Simplistic NJFET RIAA

[Salas]

Look.

[Salas]

What? Are you going to be the one to first test my circuit for real?

[nicoch58]

no I'm waiting you !

I will post your design to ska-amp forum ,Greg have some idea to avoid the elettrolitic caps with outlost gain .....

[Salas]

0.3V bias derived from battery and resistor divider instead of Rs?

[nicoch58]

HI Salas
you are invited

[Salas]

Yes I did exactly what Greg. B. has seen in my circuit. On purpose! I even avoided current sourced buffer like in Pass B1. You see? 0.8% 2nd harmonic, the others 100 times lower. Its going to be interesting. Plus an output buffer for isolation and strong drive. Very audible for changing bypass electrolytic quality. BGN vs Silmic II for instance. But -no local feedback-! You get the SE real zero feedback stuff. The buffer you can avoid if you like, if you have 100k input volume pot in your preamp for instance, but it will challenge the low current second stage subtly. I prefer the -resistor loaded- buffer there.
So its very tweak friendly for finding tone with cartridges in systems. And has all the gain. It is just another school of approach. Not the most neutral, but friendly, classic tube like approach.

[nicoch58]

HI Salas I have read about your 6v6 pre that you are expert on tube ,and after play on silicon , you came back to tube.....

You think that tube are far superior for phono ? (apart gain)

[Salas]

I have played with both genres in past and present. Keeping same analogies for simplicity and design approach, tubes have a truer tone. Sometimes, JFETS are a very clever solution to go near, given the much simpler construction effort and cost saving advantages.
Forgeting all implications and talking best, most persuasive sound, tubes reign IMHO.
The JFET RIAA that I build now is in test phase to give you an update, and sounds good next to a Steve Bench tube RIAA that I will compare head to head when I will be ready. So I will give you a more precise estimate vs tubes. The 56dB version without output buffer is on test, I am seeing about best incorporation of the battery PSU. I have to decouple the high Z out of the series batteries successfuly before I will listen for good. When I am ready I will report more. Thank you.

[Salas]

Plays very well with a finely tuned balance between full detail and no hardness at all. It is surprisingly dynamic even with low out MC (0.25mV). No noise. The local R-C decoupling of the first stage B+ for each channel is very audible. Focuses it. Batteries in general are good for noise but relatively Hi Z. Without the 10.000uF on their poles and the local JFET decoupling they create wide band interactions. I used 3X 12V 1.5Ah rechargeable batteries in series. I used Russian Silver Mica, Russian Polystyrene, Panasonic Electrolytics, & common metal film resistors. The 100R gate stoppers are Kiwame and optional. The output caps are Mundorf Supreme Silver/Oil. They were chosen as 0.68uF to create -10dB @ 5Hz to battle record warp. This is when they feed the 50K input resistance of the following Salas 6V6 line stage.

The black thing attached is the schematic. It will turn white when you click.

[Salas]