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EHHA RevA  Hybrid  2014 


Another headphone amplifier design by Alex Cavalli, a hybrid amp embedding a low voltage tube (6GM8/ECC86) as the differential amplifier front end of a solid state amp in symmetrical drive configuration. The only significant amplifer change to the previous EHHA is that emitter follower drivers have been added before the  output stage to get more bandwidth and to simplify the CCS on the input stage by using a CRD instead of a BJT. It can be buildt with either Mosfets or BJT's as the output devices. In comparison to the EHHA the RevA is more compact since each board incorporates the bipolar psu and the heater supply.




assembled boardsassembled boards




Above you can see the populated and tested boards for both channels and the heater supplies. My build is still in the planning stage for its case but will differ from the original schematic in that I will use a pair of Salas low voltage shunt regs to provide roughly +/- 28V. The amplifier is currently residing on a breadboard with the power supplies and two custom 40VA toroids. Initial listening indicates that everything is working as intended and sounding promising. For tube rolling I have a small stash of 6GM8 tubes and also their russian equivalent 6N27P.






                    The EHHA RevA project has been abandonned and sold to a fellow DIY'er in Estonia!