SUT - electrical theory and practical experience

@holmz 

Thanks for sharing those details.  I don’t know the details of how a FET works, but I’m sure it has its deficiencies, as does the SUT.

I think that 0.00003 seconds (1/c) is essentially instantaneous to the human mind and ear….just ask the digital guys about sampling, etc. . . 
 

Thanks for sharing those details.  I don’t know the details of how a FET works, but I’m sure it has its deficiencies, as does the SUT.

A FET works more like a valve/tube.
If you like transimpedance (current based) amps, they are more than likely a BJT.

When that the SUT amplifies/increase voltage.

Deficiencies:
It is more design approach than a deficiency. The FET or the BJT may have more noise compared to one another, or across the different examples of the same devices.

The SUT has resistance, inductance and some capacitance. And hence a finite bandwidth. But many transistors have capacitance effects that limit their bandwidth. 

And how high can one really hear?

If in doubt on the SUT, it may be better to slightly undershoot ratio, than to wildly overshoot the ratio… and especially if the cart has a high output impedance.

I think that 0.00003 seconds (1/c) is essentially instantaneous to the human mind and ear….just ask the digital guys about sampling, etc. . . 

Correct one cannot tell the difference in speed by ear, but that point was in relation to your statement on copper versus silver wires. The dielectric also plays a role.

In the SUT the core also play a bit of a similar role to the magnetic field, that the dielectric played upon the electric field..

It is not altogether clear, that one can easily tease out all the nuance.
And if we get a good wild eyed sales person going full on passionate, then they can appear to be conjuring a pretty compelling story.

Back to deficiencies…  we have three camps:

1. Pure electronics voltage gain
2. SUT + voltage gain
3. Current gain

The circuit designers all make good examples in each, so pick your poison.
If you have a CH phono stage, your problems are different than someone with out an existing phono stage.

Hi @pindac ,

I’m agree that EAR834p has rich and bloat the lowest frequencies character. This character of the schematic remained despite improving bass resolution and dynamics, and more clean and open height frequencies in the better implemented version. Another factor are speakers. My Altec 604E speakers have dry bass. So it works good all together at least for my taste and for classical and jazz music that I like to listen.
But I can’t agree that all SUTs have the similar sound characteristics. I heard SUT in my system that have thin sound. And in my experience, the difference between different SUTs is huge.

Regards,

Alex

I don’t know that the method by which a signal is transmitted in a transistor is any better than a transformer

A FET works more like a valve/tube.
If you like transimpedance (current based) amps, they are more than likely a BJT.

The problem you are up against using either device above is that the input side of the device is outside of the feedback loop. You will have a rather prodigious electrical peak, likely between 1-5MHz with most LOMC cartridges. It might be as much as 30dB depending on the Q value (how long as opposed to how wide) of the coil in the cartridge. That peak can be energized and easily overload the input despite the use of feedback.

So an SUT has the advantage of not being overloaded in this way and actually blocks the RFI generated in this fashion from reaching the phono stage input! That's a pretty clear advantage!

(The overload can cause ticks and pops as well as distortion which is perceived as brightness- hence the use of 'cartridge loading' resistors, which detune the electrical resonance, preventing it from going into excitation.)

If you're going to run solid state, you need to use an opamp to get around this problem, or set up the feedback look on the discrete devices in the same manner as used in with an opamp; essentially creating a low performance opamp in the process...

Hi @atmasphere ,

I have a question for you regarding the use of feedback in tube phonostage. Unlike a power amplifier, the frequency response of the RIAA implies a deeper feedback at high frequencies. Is this kind of feedback deep enough to work properly?

Regards,

Alex