Ortofon ST-70 Moving Coil Transformer Review

[JP]

Measuring speed with the Parks Audio Waxwing Phono preamp shows absolute speed accuracy every time. It does this by measuring the 1 click per rotation on the runout track. With different weight clamps- 8 ounces to 32 ounces - it still measures exactly on speed. My belt drive table would measure different speeds every time I measured it, so I don’t think speed accuracy is going to be an issue on playback. Now, if the recording lathe had a speed issue, then that is “baked” into the album.

View attachment 463381

That's an averaged measurement.

The issue is similar to how minute clock variations corrupt a null when comparing, for example, two DACs where the DAC and ADC clocks aren't synced. Except much, much, much worse.

 

[Sokel]

I'm feeling that we're going far, FAR and away from the subject we were talking about, a proper FR that is.
The whole point of these measurements were NOT to show how close a TT and digital is.

The point was to show that a LOMC followed by SUT's can have decent edges low and high at FR.
We don't care about miniature +/-1dB, clock deviations, etc. Only for a decent FR taking into account all the limitations vinyl can present.
I would welcome any proper measurement showing this or otherwise for a decent set-up.

 

[Frank Dernie]

Just before shipping the box, I made a few quick multimeter measurements:

1. The input DC resistance is just 1.1 ohm. No wonder source impedance has such a large impact. You get a ton of voltage loss even when following their spec of "<10 ohm."

2. Output DC resistance is 740 ohm or thereabouts. This would then interact with the input impedance of the phono stage.

3. RCA shells are all connected together and to the case. There is no isolation here of any kind and the system is completely single-ended and not balanced. Indeed, I had to work hard to reduce the mains leakage in the dashboard measurement.

I don't see how anyone could get predictable response out of this box without measurements and ways to compensate for what is going to happen.

Is this device not matched to the typical Ortofon MC designs output impedance?
Certainly MC transformers have never been universal in the sense of suiting any MC design.

It is a very long time ago but I bought an Ortofon MC3000II and its matching T3000 transformer (dawn of CD era iirc) and used it with my MM phono input for years.
Later I got an Ortofon Jubilee MC but by then had a preamp with MC input and didn't get the transformer out again until I had my Devialet D-Premier updated and the later MC analog preamp was disappointingly noisier (and apparently much cheaper) than the older one.
I still have an old Goldmund analogue MC phono stage but decided to use the Devialet MM input since it does RIAA in the digital domain and has multiple switchable compensation curves (suitable for very old recordings) and resurrected the T3000 to solve the noise problem, so on the odd occasion I listen to an LP it is using an Ortofon A90 cartridge and Ortofon T3000 transformer.
I assume it matches OK it has the same load impedance requirement...
Sounds fine to me.

 

[Frank Dernie]

Products are sold with zero documentation for any of this. You are supposed to just stick this transformer after any cartridge+cabling combo, to any random phono stage.

Is this really the case or just now so many years later that the technology of record players has been forgotten.
I knew that any transformer needed matching to the cartridge it was going to be used with, and the loading requirement varied a lot between MC designs (unlike most MMs) 40 years ago and nowt has changed apart from the slow spread of ignorance as the technology recedes into the distant past.
IMO no dealer who sold MC transformers back in the day would have sold one as a "black box" and it was very well known by dealers and most knowledgeable enthusiasts.

 

[Davey]

Is this really the case or just now so many years later that the technology of record players has been forgotten.
I knew that any transformer needed matching to the cartridge it was going to be used with, and the loading requirement varied a lot between MC designs (unlike most MMs) 40 years ago and nowt has changed apart from the slow spread of ignorance as the technology recedes into the distant past.
IMO no dealer who sold MC transformers back in the day would have sold one as a "black box" and it was very well known by dealers and most knowledgeable enthusiasts.

Absolutely it was well known. And they were almost always sold as a set.
Ortofon MC cartridge with STM-72...or DL-103 with AU-320...or various other combinations.
Pre-preamps at that time were much less common to pair with moving-coil cartridges. Only now, in recent decades, are they considered the better solution.

 

[somebodyelse]

Is this really the case or just now so many years later that the technology of record players has been forgotten.
I knew that any transformer needed matching to the cartridge it was going to be used with, and the loading requirement varied a lot between MC designs (unlike most MMs) 40 years ago and nowt has changed apart from the slow spread of ignorance as the technology recedes into the distant past.
IMO no dealer who sold MC transformers back in the day would have sold one as a "black box" and it was very well known by dealers and most knowledgeable enthusiasts.

