I can only speak a little to the theory. A step up transformer works on the same principle of voltage transformation used for AC power products. For instance, when you buy gear designed for US voltages but want to use it in Japan. Transformers can convert one voltage to another, but the power on either side of the transformer is roughly the same (minus losses).
That is, a 100V to 120V transformer will still have the same power (current x voltage) on either side,
That is also how I generally thing of them as well @erik_squires - but they are also a current converter to some extent… and the current coming in gets changed inversely proportional to the voltage change.
And… also they (SUTs) work on magnetic fields so they are a current device.
@drbond Maybe think of a 10:1 transformer as increasing the winding on the cartridge by 10x?
Just not making the cartridge’s motor 10x heavier.
I am still a bit uneasy as the cartridge is more of a current generating motor than a voltage generator.
Pretty sure one cannot be a fan of Sutherland, and other trans impedance phono stages… and simultaneously a fan SUTs. Maybe it is possible.
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@lewm your post gave me pause, and I reviewed Maxwell and Faraday… and I see that the voltage and current are indeed related in Maxwell’s equations.
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I’m not sure that I completely understand the matter, but it seems that there are two options in cartridge signal amplification in or before the phono stage: either 1. an SUT before the phono stage, or 2. a transistor in the phono stage.
either ~40dB of active gain and ~20dB of SUT, or more active gain to get to around 60dB… which is 50-70dB.
If that’s the case, then the sound quality would depend on how linear the electric signal is transmitted by either the SUT or the transistor.
That assumes that linear is good.
The active circuit might give more schott noise as hiss, and have lower distortion.
And the SUT may have higher distortion.
But that assumes that distortion is bad and unwanted.
Then, I suppose both approaches have certain weaknesses, but under near ideal circumstances, both would sound nearly identical.
yeah in the limit they would.
Are there any inherent weaknesses in a SUT versus a transistor, or vice versa?
One can do an opening roll of a 7 or 11 and win at the craps table.
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Now discussion of how signal is actually transmitted through a SUT would be quite interesting: does the signal actually move through the wound wire? As we know, the electrons in a wire don’t travel. . . do you think that the signal is rather transmitted via the core, and not the wires? What really happens to the signal? I don’t know if anyone really knows (but I’m not an electrical engineer), but I do know the limitations of human knowledge. Now, how much of the signal is purely electrical, and how much is magnetic, and can they even be separated? I suppose now it gets into a "religious" argument, where our minds may not be able to comprehend the exact way that everything works.
The coil(s) in the cartridge outputs a current based upon maxwells equation description of a magnetic field moving across a coil.
So it is an electric field that is pushing the electrons along in a back-n-forth AC fashion.
In the SUT, the current creates a magnetic field from the input winding of the coil, and the output winding creates a voltage and current to fight (or in response to) the magnetic field.
And yes… the electric field pushes those electrons along, which in an AC field result in no net significant movement on the average over time.
Now, how much of the signal is purely electrical, and how much is magnetic, and can they even be separated?
A cartridge, SUT and speaker driver, all have a significant magnetic field component to their design.
I suppose now it gets into a "religious" argument, where our minds may not be able to comprehend the exact way that everything works.
Maxwell’s equations are at the core of “the religion” of what is happening. EEs are generally the ones that comprehend this to provide the designs to manifest “the religion” into reality.
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rauliruegas
You quote another post above: “A phono cartridge is a voltage generator (Vs)”
To me, that sounds like a premise, and from my very limited knowledge base, it sounds like it could very well be a false premise, as phono cartridges generally produce very low voltages, which would imply that they are indeed better classified as current generators….
if that’s the case, then all conclusions based on that premise are also potentially false.
well done @drbond you are onto something important here.
Wiki says…
…or conversely, an external time-varying magnetic field through the interior of the coil generates an EMF (voltage) in the conductor.
However… the wiki for Maxwell’s equations says, (under Ampere/Faraday)…
The original law of Ampère states that magnetic fields relate to electric current. Maxwell's addition states that they also relate to changing electric fields, which Maxwell called displacement current. The integral form states that electric and displacement currents are associated with a proportional magnetic field along any enclosing curve
That link to displacement current says:
In electromagnetism, displacement current density is the quantity ∂D/∂t appearing in Maxwell's equations that is defined in terms of the rate of change of D, the electric displacement field. Displacement current density has the same units as electric current density, and it is a source of the magnetic field just as actual current is. However it is not an electric current of moving charges, but a time-varying electric field. In physical materials (as opposed to vacuum), there is also a contribution from the slight motion of charges bound in atoms, called dielectric polarization.
Hence I think that Raul could be correct.
