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SOTA Pyxi Initial Impressions

mprince

Super Member
Based on reading a lot of positive stuff on AK, I ordered a SOTA Pyxi phono pre and it arrived earlier this week. Wanted to share some initial impressions, not sure how far I will go with a "review" but we'll see (I don't do audio terms well). Sorry in advance for a long post...

Analog Chain: SOTA Star Sapphire, Audiomods Series 5 arm, Audio Technica OC9XML/Ortofon Cadenza Blue. System feeds a ZeroZone (Chinese copy of a Cary SLP-90) tube preamp. Amp is a heavily reworked Adcom GFA-545, and speakers are Ohm Walsh 2.2000.

Just a bit more background: In 2016/2017 I went through quite a transitory period in both phono and line-level preamps. Had a Luminous Audio passive preamp fed by a Vista Audio phono pre. I then decided to try MC headamps and got a Rothwell Headspace and a SOTA head amp. Had a ton of noise issues and got a Rothwell Simplex MM. Eventually landed on an Emotiva PT-100 pre as I needed a new DAC and frankly was tired of chasing problems. Got a Rothwell MCL SUT and fed the Emotiva MM stage with that, until earlier this year. Decided I wanted a better DAC, sold the Emotiva and got a tube pre-amp from China (no phono stage). So, I picked up another Rothwell Simplex to go with the SUT. What I found is that this had too much combined gain to work well with my Ortofon Cadenza (0.5mv) cartridge, so I subbed in my backup cartridge (AT OC9XML, 0.4mv output). This is about a $1K (retail) phono stage between the SUT and MM stage. Then I read about the SOTA Pyxi.

Over the past few years, I find myself listening to digital more than analog, mostly for the quick search/cue up, and with Hi-Res stuff it still sounds good (I mostly listen in my office while I work). In anticipation of ordering the Pyxi, I made more of an effort to listen to my records. Have spent the better part of the last few weeks just playing a wide variety of music. The Rothwell combo sounds great, although I've been a bit concerned about too much gain (42dB from phono stage, 26dB from SUT for 68dB total), and have been on the lookout for a Rothwell MCX, which would lower gain by about 6dB. The MCL worked well with the Emotiva, as it was a fairly low-gain (38dB?) MM stage.

In any case, the Pyxi arrived yesterday and I promptly set the dip switches (130 ohm loading, lowest capacitive load) and got it set up. Put on the first record (Pearl Jam Rearviewmirror, which I just bought) and things sounded great. Second up was a more familiar record, The Cars s/t debut. This is where I started to notice differences as I just played it on the old setup a few days ago. Where the Rothwell combo has a lot of texture/body (I told you I suck at audio terms) with very full bass, the Pyxi had a much more forward presentation, with what I would call a lot of layering of different parts of the music. What I mean is I heard clear separation between instruments and vocals as well. To get a feel for female vocals, I played a MOFI release of Carole King "Tapestry" - more of the same, and the vocals took center stage.

So a much different presentation, although I am not ready to say better. That will take several weeks of listening to a bunch of different music. Very noticeable as I feel like my ears have adapted to the more laid back/darker presentation of the Rothwell, still getting used to the liveliness/clarity of the SOTA stage. But very impressed so far. Not sure if the additional gain of the Rothwell combo (68dB vs. 65dB) plays any part in the differences I am hearing, at some point I will mount up the Cadenza and see if that plays nice with the SOTA (I expect it will).

Construction wise this is a solid chunk of engineering. Feels very well put together, and the instructions and setup were very straightforward. No pictures of my install as this is a set and forget item for me, it is not even visible in my rack as I like to keep short cable paths and as a result this is tucked back behind the preamp. I plan to leave it powered on all the time, although I guess I could reach back there and press the on/off button if I had to.

