SOTA Pyxi Phono Stage Review

[Frank Dernie]

I was a student at Imperial College

I was too in 1971!

 

[pma]

Incidentally, I spent most of the summer of 1971 at the Decca pressing plant in New Malden. At time they were indeed using Neumann Lathes and had the "elliptic" filter for the bass to suppress vertical modulation in place. I had, amongst other "gopher" jobs (I was a student at Imperial College and I begged someone I knew at Decca to just give me a job- any job because I was so in love with their records) the task of bringing the stampers to the pressing area. I also participated in the test pressing evaluations, and occasionally in comparison listening between the LPs and the master tapes.

This reminds me my own student story, I spent most of summer of 1977 at Supraphon recording studios of classical music and participated in several very interesting recording sessions with Czech philharmonic orchestras, with Miloslav Kulhan as a recording engineer. This will never be forgotten by myself.

Awards - AES

The AES recognizes and honors those who have made outstanding contributions to the field of audio in engineering, technology, service, and the arts through its Awards Program.

aes2.org

AES awards:

Miloslav M. Kulhan

Citation

2001

in recognition of outstanding contributions to the recording industry and particularly the promotion of the AES in the Czech Republic.

.... and my lecturer in electro-acoustics at the Czech Technical University (CVUT) was another awarded member, professor Josef Merhaut

Josef Merhaut

Fellowship

2001

in recognition of outstanding contributions in the fields of acoustics and electroacoustics.

 

[wynpalmer]

I've just been made aware that there is a youtube channel that has a build of the Pyxi precursor (the DIY design) being demonstrated. It uses exactly the same input and grounding topology as the Pyxi. There are several videos, but the one above is of interest because the owner starts in MM with a cartridge, then switches to an open MC and no hum is evident. The owner actually comments on the lack of hum - "I don't hear any hum..."

 

[wynpalmer]

I bet your young ears were hearing things some of the old guys weren't.

Perhaps, but that thought never crossed my mind. When you're 18 the idea that physical and intellectual capabilities degrade with age is not something you think about...

 

[wynpalmer]

@wynpalmer , please let me ask you a question. Are you that Wyn Palmer with AD?

Based on communication from ASR concerning my potential commercial interests, perhaps I should clarify my response further. I have modified my signature accordingly, but I'd like to add a bit more context.
My main purposes in being involved in these phono stages are twofold.
1. To provide some incremental intellectual stimulation in my retirement and 2. to see if the hypothesis concerning what makes audio designs sound "good" or "bad", and which "drove" the architecture choice, is at least plausibly correct.
If correct, the result should be an audibly objectively neutral design with a very high level of clarity, and superb transient performance, but which also lacks the "false brightness" of many highish feedback designs. This seems to conform to the general impression that has been reported to me.
The common user observation that the bass response also seemingly benefitted from the approach was somewhat surprising.
The subjective aspect is outside the bailiwick of ASR so I was loath to even bring it up.
Sorry for any discomfort this may have caused.

 

[pma]

Based on communication from ASR concerning my potential commercial interests, perhaps I should clarify my response further. I have modified my signature accordingly, but I'd like to add a bit more context.
My main purposes in being involved in these phono stages are twofold.
1. To provide some incremental intellectual stimulation in my retirement and 2. to see if the hypothesis concerning what makes audio designs sound "good" or "bad", and which "drove" the architecture choice, is at least plausibly correct.
If correct, the result should be an audibly objectively neutral design with a very high level of clarity, and superb transient performance, but which also lacks the "false brightness" of many highish feedback designs. This seems to conform to the general impression that has been reported to me.
The common user observation that the bass response also seemingly benefitted from the approach was somewhat surprising.
The subjective aspect is outside the bailiwick of ASR so I was loath to even bring it up.
Sorry for any discomfort this may have caused.

I appreciate you being here. It is refreshing to see the posts that make sense in both technical and sound evaluation respects. In the past, I appreciated communication with Walt Jung, John Curl and Scott Wurcer. Not many knowledgeable guys are willing to participate in forum discussions. Thank you.

 

[EJ3]

This reminds me my own student story, I spent most of summer of 1977 at Supraphon recording studios of classical music and participated in several very interesting recording sessions with Czech philharmonic orchestras, with Miloslav Kulhan as a recording engineer. This will never be forgotten by myself.

