Step Up Transformer

I’m thinking of inserting a SUT into my system, and at this point the SKY20 from Bobs Devices seems to have it. Does anyone have experience with this SUT? It will be connected to Cadenza Black and either a McIntosh C70 or a PS Audio Stellar.


I have a Cinemag 1254 based SUT built by Ned Clayton on eBay.  I find it to sound fantastic, and should be similar to one of Bob's Devices but is much cheaper.  It has 4 gain settings for ultimate flexibility, and 3 ground settings for the most quiet blackest backgrounds you'll ever hear.  I find detail and clarity and bass drive to all been kicked up a notch as opposed to going straight into my phono pre, which is quite hissy at high gain levels.  Now my MC setup is dead quiet, something I'm not used to, and paired with my old Koetsu Black, I am in vinyl nirvana.


@dover given your extensive experience, would you share with us what you consider to be the best trannies you ever heard? Thanks.

That is like asking how long a piece of string could be if you unwound it.

I have not heard any mc transformer that sounds as good as my current mc input 

In terms of best, the problem is that there is no best, it so much depends on the cartridge/sut/phono combination.

For example I have amongst my collection some Altec 4629's and 4722's. Same "specs", different construction. With most cartridges the 4629's outperform the 4722's - however with one exception, with my Garrott rebuilt Denon 103 the 4722's outperform the 4629's. With all my other cartridges the 4629's outperform the 4722's. The 4722's easily beat the Auditorium 23 specifically designed for the Denon 103.

My experience trialling a variety of SUT's with a range of top cartridges with internal impedances ranging from 3-40 ohms I have come to the following conclusions -

None of the SUT's are neutral, none sound the same despite some having similar gain structures, turns ratios etc.

The SUT's all have a unique character that you can hear regardless of the internal impedance of the MC.

I think that trying to match the SUT to a MC in terms of load presented to the cartridge ( the most common methodology promulgated on this forum ) is wrong.

Much more important than loading in my view is getting the gain structure right so you have the optimum voltage going into the phono. Many vintage transformers have too much gain for modern tube mm phonos resulting in the preamp volume pot operating in the very low region where noise and more importantly accurate tracking matching between channels is compromised.

I have never needed more gain than 1:10 turns ratio at most, using my modded Marantz 7 ( phono around 42db ), even with cartridges like my Ikeda Kiwame which is only 0.15mv.

Currently in my cupboard I have SUT's from Altec ( 4629/4722 ), various FR's, Jensen, Tims Head and some vintage Ortofon units. Many others have passed through.

Conclusions thus far ( in my system )

Jensen's - most neutral - important note - I have optimised the Nobel networks for the individual cartridges used, this is required to get the best out of them.

FR's - horrible, compressed, gluggy, flogged them all off apart from one which was a gift, so I can't sell it, never use it though.

Various Denon SUT's - very good bang for your buck, some work exceptionally well. for example with my Dynavector Karat Nova 13D one of the Dynavector engineers advised me to use the vintage Denon AU103 other than the matching Dynavector head amp and/or SUT.

Kondo's - lovely "sound" but dreadfully slow.

Auditorium 23's overrated, optimised Jensens and vintage Altecs are better.

The Head ok, nothing special.

Peerless/Altec 4629 - if I need a SUT I tend to use these, can be configured for different gain structures - midrange is nice,  but lacks bottom end extension and top end not super refined. By the way if you pull one of these vintage grannies to bits you will find individually annealed plates within the laminations - depending on the annealing process you can modify the efficiency and electrical behaviours of the transformer and in those days Jensen had 200 plus engineers fiddling around with each individual process in manufacturing for fun and learning - something no one could afford these days. They also use teflon within the windings. Probably most of ttheir research learnings have been lost. 

Unfortunately whenever I use a SUT in my system the compromises are too much and they don't last long.

I would only see a benefit from using a SUT where the MC gain stage is not very good or you want a "sound". MC transformers have phase shifts and therefore cannot accurately reproduce the fundamentals and harmonics of a note. On the other hand they can help reduce noise due to their passive nature.

Personally I value coherence and timing ( I seem very sensitive to timing and phase errors ) and therefore don't use them.

Having said that decent MC stages are few and far between. 

Also one other recollection - in discussions with a top cartridge designer there is a correlation between cartridge design ( not impedance ) and the attributes of the magnetic circuits within SUT's - for example if I recall correctly they recommended certain SUT's ( toroidal vs conventional core ) with specific cartridges based on the known distortions inherent in the individual cartridge design ( magnets, poles, layout etc ). I don't think anyone here would be ab le to explain this other than maybe Jonathan Carr.

In a word SUTs are a crapshoot. To find the best you have to try them all out on your system with each individual cartridge.. It will cost a fortune, there is no one best.








post script

I also have in the cupboard a much vaunted pure tube mc head amp and a hybrid fet/tube mc head amp that I have modded. The hybrid fet/tube head works very well with the ultra low output Ikeda, very dynamic and very coherent, slightly down on resolution compared to my current input option.