So that's it for now. Time will tell if this stays in my system, but so far I can say that if you are looking for a phono stage in this price range, I can recommend this for sure for LOMC use (I don't have any MM/MI/HOMC to test). An impressive piece of work by @wyn palmer , Bill Carlin and the folks at SOTA.
 
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I am sure I left something out, if any questions I am happy to answer. One thing I left out is that this is dead quiet (for a phonostage). Turned my preamp up to full tilt with nothing playing and only a slight hiss at the speakers (with my ear close). This is the similar to the Rothwell.

Listening to several albums today, just want to keep putting the next record on with this pre. Very engaging and fun to listen to.
 
Interesting development - getting some sort of sporadic hum in my system. Arm shield is connected to Pyxi earth post, have disconnected and reconnected everything a couple of times and triple checked all connections, also changed cables from Pyxi to pre. Get a periodic hum through the speakers with the phonostage on, doesn't matter if table is powered or not. Lasts for about a second when it happens. Might happen every 15 minutes or so.

Going to hook the Rothwell stage back up for a bit to see if I can reproduce this. Have made sure cable paths are clean (no power/signal interference), it doesn't seem to be my preamp as I can't reproduce the problem through the input my DAC is connected to...
 
Interesting development - getting some sort of sporadic hum in my system. Arm shield is connected to Pyxi earth post, have disconnected and reconnected everything a couple of times and triple checked all connections, also changed cables from Pyxi to pre. Get a periodic hum through the speakers with the phonostage on, doesn't matter if table is powered or not. Lasts for about a second when it happens. Might happen every 15 minutes or so.

Going to hook the Rothwell stage back up for a bit to see if I can reproduce this. Have made sure cable paths are clean (no power/signal interference), it doesn't seem to be my preamp as I can't reproduce the problem through the input my DAC is connected to...
If the noise is periodic and lasts only a few seconds --- maybe an external source? Like the refrigerator cooling system turning on? Or house A/C?

That noise is prolly being carried in your power line. :idea:
 
Perhaps, I'm not sure as I can't easily isolate those things (actually I can to some degree). Swapped in my Rothwell stage and no issues, on the second album side now. Weird. Plugged into the same outlet as the Pyxi and the same preamp input.
 
Perhaps, I'm not sure as I can't easily isolate those things (actually I can to some degree). Swapped in my Rothwell stage and no issues, on the second album side now. Weird. Plugged into the same outlet as the Pyxi and the same preamp input.
Use headphones to help track down the noise. :thumbsup:
 
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Use headphones to help down the noise. :thumbsup:
Another good idea, but I have no way to easily use headphones in my system, I removed and sold all my headphone stuff when I downsized/simplified my system earlier this year. Last time I used headphones to try and track down some noise it took me down a year long rabbit hole of chasing a hum which got real expensive with the end result being phono stage and preamp replacement, plus sending my tonearm back to Jeff Spall for a full rewire.

For now the safe answer is to remove the Pyxi from my system, the hum is absent. Back to blissful tunes here.
 
For now the safe answer is to remove the Pyxi from my system, the hum is absent. Back to blissful tunes here.
So, the Pyxi, for some reason, is causing the hum? Good that all is well, again! :)

Don't go down anymore rabbit holes. Sometimes, you never come back.
 
Been running the Rothwell stage all morning without incident, starting to look like the Pyxi has failed its audition. Either there is a fault in the unit (improbable), or something in my system/electrical environment that does not interact well with it (probable based on my experience a few years ago trying to find something that was quiet). Absent the noise issue, really enjoyed what this phonostage brought to my system.
 
Been running the Rothwell stage all morning without incident, starting to look like the Pyxi has failed its audition. Either there is a fault in the unit (improbable), or something in my system/electrical environment that does not interact well with it (probable based on my experience a few years ago trying to find something that was quiet). Absent the noise issue, really enjoyed what this phonostage brought to my system.
Rothwell is plugged into the same outlet? Similar interconnects? Similar grounding setup?

Thanks! :)
 
Rothwell is plugged into the same outlet? Similar interconnects? Similar grounding setup?