Awards - AES

The AES recognizes and honors those who have made outstanding contributions to the field of audio in engineering, technology, service, and the arts through its Awards Program.

aes2.org

AES awards:


.... and my lecturer in electro-acoustics at the Czech Technical University (CVUT) was another awarded member, professor Josef Merhaut

In 1975 (my Senior year of high school) I joined
Junior Achievement of Greater South Carolina, Inc.®
2711 Middleburg Drive,
Suite 301
Columbia, SC 29204

Contact Us​

(803) 252-1974 (Junior Achievement inspires and prepares young people to succeed in a global economy)
and found a mentor in John Dozier (a local radio station News Man for WCSC [both a Radio Station and a TV station] who also did volunteer work for the NPR radio station that was on the USS Yorktown).
(The USS Yorktown is an 888-foot (271-meter) aircraft carrier. The naval ship served in several wars, earning a host of battle stars. Today it lies in the water off Patriots Point in the Charleston Harbor and is open to the public as a memorial and museum. The USS Yorktown was the tenth aircraft carrier to serve in the U.S. Navy. It was commissioned in 1943 and served in the Pacific Offensive. The ship was involved in heavy battles, including the sinking of enemy battleships and providing support to troops landing at Okinawa in Japan. During the Vietnam War it earned battle stars providing anti-submarine warfare support for faster carriers. One of the ship’s last missions was recovering the Apollo 8 astronauts and capsule from the ocean in 1968. There are two museums on board, including a shipyard with photographs and tools. The Medal of Honor Museum is a memorial to sailors and officers and the hangar deck houses vintage airplanes. Two films were made aboard the Yorktown: the Academy Award–winning documentary The Fighting Lady, filmed in 1944, and the 1970 American-Japanese war movie Tora! Tora! Tora!).
With Mr. Dozier's guidance I was able to find several like minded students and we formed a radio production group, (first, we had to study and then test in Atlanta to get our Federal Communications Commission 3rd Class Radio/Telephone license so that we could learn hands on how to operate a radio station and produce a 1/2 hour Radio Show (we chose to bring new hopefully to be Top 40 music to the air) on Sunday's mid afternoon drive.
I was the production manager, on air personality and one of the one's selling and producing adds that kept our little show on the air at WCSC AM, Charleston, SC. Before this stint was over, we had expanded to a 1 hour show. We coalesced into a great team and I ended up being given an award titled Best Business Man of the Year for Jr. Achievement of Coastal South Carolina.
John Dozier is the one that introduced us to the high end audio gear and several of us joined audio/video, photography & film making clubs. For a few of us, what happened with this became our career. I was a radio & Club DJ until the mid--late 80's & also designed and built sound systems for night clubs under another friend that was 4 years older than me & involved in clubs.
Those were wonderful times and a great time to enter the crazy world of high end audio.
Thanks go out to folks like John Dozier, Amirm and many, many others who battle the snake oil and show us what is happening so that we can make choices based on TRUTH.
EJ3

 

[EJ3]

Based on communication from ASR concerning my potential commercial interests, perhaps I should clarify my response further. I have modified my signature accordingly, but I'd like to add a bit more context.
My main purposes in being involved in these phono stages are twofold.
1. To provide some incremental intellectual stimulation in my retirement and 2. to see if the hypothesis concerning what makes audio designs sound "good" or "bad", and which "drove" the architecture choice, is at least plausibly correct.
If correct, the result should be an audibly objectively neutral design with a very high level of clarity, and superb transient performance, but which also lacks the "false brightness" of many highish feedback designs. This seems to conform to the general impression that has been reported to me.
The common user observation that the bass response also seemingly benefitted from the approach was somewhat surprising.
The subjective aspect is outside the bailiwick of ASR so I was loath to even bring it up.
Sorry for any discomfort this may have caused.

Yes, thank you so much for coming on here.
I believe that your design has great merit and will likely replace the use of my APT/Holman Preamplifier's Phono stage at some point later in the 2024 year (my audio budget for next year is already mostly set in stone).
If you had not brought this Pyxi project to our attention here, I would have likely not even thought about using anything other than the phono section of my APT/Holman Preamp for those duties (I will still bring it back to it's original configuration in both of my APT/Holman Pre's, as one resister not being in place [in both of them] is causing a rise in the frequency response above 10K).

 

[Bob from Florida]

Yes, I took it out of the ranking due to test conditions being different.

