SUT - electrical theory and practical experience

@rauliruegas 

Your latter post about preferring an integrated "phonolinestage" over separate phono and pre-amplifier would also logically favor an integrated pre-amplifier / amplifier over separate components, so I'm not so sure that your ideal preference holds true to real life experience. 

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.

@holmz 

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.

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. . . 
 

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:

1. Pure electronics voltage gain
2. SUT + voltage gain
3. 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.

Hi @pindac ,

I’m agree that EAR834p has rich and bloat the lowest frequencies character. This character of the schematic remained despite improving bass resolution and dynamics, and more clean and open height frequencies in the better implemented version. Another factor are speakers. My Altec 604E speakers have dry bass. So it works good all together at least for my taste and for classical and jazz music that I like to listen.
But I can’t agree that all SUTs have the similar sound characteristics. I heard SUT in my system that have thin sound. And in my experience, the difference between different SUTs is huge.

Regards,

Alex

I don’t know that the method by which a signal is transmitted in a transistor is any better than a transformer

A FET works more like a valve/tube.
If you like transimpedance (current based) amps, they are more than likely a BJT.

The problem you are up against using either device above is that the input side of the device is outside of the feedback loop. You will have a rather prodigious electrical peak, likely between 1-5MHz with most LOMC cartridges. It might be as much as 30dB depending on the Q value (how long as opposed to how wide) of the coil in the cartridge. That peak can be energized and easily overload the input despite the use of feedback.

So an SUT has the advantage of not being overloaded in this way and actually blocks the RFI generated in this fashion from reaching the phono stage input! That's a pretty clear advantage!

(The overload can cause ticks and pops as well as distortion which is perceived as brightness- hence the use of 'cartridge loading' resistors, which detune the electrical resonance, preventing it from going into excitation.)

If you're going to run solid state, you need to use an opamp to get around this problem, or set up the feedback look on the discrete devices in the same manner as used in with an opamp; essentially creating a low performance opamp in the process...

 

Hi @atmasphere ,

I have a question for you regarding the use of feedback in tube phonostage. Unlike a power amplifier, the frequency response of the RIAA implies a deeper feedback at high frequencies. Is this kind of feedback deep enough to work properly?

Regards,

Alex

Unlike a power amplifier, the frequency response of the RIAA implies a deeper feedback at high frequencies. Is this kind of feedback deep enough to work properly?

@alexberger 

If in a discrete solid state circuit, maybe?? -a lot will depend on the semiconductors involved!! It can work OK with tubes, but if you really want to get it right, you run the amplification flat and use passive EQ. That way you can apply the feedback needed to do the job right.

Dear @drbond  : " would also logically favor an integrated pre-amplifier / amplifier over separate components, "

 

Not really, I am in favor that the amplifier stays as nearer the speaker as we can and that's why I use monoblocks with really short output cables that are soldered directly to the speakers external modified crossovers  where each speaker driver frequency range has its dedicated crossover/cable that goes soldered directly to each driver.

 

No, what I'm in favor is for a Phonolinepreamp unit but separates amps.

 

R.

One user recommended a particular search, and it supplied the following website, which I found very informative.  Here is a copy from the first two paragraphs from a transformer manufacturer, Rothwell Audio Products:

“the cartridge operating principle
Moving magnet cartridges, as their name implies, contain magnets which are moved by the stylus’ cantilever, and the movement induces the signal voltage in fixed coils in close proximity to the magnets. In moving coil cartridges the roles are reversed, so now the magnets are fixed and the coils move. The big advantage of moving coils is that the coils are much lighter than the magnets, so they are much more responsive to the motion of the stylus.
The big disadvantage is that the output voltage of moving coil cartridges is about 20dB lower than that of moving magnets, so an extra 20dB of gain is required. The extra gain can be provided by the phonostage amplifier, by an external device called a headamp, or by a transformer. The most commonly found solution is to increase the gain in the phonostage, but step-up transformers are still the best solution where cost is no object.

why use a transformer at all?
It used to be the case that a good signal-to-noise ratio was impossible to achieve from a moving coil cartridge without a step-up transformer. An extra 20 or 30 decibels of gain wasn’t a problem, but doing so with low noise using valves, transistors or op-amps was a problem. Modern transistors and op-amps can now offer much better signal-to-noise ratios but valves still usually need transformers to work successfully with low output moving coil cartridges. An alternative to the step-up transformer is the headamp (or pre-preamp). This is a transistor or op-amp amplifier which raises the output of moving coil cartridges up to moving magnet level. Rothwell offer the Headspace as a high quality, low noise headamp.
Apart from the issue of noise, the sound quality of transformers is something their advocates swear by. The distortion produced by audio transformers is of a completely different nature to that produced by a transistor amplifier. The harmonic distortion in transformers is greatest at the lowest frequencies and falls rapidly as the frequency rises, whereas in transistor amplifiers distortion more usually rises as the frequency rises. More importantly, intermodulation distortion tends to be lower in transformers than it is transistor amplifiers. The outcome is that although transformers aren't absolutely free of distortion (nothing is), the distortion is very benign compared to the distortion produced by many transistor amplifiers. This explains why the sound produced when a moving coil cartridge is used with a good transformer is so sublime and can create an open and spacious soundstage with amazing separation between instruments.
The case against transformers is simply one of cost. Transistors can be as cheap as a few pennies (or less when bought in sufficient quantities) whereas transformers always cost a lot more, by as much as a factor of several thousand, due to the expensive materials used in the core and the cost of the copper windings in terms of both material and labour.”

Rothwell Audio is a Trusted Service.

Their layman's technical descriptions on offer are very well worded and comprehensible. They are a reference point for all levels of knowledge in electronics relating to HiFi, and for some the first knowledge gathered when curiosity about the technical side of a particular device is being sought to be understood further.  

