Most SUTs, the gain and impedance load are inter-related, some SUTs have optional but not separate settings, like my Fidelity Research FRT-4, but the 4 optional choices are still inter-related, i.e. more gain = lower load. (Load = typical 47,000 ohm phono input divided by the chosen x factor squared),
SUTs or Phono Stages with separate gain and separage load settings are needed for some cartridges, as the standard ratios don’t fit properly.
Soundsmith says Paua output 0.4mv signal strength, it’s coil is 10 ohm resistance, (very much like my AT33PTGII 0.3mv/10 ohm coil). The strange to me part is they advise a load of greater than 470 ohms?????
industry guidance for MC impedance load says try coil impedance x 10, i.e. try 100 ohms. anybody know why they advise 470 ohms for their 10 ohm coil?
GAIN: they advise a TOTAL gain of 58-64db, keep in mind, that is total, including whatever your MM phono is doing AFTER you pre-boost with a SUT.
i.e. my SUT boosts my AT33PTG 0.3mv x 20.68 x factor (+26db) thus up to 6.20 mv that I then send into my MM Phono input for RIAA EQ and it’s gain. Luckily it does not over-load the MX110z’s phono stage, not sure what it’s limits are.
My SUT has a 10.55x gain option, (+20db), the load is 423 ohms, closest to Soundsmith’s stated 470 ohms.
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btw, My experience: my SUT does NOT have a sound characteristic of it’s own, it is dead silent, simply and passively boost a too weak signal, allows me to use my existing preferred MX110z Tube MM Phono Stage
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Atmasphere is also all tube high gain phono, as I mentioned earlier. I’ve owned an MP1 for two decades upgrading along the way. I also owned an Aesthetic Rhea Signature but not the Io. The Rhea is amazing for its remote controlability but was a tad noisy compared to the MP1 when I cranked up the gain.
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I have two low-output MI cartridges, one of 0.4mV output, which requires an MC input or external SUT, and the other with 1mV output sounds better that way (but could be connected via an MM input and the gain turned way up).
I have three ways of doing it - using the Musical Fidelity NuVista Vinyl and setting the input to MC, using the Quad 24p set to MC (with internal SUTs), or using an external SUT and the Quad set to MM. The last of these sounds the best of the three, so that is what I do.
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Yes, it's a moving iron but a very low output, similar to a low output Moving Coil.
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It is moving iron, but it has a .4 Mv output.
The approach of using a hybrid transistor and tube to supply the needed gain for low output cartridges is to reduce the level of noise from using tubes exclusively.
The use of a SUT also reduces noise as an issue and adds the sonic signature of a transformer. If you want tube only amplification (no transistor stage or no SUT) you have far few alternatives. I mentioned Aesthetix earlier as an all-tube design that sounds good (if a bit noisy); another good sounding example is made by Lector (quiet for an all-tube design).
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I checked and the Paua is indeed a moving iron cartridge like all the others in the Soundsmith line.
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Isn't the Soundsmith Paua a moving iron cartridge? That's the mechanism used by Grado and some others. No SUT required.
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The Herron phono stage, now out of production but possibly available pre-owned, is another that achieves high gain with an FET based input stage followed by an all tube circuit. It was very highly regarded, one might say venerated, by some who frequent this site, before Herron closed down.
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@rmcfee
I am quite familiar with both the Zesto and the Paua.
The Paua needs to see a load of at least 470ohms.
I fiound with my sample the optimum load at 1000 ohms.
I would strongly suggest you try on the moving coil input on the Zesto both the high and low MC input settings and both the 400 ohm and 1000ohm settings to find the best combination.
If you try an external SUT you must ensure that the SUT has a maximum turns ratio of 1:10 to be sure the Paua is loaded at a minimum of 470 ohms.
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My vinyl setup is a VPI Scoutmaster II table with a Soundsmith Paua MkII cart.
I had a MM cart before so this is the first time I've used the Low Gain MC circuit in my Zestos.
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Great info and advice! Thanks so much.
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Please don't take what I am about to say the wrong way. Whether an SUT would be to your liking or not is a subjective decision. It really depends on what distortions your tastes prefer. Everything has distortion. Tube phono stages have different and generally higher levels of distortion than is typical for similarly priced solid state units. Then you add an SUT and two (inlet side and outlet side) interconnects, which adds just a bit more distortion and perhaps noise as well. Against that the SUT adds greater signal, which can improve signal to noise ratio and of course every SUT has a certain audible signature (yes that is distortion but it can be and often is pleasing to the ear). So you see the addition of an SUT is not as simple or straight forward as it might seem at first glance. The only way you can answer your question is to try one and let your own tastes be your guide. No one can properly advise you beyond what I have suggested here. This is something you have to do for yourself. BTW, FWIW, in one of my systems I use a recently acquired Conrad Johnson ART Phono (their latest and greatest tube unit) with most often a Conolidated Silver Wire SUT although the C-J has enough gain to not need an SUT, so depending on cartridge and mood I often opt to forego the SUT. I also have a Bob's Devices SUT which has a warmer sound and that is used too. In my other system the phono stage is a PS Audio Stellar all solid state and it is used stand alone. There is no right or wrong in this matter, no one size fits all circumstances, and in spite strong opinions strongly expressed in this forum and others like it, there is no one best solution.
