My RIAA Pre-Amp Wit...
 

My RIAA Pre-Amp With JLH Component Values  

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JonnyAudio
(@jonnyaudio)
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Posts: 19
08/06/2019 6:06 pm  

Here is my Op-Amp version of my John Lyndsey Hood RIAA Pre-Amp using component value as used in the 1450 JLH transister Based Pre-Amp, as I wanted to compare to my JLH kit built RIAA.

js riaa 01
js riaa 02
js riaa 03
js riaa 04
js riaa 05
js riaa 06
js riaa 07
js riaa 08
js riaa 09
js riaa 11


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JonnyAudio
(@jonnyaudio)
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Posts: 19
08/06/2019 6:10 pm  

Here is the JLH RIAA which I only re-cased & built a better regulated PSU for the RIAA +-15vdc & +-5vdc power to the kit board.

JLH RIAA PreAmp 004

JLH RIAA PreAmp 005
JLH RIAA PreAmp 008


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Douglas Blake
(@douglas-blake)
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Posts: 102
09/06/2019 11:45 am  

Seems like a nice enough piece of kit.  

I think my only concern is that the RIAA feedback (the middle circle in your schematic) can be very sensitive to impedance.  In modelling my own design, changing the feedback loop's impedance would throw it wildly off of the desired curve.


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JonnyAudio
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09/06/2019 2:23 pm  

You mean the op-amp version, they sound about the same really only the op-amp has less noise on it, as in the background hiss of the high gain needed.


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JonnyAudio
(@jonnyaudio)
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09/06/2019 2:29 pm  

This is my next project, I want to build the EAR846 Valve RIAA Pre-Amp but using the JLH curve caps but not sure were it is as not done valves before ?

Any ideas anyone ?

EAR846RIAA


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Douglas Blake
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09/06/2019 4:54 pm  
Posted by: JonnyAudio

You mean the op-amp version, they sound about the same really only the op-amp has less noise on it, as in the background hiss of the high gain needed.

If they're sounding about the same, that is encouraging. 

Still, you might want to Spice Model the op-amp version to verify the part values, or spend some time with a spectrum analyser.

Here is a spice model you can use...

It generates the frequency curve found on the record itself.  If you feed this in, the output should be a flat frequency response... In an AC analysis, the average levels for MM are 4mv and for MC it is 0.4mv.

Spice InvRIAA

The LAPACE calculation is inserted into the E voltage controlled voltage source's setup panel.

These are the actual curves set out by the RIAA

1200px RIAA EQ Curve rec play.svg

Hope this helps....

 


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