Given your background I suspect you may have been unusually knowledgeable, but maybe I'm misunderstanding the general level of pre-80s knowledge. By the late 80s / early 90s none of the dealers I went to were passing the knowledge on about MM loading - possibly because I was young and of low disposable income at the start of that period. Loading options for MM were something you only heard of looking for higher end phono stages or some DIY designs. I don't remember anyone asking about which arm I had when looking for a cartridge either - my father had some idea but not detailed understanding. I only found out as part of a degree option in audio systems engineering - the penny finally dropped with the LF mechanical resonance and the higher electrical resonance, dots I should have been able to join earlier if I had thought about it. This exemplifies the spread of ignorance back then. If you look at Ortofon's ST-70 user guide they provide little to educate the potential user about the importance of matching cartridge, transformer and MM stage load. Sowter had some detail for the 8055. Their current range has less detail, but there is a table of some recommended cartridge to transformer matchings. The information is easier to find now than then, but only if you already know you should be looking for it, and can tell the wheat from the chaff.

 

[Frank Dernie]

but maybe I'm misunderstanding the general level of pre-80s knowledge

Pre-80s the only high quaility media were microgroove records and FM radio and there were magazines written mainly by knowledgeable engineers and enthusiasts were well informed.
The subjective review and (IMO) absurdly non sequitur links between design details and what gurus hear came later, and if you only have been exposed to magazines and so forth since the 1980s there is a good chance you missed out entirely on the period where enthusiasts were technically well informed.

In terms of how record transduction systems work there were documents and test procedures I was using in the 1970s which were well known, understood and used which seem to have been totally forgotten. Modern manufacturerers are quite likely to be using the non-technically valid bollox which the LP side of the business is saturated in to design components, not just in marketing, so dyed in the wool is the mythology and how apparently forgotten is the physics..

 

[morillon]

Pre-80s the only high quaility media were microgroove records and FM radio and there were magazines written mainly by knowledgeable engineers and enthusiasts were well informed.
The subjective review and (IMO) absurdly non sequitur links between design details and what gurus hear came later, and if you only have been exposed to magazines and so forth since the 1980s there is a good chance you missed out entirely on the period where enthusiasts were technically well informed.

In terms of how record transduction systems work there were documents and test procedures I was using in the 1970s which were well known, understood and used which seem to have been totally forgotten. Modern manufacturerers are quite likely to be using the non-technically valid bollox which the LP side of the business is saturated in to design components, not just in marketing, so dyed in the wool is the mythology and how apparently forgotten is the physics..

We must essentially look at the procedures - literature from the 70s, early 80s... late 80s, abandonment etc. was already well advanced... the craze for CDs was rapid...
;-)

 

[Frank Dernie]

We must essentially look at the procedures - literature from the 70s, early 80s... late 80s, abandonment etc. was already well advanced... the craze for CDs was rapid...
;-)

IMO it was less the craze for CDs which was the problem but the arrival of reviewers who had no technical understanding or ability to test kit, but whose subjective opinions became "common knowledge" and they were gurus.
There is nothing wrong with subjective reviewing up to a point but backing it up with a technical analysis like Stereophile and HiFi News have done became rare.

 

[sergeauckland]

IMO it was less the craze for CDs which was the problem but the arrival of reviewers who had no technical understanding or ability to test kit, but whose subjective opinions became "common knowledge" and they were gurus.
There is nothing wrong with subjective reviewing up to a point but backing it up with a technical analysis like Stereophile and HiFi News have done became rare.

It was made worse by some reviewers actually claiming that measurements don't matter, that measurements don't tell the whole story, that only one's ears count. That, with absolutely zero controls, indeed blind tests are stressful and therefore don't work.

It brought about the cult of the Golden Eared reviewer that put back the science of audio many years. Not unlike what's happening now with totally unqualified 'Influencers' spouting opinions to thousands of 'followers'. I wonder how long it'll be before even 'Influencers' are replaced by AI spouting equally unqualified opinions.

S.

 

[Balle Clorin]

IA already recirculate the subjective nonsense taken from many audio forums.
If it is training on lies it will tell more lies..

 

[mike70]

If you ask rightly to the IA, you get better answers ... but ... the IA works like a placebo effect, answer in the most popular stream around your question.
And, in the audio world, the objective point of view is a minority.

 

[Bob from Florida]

IA already recirculate the subjective nonsense taken from many audio forums.
If it is training on lies it will tell more lies..

Garbage in - Garbage out.

 

[Marin]

This is a review and detailed measurements of the Ortofon ST-70 Moving Coil transformer. It is on kind loan from a member and costs around US $1,500.
View attachment 461589
Other than fancier footers, the box is ordinary as you see. It is heavy though for its size. Back side shows the simple connections:
View attachment 461591

There are apparently two version of this unit: A and B. I am not sure which one I have. Here are the specs:
View attachment 461592

I tested the unit more or less like a black box to characterize its transfer function. It is kind of difficult due to inability to match the impedances but let's see what we have.

