I am not entertaining many tube possibilities for this project, as I have no intention of being awash in 8 billion alternate tube types. The screen grid limit for the 12C5 is noted. I may have to regulate the 12C5 screen voltage, as I am planning to run with 150V B+. I may also do some back-of the envelope calcs to suss out the implications of running with a lower B+ as this would simplify the power supply. I did my first proto using a 12AQ5 that wasn't pushed all that hard. This is a headphone amp after all. The important characteristic in play here was running plate-drain feedback to emulate triode characteristics for the output tube. I already have a triode-based headphone amp using a 13DR7, run like a normal triode-triode single-ended amp. It sounded quite nice. To be honest, I haven't yet listened to the 12AQ5 partial feedback beast, though I did take it all the way through to verifying loop stability and decent time-domain transient response.
The thread regarding the project is here, for the curious:
https://www.diyaudio.com/community/threads/12aq5-partial-feedback-hp-amp.347143/
The thread regarding the project is here, for the curious:
https://www.diyaudio.com/community/threads/12aq5-partial-feedback-hp-amp.347143/
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Just to get an idea about the requirements I've seen for headphone, a fair number of them are rated for ~200 mW max power. I am assuming this is RMS power... For a set of 30 ohm phones like the Grados I own, this works out to 80mA RMS, 114 mA peak current. As far as voltage is concerned, it's 2.4 VRMS, 3.42 V peak.
You own creation I'm guessing? I noticed there is at least one commercial headphone amp, the Woo Audio WA6, that could run this tube.
jeff
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