Sweet. Nice work.
charles
Thanks Charles.
This thread is about sharing about our amps - I didn't really do that.
I find that difficult because of the many details that went into this amp: it really was a bit of a thought experiment and I would not recommend an amp build like this... though it does sound lovely (slightly warm, coherent, expressive with surprisingly linear-sounding bass) despite (because of?) the high frequency roll-off expected when a low gm pentode drives a DHT.
The basic design is a classic direct-couple, not Loftin-White or monkey or variants. I like the sound of the EML and JJ 2A3 tubes with the plate at roughly 1mA:6V, in this case 42mA and 250V with a 4.2K load; AC filaments. Good for maybe 2.5W, probably a bit less. Tubes will last forever if start-up and filament voltages are well-managed. The 6C6 is run as pentode at common operating points. The only bit of trickery being that a voltage divider is used to derive screen V (rather than a simple dropper) and the screen bypass is returned to the cathode, rather than ground. PS is a simple tube-rectified pi filter designed for low impedance and fast and clean recovery - I will do it differently next time...
Build was guided by a few things I wanted to achieve and just experiment with. I wanted to be able to compare this build to a RC coupled amp of similar design that I own; ensure reliability and low noise/hum/buzz; use quality transformers and chokes; avoid 'lytic capacitors; minimise parasitic capacitance; avoid magnetic and dissimilar conductors where practicably possible; keep current loops direct (if not as short as possible) and treat them with the same care as "signal"... blah blah blah.
I don't recommend my design choices or expect others to have the same goals or make the same choices. I like that humans have diverse opinions and make different decisions.
