Crack + SB Monoblocks?

[L0rdGwyn]

Hey Bottleheads, you guys ever had anyone try buying two Crack + SB kits, paralleling the sections of the two dual triodes, and running them as headphone monoblocks?  Just came to mind as a fun little project for someone to try.

[Paul Birkeland]

We have experimented with paralleled triodes over the years and our results have been pretty meh to say the least.  There are bigger dual triode regulator tubes that could be used, and the Crack-a-two-a power transformer is beefy enough to heat some of them, so you could do a non shunt regulated HP amp with something like a 6336 to get the job done.  The 6336 datasheet has graphs for transconductance, and you could try to get to the 20,000uMho+ region to drive the output impedance way down. That'd be like 250mA of plate current per triode, what could go wrong?!

[L0rdGwyn]

Gotcha, well hey maybe I'll try it for the heck of it!  Perhaps some Crackhead will finance the project lol.

I've been messing with OTL circuits over the past year and I like the sound of the parallel section cathode follower output.  I wasn't going to mention it, but funny you should bring up the 6336, I just finished a DIY OTL that uses a pair of them, or the 6528.  Sections parallel, 275mA bias per channel with the components cold, actively loaded, note the ridiculous heat sinks.  Output Z with the 6336 is 24ohm, 15ohm with the 6528.  1mW into 300ohm with the 6528 yields 0.007% THD with a quality 6J5.

Anyway, thought the monoblock thing could be a cool Crack project!  But only because I like the sound of the parallel cathode follower.