Ortofon ST-70 Measurements
I fed the unit 0.5mv input and got this dashboard (default 20 ohm source impedance):
View attachment 461594

We get a (voltage) gain of nearly 30 dB which should be able to convert a moving magnet phono stage to one that supports moving coil (purpose of the device). At this low level of input, we are essentially noise bound other than mains noise which I could not minimize beyond what you see. There is a distortion spike that is barely visible.

Frequency response is highly dependent on source impedance. Given the choices I have in Audio Precision analyzer, this is what we get:
View attachment 461597
We are not remotely spec compliant. Even if one matched their spec exactly, how would you do that in real life?

As expected from any transformer, low frequencies is where you see distortion:

View attachment 461599
I used 1mv to slightly accentuate the effect.

Looking at pure distortion (no noise), we see that the impact is essentially the same as using electronic gain stage in our reference phono stage:
View attachment 461601

Crosstalk is very good in grand scheme of things:
View attachment 461603

I ran a test with RIAA inverse EQ active on the input and got this:
View attachment 461604

Conclusions
Without data from other products like it, it is hard to know how well the ST-70 is doing. The frequency response of note, is very poor if taken at face value. I am open to input from members on how to interpret that. Note that I am on a time crunch to send this unit back (will be boxed up today to go out tomorrow). So little time for more experimentation.

The cost is way up there. I would have thought something like this would cost a few hundred dollars.

------------
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Can someone explain me why would someone put this in a electric chain and why? Thanks for responding...

 

[sergeauckland]

Can someone explain me why would someone put this in a electric chain and why? Thanks for responding...

It's needed to raise the low voltage from a Moving Coil cartridge to the level needed for a Moving Magnet phono input. Typically, low output moving coil cartridges output one tenth (-20dB) of the level of a typical Moving Magnet.

As to why a transformer rather than a more sensitive input, that's partly Audiophile lore that a transformer sounds better than an electronic step-up, and partly if somebody already has a phono stage they like, then a transformer provided the necessary extra gain.

Mostly, however, it's the former, transformers have audiophile credibility, especially if expensive like this one.

S.

 

[Davey]

Mostly, however, it's the former, transformers have audiophile credibility, especially if expensive like this one.

"audiophile credibility"
That's viewed as a contradiction in terms now.
But, transport yourself back 50 years and "audiophile" meant something different than it does today.

A transformer was the go-to device back then, for this application.
Nowadays, this is more of a nostalgic product.

I built a little pre-preamp in HS electronics class in 1972. It was for my dad's system that had a DL-103 in an SME arm.
He's been gone for awhile now, but I still have that cartridge and the pre-preamp.
We can make fun of these things now....

All of that aside, the issue here is the mischaracterization of the performance of this particular gadget. Disappointing.

 

[Marin]

It's needed to raise the low voltage from a Moving Coil cartridge to the level needed for a Moving Magnet phono input. Typically, low output moving coil cartridges output one tenth (-20dB) of the level of a typical Moving Magnet.

As to why a transformer rather than a more sensitive input, that's partly Audiophile lore that a transformer sounds better than an electronic step-up, and partly if somebody already has a phono stage they like, then a transformer provided the necessary extra gain.

Mostly, however, it's the former, transformers have audiophile credibility, especially if expensive like this one.

S.

Moving coil of the driver(speaker)part,or am I completely wrong and it has to do with the gramophone and its connection?
I am skip that time,my low quality music almost always from FM station, don't know frequency range of the FM, but I do know that AM reach 4 500Hz. And that is about it , and magnetic tape and walkman cassette player
What a bad noise has make some of that million times rerecorded cassette in cheap on the shoulder boom box,my youth

 

[sergeauckland]

Moving coil of the driver(speaker)part,or am I completely wrong and it has to do with the gramophone and its connection?
I am skip that time,my low quality music almost always from FM station, don't know frequency range of the FM, but I do know that AM reach 4 500Hz. And that is about it , and magnetic tape and walkman cassette player
What a bad noise has make some of that million times rerecorded cassette in cheap on the shoulder boom box,my youth

It's for a moving coil pickup cartridge, not moving coil loudspeaker.
FM radio has a frequency range up to 15kHz, with a very sharp cut-off above that.
Cassette tapes can have up to a 20kHz bandwidth using something of the quality of a Nakamichi, properly aligned. Commercial pre-recorded cassettes didn't go as far, typically something like 15-16kHz.

S.

 

[Marin]

It's for a moving coil pickup cartridge, not moving coil loudspeaker.
FM radio has a frequency range up to 15kHz, with a very sharp cut-off above that.
Cassette tapes can have up to a 20kHz bandwidth using something of the quality of a Nakamichi, properly aligned. Commercial pre-recorded cassettes didn't go as far, typically something like 15-16kHz.

S.

Oooo that is good Freqvency range for FM and I always preferred stereo station then any other format until CD.

 

[Marin]

Good produced CD is just and game when it comes to music in Stereo format binaural preferred....