Passive SUT vs. active MC preamp?

[Mika K]

Lately I have been hearing some opinions that active MC preamp has proved to be superior in some systems that passive SUTs. Have heard this at my friends system while comparing Technics SU-300MC with the top class Ortofon SUT, so..

http://www.link-audio.be/su-300mctweeLR.jpg

According to my limited experiences with quality SUTs they usually exceed in the mids and especially in timbre, transparency and that kind musical openness which is hard to describe. However the active MC preamps might have advantage in rhythm, scale and dynamics, which in many cases is the achilles heel of SUTs. In my opinion at least some SUTs seem to lack that final punch and dynamics, even with nice synergetic cartridge and quality phonostage, and this might make the whole system sound a bit too soft..

What do you think of this, so is there something real here or are there SUTs that match the active MC preamps in all respects? Do you have experiences of the active MC preamps or even use one?

[Mika K]

Just realized that someone not familiar with these (as they're quite rare) might be thinking that I'm trying to compare here SUT to proper full MC phonostage but that is not the case. I'm referring to active MC preamps that are connected to MM phonostage just like SUTs..

Come on, someone must have experience of these :cool:

[The Grand Wazoo]

That would be a head amp as compared to a step up.

(..........the term head amp had another meaning before the people who use headphones all lost the 'h', 'o' and 'n' keys from their keyboards!)

[Barry]

That would be a head amp as compared to a step up.

(..........the term head amp had another meaning before the people who use headphones all lost the 'h', 'o' and 'n' keys from their keyboards!)

And "p"s ? :lol:

[The Grand Wazoo]

No....they need the 'p' (and the 'e') to spell head amp!

[Barry]

No....they need the 'p' (and the 'e') to spell head amp!

Ah yes - "think before you type". My excuse would be the half bottle of Médoc I have just consumed!

[The Grand Wazoo]

Keep drinking - a full bottle brings clarity to your lexicography (or it has to me this evening .....hic!)

[Barry]

I ought to respond to Mika's thread, as like most things in audio alternative ways of going about things all have their 'pros and cons', and I will do so. However it is late, so I'll defer my comments to a later time.

But in general, I'm largely in agreement with Mika's opinion. I have used both SUTs and head amps (some of the latter I have built myself), but for most of the time the head amps have been in use. I did have a notion to do such a comparison again, however the SUTs I have are hardly the 'last word' for such devices.

Will write more later.

[Mika K]

Nice one Barry! I already got myself a little worried that the thread will stay empty.. :)

[sq225917]

I'm genuinely interested in the answer to this I've never tried a step up but struggle to see how it can be 'better' than a low noise active gain stage. I get that the crosstalk and limits of FR extension can be pleasant in some setups but electrically speaking what can they add/ remove that an active stage can't?

[hifi_dave]

As usual, it depends on the units you are comparing. Some head-amps (active) are very good but some are very bad. Some step-up x'mers are very good and some are very bad.

If you already have a very good phono stage, addding a step-up/head-amp is the way to go. If your phono stage is average, it might be best to consider a better complete phono stage with MC capability.

[Mika K]

Exactly. And also system synergy is very important. The most important interface is the cartridge to SUT/head-amp as that really defines what you can achieve. Then after that also SUT/head-amp needs to work well with the used phonostage. These naturally also include cables etc ;)

I have really good sounding MM tube stage at my Shindo preamp, so it's natural to choose some option that I can use with this and my main cartridges. I have been using few SUTs but still don't have the best pairing here. Is the next solution SUT or head-amp I do not know. And of course can always add other separate phonostage at some point for my decks but still..

[Rowlf]

I have never used a setup. One area I could not understand with step-up though, is that the you cannot change the values of the input impedence, which was set for a MM cartridge. How is that going to work? Or have I got that wrong?

[hifi_dave]

The job of a step-up or a transformer is to load a MC properly and supply the extra gain needed to work into a MM input.

[Rowlf]

Is that to say there will be settings on the step up transformer to set the impedence to 100ohm? And leave the MM phono at default 47k ohm?

[hifi_dave]

Some SS step-ups and x'mers do have a few loading options but not all. The input impedance of the MM stage is usually 47K.

[Chris]

I use a souped up (Salas Shunt regulated) Hagerman Piccolo in front of my souped up (Salas Shunt Regulated) P10 MM stage with teflons and Tantalums all over the place and from my dim memories of my Haufe SUT used with a 103Pro into a Lehmann Black Cube I w2ould agree with the OP´s suspicions. The SUT combination was "nice" - my present set-up is "big and evil". But no idea what´s doing what.

