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?
Hello,
I tested the no-load power supply, it discharges in 6 minutes (LED off) at the same time.
Concerning the BIAS, is it possible to make a pre-adjustment with 15v rails to limit the current in the JFETs and avoid damaging them?
I tested the no-load power supply, it discharges in 6 minutes (LED off) at the same time.
Concerning the BIAS, is it possible to make a pre-adjustment with 15v rails to limit the current in the JFETs and avoid damaging them?
You could drop some voltage with an led above the drain of each jfet.
That won't limit the current but it will reduce the dissipation V x I.
That won't limit the current but it will reduce the dissipation V x I.
Which way should I place the diode?
I guess it's according to the JFET channel.
positive on the 2SJ74 Drain and negative on the 2SK170 Drain?
I guess it's according to the JFET channel.
positive on the 2SJ74 Drain and negative on the 2SK170 Drain?
You would also need to cut traces.
This might not be something you want to do, in which case just reorder some matched jfets with around 7mA idss
This might not be something you want to do, in which case just reorder some matched jfets with around 7mA idss
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 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?
Bloody Nora! Replacing the led did not solve the remaining hum. Back to the hififonix slidedeck!
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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If Idss is 8mA at 20V Vds (without any degeneration) then no way could they burn up under any circumstance, if installed correctly.
Is it possible the pads might be solder bridged?
Is it possible the pads might be solder bridged?