@pindac 

Yes, Rothwell Audio website seemingly very clearly and concisely explains even the basics of audio, as evinced by the next paragraph on impedance loading of cartridges, which can be applied to any component matching:

”cartridge loading
Before considering how to match a moving coil cartridge with a transformer, it is worthwhile considering the effects of different loads on moving coil cartridges.
When any signal source is connected to any load impedance a potential divider is formed by the source's output impedance and the load impedance. (The output impedance is also know as the source impedance or internal impedance. The load impedance is also known as the input impedance.) The signal source could be a phono cartridge, microphone, CD player, mixer etc., it doesn't matter. The load could be a phonostage, mixer, transformer, or simply a resistor – again, it doesn't matter. The potential divider formed by the source and load impedances acts as an attenuator or a pre-set volume control. If the load impedance is very much bigger than the source impedance the attenuation is low and the effective pre-set volume control is near maximum. The usual rule for audio equipment in general is to feed the signal into a load at least ten times greater than the source impedance to avoid any significant signal loss, and this is applies to moving coil cartridges as much as to anything else. If the load impedance is 10 times greater than the source impedance the signal lost by the “pre-set volume control” is less than 1dB, ie nearly all the signal generated by the source is available to the following amplifier. Any loss of signal at the source/load interface is usually considered a bad thing as it compromises the signal-to-noise ratio. More signal is lost, ie the pre-set volume control is turned down more, if the load impedance isn't significantly higher than the source impedance. When the source and load impedances are equal the signal loss is 6dB. When the source impedance is 9 times greater than the load impedance the signal loss is 20dB. Most modern moving coil cartridges have a source impedance of about 10 ohms and the “load impedance ten times the source impedance” rule suggests 100 ohms is a good choice for load impedance and causes less than 1dB of signal loss. This is well in line with the recommendations from many cartridge manufacturers (see the table of data below). Anything above 100 ohms should be equally suitable.
Does the cartridge's tonal balance change with load impedance? It certainly does if the cartridge is a moving magnet type, but low output moving coil cartridges are much less sensitive to changes in the load impedance. Users sometimes claim that higher load impedances produce a brighter sound than lower ones, but cartridge manufacturers tend be non-specific about recommended load impedances, often recommending a wide range or simply anything above a minimum impedance.
The recommendation of Rothwell Audio Products is in line with Ortofon, Audio Technica and most other cartridge manufacturers - that 100 ohms is a good value for most cartridges, and that the exact value is not critical as long as it is well above the cartridge's source impedance.
One thing is certain, and that is that the load impedance should not be equal to the cartridge's source impedance. That would produce a 6dB loss of signal (when there's often only a few hundred microvolts to start with) and seriously compromise the signal-to-noise ratio. The idea that having the load impedance equal to the source impedance achieves perfect "matching" is wrong and is the most commonly held myth about moving coil cartridges. It also gives rise to most of the confusion surrounding step-up transformers and how to select the correct one for any given cartridge. The reasons for the “matched impedance” myth are examined below.}”

….but, Rothwell Audio Products explanations also go into further detail in the next section, which would definitely imply caution against SUT use in a current based phono stage, due to geometrically increasing impedance:

”the transformer turns ratio and impedance ratio
The turns ratio of a transformer is the ratio of the number of turns of wire on the primary winding to the number of turns of wire on the secondary winding, and the voltage on the primary is stepped up (or down) by the same ratio as the turns ratio and appears on the secondary. A transformer with a 1:10 turns ratio for example will step up a voltage at its primary by a factor of ten. However, since transformers are totally passive devices with no power supply to draw energy from, no extra power can be produced by a transformer and an increase in voltage will be accompanied by a corresponding decrease in current. This is what gives rise to the concept of the impedance ratio. The impedance ratio is the square of the turns ratio and makes an impedance on the secondary winding of a transformer appear to a source feeding the primary as that impedance transformed by the square of the turns ratio. The transformer itself doesn’t have an impedance, rather an impedance on one side of it will look like a different impedance from the other side (it works in both directions). In the case of, for example, a 1:10 step-up transformer, a 20k impedance on the secondary winding will appear to be a 200 ohm impedance on the primary winding (20,000 divided by 10 squared equals 200). A 1:2 step-up transformer with a 100k load on the secondary would appear to have an input impedance to a source driving the primary as 25k (100k divided by 2 squared equals 25k).

