SUT - electrical theory and practical experience

The point I was trying to make when I pointed out that transimpedance phono stages generally are just voltage driven stages with a current to voltage converter added on to the front end is that they are subject to foibles just like voltage input phono stages. As Atmasphere pointed out in another thread, a current driven stage ought theoretically to present zero input impedance, but that is impossible as there would then be no signal at the output of the converter. So they all have a finite input impedance ranging from ~2 to ~20 ohms, based only on research I’ve done on my own. That’s a fly in the ointment of perfection. Because of differences in actual input impedance ( and probably in current gain and maybe distortion of the input devices, either an op amp or transistors), different transimpedance stages seem to act differently and sound a bit different dependent upon the internal R of the cartridge. This is evident to me based on my communication with Mijostyn. He uses a Lino and I use a BMC MCCI. And each of us has experimented with a few different LOMCs. We’ve reported somewhat different results, depending on cartridge. So there’s nothing perfect about current drive or stages that use it, though they can be very competitive with the best voltage driven stage.

@alexberger 

I use 20 Ohm input (26dB, 1:20). The phonostage has overload points - (1% THD+N) for the 834P were 69.2mV at 1kHz, 260mV at 20kHz, and 7.85mV

you seem to have a frequency number missing from the above since you have three voltages listed and only two frequencies.  

dave

20k?

Dear @alexberger  : Tamura are if not the best out transformers one of the best out there.

Now, you are just fine with those 26db of gain and if you want improve that SUT then take off all those impedance swiths and let direct solder to the one with your EMT.

R.

Dear @lewm  : can be very competitive with the best voltage driven stage. "

Why do you think that Palmer choosed voltage instead current design?

R.