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Simplistic NJFET RIAA
Simplistic NJFET RIAA
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Old 11th December 2012, 08:12 PM   #8831
RCruz is offline RCruz  Switzerland
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Simplistic NJFET RIAA
Carefull.... Riaa values depend on input stage output impedance, output stage iput impedance and second stage miller.
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Old 11th December 2012, 08:22 PM   #8832
andyr is offline andyr  Australia
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Quote:
Originally Posted by RCruz View Post
Carefull.... Riaa values depend on input stage output impedance, output stage input impedance and second stage miller.
So:
a) How does one know how much 2nd stage Miller capacitance there is?
Can we measure it with a capacitance meter? (In which case, where do we put the leads?)
and
b) How does X pF of Miller capacitance affect the value of the RIAA cap(s)?


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Andy
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Old 11th December 2012, 08:26 PM   #8833
The Space Egg Corp is offline The Space Egg Corp  England
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Hi Ricardo

Yep...
...this is the question...Miller...how much ?

I think a possible shift from 47k to say 45.3k...should be pretty minimal...
...as long as other values are 'tweeked' accordingly.
That's the general plan, anyhow.

How much Miller on 'official values' ?
Any idea ?

Cheers.

Si.
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Old 11th December 2012, 08:38 PM   #8834
The Space Egg Corp is offline The Space Egg Corp  England
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Basically...
...my K72's are 'slightly HIGH' @ 48.2, 48.2, 48.3, 48.3

( also have ones @ 47.1, 47.9, 48.0, 48.6 )

Si.
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Old 12th December 2012, 02:07 AM   #8835
Salas is offline Salas  Greece
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Simplistic NJFET RIAA
Avoid Riaa calculators, follow the recommended values. There are combined source impedance and Miller contributions in each version. Miller varies with gain and source degeneration in both stages in each version. Even cascoding in first stage just reduces it, it does not eliminate it. Mathematics about Miller capacitance or "effect" are easy to find if you will google it up.
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Old 13th December 2012, 09:15 PM   #8836
buzzforb is offline buzzforb  United States
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Salas,
Do you recommend a prefilter? Using dual SSLV1.1
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Old 13th December 2012, 10:46 PM   #8837
orelli is offline orelli  Italy
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Hi Nick ,compliment for the new folded RIIA! Apart the use of K369 and the trimmer ,I noted the presence of an active polarisation of the output buffer. I like very much to use CCS in the audio circuits, cause always they give to music more air and dynamic impact...in few words, the music breath! I've the old MC version, V1102FO, in balanced mode , and I modified it with the CCS. I measured the voltage across the reristor (1K5) that polarize the
buffer (K170), resulting about 12V. With the Ohm's Law I compute the current that flows across the resistor (12V/1500R= 0.008A = 8mA). I had some K170 with exactly this Idss and I swapped the resistor with the JFET. Very simple job, but amazing! Very reccomanded to all the owners of the old version.

P.S. Can you post also the photo of the soldering side of the folded version? I think this is very useful, for all us, to understand how lay out the single components and the rails.
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Old 13th December 2012, 11:54 PM   #8838
Salas is offline Salas  Greece
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...
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File Type: jpg FoldedProtosBack.jpg (499.2 KB, 296 views)
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Old 14th December 2012, 11:19 AM   #8839
orelli is offline orelli  Italy
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Thanks
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Old 18th December 2012, 02:04 AM   #8840
Salas is offline Salas  Greece
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Simplistic NJFET RIAA
Quote:
Originally Posted by buzzforb View Post
Salas,
Do you recommend a prefilter? Using dual SSLV1.1
Its good to break some EMI from the rectification. So drop 1 or 2 volts with an R before board's main C if with outboard bridge or by a small hack. Better still is choke input with some leftover speaker air coil.
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