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SOTA Pyxi has arrived

matteos said:
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I’ve spent a bit more time with this phono stage, now with the Denon 103R. It’s very, very good indeed and I’m very glad I bought it. I think what sets this apart from my other stages is the sense of rhythm it imparts. The snare drums seem to hit just a little harder, the guitar beat hits a little harder and this is a good thing indeed. I’m ending up tapping my feet to the music far more than with anything else and I would classify that as a pretty big win.

At some point reasonably soon I will switch the cart for my Denon DL-S1. That is a very low output MC indeed. I have the matching SUT - the AU-S1 but from my understanding in this thread that may not be the greatest match (or maybe it’s fine) with this phono stage. In terms of gain there have been no problems with the Denon 103R and I don’t use the Step up Transformer for my DL-S1 with the Project phono stage and I’m thinking it might not even be necessary with the Pyxi. It does end up being a lot of stuff to switch in and out and I’m not motivated to change anything at this point because I’m enjoying it to much.

Thanks for all your work on this Wyn! From this thread alone I see that you put a lot of attention to the details and I think it shows in the stage. Really, really good. Highly recommend.
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Thank you. I hoped to demonstrate that technical/measurable excellence and acoustic quality are not incompatible, provided the correct criteria are applied.
There does appear to be a set of pretty consistent observations concerning the sound character of the design, so I thank you for your opinion.
 
matteos said:
View attachment 2909809


I’ve spent a bit more time with this phono stage, now with the Denon 103R. It’s very, very good indeed and I’m very glad I bought it. I think what sets this apart from my other stages is the sense of rhythm it imparts. The snare drums seem to hit just a little harder, the guitar beat hits a little harder and this is a good thing indeed. I’m ending up tapping my feet to the music far more than with anything else and I would classify that as a pretty big win.

At some point reasonably soon I will switch the cart for my Denon DL-S1. That is a very low output MC indeed. I have the matching SUT - the AU-S1 but from my understanding in this thread that may not be the greatest match (or maybe it’s fine) with this phono stage. In terms of gain there have been no problems with the Denon 103R and I don’t use the Step up Transformer for my DL-S1 with the Project phono stage and I’m thinking it might not even be necessary with the Pyxi. It does end up being a lot of stuff to switch in and out and I’m not motivated to change anything at this point because I’m enjoying it to much.

Thanks for all your work on this Wyn! From this thread alone I see that you put a lot of attention to the details and I think it shows in the stage. Really, really good. Highly recommend.
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The DL S-1 is at the low end of the range of acceptable cartridges for the Pyxi. It will still be OK when the disk is being traced, but the S/N ratio will be 3dB below spec.
 
wyn palmer said:
Amir, alas, succeeded in mostly demonstrating the limitations of his test methodology and not of the unit itself.
A pity. I tried to explain how to improve his approach, and the rationale behind it, in order to overcome what was limiting his performance test, but he would not countenance a change.
When I pointed out that actual user experience contradicted his evaluation he became quite - exercised.
I guess he really does not tolerate actual listening experience as a quantitative approach even when his theory and experience are wildly divergent.
Ah well!
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Sums up why I don't waste my time at Audio Quasi Science Review.

Amir is doing his measurements without basing his choices of metrics in actual audio science, and refuses to take part in any research-based discussion about those choices. That makes his work the opposite of science - he is just a charlatan with a fancy measuring rod, cheered on by a cult-like forum crowd.

It is a pity, really. What is sorely needed would be an Audio Science Review actually reviewing audio science - that would make for a refreshing novelty in the audio world.
 
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cgallery said:
A lot of other phono stages tested by ASR have some sort of high pass filter built-in (cannot be disabled), perhaps the combination of being flat to DC (am I correct on that?), and whatever you've done for output coupling, is the difference.

There was a time where I could not live without a subsonic filter. Now with my better DIY arm, I'd not want to use one, because I don't like what they do to the bass. My DIY model has a sort, so it will be interesting to see how the Pyxi compares.
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One other thing I forgot to mention concerning the LF extension of the Pyxi. The output offset is controlled by a DC feedback loop. The feedback loop is not just a simple integrator but is slightly underdamped to make the response flatter in the LF region than would otherwise be the case.
The end result is a flatter, more extended, LF response with a more ideal phase/group delay characteristic i.e. all the benefits of a full DC coupled design, without the disadvantages.
 
