SUT - electrical theory and practical experience

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.