So, it would seem logical that a cartridge with an output voltage of, for example, 0.5mV, when used with a step-up transformer with a 1:10 turns ratio, would produce 5mV at the transformer’s output. Yes, it would if the cartridge’s source impedance (also known as its internal impedance or its coil impedance) was zero. In practice, with low impedance cartridges of about 10 ohms or less and low ratio transformers (less than about 1:20), the transformer’s output voltage is very close to the cartridge’s output voltage multiplied by the turns ratio and can be safely used as a good first order approximation for guidance. However, the cartridge’s source impedance may be low but it is never zero, and the transformed secondary load needs to be considered for a more accurate analysis. Consider as an example a transformer with a 1:10 ratio and a cartridge with a 10 ohm coil. If the load on the transformer secondary is an MM phonostage with a 47k impedance, that load appears to the cartridge as 470 ohms (47,000 divided by 10 squared) and must be driven by the 10 ohm coil. The 470 ohm load and the 10 ohm source form a potential divider (the “pre-set volume control” described in the previous section) with some of the cartridge’s voltage dropped across its own internal 10 ohm impedance. The proportion dropped internally is 10/(470+10) = 0.0208, which is not very much at all – just 0.2dB. The deviation from the first order approximation is small and probably not worth worrying about, but it is there. It’s when higher turns ratios are used with higher source impedances that the potential divider effect becomes significant. Consider a cartridge with a 40 ohm coil and a transformer with a 1:30 ratio. The 47k load on the secondary now appears as 52 ohms from the primary side. When driven by a 40 ohm source the voltage divider is formed by 52 ohms and 40 ohms. Therefore the proportion of signal dropped across the cartridge’s coil is 40/(40+52) = 0.43, which is very significant – nearly half the voltage produced by the cartridge is lost internally. Whereas only 0.2dB was lost in the previous example, here the signal loss is 5dB, and instead of achieving a signal voltage at the output of the transformer of 30 times the cartridge’s output, the output is only 0.43x30 times the cartridge’s output, ie a voltage step-up of effectively just 13 times, not 30 times. Clearly, increasing the transformer turns ratio by a factor of X doesn’t increase the output voltage by the same factor. As the turns ratio increases, the increase in the output voltage gets less and less as the load on the cartridge becomes more and more significant until a point is reached where increasing the turns ratio further actually causes the output voltage to drop.
The point at which the maximum possible voltage at the transformer’s output is achieved occurs when the transformed load is equal to the source impedance. In the case of a 47k secondary load (the usual load impedance of an MM phonostage) and a 40 ohm MC cartridge, the turns ratio would have to be 1:34.28 to get the absolute maximum output voltage. This is because 40x34.28x34.28 = 47000
It’s this that gives rise to the misguided notion that the transformer must “match” the cartridge impedance. Yes, it may be true that matching the impedances gives the maximum possible voltage at the transformer’s output, but in a hi-fi system we’re not looking for the absolute maximum voltage from the transformer, we’re looking for a voltage suitable to be fed into the following MM phonostage and we’re looking for maximum fidelity. This rarely (if ever) achieved by matching the impedances. The signal voltage suitable for an mm phonostage to handle is about 5mV. A higher voltage into the phonostage will reduce headroom and increase distortion. A lower voltage will compromise the signal-to-noise ratio. Trying to achieve 5mV into the phonostage (with maximum fidelity) should be the aim of a step-up transformer.
The big mistake most often made when selecting a transformer for a moving coil cartridge is to overlook the voltage required at the phonostage’s input and instead try to make the impedances match so that, for example, a cartridge with a 5 ohm source impedance sees a 5 ohm load at the transformer’s input. This approach takes the cartridge’s impedance as the most important factor when in reality it should be the cartridge’s output voltage.

To demonstrate how far wrong the “matched impedance” approach can be, take as an example an Ortofon Vivo Red cartridge with a 5 ohm source impedance. In order to "match the impedance”, the 47,000 ohms on the secondary side of the transformer would have to appear as 5 ohms on the primary side. That means that the impedance ratio must be 9400 (because 47,000 divided by 5 equals 9400) and therefore the turns ratio must be the square root of 9400, which is 97. So we must find a step-up transformer with a turns ratio of 1:97. However, the Vivo Red’s output voltage is 0.5mV and the voltage fed to the phonostage by a 1:97 transformer would 24mV. That would be enough to overload most phonostages and would be a long way from optimal. A much better approach to finding a suitable transformer ratio would be to work with the cartridge’s output voltage. The Vivo Red has an output of 0.5mV and the phonostage requires about 5mV for the best performance, therefore a ratio of 1:10 would appear to be much better. The first order approximation suggests a 1:10 ratio would give us 5mV. Does that still hold true if we also consider the cartridge’s 5 ohm source impedance and the load impedance presented by the transformer? Yes. A 1:10 transformer with a 47k load on its secondary winding presents a load of 470 ohms to the cartridge. The voltage divider formed by the 5 ohm source impedance and the 470 ohm reflected load means that only 5/(470+5) is dropped across the cartridge’s internal impedance and the actual voltage at the transformer’s output is 4.95mV, ie extremely close to the estimate using the approximate method. The 470 ohm load seen by the cartridge is perfectly compatible with Ortofon’s recommended load of >10 ohms. The “impedance matching” method of using a 1:97 ratio transformer would give the cartridge a 5 ohm load impedance, which is outside the manufacturer’s recommendation. Also, for the reasons explained below, a 1:97 transformer would have a seriously compromised performance compared to a 1:10 transformer.

Now consider a different cartridge, the Dynavector Karat17D3 with a 38 ohm coil. Using the impedance matching approach to find the best transformer ratio we end up with a ratio of 1:35 and the cartridge’s 0.3mV output becomes 5.25mV at the the transformer’s output. This time, the “impedance matching” approach appears to have worked out well, but is is really the best turns ratio? Maybe not, because Dynavector’s recommended load is 100 ohms and a 1:35 transformer would give the cartridge a 38 ohm load. In this instance a lower turns ratio would be better. For example, a 1:20 transformer would give the cartridge a load of 117.5 ohms and have an output of 4.5mV. Also, a 1:20 transformer is likely to have better performance than a 1:35 transformer, as explained below.”

Keep in mind, Rothwell are selling transformers.

Dear @drbond  : Can you share which is your target with all those internet links you posted?

Btw, every one but you knew the Rothwell information because it was posted several times in several other threads over many years now.

Do you think that are discovering the " black thread " ?  Please, wake up.

 

R.

@drbond Making the Rothwell info' available in the extended version as presented is quite fitting. This thread is certainly a place worthy of their descriptions being found.

As providers of a Design for a Step-Up Transformers along with their Head Amp Design, they do provide very useful information for any level of understanding to consider. I am sure the presentation from them wins favour with customers.

As seen in various posts, not all are using Step-Ups from the same Brands, and Step Ups are to found ranging from £$200ish through to £$3000ish and maybe upward if the Ikeda and MSL models are of interest.

