Simplistic NJFET RIAA

I have always found it interesting that MC carts, with their low output voltage, low internal impedance, and low load impedance, generate a lot more current than typical MM carts. I have never seen, though it probably exists, an exhaustive suite of tests on an MC cart, say playing a fixed amplitude 1KHz test track, while the load was varied. Like at what load impedance does the output voltage start to drop? Then maybe frequency sweeps and distortion measurements vs load impedance as it varied around that point. Then maybe repeated for some other carts, so starting with some of those old Ortofons with very low voltage and impedance (<10 ohms), then some with medium and higher impedance and voltage. Then, sure, some listening tests to try to correlate with sound.
Those tiny coils with relatively high current must experience mechanica and magneticl damping with low load impedance, but this is never quantified.
 
Good morning! I've been getting together the bits for my UFSP recently and just wired one of the channels up to test it last night / this morning. With the shunt not connected to the RIAA I was measuring +34v but with the RIAA attached I measure around +8.4v and measure nothing across T.P at all. I do have the leds on the RIAA lighting up though.

Is there anything obviously wrong I could have done do you think? I'm enormously grateful for any help.
 
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Try the shunt alone with 1k 2-5W dummy load resistor. That will represent one channel mc phono consumption. If there is voltage drop again means something's wrong with the shunt. If not, means there is something wrong with the phono channel and over-consumes.
 
Great, yes, that seems to have been it. I get a reading now circa 7v on T.P, there was a tiny bridge, thanks for that Salas. I can't believe I missed it before when checking the soldering...

I've got to head out now but will adjust it properly later when I get back in. I hope the sun is out down in Greece as well!
 
Hello,

I would like to ask for some record listening help.

Here's a file of a few takes recorded straight from FSP line out to Macbook line in;

WeTransfer

The setup is Rega Planar3 (various mods like motor on separate isle, ruby bearing, silicone belt, dampened table underneath etc.) , RB300 arm, Denon 103. My rest of the chain is a Cayin A-55TP amplifier and Onken loaded diy Tannoy i8 speakers.

On FSP I hear much less and more muddy bass and harsher highs on some busier passages. I was wondering if you guys could hear the same? Maybe it's because of increased resolution and misaligned cartridge? I double checked the alignment though. Looks alright. Is it my ears or maybe something else? I come from my previous Vincent pho-8 phono. It was known to be a V shaped. Maybe the change fools me. Any tuning advice is appreciated.