New phono stage from SOTA

Dear @tablejockey.

The claim was not mine. There are certainly many compromises that need to be made in a commercial design required to sell for $300. However, the measured performance is remarkably good for a unit of this price- equivalent to or better than many that are far more expensive, and the subjective listening tests were extremely positive.

As Bruno Putzeys famously wrote, " the problem is not that there is too much negative feedback, but there is too little... This design was implemented to do exactly that- correct for there being " too little feedback", and it was deliberately intended to make a frontal attack on the usual audiophile tenets in an area- MC phono preamp design- that is notoriously difficult to do well.

Several years? I was with ADI- designing a wide variety of ICs for almost forty years and was most fortunate to become an ADI Fellow and Senior Fellow.

I am not a free-lance engineer. I retired from ADI a few years ago and I design audio (and other gear) for fun and for free, and SOTA employed the design because they wanted something that truly was state of the art and it was brought to their attention by others that appreciated its qualities.

Your perspective on the effect of feedback is, in my opinion, facile, and does not recognize the psychoacoustic realities at play here.

The phono stage was explicitly designed to satisfy the known Psychoacoustic metrics and be explicitly neutral. Just because it eschews much of the audiophile preconceptions does not mean that it is inferior as substantial care was taken in all aspects of its design, from careful measurement and choice of components to the selection of an unusual architecture, to the actual creation of specs with each unit 100% tested to meet the critical ones.

Perhaps a little more introspection might be worthwhile.

Yeah, I know that is rare in audiophile circles, but perhaps warranted here.

@rauliruegas 

Here is the recognized US definition of freelancer:

A freelancer is an independent contractor who earns wages on a per-job or per-task basis, typically for short-term work. Benefits of freelancing include the freedom to work from home or from a non-traditional workspace, a flexible work schedule, and a better work-life balance.

Sometimes in certain areas (such as journalism) free lancers evan work for free to build up a portfolio or a reputation.

This is not that. This is entirely a hobby. It is entertainment in these, my declining years, with no expectation of a reward of any sort, except, perhaps, to satisfy a degree of curiosity which, fortunately, has not declined with the passing of the years.

The Pyxi architecture is, as far as I can tell, unique, or at least highly unusual.

The design is configured to be explicitly neutral. Your preferences are, frankly, inconsequential without some non-empirical basis to support them.

Despite the low-cost of the unit considerable care was taken to confer neutrality on the design, including very careful evaluation of the components and the layout.

As for, "It was recently discovered that the brain responds to signals above what we can think we can detect." what the heck does that even mean??

Oh. The Sota Acrux will be a bigger box with more functions (knobs and buttons) and even better specs and capabilities- all for 8x the price.

The Sota web site is being updated to allow for EU (and UK) purchases of the Pyxi.

How did I determine "no added colorations?’. Well, I didn’t that was SoTa’s conclusion.

I just followed a philosophy which amounts to,

1. Flat RIAA- variations over the audio band below the subjective threshold.

2.Extremely high power supply rejection, and extremely low power supply/ground interaction between stages.

3. Distortion which is below the acoustic threshold (-110dB FS) measured whatever way you choose to do it.

There are other aspects, but you get the gist, hence the designed to be explicitly neutral.

Finally in subjective testing. It actually sounds neutral, with a very high degree of clarity.

One other thing, I am well aware of the rather, how shall we say it, questionable (or at least questioned) results concerning the ultrasonic sensitivities of human hearing.

In any case what makes you so certain that those very sensitivities were not taken into consideration in the Pyxi etc. design?

In fact, the design is explicitly structured to ensure ultra-low distortion even for ultrasonic frequencies, and my test/evaluation methodology included signals up to 48khz (96kHz FS/2). Although the Pyxi does not have the extreme non-sensitivity that the Acrux has (read the paper, the multi tone tests which exceed the audio band say it all), it’s pretty darn good.

The Pyxi is not as good as I wanted it to be. SoTa had certain low cost goals that caused compromises to be taken. But it’s pretty darn good.

The larger unit does not use the 14v wall wart. It, presently, uses a very different supply.

The Pyxi WILL NOT BENEFIT FROM A CHANGE IN THE WALL WART!!!

The 240v version uses a 15v wall wart due to availability issues. 

Using a 15v wall wart in the US version could compromise the reliabilty. Even using a different 14v unit could do the same.

The filtering/regulation circuitry was carefully designed for the 14v wall wart that was used.