The PSU doesn't need to be regulated , it has to be free of "noise" , have you measured your AC noise in the mV range at the amp board ?
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Hi picoDumbs,
If I change into 2sk1530 with 0.22ohm gate resistor,
What is bias current recommended?
Same 1.5A?
Bloody Nora! Replacing the led did not solve the remaining hum. Back to the hififonix slidedeck!
i just want to find a way to make this amp work
I checked the entire circuit everything is correct, so apart from the BIAIS which is too loud, I don't see any other explanation.
The question is, how do you fix this BIAIS without continuing to destroy the components?
I will need to go back and look at what your specific problem is.
i just want to find a way to make this amp work
I checked the entire circuit everything is correct, so apart from the BIAIS which is too loud, I don't see any other explanation.
The question is, how do you fix this BIAIS without continuing to destroy the components?
Well , when everything is correct stuff work , so if it doesn't work , it means something is not correct , simply as that
you should act as an scientist not as an believer
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Merci Fabrice
I try to be as rigorous as possible in my analysis process, just the frustration of not understanding, but also the joy of learning.
I look again the texts of Mr PASS, and undertook another step, I removed the JFET, put back in place the MOSFET, in order to check the tensions of the PCB.
I will put a diagram with my measurements later, but the diode output voltages are OK (5.8v) the trimpot allows me to get 1.2v between gate and MOSFET source.
This allowed me to know the meaning of my trimpot, before replacing the JFETs, trimpot at zero. My DC voltage goes to 1.0v, but the voltage between gate and MOSFET source does not drop below 3.6v .
R10 is however there to protect the Gate of the MOSFET, so I should not have voltage so high?
Only good news, R4 no longer burns
Another track, the JFET, why the 2SJ74 burns, yet it only has an IDSS of 8mA ...
I try to be as rigorous as possible in my analysis process, just the frustration of not understanding, but also the joy of learning.
I look again the texts of Mr PASS, and undertook another step, I removed the JFET, put back in place the MOSFET, in order to check the tensions of the PCB.
I will put a diagram with my measurements later, but the diode output voltages are OK (5.8v) the trimpot allows me to get 1.2v between gate and MOSFET source.
This allowed me to know the meaning of my trimpot, before replacing the JFETs, trimpot at zero. My DC voltage goes to 1.0v
, but the voltage between gate and MOSFET source does not drop below 3.6v .R10 is however there to protect the Gate of the MOSFET, so I should not have voltage so high?
Only good news, R4 no longer burns
Another track, the JFET, why the 2SJ74 burns, yet it only has an IDSS of 8mA ...
Hello 2 picoDumbs,
Yes the JFETs are installed correctly, I bought a batch which I sorted according to their IDSS:
- 2SJ74 7,16mA
- 2SK170 8, 19mA
I used the IDSS measurement principle used by Diyaudiostore, V + on the DRAIN and GATE and SOURCE shunt, a 100 Ohm resistor at V-.
AND they are indeed BL.
I measured the polarization of the circuit, it works well, I just have a large range of maneuver on channel P2 compared to P1.
GND + R11 = 0 - 5,83v
GND + R12 = 25,9 - 17,1v
Could it be my rail voltage which is too high (26,4v) ? or the JFETs have a problem?
Yes the JFETs are installed correctly, I bought a batch which I sorted according to their IDSS:
- 2SJ74 7,16mA
- 2SK170 8, 19mA
I used the IDSS measurement principle used by Diyaudiostore, V + on the DRAIN and GATE and SOURCE shunt, a 100 Ohm resistor at V-.
AND they are indeed BL.
I measured the polarization of the circuit, it works well, I just have a large range of maneuver on channel P2 compared to P1.
GND + R11 = 0 - 5,83v
GND + R12 = 25,9 - 17,1v
Could it be my rail voltage which is too high (26,4v) ? or the JFETs have a problem?
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