The next SUT's of interest for me fall into the £500+ area depending on Spec and Coil Wire, I don't see over the £1K being of interest, but a bespoke built from the Brand will comfortably surpass this. 

It does look to be a very competitive market to maintain the greater slice of the Pie Chart.

People try to lump all kinds of technical truths into simple rules of thumb which then become the norm. After being accepted, the underlying truths these norms are built upon tend to get lost.  The three main things that need to be considered when designing / implementing a SUT are Impedance (source and load), gain and loading.  While all three of these items are interrelated by math, they all need to be addressed (juggled) individually.

The source / load impedances are what determine the required primary inductance and the winding geometry required to get the desired bandwidth.  What needs to be done for a 2Ω cartridge is different than what is needed for a 40Ω cartridge.

The turns ratio is set to elevate the cartridge output to the desired input of the phono stage it is driving.  A 0.25mV output 40Ω Denon 103 roughly fits the same impedance numbers as a 24Ω 1.0mV EMT but requires a different turns ratio.

Loading is the the part that gets way too much emphasis and really should be only a minor part of the consideration. The focus on cartridge loading as a primary concern causes much confusion and turns what should be a very simple process into a black art.  There are two aspects to the reflected load, the resistive part and the capacitive part.  The resistive part sets the actual reduction of gain from the ideal. Attention must also be given to the load capacitance as the turns ratio increases since that value can quickly truncate the top end.  I always consider the reflected load to be a liability and feel that using a transformer to reflect a desired load is misguided at best.  People tend to consider the transformer as an ideal device that will perfectly reflect the terminating load to the primary.  In reality this is far from being the case. More often than not, adjusting the secondary load to reflect back a desired value to the cartridge will have both a measured and a perceived effect on the performance of the SUT. It is this change that people incorrectly attributed to the load the cartridge is seeing. All transformers will reflect a minimum load based on the math and the goal should be to keep that number as high as possible. Increasing the 47kΩ input resistor values is a good place to start.  Once the minimum load is determined, if additional loading is deemed necessary it should then be added to the cartridge directly where it will have a minimal effect on the behavior of the SUT but can have a dramatic effect on the tracking behavior (ie sonics) of the cartridge.

dave

Dear @holmz  : " 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. "

 

Dielectric, yes I think with out facts its importance as a wire insulator and with out facts too the qualitlevel of the of the cooper/silver wire.

@intactaudio  audio that were posting in the thread can put some " ligth " about because he manufacture SUT either: cooper or silver and normally his customers prefer silver material over cooper.

So, Dave hopefully you can share your know-how and experiences about.

 

R.

As @intactaudio points out, loading is another aspect of the SUT, and this is where, based on my limited reading, things seem to start to get complicated.  Here is what Rothwell Audio's website says about transformer loading:

"transformer loading
The idea that optimum performance comes from matching the impedance of the load to the cartridge's impedance (shown above to be somewhat hit-and-miss) also gives rise to another fallacy – that of transformer loading. The misguided theory, sometimes advocated on websites and forums, says that a loading resistor on the transformer's secondary winding can be used to “correctly load the cartridge” or to “match the transformer to the cartridge”. This is a very dubious theory indeed, so lets analyse what is really happening. Take as an example the Ortofon Vivo Red cartridge examined above (5 ohm source impedance, 0.5mV output voltage). As has already been determined, a 1:10 transformer will give us the voltage we require for an MM phonostage, but the advocates of “correct loading” may be convinced that the cartridge performs best with a particular load, despite the manufacturer's recommended load being anything over 10 ohms. So what is “the correct load”? Often, it is claimed to be the same as the cartridge's source impedance, hence “matching” is achieved. As shown above, a turns ratio of 1:97 will present a 5 ohm load to the cartridge, but what if such a transformer cannot be found? What if the nearest transformer available is 1:36? Can that be made to “match the cartridge correctly”? The transformer with a normal 47k load would give the cartridge a load of 36 ohms (and produce an output voltage of 15.8mV). In order to make this transformer match the cartridge with a load impedance at the primary of 5 ohms, a load on the secondary of 6480 ohms could be employed instead of the 47k normally found on an MM phonostage. This would not only produce a load impedance for the cartridge of 5 ohms, it would also reduce the output voltage to 9mV. Has the additional loading resistor now made the system optimal? No, it hasn't. The cartridge is now seeing half the minimum impedance which the manufacturer recommends and the signal voltage into the MM phonostage is still enough to reduce its headroom significantly. Clearly, this isn't optimal, but it is a lot better than it was with a 1:36 transformer and no additional loading resistor. Anyone who is taking an empirical approach to optimising their system and experimenting with loading resistors based on the idea of “impedance matching” as advocated on some websites would conclude (understandably) that their system now sounds better because “the cartridge is loaded correctly”. In fact it sounds better because the phonostage is being overdriven less than it was before. It would be better still if a 1:10 transformer was used instead of trying to make a transformer with far too high a turns ratio “match” anything by fudging it with resistors.
The “correct loading” or “load matching” myths are fuelled further by a fortuitous by-product of loading the transformer with an additional resistor – damped ringing, analysed in more detail below.."

For those who don’t mind clicking links, and are interested in reading more, here is the link to the informative, educational page from Rothwell Audio Products, and they do mention use of different materials, such as copper vs silver somewhere on the page, although their experience may differ from others:

http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.html

 

If the information available from Rothwell answers your questions, that's great.  Just beware of the passages where they compare the relative virtues of active high gain stages to SUTs. Because they sell transformers. Also, if Intact Audio and Rothwell are in conflict, go with the former authority.

