SUT - electrical theory and practical experience

Hi @intactaudio ,

I have a DIY phonostage based on EAR 834p schematic + EMT TSD 15 + SUT Sun Audio SAT1000 Tamura.

https://www2.big.or.jp/~sunaudio/assem/sat1000_e.html

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

I tried 40 Ohm input. But it sounds less good, thinner and less musical.

Before this I used Altec 4722 SUT with Ortofon Jubilee cartage. But I don’t like this SUT with EMT TSD 15.

I tried a modern Houfe T890 SUT and Jensen JT44 SUT. But both are very low resolution and dynamic compared to Altec. I also had Tamura SUT-83TWIN. Bot Tamura transformers are the best.

Alex.

The EAR 834p is a Phonostage I have been encountering for many years.

I have been demonstrated it when it was first released and was listening to it in use on system using other EAR Amplification in the late 90's on regular occasion. 

At various events and Bake Off's I have attended throughout the past 10 years the Model has been demonstrated in both Original Build and the Clone DIY Version.

The Phon' in my assessment has a very noticeable richness and bloom at the lowest frequencies.

I find it hard to think of any SUT that will reduce this presentation to a condition where it is difficult to detect. From experiences encountered, a Head Amp' might be the most successful in reducing the perception of richness.

A better description of what was wrong with the SQ for your tastes, that encouraged the changes of a SUT, might help with understanding what your ideal presentation could sound like.

When my Bespoke Built Phon' was being built and I was experiencing it at different stages of Design, Topology and Circuitry, I rejected the prototype on more than one occasion, due to the detectable Richness and Bass Bloom that was being perceived. It took a careful organisation of the Topology and Circuit to use Boutique Cap's and Resistors, that were selected through component rolling to tame the ECC 83's. I use this with SUT's or occasionally a Head Amp with Ortofon Cart's.

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?