SUT - electrical theory and practical experience

Dear @holmz  : As always thank's for your post:

 

R.

I have an experience of listening to a minimum of approx' 10 SUT's in my own system and have been demonstrated somewhere near this quantity again in other systems.

Along with the above, I have listened to, in my own system, a Head Amp, Amps with a built in MC Stage, as both Valve Hybrid and SS.

It is the extended usage in the home system of configurations for devices, that really helps with understanding the impact of a device and enable a reasonable evaluation on the influence during comparisons. 

My most recent experiences of encountering New Devices that have left a very good impression are only a few months past.

Outside of my system, I have listened to too many to count Phonostage configurations, using Phono Pre- Amp > SUT or Head Amp, Valve Hybrid MC and SS with the most expensive dedicated design having a £10K price.   

I have spent numerous years learning about how the designs and configurations for a Dedicated Phono Amplification can impact on the presentation on offer from a Vinyl LP Source.  

I am not prejudiced; I have heard very good performances from a SUT in use, or a Head Amp in use. A SUT does inject a Colour to the presentation, but there are SUT's that in comparison to another could be described as having a Transparency.

Put a perceived as Transparent SUT in use alongside a Head Amp as a comparison demonstration and the SUT will quite quickly have a detectable colour in the presentation.

I see the SUT > Head Amp in use, as real bonus to the user who does not prejudice against the devices, as there is a huge scope to fine tune a system to one's unique preference, the cut off point for detectable colouration is the end users choice. This is achievable, in all Phono Amp Designs, Valve Input/Output, Valve Hybrid and Solid State.

I have pursued the perception of Transparency for a long time, and as a result, have found it difficult to accept an undeniably transparent presentation as attractive. With this in mind, my investigations have shown it is hard to discover SS designs that really appeal, (there are a few that I have appraised with a positive evaluation, as a Brand Soulution is presenting in a way that is very agreeable.)

As a means to achieve the perception that a presentation is attractive, for my own preference, a little detectable colouration is welcome, even though easily able to be overlooked, is the presentation that is very attractive for me. As always each to their own, based on the influences made as a result of their own experiences.

Most recently I was demonstrated SUT's with a design that uses a material referred to as a Nano Crystaline Core. Two different ratios were in use and a Copper and Silver Wire was in use as well. I was shocked (definitely not expecting ) how the devices were able to impress, these are top of the list for a home demonstration, alongside a Solid-State Phon' I have been impressed with, when my system is once more assembled. 

At the same demonstration one of the SUT's with a Ratio to perfectly match the Cart' in use was to be used in conjunction with a Brand-New SS Phonostage with a value of £4000, that was a loaned device being demonstrated. The SS Phon's MC Stage was attractive for a New Device, with an allowance being given for further settlement through usage, there was without doubt, potential projected for the device. 

With the SUT being used in place of the SS Phon's MC Stage, the impression made was notable, it was a much improved presentation, and all attendees listening were in agreement, even the SS Phon's owner. 

The most difficult Phon' design, I have struggled to reconcile with is a common design, from an affordable range, from both Brands and a DIY approach, where using a circuit that is Valve Hybrid with a JFET for the MC Stage, usually if bought through a Brand comes with a pricing from £1500 - £3000. There seems through the consistency of the Sonic I am able to detect, to be an indicator typical parts are used for the circuit. In my evaluation there has been seemingly identical presentations, and not the most attractive of ones heard, that appeal to my preferences.

My experiences pretty much break down into the evaluation, that there are options on the configurations to produce a Phonostage.  A Phonostage does not necessarily need to be a one box affair only, using off board ancillaries are totally worthwhile trying out.

An end user can be quite creative in how they are able to produce a presentation that has a very positive impression on them. 

Add to the permutations, the trying out of different umbilical's and with Valve Designs the option to try out alternative Valves and the opportunities for creativity really 'gets it freak on'.

Why limit oneself, when numerous options are available without the need to be adorned with any great skills to put them in place.

 

I had a chance to listen to EM/IA SUT in my stereo yesterday.  It was a 1:10 Cu version made for my friends combination of a Lyra Atlas and Marantz 7C preamp. Cable was a .6 meter Nordost Quatrofil. On my turntable yesterday was a SoundSmith Hyperion MKII/Kuzma4p9 going into my Pass Labs XP-27 phono pre. I usually have the pre set on high gain and 500Ohm resistance. So for the SUT, I switched to low gain and 47k resistance. 
 

This experience supports a lot of what has been discussed on this thread.  The addition of the SUT made things sound a touch more crystalline and at the same time a touch more dynamic. Bass definition and soundstage depth suffered just a little as did overall transparency. Clearly this SUT works better for the tube MM stage that my friend uses.  Not that it sounded bad in my setup.  Just different and a little farther away from my preferences. I didn’t have time to swap in a Lyra Etna SL or my Koetsu RSP.  I bet that may have identified a better match with the SUT.

One of the things I love about the Pass is that I can use a wide variety of cartridges and find the optimal setting with the front panel switches. 

Your XP 27 Phono Pre, has quite a value attached to it.

'Hats Off ', to you for trying out something new in conjunction with it. I'm glad you found value in the encounter and the experience.

With a short duration demonstration, especially as a comparison, usually the most noticeable differences are detected and not usually the subtle ones. The subtle differences, when detected can be perceived as a betterment or slightly lesser/different to the other device/devices in use during a comparison.

Discovering a variation in the perception of Transparency between a SS MC Stage and SS or Valve MM > SUT Stage is in keeping with my experiences. Additionally, a Valve MM > Head Amp is noticeably able to be perceived as Transparent in comparison to a SUT in use, for the same role.  