@intactaudio has already stated "In fact assuming the frequency response safely covers the audio band, I find core material, dielectric choice and winding wire to be far more dominant factors in the final sound. I find extending bandwidth (particularly at high frequencies) is simply more icing on an already delicious cake".

I have no issues with this Statement, I have had specific type Transformers Hand Produced for owned devices and have been involved in the dialogue between the EE Designer/Builder and their supply chain Tranx producer. There is indelible recollection of use of the construction materials as well as the Math involved.  

"if Intact Audio and Rothwell are in conflict, go with the former authority".

There is more than one road to Rome.

Rothwell are seemingly ubiquitous in their support and have available devices that can be used in conjunction with a Typical Cartridge Design, at reasonable/competitive cost to enable an interested individual to get on board and share in the experience.

Intactaudio are quite different, the device on offer is Bespoke Built and Designed to be an Optimised Interface.

The end user is quite sure about the choices for Cartridge and the supporting ancillaries they choose to use in conjunction to create the Phono Signal Path.

Additionally, the end user is quite sure who's experience they want to assist with producing their Bespoke Built devices.

I get the idea of approaching Intactaudio, it is not a strange approach or a pursuit of a luxury item. The approach is made with a intention to have the best support put in place for the Luxury Items. If one has a TT>Tonearm>Cart'>Phonostage at approximately £$20 000. If a further ancillary is attractive to be used in conjunction with the System, why would a Bespoke Built device not be a consideration. 

I've been having Bespoke Built Devices produced for 25 Years+, where I have relied totally on an EE's Experience and Skills and their supply chain, to bring the idea to a realisation. I do not feel short changed in anyway.

In the earliest days, if I were to also include a Design Service and have a Blingy Encasement produced, I may have started to feel a little out of pocket. There are many nice enclosures 'off the shelf' on offer today, so this is not an issue of concern anymore. 

 

 

@drbond 

from rothwell...

In order to make this transformer match the cartridge with a load impedance at the primary of 5 ohms, a load on the secondary of 6480 ohms could be employed instead of the 47k normally found on an MM phonostage.

Lets say for example the goal is to load a cartridge @ its internal impedance.  I agree with Rothwell that heavily loading down the secondary of a SUT to reflect the desired load to the cartridge is a mistake.  However....  One could simply accept the 47kΩ termination on a 1:36 will reflect back 36Ω. In order to reduce the cartridge load to 5Ω, simply parallel a 5.8Ω resistor with the cartridge. (it is kinda cool how 36^3=47K)

I have done this experiment and can emphatically state that in this case 5Ω≠5Ω.  In the case with the load applied through the transformer it seems like a blanket has been thrown over the speaker.  This is the exact "thick" sound people report from this type of loading.  The error all too often made is incorrectly attributing the sound of the reflected load to the cartridge when it is actually the sonic nature of the loaded transformer.  Simply doubling the turns ratio of the SUT and then loading the cartridge at the same 5Ω nets a very different sonic result. Thick, dark and muddy are the last terms I would use as descriptors.  To complete the circle on this I have then taken a transformer loaded Jfet based head amp and compared the same cartridge above loaded at 47kΩ and at its internal impedance and I would say the overall pattern of sonic character followed that of the transformer with the additional load placed on the cartridge directly and the sound of the "traditional" heavily loaded transformer secondary is the outlier.

dave

@rauliruegas 

So, Dave hopefully you can share your know-how and experiences about.

All I can give is my subjective opinions from my experiences comparing the myriad of options out there.   In my system the SUT's are always silver wire on 80% round loop nickel cores with an emphasis on air as a dielectric.

dave

@intactaudio Your last response is what I would call an IP reveal and very generous as an offered information. 

I carry info' like this from my Bespoke Designs I own,but have always felt my liberty was best constrained when the opportunity arose for sharing the Designer/Builders IP.  

I once had an awkward conversation with a not very well known to me EE at an event where I was demonstrating a device, they were keen for me to allow them to remove a Chassis bottom plate and let them see inside. I was adamant that that would be quite a betrayal to the designer with whom I have developed a close to 30-year friendship.  

Some observations:

I always found the specs for a cartridge confusing: 0.25mV output at 5 cm/second.  Into which load?  Open circuit?  Load=Cart impedance?  Load=recommended impedance?  Why not state the output voltage and the impedance at which it is measured?  Most recommended load impedances are specified over a large range (100Ω-1K), and they are all usually 10x the cart source impedance so the voltage divider effect will be small, but in some cases, it could have a significant impact on the output.

 

Matching the cart source impedance into the load would only be relevant if you are trying to transfer the maximum power from source to load which is not the goal of a phono preamp.  It would be like trying to match the load a speaker presents to the output impedance of an amplifier which can have an output impedance measured in milli-Ohms.

 

What you do want to match between cart and load is the conjugate match of the imaginary (reactive) part of the impedance so the cart sees a purely resistive load.  The cart has a complex source impedance which may not be a simple series or parallel capacitive or inductive component but a combination of those elements.  The complex impedance will most likely change with frequency as well, complicating the matching network calculations. 

 

Perhaps what is needed is an S-parameter measurement file for the cart that can be used in a linear simulator to design an appropriate conjugate matching network.  Most RF devices are spec'd this way and is the only practical way to design matching networks that work;  absent this data, it's like trying to find your way out of a maze with your hands tied behind your back and wearing a blindfold.

Dear @intactaudio  : Thank's.  I understand that normally the dielectric in SUT is air but I can be wrong.

The only SUT silver wired I tested in my system vs SUT's cooper wired was the Audio Note Kondo that was compared vs the AT 1000T, Denon 340 and Denon AU-1000 and in all tests I prefered the cooper wired SUTs ( phono input 100k. ) and you the silver wired ones.