wyn palmer said:
One other thing I forgot to mention concerning the LF extension of the Pyxi. The output offset is controlled by a DC feedback loop. The feedback loop is not just a simple integrator but is slightly underdamped to make the response flatter in the LF region than would otherwise be the case.
The end result is a flatter, more extended, LF response with a more ideal phase/group delay characteristic i.e. all the benefits of a full DC coupled design, without the disadvantages.
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Do you think this phase/group delay is in fact audible? I'd like to think so, considering the tight bass reproduction from my diy box. But mostly anything published one can can find on the subjects of phase and LF group delay seems to dismiss any such effect as inaudible, unless the measurements are miles off.
 
tothmes said:
Do you think this phase/group delay is in fact audible? I'd like to think so, considering the tight bass reproduction from my diy box. But mostly anything published one can can find on the subjects of phase and LF group delay seems to dismiss any such effect as inaudible, unless the measurements are miles off.
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In all honesty I have no idea. It's just a consequence of the design goals. The few evaluations of the effect of GD I've seen suggest that LF audibility occurs at vastly higher GD levels than pretty well all circuit implementations offer, and of course at LF the room characteristics are dominant in both the temporal and magnitude response characteristics.
As I've mentioned. The improved LF "audibility" characteristic that has been reported by many and that I've experienced myself across several different systems, is both a surprise and a puzzlement.
But then again, the perception of bass is not merely that of the tonal frequency response but at least a complex interaction of the various harmonics- remember the UK Hifi reviewer's assertion that his use of an extremely imperfect "super tweeter" in a vertical firing position greatly improved his system's perceived bass response?
 
At a minimum, any question of LF "tightness" is of course dependent on the higher frequencies. Both as a reference point against which the LF can be considered as more or less tight, and also as the overtone spectrum of the LF signal under consideration. A LF signal can't be more or less "tight" in itself. As a failed bass player myself, I'm pretty certain there are audible differences in timing of the LF reproduction from different audio gear - I trained for years in listening for such traits while playing myself. I find it fascinating that such audible differences between gadgets still can't be quantified by solid measurements.

One funny thing with those super tweeters of course is that the studio microphones used for recording mostly every production never go higher than 15-20 kHz. This even before any further processing of the signal in the following production stages. I don't doubt the effect of super tweeters can be audible, but if so, it certainly isn't because they reproduce anything that exists in the source material - apart from the spilloff from their LP filters, normally cutting at about 15 KHz with 12-18 dB/octave, leaving plenty of room for audible HF content in parallel with the ordinary tweeters.
 
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tothmes said:
At a minimum, any question of LF "tightness" is of course dependent on the higher frequencies. Both as a reference point against which the LF can be considered as more or less tight, and also as the overtone spectrum of the LF signal under consideration. A LF signal can't be more or less "tight" in itself. As a failed bass player myself, I'm pretty certain there are audible differences in timing of the LF reproduction from different audio gear - I trained for years in listening for such traits while playing myself. I find it fascinating that such audible differences between gadgets still can't be quantified by solid measurements.

One funny thing with those super tweeters of course is that the studio microphones used for recording mostly every production never go higher than 15-20 kHz. This even before any further processing of the signal in the following production stages. I don't doubt the effect of super tweeters can be audible, but if so, it certainly isn't because they reproduce anything that exists in the source material.
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All true, and thank you.
If I remember correctly, we speculated that it was due to combing of the mid-range response due to the rather odd characteristics of the "super tweeter" that might have created the impression. But then again, his bass system was doing other strange things like frequency doubling at the c. 35Hz fundamental resonance of his transmission line.
Audio can be a funny business. So many strong assertions, so little actual understanding- even from those that ostensibly should know better.
 
tothmes said:
At a minimum, any question of LF "tightness" is of course dependent on the higher frequencies. Both as a reference point against which the LF can be considered as more or less tight, and also as the overtone spectrum of the LF signal under consideration. A LF signal can't be more or less "tight" in itself. As a failed bass player myself, I'm pretty certain there are audible differences in timing of the LF reproduction from different audio gear - I trained for years in listening for such traits while playing myself. I find it fascinating that such audible differences between gadgets still can't be quantified by solid measurements.

