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Simplistic NJFET RIAA
Simplistic NJFET RIAA
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Old 10th March 2019, 08:35 PM   #17401
Salas is offline Salas  Greece
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Simplistic NJFET RIAA
Turn DMM's mode to Hz as you measure that, if it will display 120Hz then its surely mainly about rectification ripple. Haven't got a target figure noted in my files. But its low raw ripple level what you measured anyway.
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Old 12th March 2019, 08:56 PM   #17402
Hikari1 is offline Hikari1  United States
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Salas: for the MC step up in the original Nfet phono do I need to change any resistor values (R1?) when using 8.2mA jfets?
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Old 12th March 2019, 10:08 PM   #17403
Salas is offline Salas  Greece
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Keep it the same. There will be inconsequentially small difference in the DC drop across R1 and maybe one extra dB of gain.
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Old 14th March 2019, 07:17 PM   #17404
exw9 is offline exw9  United States
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I just finished my build and switched it on. One channel I get all the LED's and the other channel the 4 on the side never come on. I am overwhelmed where to start, are there common issues that would cause this?

Also, my Raw PSU is putting out about 27V DC. Is that enough? I saw in the biasing that it is looking for 35V
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Old 14th March 2019, 08:32 PM   #17405
Salas is offline Salas  Greece
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Hi

You need 42-50V RAW DC level to start with
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Old 14th March 2019, 09:13 PM   #17406
Salas is offline Salas  Greece
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Get a 32V+32V toroidal (four wire). One secondary to each RAW DC board's input.
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Old 14th March 2019, 09:42 PM   #17407
exw9 is offline exw9  United States
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Get a 32V+32V toroidal (four wire). One secondary to each RAW DC board's input.

perfect, thank you! I will get that installed and then see what the board LED's are doing.
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Old 14th March 2019, 09:51 PM   #17408
Salas is offline Salas  Greece
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We see about that next. Maybe one LED is in reverse, or somewhere around them a voltage isn't right, something. If one channel is alright you can compare the bad one's voltages at points.
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Old 18th March 2019, 08:05 PM   #17409
Hikari1 is offline Hikari1  United States
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Salas: for the MC step up in the original Nfet phono do I need to change any resistor values (R1?) when using 8.2mA jfets?
I built the MC step up. Sounds very, very good. But it's very sensitive to placement. It must be a meter away from my big class A amp for best results. But it is not in a metal box yet.

Running off batteries for now. Works as advertised.

Anybody compared this against a transformer SUT?
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Old 18th March 2019, 10:06 PM   #17410
Salas is offline Salas  Greece
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Good screening for sensitive circuits in traditional diy fashion comes with dead bug style construction on a raw board's copper back housed in a tin can.

I prefer direct high gain input where hum and buzz problems can be solved without a step up transformer.
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