 

Maybe the SUT kind of wire is more or comes along with the room/system and owner targets. Different with speaker croosover inductors where silver is superior to cooper wired and ribbon shape over rounded ones.

 

Btw, the Kondo goes down to 2hz ! ! and Audio Note builded around the end of the 70's a SUT with an exceptional FR: 2hz to 200khz at -o.5db and 0.001% distortion. I never seen in the market and I don't know neither if was silver wired but probably not because was at the midle of Audio Note SUT line.

 

R.

 

Maybe just maybe drbond is just " trolling " in his latests posts, lewm in the very first page of the thread posted:

 

Audiogon Discussion Forum

 

Of course that the op as any one of us has the rigth to post almost what ever we want.

 

R

This Thread with the content on SUT's has served as a very valuable and relevant thread for anybody with a curiosity about the method to be used with a MC Cartridge.

There has been very valuable Posts contributed to this Thread and if read in Conjunction with the SUT Thread that resurfaced as this thread has developed is potentially a reference place for subjective evaluations and guidance on how a inclusion of a SUT might be perceived.  

For the record,

I have been influenced by Copper Wire over Silver Wire, for all interface cables s and Transformers used in my system.

I have had a period of using a Silver OCC Wire Phono Cable, but this is now Superseded with a Copper Wire Cable.

I even had two very heavily modified CDP's trialed where the main differences were that one model was with Bespoke Produced Silver Tranx's and the other Copper.

I was quite impressed with the Copper, and it was this design that was instrumental in my consideration of a CD source in my system.

More recently I was being demonstrated Two SUT's in another system, one with Copper Wire Windings and produced to be an ideal match for a Miyajima Cart'. 

The other a usable match for the Cart' with Silver Wire Windings.

I thought I was done on the SUT front and was where I wanted to be, with the EAR TX4 (The Head) being the Holy Grail to aspire to.

What was experienced was beyond what was expected.                                            I was blown away by the demonstration of both SUT's, as were the other attendees, of which a few have the opportunity to receive demonstrations of (The Head) in the system in use. Their assessment being there are similar impressions being made and it would be great to hear The Head and these Models A/B compared. Not many models would be considered as a contender.

A SUT that is an ideal match for a Cart' is quite something and to have the Brands Models demonstrated in my own system in a winding ratio that is a match for my Cart', along with the Silver Wire version is the Top of the List for when I have a Vinyl Source back in action.   

Dear @phoenixengr : If LOMC cartridges are almost no sensitive to load impedance then which your real point that I don’t understand for sure and which is your solution and advantages on the cartridge quality level performance?

 

For some years in my system the active high gain phono stage came with a 100 ohm input resistor and through all those years I had not any single trouble ( that I been aware of. ) with several and different LOMC cartridges that I owned and own.

 

" recommended load impedances are specified over a large range (100Ω-1K), and they are all usually 10x the cart source impedance so the voltage divider effect will be small, but in some cases, it could have a significant impact on the output. "

 

Ly ra states that load range with its different cartridge models and Ortofon says over 10 Ohms even that its cartridges internal DC resistance is 7 Ohms. Clearaudio even does not gives any advise and in all its LOMC models the internal cartridge impedance is 50 Ohms and I tested the Goldfinger in my phono stage with n very good cartridge quality levels. I owned/own the Discovery and Insider Gold that came with the same internal impedance and again I had no trouble with even that in the past the Clearaudio advise was over 500 ohms ( 10x ) and that I remember that input resistor was not changed  but before my today phonolinepreamp I owned the Classé DR-7 that is an active high gain design too and performed very well with that same resistor value.

 

So other that a change in SPL which is that " significant impact on the output generated by the cartridge not by the phono stage it self but the cartridge that’s what you and me( I understand ) are talking about.

Your answer is appreciated. Always is time to learn for all of us.

 

R.

 

@rauliruegas 

My point about the specified impedance along with the output voltage was to make the necessary gain calculations easier.  In your Lyra example, using a 10 Ohm load with a 7 Ohm impedance cart will drop the output level by 4.6dB, which could be significant.  The output level will only be insensitive to the load if the load is 10x the cart impedance or higher.

 

My point about conjugating the imaginary (reactive) impedance of the cart is to cancel out any inductive or capacitive reactance so the cart sees a purely resistive load which will give the flatest frequency response with no peaking at high frequencies.  If the complex impedance of the cart could be measured or calculated, then the proper termination could be easily determined instead of guessing or by changing loads and listening for a difference.

For some years in my system the active high gain phono stage came with a 100 ohm input resistor and through all those years I had not any single trouble ( that I been aware of. ) with several and different LOMC cartridges that I owned and own.

If you never tried any load other than 100 ohm, then you cannot know if there was a problem due to loading at 100 ohm .

My point about conjugating the imaginary (reactive) impedance of the cart is to cancel out any inductive or capacitive reactance so the cart sees a purely resistive load which will give the flatest frequency response with no peaking at high frequencies. 

@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.

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?

Ah! I forgot about being shown a Square Wave by the EE producing the Phon'.

From recollection this Scope Reading was shown in conjunction with the 'mv' output per channel as a valuable reading to be assessed.

I don't get too bogged down in such a presentation, I am trusting in the EE and their abilities, if they are claiming there is something present that is impressive and of value to the electronic function of the device, who am I to nit-pick at their explanation.

The follow up listening has always been where I do my evaluations, and decide how much monies are to be removed from one's account, to achieve the experience permanently.

…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?

Dear @dover  : Yes I did it during the " thousands " of tests with the prototypes of the phonolinepreamp and through measures and listening tests the only parameter we can been aware was changes in SPL but not in FR but additional to that normally LOMC cartridges come with the " rigth " internal resistance to work very good looking those 100 ohms. Clearaudio is something espcial with those 50 Ohms.

