Well, until today I lived without transformer, using MC input of Gold Note pre. Painfully waiting for cartridge to break-in. However it became clear that something is not right, and midrange is lost, cartridge sounded a little harsh and almost "artificial". Now, it "competes" with Grado Statements, cartridge more expensive and just as musical as accurate, but still. So I decided to go transformer route, because what everyone and there ant recommend for SPU. And got myself Phasemation T-300. Now here are specs (relevant) - Ortofon Output voltage at 1000 Hz, 5cm/sec. 0.2 mV Internal impedance, DC resistance - 7 ohm Recommended load impedance > 100 ohm T-300 Applicable Cartridge's Output Impedance 1.5 to 40 ohm Secondary Impedance Loading 47 k-ohm Step-up Ratio ( voltage gain ) 26dB Sound definitely became more "euphonic", much softer, with way more liquid midrange. With a little slower transients and less punchy lower bass. Is this so called "famous SPU sound"? But is there a better much or this one good? (I probably should ask BEFORE I got T-300, but you know )) ). I honestly do not know. Are there any calculations to compute proper transformer values? Phono pre gain can be varied from 42 to 51 db (it is 42 now). Before it was MC with +68 gain (220 Ohm load) My ears are happy though..
OK, found on Bob's devices site calculations, end up up having 4.7mV output. Unless there is something else I am in perfect match!
I think it will be closer to 3.8mV at the phono preamp input based on the info in your first post, but should be fine either way.
I got Reflected Impedance 47000/(26*26)=69 Actual voltage 0.2*26*69/(69+7) = 4.7 Where is my mistake?
The winding ratio is 20, which equates to a gain of 26dB. You should use 20, not 26 in the equation. Reflected impedance = 47000 / 20 / 20 = 117.5 Voltage gain = 20 * 0.02 = 4.0mV Resistance loss = 4.0 * 117.5 / (117.5 + 7) = 3.775mV
Sculpture A Mini Nano SUT with 1:26 gain would be my choice with the SPU Classic G - quite astonishingly open, vibrant and engaging sound that's way better than any Ortofon SUT can manage, at a very reasonable price. The 1:26 gain ratio gives pretty much the ideal reflected impedance for the SPU's 2 ohm coils. Michael Fremer liked it: https://sculpture-a.com/wp-content/uploads/2021/04/4405_ANALOG-revised-3.pdf
Oops - I see the OP has the SPU Royal G, so actually 1:20 gain is more appropriate, but I still recommend the Sculpture A Mini Nano SUT
Yes 15-20:1 for a royal g loading >100 ohms. im using the SPU royal G with hashimoto hm-7 and it sounds fantastic. however, keep in mind that the higher up you go in the current SPU line, the further away you get from the “SPU sound.” I have a few SPU’s and the Royal G is more of a modern mc sound. If you want that rich, punchy, spotlit SPU sound then you’re better of with the Classic series or Wood A.
I actually was looking into classic line and then I was able to get Royal for half the price, so I could not resist )). may be one day I'll try classic...
The Royal is better, just not as SPU sounding I really want to try the Wood A, I’ve been told that one is special, but I think it’s just been discontinued.
I go along with that - the Royal is pretty much a modern MC cartridge in an old fashioned package and nice as it is, it does not (for me) have the sheer musical joie de vivre of the lower models, which have their flaws but are musically exciting and rewarding; even the entry level SPU#1 models are true SPUs in this respect. The SPU Wood A is the pinnacle of SPU loveliness and the late (and sorely missed) Art Dudley once noted that it "teased poetry from mere sound" , which is a nice way of saying that it's very special indeed. I am running one here into a 1:26 gain Sculpture A SUT and in most respects it's the finest thing that I've ever heard; more 'modern' MC cartridges can and do give better 'HiFi' stuff like shimmering top end detail and better tracking, but none provide such tonal richness nor give a musical 'hug' like the SPU Wood A. Shame that Ortofon discontinued it - I know why but it's a shame nevertheless.
Thank you so much, you clearly an experienced "SPU man", unlike me )). I wonder if you had similar observation while using SUT with SPU. Is itt always (may be in a different way with Royal) changes sound signature of the cartridge, or it is simply idiosyncrasy of my Phono Pre?
Others may and probably will have different experiences and opinions, but I have a very strong preference for SUTs over phono amps with active MC gain. The sound character that you described at the start of this thread ring bells with me - I think that a good and well matched SUT will open up the sound character significantly, improve tonal color, and quite simply make the music sound more 'natural' and more enjoyable. The SPU Royal is electrically a little different compared with other SPUs but with that I still prefer a SUT. Many folk think that a SUT is a simple matter of the gain ratio, but in reality there is much more to building a good one (I know, I tried). There are many SUTs on sale, old and new, good, bad and indifferent, so the key is to try some at home before buying.
