Ortofon ST-70 Moving Coil Transformer Review

[mike70]

Commercial pre-recorded cassettes didn't go as far, typically something like 15-16kHz.

Surely as your ears

 

[sceptical1]

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

An MC cartridge is a current source. Using a xformer to convert that to a voltage gives you a gain free of noise and distortion. Theoretically and practically what an objectivist audiophile wants. Being able to hear a difference between that and a head amplifier or if the residual noise of an LP exceeds what is possible using the best means of amplification is immaterial.

 

[Cbdb2]

Is this device not matched to the typical Ortofon MC designs output impedance?

Of the 3 different ortofon MC series I looked at, one recommended a load greater than 10 ohms, another 20 ohms, and the last 50 ohms, 5x smaller load than the first. So whats typical?

 

[Davey]

An MC cartridge is a current source. Using a xformer to convert that to a voltage gives you a gain free of noise and distortion. Theoretically and practically what an objectivist audiophile wants. Being able to hear a difference between that and a head amplifier or if the residual noise of an LP exceeds what is possible using the best means of amplification is immaterial.

I think there's some confusion on the difference between a current source and a voltage source.

 

[Newman]

I think there's some confusion on the difference between a current source and a voltage source.

The principle of electromagnetic induction is that a current is induced in a coil by the relative movement of a coil and a magnet.

[edit: although the above is pulled from an online electronics tutorial, see discussion below for contention in the light of Lenz's Law]

 

[Sokel]

Of the 3 different ortofon MC series I looked at, one recommended a load greater than 10 ohms, another 20 ohms, and the last 50 ohms, 5x smaller load than the first. So whats typical?

It's for the Cadenza series, I posted it earlier in the thread:

MC Cadenza Series

Ortofon is a micro-mechanical powerhouse, which develops, manufactures and markets the world acclaimed Ortofon phono cartridges.

ortofon.com

 

[morillon]

for reminder...
(some sut suggest it as a setting)
;-)

 

[Marin]

An MC cartridge is a current source. Using a xformer to convert that to a voltage gives you a gain free of noise and distortion. Theoretically and practically what an objectivist audiophile wants. Being able to hear a difference between that and a head amplifi er or if the residual noise of an LP exceeds what is possible using the best means of amplification is immaterial.

And now I finally realized that the part above is above the needle that converts vibrations into electricity

 

[Davey]

The principle of electromagnetic induction is that a current is induced in a coil by the relative movement of a coil and a magnet.

I suggest to do some further reading on the topic.

 

[Newman]

I suggest to do some further reading on the topic.

I agree. I was quoting an electronics training website. It could be that they were wrong. I am aware of Lenz's Law and it refers to EMF/voltage.

OTOH your post is as unhelpful as you could make it. Deliberately?

 

[sergeauckland]

The principle of electromagnetic induction is that a current is induced in a coil by the relative movement of a coil and a magnet.

Only if the coil is short-circuited! In a MC cartridge, the assumption is that the load is some 10x the cartridge's own impedance, and therefore the cartridge is acting as a voltage source. This voltage then needs amplifying to the input sensitivity of the amplifier, hence the transformer, or an alternative electronic step-up.

S.

 

[sceptical1]

And now I finally realized that the part above is above the needle that converts vibrations into electricity

MC=load dependent voltage source
SUT=impedance matching device
Am I getting closer?

MM is better than good enough anyway.

 

[Newman]

Only if the coil is short-circuited! In a MC cartridge, the assumption is that the load is some 10x the cartridge's own impedance, and therefore the cartridge is acting as a voltage source.

Would that not mean that the voltage is maintained across varying loads? And yet, when we change the load of an MC cart, even within its limits, its output varies.

This voltage then needs amplifying to the input sensitivity of the amplifier, hence the transformer, or an alternative electronic step-up.

S.

Agreed.

MC=load dependent voltage source

Is "load dependent voltage source" somewhat of an oxymoron?

"A voltage source is a two-terminal device which can maintain a fixed voltage." - Wikipedia

cheers

 

[sergeauckland]

MC=load dependent voltage source
SUT=impedance matching device
Am I getting closer?

MM is better than good enough anyway.

Yes, provided that the loading conditions are right for that particular MM. The frequency response at HF of a MM cartridge varies hugely with capacitance and resistance. The resistance is pretty standardised at 47k, but the capacitance can be all over the place.

At least a MC cartridge is pretty much immune to loading effects. However, that's assuming an electronic input. With a transformer, that too is subject to the loading on the secondary and to a lesser extent on the primary. So, whilst the cartridge may not have too many errors in frequency response, that's moved to the transformer!

S.

 

[sergeauckland]

Would that not mean that the voltage is maintained across varying loads? And yet, when we change the load of an MC cart, even within its limits, its output varies.

Yes, but not by much. If the load is some 10x the cartridge's own impedance, varying the load to an open circuit would increase the voltage by something around 1dB only. Halving the load impedance (so 5x the cartridge's impedance) would reduce the output around 1dB so not a lot.

A MM cartridge is designed to operate into a resistive load of 47k in parallel with some capacitance. This capacitance is made up of the input stage's own capacitance plus the phono cable and arm wiring capacitance. These are less likely to be known and optimised for the cartridge.

S

 

[Marin]

MC=load dependent voltage source
SUT=impedance matching device
Am I getting closer?

MM is better than good enough anyway.

Idemo tamo, ali što ja zapravo imam na AVR-U PHONO ulaz s uzemljenjem.Ili mi je ovo zapravo nepotrebno u lancu integralni Idemo tamo, ali što ja zapravo imam na AVR-U PHONO ulaz s uzemljenjem.Ili mi je ovo zapravo nepotrebno u lancu integralni

MC=load dependent voltage source
SUT=impedance matching device
Am I getting closer?

MM is better than good enough anyway.

Now we are going somewhere, but what I actually have on the AVR is a PHONO input with ground.
I need Gramophone

 

[sceptical1]

Would that not mean that the voltage is maintained across varying loads? And yet, when we change the load of an MC cart, even within its limits, its output varies.


Agreed.


Is "load dependent voltage source" somewhat of an oxymoron?

"A voltage source is a two-terminal device which can maintain a fixed voltage." - Wikipedia

cheers

That sounds correct. For D.C.

 

[Davey]

Would that not mean that the voltage is maintained across varying loads? And yet, when we change the load of an MC cart, even within its limits, its output varies.

An MC cartridge is not a voltage source. But as JP coined it correctly above..."it practically is"
With varying load its output 'level' varies.....but not the frequency response. (Within practical limits.)

 

[sceptical1]

mc step-up transformers explained

This made sense to me. Basically optimize for cartridge output voltage.

 

[sceptical1]

An MC cartridge is not a voltage source. But as JP coined it correctly above..."it practically is"
With varying load its output 'level' varies.....but not the frequency response. (Within practical limits.)

Within practical limits, the conditions stated by the manufacturer for correct operation, the output level and the FR will both not vary.