 

R.

@holmz 

While I'm not certain, I think @dover may be referring to the reaction of the square wave to various loading, resistance, and capacitance properties, when dealing with SUT, which is found on that same Rothwell Audio Products site:

"

figure 1a

figure 1b

figure 1c

figure 1d

Transformer ringing All transformers have limitations due to the inevitable capacitance between windings, leakage inductance etc. and these determine the transformer’s bandwidth and can produce “ringing”. Ringing can be seen as overshoot at the corners of a squarewave, as illustrated in the figures above. A lower load impedance on the transformer's secondary winding has two effects: reduced output and damped ringing. This perhaps explains why people attempting to tune their system by ear have reported that loading resistors (intended to load the cartridge correctly) have a beneficial effect. However, in reality the improvement in sound quality isn't due to the cartridge being loaded correctly, it's due to the phonostage being overdriven less, and due to transformer ringing being damped. A much better approach to optimising sound quality would be to separate the two issues and deal with them individually. Overloading the phonostage would be addressed by using a transformer with a lower turns ratio, and that alone would have the added benefit of better performance. Ringing can be dealt with by employing a suitably chosen resistor-capacitor network without the penalty of excessive signal loss. In the case of the Ortofon Vivo Red in the example above, a reduction in output voltage is a benefit, but more often than not it isn't a benefit. With cartridge's such as the Denon DL-304 with its feeble 0.18mV output, any loss of signal voltage caused by attempting to damp ringing with a resistor is unwelcome. Achieving the correct signal level is one issue and damping transformer ringing is another. Trying to treat both issues with one cure isn’t advised. Fortunately, ringing can be damped by a suitably chosen resistor-capacitor network without the penalty of a reduction in output. The oscilloscope screen shots in figure 1 above illustrate ringing and the effects of different loads on the transformer's secondary winding. Figure 1a shows the output with a 47k ohm load on the secondary of a fairly modest transformer. The slope on the top and bottom of the waveform is caused by the low frequency limit of the transformer due to inadequate primary inductance. The peaks at the corners of the waveform are due to transformer ringing, also known as overshoot. Figures 1b, 1c and 1d show what happens to the waveform when the secondary load is reduced to 22k, 10k and 5k1 respectively. The slope of the waveform straightens out as the impedance is reduced and the corners lose the unwanted peaks, but the overall signal level also drops significantly. The level with the 5k1 load is about 10dB less than the level with the 47k load. This shows that although the performance of the transformer can be improved by reducing the load impedance, the benefit comes at the expense of a serious loss of signal level. Since the point of using a step-up transformer with a moving coil cartridge is to gain an extra 20dB or so of signal level, any loss due to incorrectly loading the transformer is unacceptable. The transformer ringing which can be seen as peaks at the corners of the waveform in figure 1 is a common problem and arises from inductive and capacitive elements (leakage inductance and inter-winding capacitance) combining to produce resonance. The capacitance of the cable connecting an mc step-up transformer to the following phonostage also plays a part, which is why the interconnecting cable should be a low capacitance design and kept as short as is practical. Ringing can be found in many commercial moving coil step-up transformers, regardless of price. Sometimes the ringing occurs at very high frequencies and is reasonably well damped and therefore quite benign, but often it occurs at a much lower frequency or rings for such a long period that it can cause quite audible effects. Even expensive transformers from well-known audiophile brands often exhibit poor performance as regards ringing. Figure 2 below shows oscilloscope screen shots of a step-up transformer from a manufacturer of expensive valve amplifiers. The input signal is again a 1kHz square wave from a 10 ohm source. Figure 2a shows the transformer's output when there is no load and the overshoot is quite clear to see. Figures 2b to 2e show the 1kHz waveform with different loads on the transformer's secondary. A 47k load has barely any effect on ringing, but as the load is reduced through 22k, 10k and 5k1, the ringing is progressively damped. At 5k1, the ringing is gone but the signal level is reduced. With this particular transformer, the signal loss with the 5k1 load is not as bad as the signal loss suffered by the first transformer, but any loss of signal should be avoided. Note however that the top and bottom of the waveform are very flat, indicating that this transformer has very good low frequency performance. Figure 3 is a closer look at the corner of the waveform and shows clear ringing which lasts for several cycles before subsiding. The frequency of the ringing is about 100kHz - well above audibility - so there's no chance of actually hearing a ringing sound, but it is clear that the signal produced by the signal generator is being severely deformed. Figure 4 shows the output from a 10kHz square wave input. The waveform is hardly recognisable as a square wave at all and it is not difficult to imagine what effect such deformation could have on a music signal. The leading edges of crash cymbals, ride cymbals and snare drums or the attack of plucked strings could easily lose integrity and become a confused jumble of sound. When several percussive instruments are playing together, as is very common, separation between the instruments will not be helped by the severe ringing shown in figure 4.

