -50 V supply;
Current mirror on top of the ECC88;
All BJTs in VAS, VBE and Drivers stages swapped with more robust ones;
Bootstrap network replaced with a real CSS;
Doubled power stage BJTs.
3rd proto schematic:

The 3rd proto is much better.