While I was pretty sure that a cartridge is a current generating device, I am not so sure anymore.
The statement of, “a time varying electric field” also explains why a transformer voltage does not vary much with load.
A speaker and a cartridge are not too dissimilar.
If we consider a speaker, and yell into it, then the movement of the cone, generates a movement of the voice coil, and a change of how it sits in the magnetic flux of the motor. And if we are hoarse we can push it with a finger tip.
- if it was generating a voltage:
- then when the speaker terminals are open, there is no load against the voltage, and whether we push on the cone with a finger or thumb, it should move freely.
- And if we put a 2 ohm resistor across the speaker terminals then that voltage will need a lot more current as it moves, and the speaker should feel stiffer to the finger tip.
- if it is a current generating device then:
- The movement will generate a fixed current and in a shorted speaker it should easily pass the fixed current and the cone should feel limber
- and with an open set of speaker terminals, then the cone will be trying to drive current into an infinite load and require the voltage to rise towards infinity and the speaker cone should feel stiff.
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Dear @holmz : I was in a hurry when my post to op but I gone thinking that's the whole context what is behind what Palmer posted. He participated in that technical loading thread that after some posts took other road.
I can't remember but I think that in other threads you and he had a very interesting technically posts.
R
Thanks Sir.
Which Palmer, or what is their moniker?
@atmasphere also posted in that thread a bit.
Those threads may also help @drbond
Was it in here
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Here’s my current assessment, which has been nicely summarized by @intactaudio : basically, the cartridge is naturally developed as a current generator,
I was pretty convinced of ^that^ myself, but I still have some lingering confusion.
however for the past decades, phono stages were created to unnaturally transform the cartridge into a voltage generator by adding the load in the phono stage.
Unnatural is a bit subjective. If one shoves the current across a resistor then they can measure the voltage across the load like ohms law states. Ohms law seems like it is “natural”.
However, when the cartridge operates as a current generator, no external arbitrary loading needs to be added to the signal created by the cartridge. So, it seems, based on my limited knowledge, that the current based phono stages would be most naturally associated with phono cartridges.
Many people use the Sutherland, and other trans -impedance phono stages, and love them. Usually with carts that have a very low output impedance.
And they do have an allure.
And many phono stages use a voltage based design, and/or SUTs and love them.
I was leaning heavily towards the Sutherland, but got a phono stage with SUTs built in, mostly because I liked the look of it, and it had two inputs.
if we look at a step up transformer, with an input to output ratio of 1:2, then we see that the voltage is doubles, and the current is halved.
If it is 1:20 then the voltage is x20 and the current 1/20.
A cart does not look too dissimilar as the input winding is serviced by the magnetic field of the magnet. The magnetic flux varies with the cantilever movement.
The output winding is the coil.
- When there is a lot of windings, like on a MM, we get more voltage and less current. (Probably better for a voltage based amplification.)
- When there are fewer windings we get less voltage and more current. (Maybe it is better for a current based amplification?)
- Then there is a middle ground with a bit higher output voltage or with a higher output impedance were it seem like it is unclear and all bets are off.
^This^ is not much of an answer, other than the choice of phono stage sort of relies on a cartridge in front of it.
And in this case we sort of need to “put the cart before the horse”.
Or…
We already have the selected phono stage, and we damned well better select a cart that will work with it.
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… , L+R Channel Gain,…
@pindac is a gain imbalance common in cartridges?
(I have a cart with some channel imbalance, hence the question.)
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@drbond
Basically a voltage amplifier will deliver voltage gain with whatever current is required to do the job.
Hence in a power amp, sometimes there is not enough current to maintain the voltage at the speaker
If there is not much voltage, but a bit of current then a current amplifier can be a good solution.
A current amplifier can later push that current across a resistor to compare the voltage… and drive a voltage amplifier in an output stage or RIAA circuit.
I think I mentioned earlier that this is using “the natural” ohms law.
and, in fact, the cartridge itself can push try and push the current across a resistor and use compare the voltage with a voltage amplifier.
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Well done @pindac A trebuchet both looks, and acts, a lot like a tone arm.
(Or at least a tone that is not a great match to a cart.)
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I think this video from Veritasium does a rather informative job of explaining how current actually travels:
I believe it is the field that “flows” around the conductor.
no it doesn’t travel in the wires but in the surrounding electromagnetic fields, and electrons don’t "flow" in the wires, either in AC or DC,
The electrons actually do flow, just not very fast.
And without the wire there, the field doesn’t really propagate the same way.
It will not :know” where to go, and in a 100km long wire or a SUT, how will it know to have a 1:10 ratio, etc.
and in a wire with no resistance, the current flow is instantaneous, whether 0.001 m long or 100,000 m long.
