I built this 2-stage 300B Push Pull amp.
It was pedestrian with garden variety 12AT7/ECC81,
but really sings with super ECC81 tubes like
GEC A2900 and ECC801S.
After several failures building PP amps, this is a keeper.😗
Inspiration came from John Tucker's parafeed 45, which uses
CCS loaded parallel 5965 (12AT7 variant) triodes as driver.
I am in the process of building a 5691 (super 6SL7 ??) drives 300B/45 PP version,
6SL7 has more mu.
Not sure if 5691 has as much super power as A2900 or ECC801S ?
Currently, it is using the secondary of LL1660S (an interstage transformer)
as the phase inverter (center-tapped choke).
It is lacking some lower ends due to the inductance (~20H).
Suggestions on the availability of higher inductance ( > 40H)
center-tapped chokes (or 1:1 inverted transformers),
and comments are welcomed.
It was pedestrian with garden variety 12AT7/ECC81,
but really sings with super ECC81 tubes like
GEC A2900 and ECC801S.
After several failures building PP amps, this is a keeper.😗
Inspiration came from John Tucker's parafeed 45, which uses
CCS loaded parallel 5965 (12AT7 variant) triodes as driver.
I am in the process of building a 5691 (super 6SL7 ??) drives 300B/45 PP version,
6SL7 has more mu.
Not sure if 5691 has as much super power as A2900 or ECC801S ?
Currently, it is using the secondary of LL1660S (an interstage transformer)
as the phase inverter (center-tapped choke).
It is lacking some lower ends due to the inductance (~20H).
Suggestions on the availability of higher inductance ( > 40H)
center-tapped chokes (or 1:1 inverted transformers),
and comments are welcomed.
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Yes, good catch. Thank you. The drawing is in error. I checked my build, fortunately, it is connected to B+.
Understood. Would the addition of a mosfet follower help driving C2 and LL1660S? or a mu/whites cathode follower. E88CC is an alternative to 12AT7 with a little bias change.
Thank you for your suggestions. I already have a ECC88/300B single-ended amp setup.
I will look into the idea of using a follower after replacing the LL1660S. Thanks.
I will look into the idea of using a follower after replacing the LL1660S. Thanks.
I wonder why you don't use the LL1160S as intended ie the primary between U3, U4 plate and HT. You could even make U3 U4 a LTP and drive the primary differentially avoiding the DC offset in the transformer. Lots of options.
I had tried the LL1660S primary as a splitter. It didn't sound right.
I think the primary is gapped for a certain account of bias current.
I had also considered using 12AT7/12AU7 as a LTP, as you said, but it does not have enough gain
in my system. I don't have a preamp.
I think the primary is gapped for a certain account of bias current.
I had also considered using 12AT7/12AU7 as a LTP, as you said, but it does not have enough gain
in my system. I don't have a preamp.
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