Ortofon ST-70 Moving Coil Transformer Review

[kyuu]

Laughs in electrotechno

Has no idea what that means

 

[Billy Budapest]

Anyone who is listening to vinyl for superior sound quality is doing it wrong, with the exception of superior mixing (lack of compression).

You mean superior mastering, not mixing.

It is true that the original vinyl releases oftentimes employed much less wide-band compression/limiting than modern reissues—many are victims of the dreaded “loudness wars.”

However, the overall fidelity of vinyl cannot come close to digital releases. Vinyl will always suffer from noise (surface noise and lower SNR) and distortion (inner groove distortion and otherwise), as well as inferior channel separation and dynamic range—all constraints of vinyl as a medium.

 

[Ropeburn]

Has no idea what that means

A lot of techno is highly compressed, and especially so on vinyl releases. It's supposed to be loud as fuck and shake the club.

 

[Billy Budapest]

Aren’t MC step up transformers supposed to be used in the signal chain right right before a phono preamp providing RIAA EQ and gain? Given this use case, I’m not sure if FR measurements of a step up transformer make sense, seeing as it is will be immediately EQ’ed by the downstream phono preamp.

 

[amirm]

Aren’t MC step up transformers supposed to be used in the signal chain right right before a phono preamp providing RIAA EQ and gain? Given this use case, I’m not sure if FR measurements of a step up transformer make sense, seeing as it is will be immediately EQ’ed by the downstream phono preamp.

That's the way I assumed it would be used. But no, the EQ in phono preamp can't fix any variations introduced by the transformer. It is blind to what is upstream of it. If the transformer changes things, that gets cooked in the response/output of the phono stage.

 

[PristineSound]

Anyone who is listening to vinyl for superior sound quality is doing it wrong, with the exception of superior mixing (lack of compression).

Right on. And with that, aside from know the value you get for this product, not even sure if this review is matter.

 

[JSmith]

It is on kind loan from a member and costs around US $1,500.

Thanks to the member and for your testing Amir, but geez... $1500 for this!?

Pics;

JSmith

 

[Billy Budapest]

That's the way I assumed it would be used. But no, the EQ in phono preamp can't fix any variations introduced by the transformer. It is blind to what is upstream of it. If the transformer changes things, that gets cooked in the response/output of the phono stage.

I get that it’s still cooked in the signal, but I thought that the frequency response discrepancies would be better/worse depending on the performance of the downstream EQ.

 

[Billy Budapest]

Thanks to the member and for your testing Amir, but geez... $1500 for this!?

Pics;

View attachment 461645

View attachment 461646


JSmith

It’s certainly not the sheet metal construction that’s responsible for the high price!

 

[sceptical1]

 

[Hayabusa]

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

Ortofon MC's have an output impedance below 10 ohm.
You could try to create a low Z source with a resistor divider (drive a higher signal in 1000+1 ohm for instance) and see if things go better.

 

[EERecordist]

You might reach out to Jensen Transformers (or other maker) technical support and see what they have to say about design and testing of transformers in this application. They are a long time manufacturer of audio transformers for professional applications. They were the important supplier of small signal input and output transformers when those designs were popular.

Right now their support page is lacking on this application.

Moving Coil | Jensen Transformers

Step-up Transformers Step-up transformers (SUT) match low-output moving-coil pickups to standard phono preamps. Jensen’s extended frequency response and time accuracy produces legendary sonic transparency while Faraday and double magnetic shields gives them immunity to hum and RF interference...

www.jensen-transformers.com

Cinemag (US) has products in this application. Carnhill and Sowter are similar UK transformer makers. From the documentation, the one you tested used Lundahl (Sweden) transformers.

 

[JSmith]

Lundahl (Sweden) transformers

Pro Audio - Lundahl Transformers

Pro Audio Our Pro Audio line is specifically crafted to deliver unparalleled performance in recording studios, live sound setups, broadcast environments, and beyond. Designed with meticulous attention to detail, our transformers offer pristine signal transmission, remarkable dynamic range, and...

www.lundahltransformers.com

JSmith

 

[amirm]

You might reach out to Jensen Transformers (or other maker) technical support and see what they have to say about design and testing of transformers in this application.

And you may want to look at my reviews of their transformers: https://www.audiosciencereview.com/...ax-ci-1rr-review-isolation-transformer.24104/. I know the company well and they wouldn't produce such a product, and certainly not without proper specifications.

Anything I have to do for testing it better also be in the manual. Such things as frequency response spec, if highly dependent on load, need to have that specified as well.

 

[Hayabusa]

Anything I have to do for testing it better also be in the manual

How to change version A or B is clearly in the manual I see online.
I would have spend a little more time finding out what is wrong when seeing so much deviation from spec.

 

[morillon]

It was set correctly in the 24db position and not <10ohm?

 

[Hayabusa]

Also what was the input impedance of the AP555 with this measurement, as 47k is the rated load?

 

[Hayabusa]

It was set correctly in the 24db position and not <10ohm?

I would have at least try to change the source impedance to find out the effect and if it explains the large deviation seen.
I am an engineer and curious to find out why.

 

[morillon]

(I don't think I've ever come across a transformer of this type without a bit of impact on the bass side, but Lundall is a very serious manufacturer and such measurements are probably due to a procedural issue.
phono tests require a lot of precautions regarding impedance level, egc...we recently saw here that the protocol without a dedicated adapted load produced irrelevant values in mm on ap...)

 

[Leporello]

How would you spin an LP in an iphone?!?

Oh, I am sure there is an app for that.