2 years ago I bought a used Copland CTA-501. And I wonder if I could ask a question about biasing a Copland 501.
FROM COPLAND BIAS PROCEDURE
1. Set P1-P2 in middle position. Turn P3 fully in clockwise direction.
2. Measure with + on the left side of R31 and - on the left side of R32. Adjust P1 to 0 mV. Repeat with R131-R132 and P2.
3. Measure mV over R32 and R132, choose the one with highest rating and adjust with P3 to 430mV
MY PROBLEM IS AS FOLLOW:
I have no problem adjusting P3 to 430mV for both pars of EL34. And I reach 0mV with P2 for R131-R132
BUT for P1 I get not mV but about 28-32 Volts! with + on the left side of R31 and - on the left side of R32.
When I got in contact with my dealer he just say: " If its sound okay, it's okay" The sound is okay though, but I¡¦m not particularly happy with that answer.
Why can I not adjust P1 to 0mV for R31-R32?
http://www.audiokit.it/ENG/Frames/Introduction1.htm
Here is a schematic for Copland-CTA-401, its out put stage is similar to my CTA-501
I have replaced diodes in the power supply with soft recovery diodes. And I noticed a more solid bass. I¡¦m very pleased with my amplifier, especially in the midrange and heights. But low bass is to slow, compared too a good solid state design. Anybody with an advice on this:
„h With it help changing the original power supply caps?
„h Use a choke in the PS?
„h Regulate the filament PS?
I hope this was not too much.
Best regards
Baard
FROM COPLAND BIAS PROCEDURE
1. Set P1-P2 in middle position. Turn P3 fully in clockwise direction.
2. Measure with + on the left side of R31 and - on the left side of R32. Adjust P1 to 0 mV. Repeat with R131-R132 and P2.
3. Measure mV over R32 and R132, choose the one with highest rating and adjust with P3 to 430mV
MY PROBLEM IS AS FOLLOW:
I have no problem adjusting P3 to 430mV for both pars of EL34. And I reach 0mV with P2 for R131-R132
BUT for P1 I get not mV but about 28-32 Volts! with + on the left side of R31 and - on the left side of R32.
When I got in contact with my dealer he just say: " If its sound okay, it's okay" The sound is okay though, but I¡¦m not particularly happy with that answer.
Why can I not adjust P1 to 0mV for R31-R32?
http://www.audiokit.it/ENG/Frames/Introduction1.htm
Here is a schematic for Copland-CTA-401, its out put stage is similar to my CTA-501
I have replaced diodes in the power supply with soft recovery diodes. And I noticed a more solid bass. I¡¦m very pleased with my amplifier, especially in the midrange and heights. But low bass is to slow, compared too a good solid state design. Anybody with an advice on this:
„h With it help changing the original power supply caps?
„h Use a choke in the PS?
„h Regulate the filament PS?
I hope this was not too much.
Best regards
Baard