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SoTa Pyxi MM version test thread

What loading choices, one fixed, two switchable, would be best for a MM/MI/HOMC only phono stage?


  • Total voters
    9
  • Poll closed .

wyn palmer

Addicted Member
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 most SUT combos.
The prototype has load options that are 47k fixed with switchable 12k and 1k giving 47k, 9.6k, and c. 900, but this could be different (see poll above).
It also has the exceptionally tight RIAA compliance and ultra-low distortion that the original has.
There is a single prototype available for end user evaluation, and I invite anyone that might be interested to take this opportunity to be on the round-robin list. The unit is a representative production item, with no selected components or anything that would not appear on the production box. The front panel is a prototype.
The unit went through the production test run, but with the gain changes included.
The condition is that each participant will keep the unit for at most one week, then will be responsible for shipping to the next participant, and then finally to me. I will pay for the first shipping out.
Participants must be willing to provide a brief "review" of the unit on this thread- good or bad- and be willing to enter into discussions concerning any observations, again good or bad.
Current requests are from @franspambot, @GChief, @cgallery, @robnec, @specialcase, @Nashou66, @hoodie and @Decibel_116.
This offer will remain open for one week, after which the "round robin" will commence.
I believe that this is in compliance with AK rules. There is no attempt to sell this item, just to obtain feedback on the utility/performance/audio quality of the unit, which may or may not go into production at some point.
If I am incorrect in this, then I assume that the mods will inform me and shut this effort down (Mods are indeed OK with it).
 
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Just a comment, Wyn, but I'd deem the +12 kOhm/9.6k Ohm & +1kOhm / 900 Ohm loading options not all too useful for an MM-only variant. Might be smarter to start with ca. 100 kOhm and make the other two ca. +100 kOhm / ca. 50 kOhm and ca. +63 kOhm / ca. 38 kOhm (and +both / ca. 28 kOhm). That should please the fans of classic CD4 carts, fans of standard loading, fans of somewhat lower loading (e.g. for quite a few ATs) - and the ca. 28 kOhm might be ok for HOMC.

Greetings from Munich!

Manfred / lini
 
Just a comment, Wyn, but I'd deem the +12 kOhm/9.6k Ohm & +1kOhm / 900 Ohm loading options not all too useful for an MM-only variant. Might be smarter to start with ca. 100 kOhm and make the other two ca. +100 kOhm / ca. 50 kOhm and ca. +63 kOhm / ca. 38 kOhm (and +both / ca. 28 kOhm). That should please the fans of classic CD4 carts, fans of standard loading, fans of somewhat lower loading (e.g. for quite a few ATs) - and the ca. 28 kOhm might be ok for HOMC.

Greetings from Munich!

Manfred / lini
Users of 100k loading (CD-4) are probably mostly extinct by now, but it is a nice option to have to play with.
 
Just a comment, Wyn, but I'd deem the +12 kOhm/9.6k Ohm & +1kOhm / 900 Ohm loading options not all too useful for an MM-only variant. Might be smarter to start with ca. 100 kOhm and make the other two ca. +100 kOhm / ca. 50 kOhm and ca. +63 kOhm / ca. 38 kOhm (and +both / ca. 28 kOhm). That should please the fans of classic CD4 carts, fans of standard loading, fans of somewhat lower loading (e.g. for quite a few ATs) - and the ca. 28 kOhm might be ok for HOMC.

Greetings from Munich!

Manfred / lini
Oddly enough. The requests that I've had for MM/HOMI and HOMC are for 47k, c.10k and 1k. No-one has asked for anything higher than 47k, and I've had a couple of requests for around 1k for HOMC.
The choices are set by the three Rs (one fixed, two switchable) unless a cap choice is eliminated, and the cap choices seem to be OK.
It seems like some kind of poll is required.
Does anyone else have an opinion?
The evaluation unit is what it is as I'm not going to go in and replace the SM resistors, but the eventual choices are up for grabs.
 
10 and 1K options are more or less useless for MM cartridges, so calling it a MM version is misleading. It is more geared for HOMC and LOMC/SUT crowd.
 
10 and 1K options are more or less useless for MM cartridges, so calling it a MM version is misleading. It is more geared for HOMC and LOMC/SUT crowd.

But don't some of the Grado cartridges like loading as low as 10k?

It seems both Grado and Audio Technica users sort of stand-out for wanting options for something other than 47k.
 
10 and 1K options are more or less useless for MM cartridges, so calling it a MM version is misleading. It is more geared for HOMC and LOMC/SUT crowd.
Again, I'm looking for opinions. I've had half a dozen opinions from local MM/MI users, and they are mostly fine with 47k.
There have been a few opinions that want 10k - possibly for Grado cartridges?
A few inputs from LOMC users that like 1k. Absolutely no-one, prior to this, has asked for something above 47k.
The present unit does pretty well with all of the various types of cartridges, except it could use a higher load R than 470 ohms, and lower than 47k according to several reports.
Demonstrations have occurred with many high output cartridges with 47k.
So, 47k is absolutely a given.
However,
Load the Magnets!!! - [English] (tnt-audio.com)
Cartridge loading explained (austinaudioworks.com)
Hagerman Technology LLC: Cartridge Loading (hagtech.com)
Some of the 'evaluations' are quite deficient insofar as they ignore the various mechanical resonances that are produced by the cantilever/PU arm mechanical system, and the reality in my opinion is that the cartridge manufacturer is probably the best reference for the near ideal loading condition as they will try to optimize the response flatness taking as many parameters into account as possible.
Hence the choices that were made.
 
