Simplistic Mosfet HV Shunt Regs - Page 56 - diyAudio
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Old 8th October 2009, 01:15 PM   #551
disco is offline disco  Netherlands
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Quote:
Originally Posted by quanghao View Post
This is my pre for output DAC.
6C45pi is notorious for oscillation, there's some info on applying cathodestoppers (!) at diyaudio.
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Last edited by disco; 8th October 2009 at 01:30 PM.
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Old 8th October 2009, 01:38 PM   #552
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Quote:
Originally Posted by disco View Post
6C45pi is notorious for oscillation, there's some info on applying cathodestoppers (!) at diyaudio.
Can you show me what is link! about 6c45pi
Thank
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Old 8th October 2009, 01:47 PM   #553
iko is offline iko  Canada
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Hey quang, do you have one shunt regulator feeding both pre channels? How much current does each preamp channel draws?

I think you setup your shunt reg current limit too low. This could explain the voltage so low on the output.

From your measurements it shows that the total current through R1 is 47mA = 2.21V / 47R. Seems a bit low.
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Old 8th October 2009, 01:54 PM   #554
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Hi ikoflexer! help me!
do you have one shunt regulator feeding both pre channels? = yes one shunt for two chanel my pre!

How much current does each preamp channel draws?
17ma one chanel!

I think you setup your shunt reg current limit too low. This could explain the voltage so low on the output.
What Do i can?? for mya pre? and Shunt?
QuangHao
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Old 8th October 2009, 02:04 PM   #555
iko is offline iko  Canada
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OK, let's see. You got 47mA total going through. If you are 100% sure that each channel takes 17mA, then 47 - 17 - 17 = 13mA. That is the total current that is left for biasing and shunt mosfet. I think that's too small. Make R1 just a little smaller value and measure everything again. Do you have a resistor around 40 ohm for R1? You could use two 75R in parallel.

Also, insert a 1R or a 0R1 resistor between the source of Q3 and ground, and measure the voltage across it, with the circuit powered.

You're working with high voltage, be careful! I see you don't have a bleeder resistor in your PSU filter. Your caps retain high voltage, so make sure they are discharged when you work on the circuit.
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Old 8th October 2009, 02:12 PM   #556
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Quote:
Originally Posted by ikoflexer View Post
OK, let's see. You got 47mA total going through. If you are 100% sure that each channel takes 17mA, then 47 - 17 - 17 = 13mA. That is the total current that is left for biasing and shunt mosfet. I think that's too small. Make R1 just a little smaller value and measure everything again. Do you have a resistor around 40 ohm for R1? You could use two 75R in parallel.

Also, insert a 1R or a 0R1 resistor between the source of Q3 and ground, and measure the voltage across it, with the circuit powered.

You're working with high voltage, be careful! I see you don't have a bleeder resistor in your PSU filter. Your caps retain high voltage, so make sure they are discharged when you work on the circuit.
Ok! I try to do that!
Thank! let wait for me!
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Old 8th October 2009, 02:39 PM   #557
iko is offline iko  Canada
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What takes you so long?

Just kidding, take your time and above all, do it safely!
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Old 8th October 2009, 02:58 PM   #558
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Quote:
Originally Posted by ikoflexer View Post
What takes you so long?

Just kidding, take your time and above all, do it safely!
ok! i change r= paralle 75 R R1 =35R. V= 2.16 v!
An R 1 r = 226V!
ok or no??
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Old 8th October 2009, 03:02 PM   #559
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Looks a bit better now. I also asked you to insert a 1 ohm or a 0.1 ohm resistor between the source of Q3 and ground, and measure the voltage across it, with the circuit powered. Have you done that?
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Old 8th October 2009, 03:12 PM   #560
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Looks a bit better now. I also asked you to insert a 1 ohm or a 0.1 ohm resistor between the source of Q3 and ground, and measure the voltage across it, with the circuit powered. Have you done that?[/QUOTE]

Yes, I do that!
My pre is stil ees ..esss ! * not change*
I do sample you show!
1 ohm or a 0.1 ohm resistor between the source of Q3 and ground,
I use 1R between Q3 to ground and V= 220V.
i think my pre use tube 6c45, Is is noise!
I check my pre!
Thank
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