Hi genrg,
I matched the k170 to j74 to about 10%.
Most of the characteristic 2 harmonic is due to lower feedback rather than fet matching. You can increase feedback and get lower distortion but the sound seems to suffer.
Contrary to popular belief I did not intentionally design 2nd harmonic into the HPA-1 but what let listening decide what the amount feedback were set at.
Also, which might surprise a lot of people, is my main reference for the sonic character were electrostatic speakers and not headphones also the unit had to sound great as a preamp. When these were satisfied did I start to use headphones.........probably a different way of doing things but it worked for me. For a reference I also used a moth 2A3 tube amplifier.
Please no flames.
Regards,
Jam
I matched the k170 to j74 to about 10%.
Most of the characteristic 2 harmonic is due to lower feedback rather than fet matching. You can increase feedback and get lower distortion but the sound seems to suffer.
Contrary to popular belief I did not intentionally design 2nd harmonic into the HPA-1 but what let listening decide what the amount feedback were set at.
Also, which might surprise a lot of people, is my main reference for the sonic character were electrostatic speakers and not headphones also the unit had to sound great as a preamp. When these were satisfied did I start to use headphones.........probably a different way of doing things but it worked for me. For a reference I also used a moth 2A3 tube amplifier.
Please no flames.Regards,
Jam
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Hello Jeff,
I was getting ready to order the PCB for my version and I noticed that R11 on your schematic is 332 but R41 on the other channel is 475. Is that a typo? If so, what is the correct value? Any other changes or updates?