Thanks! :)
Yessir, 100%. Audiomods screen wire connected to SUT earth, the MM stage is in the same plug using the same wire route as the Pyxi. Phonostages even in same physical locations relative to other components. I ran into something similar when I tried the Rothwell head amp several years ago, sent amp back to distributor who tested it and said it worked fine in his system, even took parts of my analog system to him so we could test. After a year of fighting with it the distributor wouldn't offer any recourse and I gave the head amp away (AK auction).

May have a similar outcome with the Pyxi unfortunately (without any long battle though). Sometimes stuff just doesn't blend into a system no matter how hard we try..
 
So Are you using the Pyxi with the SUT as well or were you just using the MC side?

EDIT: Did you also try the Pyxi with no GND wire from the TT/Arm connected?

Nashou
No, I only used the MC side as that was my intended use case. I guess I could try that as a troubleshooting step.

I can't remember if I disconnected the tonearm screen from the ground post, another thing I can try.

Easy enough to do a temp hookup of the Pyxi tomorrow to try both of these, I had boxed it up earlier today. I'd like to complete the troubleshooting cycle so I can figure out what to do with it, move it on if good or pursue a return with SOTA if it's defective.
 
Also is the hum in both channels or just one?

Many prefer the DIY unit that Pyxi was based on through the MM section with a SUT. But , again as you hypothesized , the hum can be system dependent so some users prefer the MC side vs the SUT/MM combo.

Again every system is different.

Athanasios
 
Excellent question, I do not know the answer as it is sporadic. I guess when I set it up tomorrow I can sit between the speakers for a while to see if it is on one side or the other when it happens.

You've given me a lot to do tomorrow...haha
The reason I ask Is I am chasing down a hum on the right side of my DIY pre the Pyxi is based on.

Left side is great and the MM section has no issues either. Also so my DIY versions MM can actually play MC but you need to crank the volume , but it works and sounds just as good as the MC section. as its based on the same circuit just one has more gain.

Also try not using GND to pre Amp or amp, but I doubt thats it and will most likely have more hum, but you never know.

Nashou
 
The reason I ask Is I am chasing down a hum on the right side of my DIY pre the Pyxi is based on.

Left side is great and the MM section has no issues either. Also so my DIY versions MM can actually play MC but you need to crank the volume , but it works and sounds just as good as the MC section. as its based on the same circuit just one has more gain.

Also try not using GND to pre Amp or amp, but I doubt thats it and will most likely have more hum, but you never know.

Nashou
It might be your wifi. Try turning off any local nodes or routers and see if it goes away. If so, try orienting the Pyxi and/or phono cables and/or the router for minimum noise.
 
Is the sound a sort of burbling "motor boating" noise. If so, it's likely caused by wifi pickup on the phono socket being detected by the bipolar input stage. It tends to be worse on the right channel than the left. If so, you are the third person to report it. I was the first and I discovered it after release. In my case it was because I upgraded to a wifi 6 mesh network with the local node a couple of meters away from the Pyxi.
 
Is the sound a sort of burbling "motor boating" noise. If so, it's likely caused by wifi pickup on the phono socket being detected by the bipolar input stage. It tends to be worse on the right channel than the left. If so, you are the third person to report it. I was the first and I discovered it after release. In my case it was because I upgraded to a wifi 6 mesh network with the local node a couple of meters away from the Pyxi.
Yes, pretty much and I believe it's on the right channel, I can confirm tomorrow. If it's a WiFi issue I may not have a solution as my system is in my office, which has 2 computers (1 on WiFi and 1 on Ethernet) as well as a hardwired Bluesound Node on the equipment rack. This pretty much requires me to have a mesh node in the office. The node is probably 3 meters away from the Pyxi. I'll unplug the node for troubleshooting tomorrow, that will at least allow me to remove the variable temporarily.

Thanks for the tip.
 
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