Steve Deckert:
Quote:(…) so that the reflected impedance is what you want the tube to actually see.
… but what
is the reflected impedance in ohms that I do want the 6P15P-EV to see??
Over the past weeks I’ve done lots of forum searching here and there and data sheet interpreting to be able to put a number on what primary impedance would be the “best” one, but am still a far cry from a clear answer.
Here in this thread and elsewhere it’s mentioned that one great feature of this design is that even 2 ohm speakers can be driven, but with a reflected impedance that’s vastly different compared to having the same amp hooked up to an 8 ohm speaker must sound vastly different as well?
E.g. ca. 3.2kohm vs. ca. 13kohm on the original design (9.8kohm-6ohm OPT).
If I’ve deciphered the 6P15P-EV data sheet correctly, the plate load resistance is 10kohm at 300V.
The current (?) 10-2021 schematic for the ZKIT1 recommends anything between 3.3 and 9.8kohm as OTP primary impedance. Unclear is whether this is already reflected, or based on the secondary of 6ohms that’s in the schematic.
To come back to the beginning of this post: Assuming my 8ohm speakers are really 8ohm speakers and the amp will never have to drive any other speakers, what’s the impedance I want the 6P15P-EV tubes to see?