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But don't some of the Grado cartridges like loading as low as 10k?

It seems both Grado and Audio Technica users sort of stand-out for wanting options for something other than 47k.
Ah, our posts "crossed".
Most of the MM cartridges that the unit has been used with are Audio technica, with 47k and the minimum cap value. I've not encountered anything other than 47k.
I'll have to investigate that.
 
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But don't some of the Grado cartridges like loading as low as 10k?

It seems both Grado and Audio Technica users sort of stand-out for wanting options for something other than 47k.
Grado's are probably the only MI's (or MM's) which would tolerate 10K loading, and only a few models. 20 or 30K options are more useful even with Grado's that supposedly work best with 10K (I tried). AT's are sometimes tipped up in response (regardless of proper capacitance or not), so they could be tamed down nicely at 30K, as well as Ortofon 2M series, since brighter MM's become fashionable to try to compete with MC's. But of course, so few care about tonal neutrality these days, it is maybe a moot point for most anyway.
 
(...) It seems like some kind of poll is required. (...)

Wouldn't be a bad idea, I'd think.

Greetings from Munich!

Manfred / lini

P.S.: Oh, forgot to add, that I'd suggest to also ask the poll participants for the reason(s) for their choices.
 
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OK. Given that there are, at most, 4 possible R values using a fixed R and two switchable, and if the Rs are more than a factor of approximately two different then for all intents and purposes there are actually only three values.
What would those three or four values be?
 
30 or 25K instead of 10K. I assume 1K and 47K have to stay.
If it was for me (or regular MM user), than 33, 47 and 100K like they used to provide in good old days (of discrete phono stages) on upscale equipment. But I know this is not realistic to expect today.
 
Just a comment, Wyn, but I'd deem the +12 kOhm/9.6k Ohm & +1kOhm / 900 Ohm loading options not all too useful for an MM-only variant. Might be smarter to start with ca. 100 kOhm and make the other two ca. +100 kOhm / ca. 50 kOhm and ca. +63 kOhm / ca. 38 kOhm (and +both / ca. 28 kOhm). That should please the fans of classic CD4 carts, fans of standard loading, fans of somewhat lower loading (e.g. for quite a few ATs) - and the ca. 28 kOhm might be ok for HOMC.

Greetings from Munich!

Manfred / lini


My Acutex carts that a I am very fond of perform best with he loads I put in my DIY Wyn Pre, I used 10k, 33k, 47k, 68k, 75k and 100k with the latter 3 sounding the best.

10k and 33k I use for Grado carts.

Athanasios
 
Wyn: I'd assume, there might be two, maybe three camps. One, that would like to see at least one rather low load for HOMC - and another, that would like to see a value above 47 kOhm, around the high 50 kOhm/low 60 kOhm range for brightening up somewhat dull-sounding MMs/MIs, then one around 47 kOhm to 50 kOhm for standard loading and one or two (e.g. around the mid to high 30 kOhm range or one around 40 kOhm and one around 32 kOhm) to tame bright-sounding MMs/MIs, forget about HOMC. Possible third camp as already mentioned above.

Greetings from Munich!

Manfred / lini
 
A lower R can always be added using a Y, so I guess that it could be reduced to say, 75k, 47k, 29k, 23k using 75k, 120k, 47k Rs.
or, 62k, 47k, 38k, 32k using 62k, 200k, 100k.
 
Oddly enough. The requests that I've had for MM/HOMI and HOMC are for 47k, c.10k and 1k. No-one has asked for anything higher than 47k, and I've had a couple of requests for around 1k for HOMC.
The choices are set by the three Rs (one fixed, two switchable) unless a cap choice is eliminated, and the cap choices seem to be OK.
It seems like some kind of poll is required.
Does anyone else have an opinion?
The evaluation unit is what it is as I'm not going to go in and replace the SM resistors, but the eventual choices are up for grabs.

I seem to remember discussions about the Shure M97xe loading was best at 62 kohm. Just a thought...
 
Now that there are possible choices for loading options I was going to attach a poll, but I no longer seem to be able to access the thread tools to do so.
 
Wyn: Maybe that only works for a fresh thread or within the time window for edits - or maybe it's due to the forum software update, that polls can't be attached to pre-update threads.

Greetings from Munich!

Manfred / lini
 
Wyn: Maybe that only works for a fresh thread or within the time window for edits - or maybe it's due to the forum software update, that polls can't be attached to pre-update threads.

Greetings from Munich!

Manfred / lini
Yes. I considered those possibilities.
Whatever the cause is, it seems that I will have to create a new thread specifically for the poll.
Prior to that, when I have some time on my hands, I'll post the set of options and request further suggestions.
 
Yes. I considered those possibilities.
Whatever the cause is, it seems that I will have to create a new thread specifically for the poll.
Prior to that, when I have some time on my hands, I'll post the set of options and request further suggestions.
Wyn did you look at the three dots with the down triangle next to the Unwatch ?

it looks like this on a thread I created and also watch

52975133713_f8bdfa9a2d_h.jpg




I can add a poll to a thread I started over a year ago.

Nashou
 
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