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The Zesto employs a step up transformer for its MC input. If you go with a separate step up transformer into the MM input, you will be substituting step up transformers. Whether you will like an alternative step up transformer is dependent on the quality of the alternative, compatibility with the phono stages, compatibility with your cartridge, and personal preference.
The cost of any alternative step up transformer would also have to factor in the cost of another pair of interconnects. Some of the better standalone devices can be quite high. The right choice depends primarily with your chosen cartridge, and some companies even wind them specifically for your cartridge. If you go that route, you might want to learn a lot more about matching.
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The Zesto employs a step up transformer for its MC input. If you go with a separate step up transformer into the MM input, you will be substituting step up transformers. Whether you will like an alternative step up transformer is dependent on the quality of the alternative, compatibility with the phono stages, compatibility with your cartridge, and personal preference.
The cost of any alternative step up transformer would also have to factor in the cost of another pair of interconnects. Some of the better standalone devices can be quite high. The right choice depends primarily with your chosen cartridge, and some companies even wind them specifically for your cartridge. If you go that route, you might want to learn a lot more about matching.
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The Zesto employs a step up transformer for its MC input. If you go with a separate step up transformer into the MM input, you will be substituting step up transformers. Whether you will like an alternative step up transformer is dependent on the quality of the alternative, compatibility with the phono stages, compatibility with your cartridge, and personal preference.
The cost of any alternative step up transformer would also have to factor in the cost of another pair of interconnects. Some of the better standalone devices can be quite high. The right choice depends primarily with your chosen cartridge, and some companies even wind them specifically for your cartridge. If you go that route, you might want to learn a lot more about matching.
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My Zestos does have a MC section - it has settings for Low Gain or High Gain.
My confusion was because a friend with the same phono preamp as mine was telling me a SUT would improve the sound. And others online were saying similar things.
Your Zesto Andros already has SUTs for MC application internally, followed by an internal tube MM phono section. They are Jensen's as used by Lamm, Conrad Johnson, ARC and others.
You would only benefit from using an external SUT if it was higher quality or suits better your cartridge than the internal SUT's in the Zesto. Having installed a Zesto with a variety of top MC's it is a very flexible SUT with multiple loading options. You would have to spend large to get a significant improvement.
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Thanks for all the responses - it's great to have access to all the experience out there.
My Zestos does have a MC section - it has settings for Low Gain or High Gain.
My confusion was because a friend with the same phono preamp as mine was telling me a SUT would improve the sound. And others online were saying similar things.
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Aesthetix offers all-tube high gain phono stages which I like, but, they have more noise than most tube stages employing only tubes for active amplification. Among my favorite tube phonostages are those made by Audio Note which require an additional step up transformer, Zanden (built in transformer), and Viva (built in transformer).
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There are many fine quality tube based phono stages that offer sufficient gain for a LOMC cartridge and do not contain a step up transformer internally. Many of those use a solid state or hybrid gain stage in order to achieve that goal (Manley, probably ARC), but some even do it all with tubes (Atmasphere) and that can be done while preserving a good signal to noise ratio, contrary to what some will say.
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I recently purchased a Zesto SUT for an EAT eglo petite tube hybrid MM/MC phono stage. The overall sound from the Rega Aphelion2 cart is fuller with the SUT with MM gain settings compared to without SUT and higher gain on PS. The SUT adds a bit of transformer hum, but cuts the tube hiss. This is not noticeable at normal listening levels, only when I put my ear right next to speakers with nothing playing.
I am also thinking about upgrading my PS, and given the various flavors of noise, I may tend towards a SS PS. No idea what kind yet.
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Most tube-based phonostages either have built in step up transformers or expect the buyer to use his own step up transformer to supply enough gain. The typical tube-based phono stage would need to add more tubes and would run the risk of excessive noise if they tried to supply the needed extra gain without using a step up transformer.
The extra gain needed for low output moving coil cartridges can more easily be supplied by solid state phonostages so they rarely include one in their design.
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I think you already have stepups in your Zesto. Most of the MC phonostages I am aware of seem to use SUTs.
Bill
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