[Barry]

SUTs vis à vis Head Amps


Moving-coil cartridges tend to have a much lower output than that from fixed coil designs. To allow moving coil cartridges to be used with preamplifiers having a standard sensitivity of 2 – 3mV, with a load impedance of 47kΩ, additional voltage gain has to be provided. This can be achieved in one of two ways: through the use of a step-up transformer (SUT) or by using a specialised amplifier, a so-called ‘head amplifier’.

Like many things in audio, where there are alternative ways of doing things, it does not necessarily follow that one method is preferable to the other: each have advantages and disadvantages.

Step-up Transformers (SUT)
The first moving-coil cartridges used a SUT to provide a suitable voltage output. Often these transformers were integral with the cartridge, later to relieve the cartridge weight the two were separated, making the transformer an ‘off-board’, item.

Transformers have much to commend them. The most obvious is that of simplicity, and with it reliability: there is little to go wrong or fail with a transformer. Another advantage is transformers have a very low noise figure. They are passive devices (they achieve voltage gain, but cannot produce power gain) so the Nyquist (thermal) noise generated, being determined by the resistance of the windings, will be low - lower than that of a head-amp.

Transformers can have a sufficiently wide bandwidth: a response 10Hz - 20kHz, flat to within 1dB, is readily achievable with good design. The design of the transformer core will largely determine the low-frequency response, whereas the high frequency response is largely determined by the intra-winding capacitance. The frequency response will depend on the loading of both the windings. Excessive preamplifier capacitance will tend to suppress the treble response, whereas a low cartridge coil resistance will curtail the bass.

The voltage gain provided by a transformer is given by the turns-ratio, that is, the ratio of the number of turns of the secondary winding to that of the primary. Thus if the secondary winding has 10x as many turns as that of the primary winding, then the voltage gain will be 10:1 (≡ 20dB).

Just as the voltage will be increased by the turns-ratio, so the current be reduced by the same amount. This means the impedance is ‘transformed’ as the square of the turns-ratio. So taking the above example, a 10:1 transformer will transform the input impedance of the preamp by a factor of 100, that is, the nominal 47kΩ impedance will be reduced to 470Ω, and this is the impedance that will load the cartridge. In general it is best to provide a load that is at least 3x that of the coil resistance. A figure of 100 - 200Ω is usually recommended, and will be achieved by shunting the secondary transformer winding with a resistor.

However, as far as the preamplifier is concerned, the transformed cartridge impedance provides a poor match to the preamp. A typical preamplifier fixed-coil cartridge input is designed to achieve its best noise and bandwidth when fed from a source of 1kΩ or less. Some moving coil cartridges can have a coil resistance of 30Ω and require a gain of 20x (26dB), so the transformed impedance as seen by the preamplifier will be 12kΩ.


Head amplifiers
Head amplifiers are specialised audio amplifiers designed specifically to load the cartridge with 100Ω or so, provide a gain of up to 30dB with low noise. They are much more versatile than transformers: the loading and gain is virtually independent of frequency; and the frequency response itself is as wide as is necessary.

Being much more complicated than transformers, and involving possibly dozens of components they will of necessity be less reliable. Amplifiers cannot be a low noise as transformers. One way to achieve a low noise figure is to use multiple transistors in parallel, though there is a limit to how many can be used; eight seems to be the limit before problems due to Miller capacitance start to have an effect. A very few head amps use a pair of ‘low noise’ triode valves in parallel. As a guide, a moving-coil cartridge having a coil resistance of 3.3Ω will have a noise voltage of –147dBu, whereas discrete transistors (such as a 2N4403) will have a noise of –135dBu and the best integrated circuits have a noise of no better than –125dBu. These figures are to be compared with a typical cartridge output of say –73dBu. What this means is a typical solid-state head amp can have a signal to noise ratio of 80dB. Being active devices they need a power supply, which can impact on the noise performance - enthusiasts will use batteries to achieve the best performance possible.

Whilst producing a very flat and wide frequency response, the overall distortion performance is also commendably low, though in the mid band transformers can often display lower distortion than their head-amp counterparts.



So to summarise, transformers provide a simple, reliable means of providing voltage gain, with an adequately wide and flat frequency response, provided care is take with the loading on both windings. Despite being the lowest noise devices, the overall system noise performance will not necessarily be optimum. The mid-band distortion via transformers can often be lower than that of head-amps.

Head-amps are more versatile providing adjustable loading and gain that is independent of frequency. The overall system noise performance can be better than those using a transformer, and the distortion will often be lower at the frequency extremes compared with transformers. Not being passive, head-amps require an external power supply.