One funny thing with those super tweeters of course is that the studio microphones used for recording mostly every production never go higher than 15-20 kHz. This even before any further processing of the signal in the following production stages. I don't doubt the effect of super tweeters can be audible, but if so, it certainly isn't because they reproduce anything that exists in the source material - apart from the spilloff from their LP filters, normally cutting at about 15 KHz with 12-18 dB/octave, leaving plenty of room for audible HF content in parallel with the ordinary tweeters.
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Perhaps, infra- and ultrasonic harmonic characteristics? :idea:
 
Just found this thread a few pages back. Did I understand the MM only unit will have better SNR than the combo? And will it drive a 10’ interconnect?
 
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wyn palmer said:
It looks like SoTA will build a few MM only versions of the Pyxi, with 35dB and 45dB gain and MOSFET inputs. They will likely try them in house and with select potential customers.
This unit is specifically tailored to the MM, MI high output cartridge and SUT/MM crew. It will have worse short circuit input noise but better real world use noise than the current Pyxi under these circumstances and will meet the very high output cartridge need. The MC2000/T2000 case, for example will have essentially indistinguishable noise from the intrinsic noise of the cartridge. The RIAA compliance will be the same in both gain modes, which are controlled by the front panel switch. The distortion will be better for MM etc. than in the Pyxi "duo".
The load Rs are presently set at 47k, 9.6k and 1k, consisting of 47k fixed, 12k and 1k switchable. The Cs are the same.
Understand that this is in the prototype phase and may not become a real product, but I would welcome any input.
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Mr Palmer,
I have 2 carts I’d be interested in trying this with. A Shure V15Vxmr which needs a bit more capacitance than the DL MP7 I’m using now has, and a Grado Signature XTZ that only has 1.5mv of output. The Darlington’s 40db of gain just is not quite enough to wake it up. Hope this pre is available this year for audition.
Regards. Edit: Sorry, just saw the C’s are same……meaning capacitance is fixed? Oh well,
 
lsipes1965 said:
Mr Palmer,
I have 2 carts I’d be interested in trying this with. A Shure V15Vxmr which needs a bit more capacitance than the DL MP7 I’m using now has, and a Grado Signature XTZ that only has 1.5mv of output. The Darlington’s 40db of gain just is not quite enough to wake it up. Hope this pre is available this year for audition.
Regards. Edit: Sorry, just saw the C’s are same……meaning capacitance is fixed? Oh well,
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No, the input capacitance is not fixed. The Pyxi- original or MM has back panel switchable capacitances- 47pF fixed plus 100pF and 220pF switchable. This allows you to select from 47pF, 147pF, 267pF and 367pF.
 
lsipes1965 said:
Just found this thread a few pages back. Did I understand the MM only unit will have better SNR than the combo? And will it drive a 10’ interconnect?
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For high inductance/resistance cartridges or in the case where a SUT is used and the transformed impedance of the cartridge (the impedance times the square of the step-up ratio) is greater than 1.5k or so the FET input Pyxi will be quieter- and we're talking A weighted numbers that are approaching CD levels so that the noise is limited by the source.
Oh, and it will almost certainly drive a 10' interconnect- but do you know the cap/unit length of the cable so I can do a quick check?
 

SoTa Pyxi MM version test thread

A well known audio company is proposing a MM only version of a low cost phono stage with front panel switching between 35 and 45dB gain, and MOSFET input devices so there is no noise penalty for high resistance/inductance cartridges like most Moving Magnet units, and it should work well with...
audiokarma.org
For those who are interested in contributing to the evaluation.
 
wyn palmer said:
For high inductance/resistance cartridges or in the case where a SUT is used and the transformed impedance of the cartridge (the impedance times the square of the step-up ratio) is greater than 1.5k or so the FET input Pyxi will be quieter- and we're talking A weighted numbers that are approaching CD levels so that the noise is limited by the source.
Oh, and it will almost certainly drive a 10' interconnect- but do you know the cap/unit length of the cable so I can do a quick check?
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It’s Blue Jean lc1 cable. 12 pf/ft. But that’s after the phono pre, so capacitance not in play there. I’ve only got the one Shure, 5 vintage Grado and a Soundsmith Voice. I know the MI are unaffected by capacitance , but seen some charts that would indicate the Shure would benefit from some extra.
 
lsipes1965 said:
It’s Blue Jean lc1 cable. 12 pf/ft. But that’s after the phono pre, so capacitance not in play there. I’ve only got the one Shure, 5 vintage Grado and a Soundsmith Voice. I know the MI are unaffected by capacitance , but seen some charts that would indicate the Shure would benefit from some extra.
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Actually, the capacitance of the 10' output cable is important as it contributes to a reduction in stability of the output amp. That's why I asked.
It should be fine.
 
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