@amirm - Regarding the ifi Zen. Can you explain what changed with test conditions to pull it from the rankings? Just trying to understand the evolution of the phono testing protocols.

 

[Bob from Florida]

Based on communication from ASR concerning my potential commercial interests, perhaps I should clarify my response further. I have modified my signature accordingly, but I'd like to add a bit more context.
My main purposes in being involved in these phono stages are twofold.
1. To provide some incremental intellectual stimulation in my retirement and 2. to see if the hypothesis concerning what makes audio designs sound "good" or "bad", and which "drove" the architecture choice, is at least plausibly correct.
If correct, the result should be an audibly objectively neutral design with a very high level of clarity, and superb transient performance, but which also lacks the "false brightness" of many highish feedback designs. This seems to conform to the general impression that has been reported to me.
The common user observation that the bass response also seemingly benefitted from the approach was somewhat surprising.
The subjective aspect is outside the bailiwick of ASR so I was loath to even bring it up.
Sorry for any discomfort this may have caused.

@wynpalmer - thank you for the clarification of your role with this phono stage. The variable capacitive loading is nice, but would be even nicer with a 0 pf load option for those of us stuck with a high capacitance tonearm cable. Phono preamps with that option seem to be rare.

 

[wynpalmer]

@wynpalmer - thank you for the clarification of your role with this phono stage. The variable capacitive loading is nice, but would be even nicer with a 0 pf load option for those of us stuck with a high capacitance tonearm cable. Phono preamps with that option seem to be rare.

Alas, with only two switches available for capacitance, compromises needed to be made to satisfy the expected MM cartridge/cable choices.
Perhaps, stating the obvious, a lower capacitance/unit length and/or shorter cable is in order?

 

[Bob from Florida]

Alas, with only two switches available for capacitance, compromises needed to be made to satisfy the expected MM cartridge/cable choices.
Perhaps, stating the obvious, a lower capacitance/unit length and/or shorter cable is in order?

Well, my Clearaudio Satisfy arm is wired straight through- no din plug, like my previous table. It has 172 pf in the cable, which gives you a peak around 8K with a high inductance cartridge like a Maestro 2. I am using a Hana SL MC which gets around the capacitance issue, but it would be nice to use a MM if I wanted to change it up for awhile.

 

[mike70]

the only one with balanced outputs that stays in the top is the Musical Fidelity ... almost 1k USD.
the ifi zen was a spot of light in the budget level (balanced outputs), i hope that some preamp take that place soon.

 

[wynpalmer]

the only one with balanced outputs that stays in the top is the Musical Fidelity ... almost 1k USD.
the ifi zen was a spot of light in the budget level (balanced outputs), i hope that some preamp take that place soon.

Balanced outputs, in my opinion, are hugely overrated. The Acrux has single ended and balanced outputs. The performance of the balanced output WRT the SE output is identical, except for the doubled output swing. and the level is sufficiently large that pickup in the interconnect is, in home systems, inconsequential.
Having said that, I do use the Acrux in balanced out mode into the RME box and balanced out mode from the RME box to the two AHB2 amps, so there's clearly some hypocrisy here. However, I never purchase anything based explicitly on the balanced/unbalanced nature of its IOs.

 

[pma]

the only one with balanced outputs that stays in the top is the Musical Fidelity ... almost 1k USD.
the ifi zen was a spot of light in the budget level (balanced outputs), i hope that some preamp take that place soon.

This is another one - the prototype dated 2008. I designed several phono preamps, sold the designs and prototypes, and they were produced by various manufacturers. The schematics posted is incomplete, DC servo not shown e.g. Click on the thumbnail.

 

[wynpalmer]

Well, my Clearaudio Satisfy arm is wired straight through- no din plug, like my previous table. It has 172 pf in the cable, which gives you a peak around 8K with a high inductance cartridge like a Maestro 2. I am using a Hana SL MC which gets around the capacitance issue, but it would be nice to use a MM if I wanted to change it up for awhile.

Well, that's unfortunate. That's an astonishingly high capacitance. On the VPI 3D arm with a Miyajima Madake snakewood that I use the cartridge/arm capacitance to the TT phono connectors I measured as 48pF, and the 1m interconnect as 200pF. The interconnect was not chosen for its low capacitance as I use only MC cartridges.