They are not instantaneous, as the electric field propagates as the speed of light/dielectric constant.
The electric field essentially pushes, or sweeps, the electrons along.
The electric field can be super high, but with no current there is little or no magnetic field. And the voltage (electric field) can be super low, but have a massive current… and then we get little electric field and a huge magnetic field.
in the devices we are considering the impedance is not zero like in a super conductor, nor it is it infinite… it is pretty constant. So there is a fixed proportionality between the voltage and current… and hence a fixed proportionality between the electric and magnetic fields.
I suppose the magnetic properties of the silver and copper account for the difference in sound, and while I really don’t know all the details, I don’t know that the method by which a signal is transmitted in a transistor is any better than a transformer
There are all sorts of hypothesis as to why the metal choice might impart a different sound, but most are a bit light and fact and oversubscribed in magic.
It is possible that the dielectric is as important as the metal.
In a transformer, similarly it is possible that the core material is as important as the choice of wire used for the windings.
In a “Field Effect Transistor” (FET) it is the electric field that controls the gate.
In a Bipolar Junction Transistor, the current flow controls the junction.
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Thanks for sharing those details. I don’t know the details of how a FET works, but I’m sure it has its deficiencies, as does the SUT.
A FET works more like a valve/tube.
If you like transimpedance (current based) amps, they are more than likely a BJT.
When that the SUT amplifies/increase voltage.
Deficiencies:
It is more design approach than a deficiency. The FET or the BJT may have more noise compared to one another, or across the different examples of the same devices.
The SUT has resistance, inductance and some capacitance. And hence a finite bandwidth. But many transistors have capacitance effects that limit their bandwidth.
And how high can one really hear?
If in doubt on the SUT, it may be better to slightly undershoot ratio, than to wildly overshoot the ratio… and especially if the cart has a high output impedance.
I think that 0.00003 seconds (1/c) is essentially instantaneous to the human mind and ear….just ask the digital guys about sampling, etc. . .
Correct one cannot tell the difference in speed by ear, but that point was in relation to your statement on copper versus silver wires. The dielectric also plays a role.
In the SUT the core also play a bit of a similar role to the magnetic field, that the dielectric played upon the electric field..
It is not altogether clear, that one can easily tease out all the nuance.
And if we get a good wild eyed sales person going full on passionate, then they can appear to be conjuring a pretty compelling story.
Back to deficiencies… we have three camps:
- Pure electronics voltage gain
- SUT + voltage gain
- Current gain
The circuit designers all make good examples in each, so pick your poison.
If you have a CH phono stage, your problems are different than someone with out an existing phono stage.
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…I don’t get too bogged down in such a presentation…
I like to get bogged down.
What does an electrical square wave look like on an LP in the groove?
I am assuming it looks like a triangular wave track that they stylus is following?
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phoenixengr
Flattest frequency response or best square wave ? Are these codependent ?
With Jensen SUT's that are designed to be used with a zobel network they suggest adjusting the network to the source load by scoping a square wave
@dover ^thanks!^
I suppose I should ask where does one get the square wave track from?
Does Jenson say to do this after the phono stage, or directly after the SUT?
Or is there a link?
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I am trying to figure out:
- whether they generated a square wave with the same output impedance as the cart and fed the SUT with that.
- Or if they had a test LP with a square wave
- and then if it is a test LP is that square wave a triangular shape on the track to make an electrical square wave.
?
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Dear @holmz : What Dover posted. You can read the link rigth from the Ortofon cartridge/SUT specs and then the measured square wave.
R.
it would have been handy to have a physical triangular wave - cut into the track… and then everyone would be able to generate the square wave without needing a signal generator,
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holmz
the CBS STR-112 has a 1kHz square wave for the test you propose but be warned the results of this test from a cartridge is not for the feint of heart. And yes as you suspect due to the riaa filter the actual cut of the track appears as a triangle wave.
dave
Thanks Dave - I ordered one.
It might not be a triangle shape from the RIAA. But it will be good to try it.
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Dear @holmz : Things are that's really weird that the rise time in a MM cartridge been faster than in a MC cartridge because it must be the other way around and maybe was the SUT who could had the culprit, at least everything point at the sut.
R
If you had an ishikawa chart of causal mechanisms, then it is possible that the inductance of a SUT could be on the list of things that limit the bandwidth.
Whether 500kHz or whatever the rise time corresponds to… is better or not, is uncertain.
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With out facts my common sense tells me that a LOMC through an active bipolar hifgh gain design is way fast than the same LOMC cartridge + the additional IC cables and the SUT it self where both signal must pass through. So transient response that defines the notes/harmonics is slower through a SUT and this sole characteristic is an additonal and crucial disadvantage for a SUT.