I have two SUT's retained for my use, one is seemingly without a Colouration when compared to other SUT's I have used. The other sits about 3/4's around the dial to being perceived as Transparent, when compared to other SUT's I have used. I like a little noticeable colouration with my Chicago Blues Music.

I can declare, I have a colour in my music, even though generally not detectable and easily overlooked. A SS Device has proved its value at showing where there is Colour to be detected in the SUT's I have chosen to retain.

Your report, making it known the Transparency suffered just a little, would suggest to me, the EMIA is a SUT that can be referred to as Transparent in comparison to other SUT's and will only reveal it has a Hue of Colouration, when compared to a SS Designs MC Stage. 

It would have been good feedback, if the other Cart's could have been used, as said previously, the permutations on offer by using an off board ancillary can be quite vast.   

@lewm 

A brief internet search pulled up this basic, but informative article:

Audio Transformers are electromagnetic devices that transmit and modify input electromagnetic signals into output signals via inductive coupling. They isolate an input circuit from an output circuit and filter signals; operating on the audible band of the frequency spectrum (20Hz to 20kHz). As such they can have applications in the input stage (microphones), output stage (loudspeakers), as well as coupling and impedance matching of amplifiers. In all cases, the frequency response, primary and secondary impedances and power capabilities all need to be considered.

Materials and Structure

A transformer is an electrical device which allows an input signal (such as an audio signal or voltage) to produce an output signal or voltage without the input side and output side being physically connected to each other. This coupling is achieved by having two (or more) wire coils (called windings) of insulated copper wire wound around a soft magnetic iron core. Audio transformers are typically composed of copper wire windings around a steel or nickel-iron alloy core. Each core material transmits electromagnetic signals differently. Steel has a higher degree of hysteresis (magnetic signal lag), making it better for lower frequency transfer. The higher permeability of nickel makes it ideal for transmitting higher frequencies. The windings around the core determine the impedance level, which increases, decreases, or maintains the signal level as it passes through the transformer.

When the signal enters the transformer via the input (primary winding), it then gets transferred to the output secondary winding due to the inductive coupling of the soft iron core. The ratio between the number of coil turns on the primary winding (N_P) to the number of coil turns on the secondary winding (N_S) is called the “turns ratio”. The turns ratio between the input and output wire coils provides either an increase or a decrease of the applied signal as it passes through the transformer. More windings around the core correspond with a higher impedance, so if the primary winding has more than the secondary, the signal will decrease (step down). Conversely, if the secondary winding impedance is greater than the primary, the signal will increase (step up).

The number of turns on each winding determines whether the transformer provides a gain or loss of the signal:

• If there are more turns on the input winding, the signal will decrease or step down.
• More turns on the output winding will result in a step up.

Audio transformers are produced for a range of specific audio functions; many are similar in construction to power transformers and they often perform several functions at once. They can be considered as either a step-up or step-down type, but rather than being wound to produce a specific voltage output, audio transformers are mainly designed for impedance matching, isolation, and a variety of applications (see Data/Voice Coupling Transformers).

Impedance Matching

Transformers can step impedance up or down in the same way they do with voltage and current. Whereas they change voltage by the turns ratio and current by the inverse of the turns ratio, audio transformers change impedance by the square of the turns ratio. The same amount of voltage is induced within each single coil turn of both windings. The primary to secondary voltage ratio (V_P/V_S) will therefore be the same value as the turns ratio (N_P/N_S). Impedance matching audio transformers always give their impedance ratio value from one winding to another by the square of their turns ratio. That is, their impedance ratio is equal to its turns ratio squared and also its primary to secondary voltage ratio squared:

Impedance is determined by the efficiency of the conversion from voltage into magnetic flux. Audio transformers are ideal for balancing amplifiers and loads together that have different input/output impedances in order to achieve optimal power transfer, as in the case of a transformer at the amplifier input to match the impedance between microphones, connecting cables and the amplifier input. The input and output impedance levels are matched to create efficient power transfer without distortion or signal overload. Impedance matching transformers are similar in design to low frequency voltage and power transformers, but they operate over a much wider range of frequencies (for example, 20Hz to 20kHz voice range).

Isolation or Unity Transformer

Transformers have another very useful property, isolation. Since there is no direct electrical connection between their primary and secondary windings, transformers provide complete electrical isolation between their input and output circuits and this isolation property can also be used between amplifiers and speakers. A transformer with a turns ratio of 1:1 does not change the voltage or current levels but instead isolates the primary circuit from the secondary side. This type of transformer is commonly known as an isolation transformer.

As the impedance is identical for the primary and secondary, the signal level does not change. The transformer allows an audio signal to pass unmodified from the primary to the secondary while blocking DC voltage and radio frequency interference (RFI). Since the primary and secondary circuits are insulated from each other, the transformer will electrically isolate different pieces of equipment. This can solve hum problems by isolating or "lifting" the grounds of different devices. Other unity transformer applications include providing multiple outputs from a single mic input by using multiple secondary windings, and changing balanced signals to unbalanced signals or vice-versa.

Audio transformers are designed to operate over the audio frequency range, or much higher for radio-frequency (RF) transformers. Due to this wide frequency band, one of the main disadvantages of audio transformers is that they can be somewhat bulky and expensive. This is because a transformer's core size increases as the supply frequency decreases. Smaller designs can be achieved by using special core materials. Audio transformers have played an important role since the birth of audio electronics. When compared to modern miniaturized electronics, transformers seem large and heavy but they continue to be the most effective solution in many audio applications. The usefulness of a transformer lies in the fact that electrical energy can be transferred from one circuit to another without direct connection, and in the process the energy can be readily changed from one voltage level to another.

 

taken from this article:

What are Audio Transformers? | CircuitBread