when I started working with Step Up Transformers in the 90 ies of the last century most of the magazinsˋ writers were not mentioning this kind of sound improvement in a phono chain.
I collected and built up about 15 SUTs. This one here is completely silver wired like the Kondos are. Silvercore built most of Silbatone ˋs SUTs and other silver parts.
with a ratio of 1:20 (Silvercore ) as with all other ratios you need to adjust carefully. Most of the disappointments with SUTs do result from improper matchings.
- over dimensioned finemet toroidals
- thus an extremely low primary internal resistance of a mere 0,1 ohms
- an almost lossless transmission, extreme dynamic capabilities and a perfectly flat frequency response
- a step up / turns ratio of either 1:10 or 1:20; in addition we make special types for EMT or Ortofon SPU cartridges
- wound in Silberlegat20 or 4N, also in 99,99% pure silver wire
- sorry the description is only in German
2 thoughts on “only SUTs”
even though christof kraus is a good friend of mine and i have the MC pro in 1:5 and 1:10,i beg to differ with his explanations in two instances:
a) “Ein Übertrager verstärkt ein Signal grundsätzlich rauschfrei” (a SUT amplifies a signal noisefree by principle). if this were true, we’d have no Johnson noise. just like resistors add noise, a transformer will, too. let me quote Burkhard Vogel, author of “Sound of Silence”, *the* reference on lowest-noise phono stages. he starts the chapter on SUT as follows:
“Transformers are a very good substitute for MC cartridge pre-pre-amps. Without big development efforts they can be connected to a MM phono-amp’s input. Unfortunately, and despite the many claims one can read from time to time in test magazines, transformers substantially add noise to the cartridge-transformer-phono-amp-chain.”
on https://bit.ly/3SVfUdJ he writes in german: “(…) MC Eingangstrafo (…) erzeugt durch seinen Innenwiderstand zusammen mit dem am Eingang befindlichen MC System, entgegen der Mär vom rauschfreien Trafo, eine relativ hohe, auf seinem Innenwiderstand Rtr beruhende, zusätzliche Rauschspannung zu der des MC Systems,”
the logical conclusion is that the higher the termination (Rload on the secondary and/or Zin of the first amplification stage), the higher the noise will be. he uses Jensen Transformer’s JT-347 and JT-346 as examples. the 346 is designed to work optimally with a load of 6k8. because audiophiles constantly used the JT-346 into 47k inputs and then complained about lack of bass, Jensen introduced the JT-347, which is essentially the same SUT, but optimized for 47k load. Vogel proves that using the same cartridge, the 347 into a typical 47k MM input will have -85.3 dB S/N. the same cartridge with the JT-346 into a 6k8 input will improve this by -1.3 db to -86.7 dB. mind you, this is just the noise the MC cartridge and the transformer will produce.
since the load reflected to the cartridge will depend on the step-up ratio and the Zin/Rload, the 346 with 1:12 into 6k8 will load the MC cartridge with 47 ohm, the 347 into 47k with roughly 330 ohms. 47 ohms is fine load for low-Z cartridges up to, say, 10 ohms, the 330 ohm will suit a mid-Z MC such as the Benz Ruby quoted on the Silvercore website. this proves Kraus’ claim that the SUT should be matched to both, the source Z and the load Z. (and if you think that 1.3 ddB noise improvements are peanuts … noise optimization in phono stages often results in improvements of 0,2 dB.)
b) Kraus writes “Ist die Impedanz des Übertragers mindestens zweimal größer als die Impedanz des MC-Systems, passt das gut zusammen” (“as long as the impedance of the SUT is at least twice the impedance of the MC cartridge, it will work just fine”). in my opinion, a transformer does not have an impedance, period. it has a turns ratio which will define the step-up factor, its primary and secondary windings will have a certain amount of DC resistance, and there will be stray capacitances plus of course the inductance created by the number of turns.
all this will not create an impedance per se, it will only define whether the transformer is optimized for MC cartridges with few turns of wire as coils (=low Z) or with more wire and thus higher DC resistance i.e.mid- or highZ. the SUT’s impedance is created by the load which is reflected in the square of the turns ratio. and that counts not only for the value of the resistor, but also for any capacitance on the secondary side of the SUT. a 1:20 step-up ratio means that any resistance, capacitance, and inductance will be reflected 20^2 = 400 times to the primary side. if you have a typical MM input with 47k and 130pF, the cartridge will “see” 47k/400 = 117 ohms and 130 pF*400=52’000pF= 520 nF.
that is a lot of capacitance – and luckily, MC carts are not that sensitive to capacitive loads as MM. but it explains why, as Kraus correctly notes, many MC carts sound muffled and closed in with high step-up ratios (“Deshalb klingen viele Systeme an hohen Übersetzungen muffig und eng”): the reflected impedance acts as a lowpass filter – the same RC filter you use in a power supply to attenuate the ripple, only that in the case of the SUT, the RC is not calculated for 100 Hz ripple, but becomes effective at much higher frequencies. (and for the very same reason, any Zobel filter (RC across the secondary) is based on the load that the primary reflects to the secondary (overly simplified). again: without a load on both windings, the transformer has no impedance,
Consolidated Audio Berlin, Michael Ulbrich may build the best SUTs today. My next one will be a 1:15 silver SUT from him.
It should be even better than the Kondo SUTs, and that should mean something!
Your technical description is excellent!