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-   -   Simplistic NJFET RIAA (http://www.diyaudio.com/forums/analogue-source/129126-simplistic-njfet-riaa.html)

Salas 3rd September 2008 11:40 AM

I guess that the best real test for any phono stage's RIAA compliance is the Hagerman, as suggested by Zoran.

Zoran 3rd September 2008 11:41 AM

No, You still will have Q2 connected to gnd
try to simulate and then You can have a try in real
any kind of termination will change the low end
You can choose a higher impedance riaa net
components also, to be less affective on Rload of Q1.

Salas 3rd September 2008 11:48 AM

The first stage on my schematic has 11k Zout (Ro=Rriaa(V1GOhmload-VoRIAAload)/Vo. If I go 50xtimes that for series RIAA resistor, then the RIAA capacitors will be fictionally small and bad for tolerances or quality dielectric availability. If the Zout is embedded in the RIAA, where is the difficulty? Q2 with 2.2Meg input is 50x the 47k combined driving impedance. Will it get seriously loaded?

P.S. Which schematic is your tube RIAA? Can you post it? So I can see why you had to do those mods. If its not proprietary of course.

nicoch58 3rd September 2008 11:51 AM

dual mono design ?

As not more of 30db separation , worth to upgrade ?



no 1k but not differ too much from 3k , lowering the load close the sound , as modern hi gain mc work with standard 47k

Salas 3rd September 2008 11:58 AM

Don't know for double mono, it seems unworthy the way you put it. Maybe side benefits from using 2 power supplies. No cross of GNDs etc.

The Denon has 160 Ohm Zout, so 1.5k upwards is fully testable for system tonal matching.

jackinnj 3rd September 2008 03:03 PM

Kevin posted triodeguy's (John Sears) RIAA -- I tweaked it a bit with my "LaPlace-i-nator". The 2N3819 is a fraction of the cost of a 2SK170, I haven't measured the noise, however.

http://www.tech-diy.com/RIAA/Sears_RIAA.gif

kevinkr 3rd September 2008 03:07 PM

Quote:

Originally posted by jackinnj
Kevin posted triodeguy's (John Sears) RIAA -- I tweaked it a bit with my "LaPlace-i-nator". The 2N3819 is a fraction of the cost of a 2SK170, I haven't measured the noise, however.

http://www.tech-diy.com/RIAA/Sears_RIAA.gif


Richard Sears.... Otherwise cool work..

IMO The 2N3819 might prove to be just a bit noisy in this application.

Salas 3rd September 2008 03:09 PM

2 Attachment(s)
Quote:

Originally posted by Zoran
This is good concept...
..
Use passive inverse riaa network for simulation
not only straght signal...
try haggerman inverse riaa
cheers
You will be amazed

Hi Zoran. Did the Bode plot driven from Hagerman inverse. I added the ''lost constant'' too.:D
Well it looks doable, wasn't off. I also sized the source resistors bypass capacitors more generously for better low bass phase shift. I will use 500R trimmers there. That and matched 2SK170BLs should do the channel matching trick.
Hope that it will remotely resemble the gain and time constants in real life test!:smash:

Salas 3rd September 2008 03:10 PM

2 Attachment(s)
P.S. The plot above appeared as a joke when uploaded. :xeye:
Info on its scaling:
It has 10Hz to 100kHz limits, its 20Hz and 20khz are -0.4dB. Its octave spaced per main lines horizontally and 0.1dB per vertical dent.

And the ''promissing'' circuit. Shown driven from a Hagerman inverse RIAA with 60dB attenuation of input generator.

Salas 3rd September 2008 03:27 PM

2 Attachment(s)
OK, captured a not that shiny looking one, but it has all the stuff. Why some .gif goes bonkers when it uploads here it escapes me...


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