 

[mike70]

Balanced outputs, in my opinion, are hugely overrated. The Acrux has single ended and balanced outputs. The performance of the balanced output WRT the SE output is identical, except for the doubled output swing. and the level is sufficiently large that pickup in the interconnect is, in home systems, inconsequential.
Having said that, I do use the Acrux in balanced out mode into the RME box and balanced out mode from the RME box to the two AHB2 amps, so there's clearly some hypocrisy here. However, I never purchase anything based explicitly on the balanced/unbalanced nature of its IOs.

In the standard home context, I think you're right. But ... but ... if I have a decent balanced implementation at (more or less) the same price ... I'll choose the balanced implementation.

It's not one option "against" the other, is one option with some advantages at the same cost.

 

[mike70]

This is another one - the prototype dated 2008. I designed several phono preamps, sold the designs and prototypes, and they were produced by various manufacturers. The schematics posted is incomplete, DC servo not shown e.g. Click on the thumbnail.

View attachment 289362

I appreciate that ... but my knowledge and laziness only allows me to use commercially finished products.

 

[ronniebear]

This reminds me my own student story, I spent most of summer of 1977 at Supraphon recording studios of classical music and participated in several very interesting recording sessions with Czech philharmonic orchestras, with Miloslav Kulhan as a recording engineer. This will never be forgotten by myself.

Awards - AES

The AES recognizes and honors those who have made outstanding contributions to the field of audio in engineering, technology, service, and the arts through its Awards Program.

aes2.org

AES awards:


.... and my lecturer in electro-acoustics at the Czech Technical University (CVUT) was another awarded member, professor Josef Merhaut

If memory serves me correctly, many 1970s Supraphon classical music recordings were co-productions with Nippon Columbia (Denon). As inventor of PCM (pulse code modulation) digital recording, Denon was eager to build up a catalog of digitally-recorded audiophile LPs in order to showcase the emerging PCM digital technology a couple of years earlier than the big classical companies of the era (CBS, Decca, Philips et al). As such, many of the recording sessions involved simultaneous transcriptions: Supraphon used multi-channel analog tape (to be encoded using SQ stereo/quadraphonic matrix for cutting on LPs), while Denon used its PCM digital taping system to be cut onto audiophile-grade consumer LPs.

Supraphon's recordings from that era, whether on Supraphon or Denon LPs, were quite natural sounding and vibrant. The musicianship on the recordings was very fine as well.

 

[ronniebear]

In the real world of phonograph disc playback, SOTA's Pyxi playback is perfect to a fault: contrary to what many think, it's nearly impossible to eliminate sub-sonic resonances without using an effective subsonic filter (also called infrasonic filter). This filter initiates a sharp cutoff of frequencies which are below 20 hz, frequencies which are inaudible and non-musical but which can and do generate excessive speaker thumping and "woofing". Only God knows how many fine high-fidelity speaker systems have ended needing premature woofer refoaming or resealing after one too many episodes of "woofing" caused by subsonic frequencies. Additionally, that subsonic energy was at such low frequencies as to absorb massive amount of amplifier power, often causing amp clipping not so much from "loud" volume as from power-robbing sounds of a badly warped or off-center LP pressing.

In earlier times, notably during the first 10+ years of stereo LP, a broader high-pass filter called a rumble filter was offered on many phono preamps and receivers. Unlike the subsonic filter, the rumble filter rolled off at a much higher frequency range, starting around 60 hz or even 70 hz. The specific intent was to eliminate the sound of turntable rumble and hum caused by the mechanisms of many record changers commonly used in that day and age. The "rumble" noise would often be insignificant during monaural playback with a mono-only cartridge and mono record, but clearly audible when using a stereo cartridge that required horizontal stylus movement in tracing Westrex 45/45 stereo discs.

At some point around 1980, most manufacturers of phono playback electronics started addressing the subsonic/infrasonic issues. In many cases, a subsonic filter was integrated into the design of the phono stage (i.e. Advent 300 receiver, NAD 3020 integrated amp). In other cases, a user-selected front-panel subsonic filter was made available on the device's front panel. Additionally, up until the mid-1980s most stereophonic integrated amps and receivers offered a user-selectable mono switch.

Final thought: although turntable-induced subsonic noise is not present in live performances of music, the fact that this subsonic distortion exists in vinyl LP playback may be part of what LP connoisseurs regard as the "warmth of playing vinyl". For some listeners, the sensation of subsonic information is perceived and felt in a pleasing and enjoyable way, even though that subsonic information was not present during the actual musical performance.