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Simplistic NJFET RIAA
Simplistic NJFET RIAA
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Old 3rd January 2018, 07:53 PM   #16911
Salas is offline Salas  Greece
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Simplistic NJFET RIAA
Quote:
Originally Posted by royville View Post
Hi Salas,

I too had a 10x4 a few years ago which I traded in for the 10x5 and I recall that the 10x4 sounded better to me. The 10x5 always sounded a little softer as though it had a slightly rolled off treble.

Anyways I am just curious how it would sound using your pre-pre between it and a mm phono stage (nad). Maybe it would open up the sound a bit more.

I want to build your RIAA to use with an AT745 MM I hope to be purchasing soon, so you see I was talking about two separate issues really.

Kind regards
Roy.
Roy, better use 47K Z-Foil R1 and no other Rx load options so the 10x5 will sound at its most open in the highs. Use Z-Foil for R14 too if the budget permits.
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Old 3rd January 2018, 08:24 PM   #16912
Jonathan Bright is offline Jonathan Bright  Australia
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Just about to start serious thinking about an RIAA pre-amp.
Can I ask where to find the latest development (or version) of this pre-amp please?
Happy New Year, and thanks to all those who contribute to threads like this,
Cheers Jonathan
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Old 3rd January 2018, 11:15 PM   #16913
Salas is offline Salas  Greece
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Hi, post#1 link #3.
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Old 15th January 2018, 09:34 PM   #16914
jswen is offline jswen
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I just tore into my unit to change the gain. D1x is out on one channel. Rails and bias are fine. I did note 80mV on the output. Any thoughts?
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Old 16th January 2018, 01:25 AM   #16915
Salas is offline Salas  Greece
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Simplistic NJFET RIAA
Has D1x shorted? Its the only way it could keep the rail up, if it had failed open it would have cut any current running in the reg's Vref. Replace it of course.

Also load the output with a 10-50K resistor to simulate its connected to a preamp, see if it still shows any DCmV. Leaking modern output capacitor is unlike.
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Old 16th January 2018, 01:36 AM   #16916
jswen is offline jswen
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Thanks Salas, I'll checked in a few days. It's AC @ 80mV, the other channel is 5mV.
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Old 16th January 2018, 01:45 AM   #16917
Salas is offline Salas  Greece
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AC is another thing. Means some signal or noise. Is the 80mV AC on the same channel that has the dead D1x? Better fix that first and check that Q3x Q4x Q5x are good also. By normal circa 0.6V Vbe in Q4x and by normal RDS Ohms in the others (JFETS). Few decades of Ohms. Not shorted, not open, not just few Ohms not hundreds of Ohms or kOhms.
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Old 16th January 2018, 09:21 AM   #16918
Cold Beer is offline Cold Beer  Croatia
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Hi
I am pretty new in this forum, and trying to build a simple and good MM phono preamp for my daughter. Went back for 30 pages and found a lot of upgrades, but an not find a schematic.
Can anyone, PLEASE, draw one with current upgrades ?
Thank
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Old 16th January 2018, 10:30 AM   #16919
AndrewT is offline AndrewT  Scotland
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Have you looked at post1?
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Old 21st January 2018, 12:04 PM   #16920
jswen is offline jswen
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Quote:
Originally Posted by Salas View Post
AC is another thing. Means some signal or noise. Is the 80mV AC on the same channel that has the dead D1x? Better fix that first and check that Q3x Q4x Q5x are good also. By normal circa 0.6V Vbe in Q4x and by normal RDS Ohms in the others (JFETS). Few decades of Ohms. Not shorted, not open, not just few Ohms not hundreds of Ohms or kOhms.
Pulled D1x, it measured fine and lit up??? Though after replacing, all is back in working order. Making great music! Thanks Salas.
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