[Marco]

Missed this thread until now, but as I have considerable experience of experimenting in this particular area with a variety of cartridges, SUTs and head amps, I'll add my thoughts later, which will hopefully be helpful to Mika :)

One question, which cartridge do you intend to use with the eventual head amp/SUT of your choice?

Marco.

[Mika K]

Cheers Marco, that's great!

I've been playing with the idea of retip my Zu modified Denon DL-103 at some point but at the moment I'm mainly using Transfiguration Phoenix II with my SUT. So the insight for this type of modern MCs from makers like Transfiguration, Lyra, Dynavector, Ortofon etc. are also equally valuable in this case..

[Mika K]

Bump!

And additional question to Marco - any change you would have experience also of the Graham Slee Elevator EXP?

[Marco]

Sorry, Mika, with the recent shenanigans with the Google Malware thing I forgot all about this thread! :doh:

Just off to bed now, but I'll get round to it tomorrow. Should I forget again, PM me to remind me! :)

Marco.

[Tony G]

Hi Mika,
I do not have the breadth of experience of our host, however I do have direct experience of the GSP Elevator and use one with a Denon DL-301 and DL-103.
My primary phono stage is a GSP Reflex and initially I used a Denon AU300LC SUT (no Auditorium 23 but designed to match the 103/301) with the Reflex.
I was sufficiently happy with that pairing to be quite uncertain about the considerable expense of the Exp. After 6 months of indecision, I purchased the Exp and from the time of connecting it up was in no doubt that I had made the right decision.
While I have generally used the DL-301 with this pairing, I recently needed to send it away for rebuild and reverted to the vanilla DL-103 and on a whim decided to try it @ 1K load rather than 100 Ohm (based on the fact that Denon test the cartridge @ 1K load). I am very happy with the result of that experiment.
By using "T" adaptors and home made load plugs on the input to the Exp, I can obtain loadings not available via the front panel switches - I prefer an approximate 220 Ohm load with the 301 and use the plugs to achieve this.
The rest of my system comprises BLH speakers driven by a 2A3 SET amp.
Perhaps this will be of some help.

[Mika K]

Maaarrrcooooooo...!!! :D :D :D

[Marco]

Lol... I know, mate. Just busy at the moment, as you can probably tell because I've not been posting much on the forum. It's on my 'things to do' list, so I'll get to it as soon as I can :)

Marco.

[Mika K]

I have now listened my friends Technics SU-300MC headamp mentioned at the first post with my own system for some days. Have also dome some direct comparisons to my japanese Impress Laboratory Model 999 SUT and it seems the differences already discussed are valid also in this case.

The SUT excels in natural presentation with the richer timbre. However on the other hand it has softer touch to the rhythm e.g. the leading edges are rounder through the bandwidth. The headamp excels in frequency extremes. Despite the whole presentation is tighter and rhythmic more capable, you can definitely tell the difference especially with the taut and firm bass department and also hear it in the highs.

I guess there might be also differencies between the SUTs and headamps depending of the system synergy but at the same time think my findings reflect the general consensus pretty well. Based on this short trial I think I'm willing to try out the GS Elevator EXP or some other active headamp at my system. But still if you have'd like to share some opinions of the subject please feel free to do so.. :)

[Nigel]

I've never heard a SUT but thought it worth mentioning that I prefer my battery powered Rogers headamp into the MM stage of my Cambridge phono amp rather than using the MC section for my moving coil cartridge.

[Marco]

Hi Mika,

Before I offer my input on this subject (yes at last...!;)) could you please confirm what preamp and phono stage you've got. The list on your signature is a little unclear as to what is what :)

Marco.

[Marco]

Lol... Ignore that. I've just scrolled back and noticed that the answer is your Shindo, which is a valve preamp with built-in valve phono stage.

Okies, laters! :)

Marco.

[Mika K]

At the moment I'm mostly using Transfiguration Phoenix II cart and the phonostage is the tube stage of my Shindo Aurieges MM preamp. I've also one old DV cart and Zu Dl-103 at my possession and have planned to retip the Zu in near future and use also that one more as really like the things that old spiced up design can do.. ;)

EDIT: Damn, Marco acted already like a ninja.. :D

[trio leo]

It's been an interesting thread so far, I used an Ortofon SPU with a transformer built into the headshell and from that into the mm section of my pre-amp so I guess from what Barry said, that is a SUT.

So is the Albarry MCA11 I use a head amp or a phono stage? does the fact it is battery powered mean it is active? It is switchable to 25.50 and 100 Ohms.

I'm not good with electrickery, but to be fair the MCA11 has lifted my system to a new level.

regards Al