A Very Compact Tube Hybrid
This amp was born from the coincidence of two independent design efforts. One was cfcubed's efforts to make a teeny tiny hybrid amp as discussed on Headwize (now defunct). The other was my own background work on designing a hybrid that ran from a 24VAC wallwart but that would have a higher plate voltage like the SOHA II amp. I learned of cfcubed's thread when he wrote to me about using some of the design ideas in the SOHA amp in his Teeny Tiny amp. With a few emails we began work on this amp.
Features of the amp:
- Compact Tube Hybrid fitting on a 75mm X 120mm board (able to fit: Hammond 78mm X 120mm X 43mm case).
- No trimpots in front end. Rolling 12AU7 class tubes consists of turning off amp, pulling one tube & inserting another. Can be 6922 class tubes too (switch for 6.3V / 12.6V heated tubes). Many other tube types have also been found to work well (6F8G, 6CG7 6GU7).
- Runs tubes at 80V, about twice plate voltage of some other hybrids.
- Uses discrete output buffers, rail splitter, driving most all conventional/dynamic headphones with ease.
- Implements variation of AMB's e12 muting delay & offset protection (with red and green LEDs).
- DIYers can expect to be able to complete builds w/case, tubes & 24VAC 0.8A+ A/C adapter for under $200USD total.
I want to thank cfcubed for all of his great ideas, collaboration and time, and prototyping work.