Matching SUT's and cartridges

[Intenso]

Anyone know much about SUTs and matching?

I've recently been loaned a AT630 to match with my Ortofon Quintet Bronze to see what a SUT might bring to the party before spending.

Whilst it improves dynamics and detail I've begun to notice an edginess to the treble that wasn't there before.

I have no specs on the AT630.

Would this suggest a mismatch between SUT and Cartridge?

[walpurgis]

I've had a few AT-630'S come my way. I moved them on quickly. They're not great. Can't comment on the match with the Quintet.

[hifi_dave]

It's not the best MC step up out there, just a stop-gap really. A good MC cartridge with an indifferent step-up is probably worse than a MM cartridge.

If you want an excellent but very reasonably priced step-up, visit the Rothwell website www.rothwellaudioproducts.co.uk

[RothwellAudio]

Most step-up transformers aren't labelled with what I consider the most basic information - the turns ratio. If I remember rightly the AT-630 has a ratio of 1:14, which is about right for the Ortofon.
Are you confident the edginess is down to the step-up transformer? Or could it be due to a slight misalignment of the cartridge? Have you tried the cartridge with another phonostage or SUT?

[walpurgis]

A good MC cartridge with an indifferent step-up is probably worse than a MM cartridge

Very true.

[Intenso]

Well someone on fb gave me the following advice and it has completely removed the edginess with much improved sonics. Not sure where that leaves me when I upgrade to a MM valve phono stage shortly?

'Tony looking at the Vanguard II manual and the input impedance of the phono pre can be changed a bit. I would try the 1.7K setting and see if that improves the sound. Using that seeting the cart will see a load of 17 ohms, still lower than the mfr recommendation of >20 but will head you in the right direction. In the current situation your cart is seeing a load of 470 ohms. If the HF irritation is gone that will give you an idea of what loading you should target when buying an SUT. Take a look at the Rothwell site for finished SUT's and Sowter for transformers, both UK based.'

[RothwellAudio]

Well someone on fb gave me the following advice and it has completely removed the edginess with much improved sonics. Not sure where that leaves me when I upgrade to a MM valve phono stage shortly?

'Tony looking at the Vanguard II manual and the input impedance of the phono pre can be changed a bit. I would try the 1.7K setting and see if that improves the sound. Using that seeting the cart will see a load of 17 ohms, still lower than the mfr recommendation of >20 but will head you in the right direction. In the current situation your cart is seeing a load of 470 ohms. If the HF irritation is gone that will give you an idea of what loading you should target when buying an SUT. Take a look at the Rothwell site for finished SUT's and Sowter for transformers, both UK based.'

That fb (facebook?) advice is both right and wrong. It's absolutely right in that a lower impedance load - 1.7k in this case - on the transformer's secondary will affect the performance. It's also right that the cartridge will see a lower impedance load. However, it's wrong that the effect on the performance is due to the cartridge seeing a lower impedance load (if that is what the advice is claiming). The reality is that the transformer's performance is being affected, not the cartridge's.
It could be argued that is doesn't really matter whether the added load affects the cartridge or the transformer - the result and what you hear is the same. I would argue that it does matter because it misleads people into thinking that the same will apply when using an mc phonostage, ie that a particular load on the cartridge is somehow "correct". The logic goes something like "my mate's Brand X cartridge is loaded at Y ohms and sounds great, so I'll set my phonostage to that load impedance". Yes, but if your mate is using a step-up transformer and you're using a solid-state mc phonostage, you're dealing with different things.
What's most likely happening is that the transformer is suffering from overshoot, causing an edginess to the sound, and the added load is damping the overshoot. The transformers I make already have the overshoot issue dealt with by incorporating an optimised load network rather than a simple resistor. A simple resistor will damp overshoot but can also end up throwing away the voltage gain which you're using a transfor for in the first place.

Anyway, the fb advice is absolutely correct when it says "take a look at the Rothwell site for finished SUTs..."

[Intenso]

Thank you Andrew for that detailed response.

I think I've already made up my mind that I will be purchasing a Rothwell SUT or even the Headspace shortly as soon as my new tube MM Phono Stage arrives.

My dilemma is now which to choose...

I'm hoping that I may be able at some point to have a home demo to help with the decision

[RothwellAudio]

^ You're welcome
Ortofon's cartridges are all pretty transformer-friendly. They have a nice, low source impedance (5 ohms for the Quintet Bronze), which is a good thing, and their output voltage is quite high - or at least a lot higher than their cartridges from the 1980s.
The Quintet Bronze should be happy with any turns ratio in the range 1:10 to 1:20. Since you're considering a valve phonostage you might want to maximise the signal-to-noise ratio by having a turns ratio at the higher end of the range rather than the lower.

Anyway, I'm glad you've cured the edginess you were experiencing. Most problems have a solution

[DSJR]

At the price n AT630 now goes for (I've got the Dual labelled version and it suits my Ortofon MC30 Super quite well and I thought it better than my Lentek, which eats batteries and sounds lean toned - it was designed for the original Entre 1 which Lentek distributed), you could get a Tisbury head amp, now reportedly with a 100 ohm MC loading which I think is safe for most MC types. No idea whatsoever if it's any good and how different it is from the Schiit Mani, but a not-quite-right SUT can't be as good.

Decent transformers for this purpose aren't cheap and even if you are to make your own, I think a couple of decent? Sowter ones are over £150 for a pair with OCC wiring I think and that's before a posh case to put them in.