I am not a bat, nor hear like one.
I suppose that we can argue whether it is 20kHz, or higher bandwidth.
If the SUT was limiting the RF bandwidth, then it would also take care of the ringing at the high RF frequency that people talk about loading a SUT to stop.
How fast of a rise time do we need?
I would guess that the lower winding ratios would also have a higher bandwidth, or is that inductance also dependent upon the transformer core ?
I forgot that rise time is from steady to the time to achieve 10% to 90% of the step response.
If it is 50% duty cycle then it is “on”, in the half period, at the equivalent of a 2kHz rate.
10% of that would be 20kHz…
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Differences between the MM/MC other the kind of motor design was that the LOMC cartridge was paired with an additional SUT and this is by common sense why the MM is faster in that transient rise time when obviously must be the other way around. SUT/cables is the culprit. Maybe not?
It is a system that most people have.
So looking these things in isolation is best, but it may be difficult.
We are pretty much looking at the transient response like slew rate.
At some point the thing is trying to make sounds >20kHz if the response time is going to zero.
In any case I ordered the test LP.
And I have an ADC, so I can capture the results digitally.
I’d rather not guess at what is happening.
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Anyway, thank's for the links, very informative. We are waiting for the Holmz measures about
@rauliruegas Things are moving slowly, and i am not providing evidence.
I am just trying to get the loading right by using a graph,
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holmz : No problem, my mistake.
R
@rauliruegas
When I left the TT a few weeks back, it was looking like this:
So it is on the table of the operating theatre and a new bearing is en route.
I was not able to find an anodiser to anodise the arm board, so I’ll put in, in the shiny raw alloy state.
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…
Somewhere behind all the above that coming together in one permutation or another is Math. It is quite difficult to see where the individual place much care on the Math that is not the commonly used criteria for matching a Device to another Device.
The Topic of Math most recently under discussion and now dominating as a Spoiler, is as far to the extremities and circumscribed in content, as can be imagined, when comparing the content to the OP's original request for information.
Respectfully I’ll offer an alternative…
The section with the URL link on “the gain of SUTs” had some compelling maths that to help to show how some SUTs may be a better match for some carts.
I would say that that “linked info” falls squarely within the second paragraph of the OP’s ( @drbond ) question.
Para2:
…
Assuming an appropriately / ideally matched SUT and MC, What are the inherent advantages or disadvantages of inserting a SUT after the MC in the audio chain? Does the SUT theoretically enhance or degrade the sound quality? What does the SUT actually do to the sound quality?
Even the OP’s first paragraph mentioned wanting to understand the theory behind a SUT. So the beauty of Maxwell’s equations sort of is a real manifestation of scientific understanding becoming an engineered product.
While many an end user may not want to understand it, and would rather have a recommendation of one particular SUT and similarly one specific cart… it is none the less a true thing of beauty how both the cart and SUT work.
There is more science and math in it than magic .
But the OP can (and should) certainly drive the conversation in a way that helps them.
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I’ll “step up” 😀 and wish you “happy holidays” as well.
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n your most recent post, the last paragraph, is the area where this thread has caused a concern for myself, and the one that is the encouragement that has prompted me to avoid the evolving discussion.
This attitude to avoid, is due to the fact the countering from differing parties to the developing discussion evolving, is already convincing enough to suggest the Thread is now on a route of Conjecture/Theory and the outcome will be as far from a Theorem as can possibly be. There is nothing seen to substantiate the avenue of investigation as having a end result that can be relied upon.
@pindac I am only trying to find a way to load the cart for my 1:4 SUT.
So that CBS square wave record may be helpful..or maybe not… I’ll find out.
But I do admit that I like to know what, say, a SUT is doing… like on a plot…
If it helps me to get it loaded right, then all is good. And if not then I will also know that.
In any case, I wish everyone on the thread from @drbond OP right through to your last post, a happy holiday season.
Felix Navidad
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Am I the only one shaking my head?
No @antigrunge you are not.
Holmz, Make no mistake, Dave (Intact Audio) knows more about this subject by far than I ever will. So if my advice to check out the Jensen website seems counter to or only partially correct in view of Dave’s insight, go with what Dave says.
I am open to understanding, so anything many say is received including @intactaudio comments.
But I’ll need to check the diagram to see if that built-in 1:4 SUT is loaded on the primary or secondary side.
I don't believe I have expressed any negativity (or keeping it Seasonal 'Nativity' towards your endeavour 🎅🤶).
@pindac I may have seasonal naïveté 😀
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