Hi Jam,
may I ask you, did you use for J74 and K170 the same Idss value?
The stereophile measurements show some H2 dominance so I am inclined to take a bit different values.
may I ask you, did you use for J74 and K170 the same Idss value?
The stereophile measurements show some H2 dominance so I am inclined to take a bit different values.
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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The best way to eliminate H2 is by going fully symmetrical (balanced outputs).
Then everything can remain the same and you can reduce H2 by say 20~30dB..
Patrick
Then everything can remain the same and you can reduce H2 by say 20~30dB..
Patrick
What do you mean ? Dull without H2 ?
Then all the Pass Labs Super-Symmetry products, as well as those from JC, Ayre, ... sound dull ?
Patrick
Then all the Pass Labs Super-Symmetry products, as well as those from JC, Ayre, ... sound dull ?
Patrick
No, no I wrote with 20dB H2 higher than H3, I did it with the HPA, the sound was too dull in the sense of dark, without any excitement....
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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?
Huh. That's a typo.
It shouldn't matter which you use though as there should be plenty of adjustment for the offset in the pot. FWIW, my LTSpice file shows 330, so that's a better guess as to what will center the pot.
No other updates.
Cheers,
Jeff.
It shouldn't matter which you use though as there should be plenty of adjustment for the offset in the pot. FWIW, my LTSpice file shows 330, so that's a better guess as to what will center the pot.
No other updates.
Cheers,
Jeff.
FWIW, mine has now been on 24/7 (barring a couple of power outages) for nearly 2 years. Still sounds great!
Actaully Vader is partial to a White Russian.
For you DIY'ers out there
INGREDIENTS
2 oz. vodka
2 oz. coffee liqueur
2 oz. heavy cream
and some ice.
For you DIY'ers out there
INGREDIENTS
2 oz. vodka
2 oz. coffee liqueur
2 oz. heavy cream
and some ice.
Attachments
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Hi boys. I can use heatsinks??? Thanks
https://www.fischerelektronik.de/web_fischer/en_GB/heatsinks/A04/Extruded%20heatsinks%20for%20PCB%20mounting/$catalogue/fischerData/PR/SK600063.5stc/search.xhtml
https://www.fischerelektronik.de/web_fischer/en_GB/heatsinks/A04/Extruded%20heatsinks%20for%20PCB%20mounting/$catalogue/fischerData/PR/SK600063.5stc/search.xhtml