figure 2a

figure 2b           figure 3     figure 2c   figure 2d   figure 4

figure 2e

Fortunately, ringing can be totally eliminated without sacrificing signal level by loading the secondary winding correctly with a resistor-capacitor network, not a simple resistor (though far too many commercial step-up transformers totally neglect this). Although lower values of resistive load on the secondary do tend to reduce ringing, as illustrated above, loading with a correctly optimised resistor/capacitor network will produce far superior results. Since different transformers are constructed with different core materials, wire thickness, number of turns and winding techniques, the optimum load network will be different for each, and the only way to determine the correct network is through measurement. Figure 5 below shows the transformer of figures 2 and 3 after an optimised load network has been applied, again with a 1kHz square wave input. The ringing has been eliminated and the signal level available into a 47k load has been maintained. Figure 6 shows the effect of applying a non-optimum loading network. In this case the incorrect component values (out by only a few nanofarads and a few kilohms) have resulted in quite a peculiar deformation of the waveform. This illustrates the need to get the loading network right rather than copying a network which is optimised for a different transformer. As an aside, the use of silver wire for the windings might appear impressive but does little or nothing for performance due to the fact that silver has only marginally less resistance than copper and the limiting factors in transformer performance are due to the finite size and permeability of the core, leakage inductance and inter-winding capacitance, none of which are improved by the use of silver wire. However, it does have a significant impact on cost. It should go without saying that elaborate cases with 3D milled aluminum front panels or gold plated turrets, while very nice to look at, also have no benefit for audio performance but, again, do have an impact on cost.

figure 5

figure 6

"

Dear @phoenixengr  : " My point about the specified impedance along with the output voltage was to make the necessary gain calculations easier.  "

I was very clear and stated that my phonolinepreamp is an active high gain design and I can tell very good design or at least competitive today.

Why should I care about gain  when here I explained and told you that " other that SPL changes " whic other advantages? and I posted that we had not changes in FR.

I'm not talking of phono stage + SUT.

 

R.

Dear @holmz  : In the good old times cartridge reviews where really great with all the information you can imagine. Here the LOMC Ortofon MC2000 ( that I owned ), page 83:

https://worldradiohistory.com/Archive-All-Audio/Archive-Audio/80s/Audio-1984-12.pdf

 

R.

 

 

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.

?

@holmz 

this one -

• whether they generated a square wave with the same output impedance as the cart and fed the SUT with that

Dear @dover  : Yes I did it during the " thousands " of tests with the prototypes of the phonolinepreamp and through measures and listening tests the only parameter we can been aware was changes in SPL but not in FR but additional to that normally LOMC cartridges come with the " rigth " internal resistance to work very good looking those 100 ohms. Clearaudio is something espcial with those 50 Ohms.

There are plenty of MC's up to 40 ohms ( eg Benz, Dynavector, Sony to name a few ) for which 100 ohms loading in my view is killing the cat.

If your phono linear were stable you would be able to load at any value.

It would seem that any observations or cartridge evaluations posted by you with this phono stage would be jaundiced by improper loading. 

Dear @dover : Yes, is totally stable. Now, till today 7-8 other owners never reported issues about and satisfied with their units.

A " trouble " with the phonolinepreamp is that any load resistor change means to unsolder/solder the new one and to do that we have to open/take out the top plate and make the job carefully because the boards are 4 layers and we have to make 2 changes because is a dual mono design.

During the unit presentation/show in USA I was at around10 different room/systems with different cartridges with no compliant for the system owners.

I was not the designer engeenering in chief but I learned a lot down there and maybe theory not always works as should be depending of the kind of design.

Rigth now I have not a clear explanation why performs so well against the 10x load other than minor SPL changes where noise level is no issue due that the unit has very low noise and distortion levels.

The audio friends at my place with their own cartridges almost always were " impressed " by what their cartridges showed here through this phonolinepreamp.

Jaundiced? you can be sure that’s not that way: theory vs real facts, including measures during prototype tests.

In my vitual system says: " current mode " design ( what José stated. ) that comes from around 15 years ago and perhaps not estrictly " current mode " by today standards or a current mode " variation ". The issue is that works in excellent conditions over any " scenario ".

 

I can remember very clear that when I was showing it in Houston at a top Agoner and today reviewer ( he owns Rockport TT , Acapella Triolon’s, JC-1’s, ) that his Lyra was out of work in the same just time he was showing his system in its dedicated room and when the Lyra " hit " the first LP grooves he took in count that the Lyra was with out stylus : just disappeared and then we chage it by a Clearaudio he owned and we made the set up in his Rockport and he was really " surprised " for what he listened through my unit ( yes 100 ohms resistor ). Here what he posted:

Audiogon Discussion Forum and this the first time down there:

Audiogon Discussion Forum

Audiogon Discussion Forum this gentleman with a Ruby2 in a Triplanar.

 

This the first version of the unit and VDH cartridge:

Audiogon Discussion Forum

another ones:

Audiogon Discussion Forum

Audiogon Discussion Forum

and I can go on andd on. Lewm owns a 3160 and mine is the 3180.

 

Other cartridges as the Magic Diamond in a Walker TT in Phuladelphia with 15-20 listeners including Lloyd Walker him self and other presentation in San Diego with 15-20 listeners at an Audio Salon big audio distributor. Different cartridges same " resistor ".

 

R.

 

 

R.

 

In Georgia with Aolivero he owns the Proteus, Dallas with Albert Porter the 47 Labs, with the group in San Diego Lyra Skala and in the same area a gentleman with all Air Tigth electronics and with Air Tigth cartridge too. Other cartridge Allaerts and over there in a shoo-out vs Dartzeel  with 3 different cartridges the owner of this unit made one load impedance change that in the Dartzeel and in the Essential nothing change and even the owner prefered ( not night and day differences. ) the Essential. In other place Dougdeacon with the Universe II and in Boise the Lyra Olimpos. I can't remember the cartridge at @sbank  place .

Dover, have you an explanation?

 

R.

Propa P***ing Match now in the making.

It's all about the Bass about the Bass is knocked well out of the Ballpark, and the next Pitch is "What about Me, I don't like SUT's", I want to ruin this discussion with my usual BS.    

What a waste of a Good Thread, SUT Discussion well and truly of the rails for a while, I'm out of here. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Dear @holmz  : What Dover posted. You can read the link rigth from the Ortofon cartridge/SUT specs and then the measured sqare wave.

 

R.

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,