Which Sowter Transformer would I use for my cartridge?

[ArtnShit]

Hi,

I am in the process of building my Eros II and am planning on adding SUT's to accompany the Sumiko Songbird Low cartridge (https://sumikophonocartridges.com/product/songbird-low-mc-phono-cartridge/).

Which Sowter transformer would adequately cover this?

Thanks in advance!
Noah

[Paul Birkeland]

The cartridge is rated for 500mV and wants a loading impedance greater than 100 ohms, though really I'd say 300 would be nice.  A 1:10 step-up will give adequate output voltage for the Eros, and I would suggest either the 9570 or the 1990.  The 9570 is a few quid less than the 1990 and is more optimized for your cartridge, while the 1990 offers flexibility down the road if you end up needing a 1:20 for a lower output (and lower impedance) MC cart in the future.

[joralieu]

I have Denon DL-S1 cartridge .18 mv output 47K ohm load. What transformer would I need if I decide to build an EROS Phono stage?
Thanks
Joe

[Paul Birkeland]

The DL-S1 is 0.18mV and calls for a load of at least 100 ohms, but the cartridge itself is around 40 ohms (some Denons are like this).  This isn't a cartridge I would recommend for use with our products since you'd really want a 1:30 step-up but the high impedance of the cartridge won't work properly with that.

[ArtnShit]

Hi Paul,

Thanks for your advice!

Quick follow-up - When you say 300ohms would be nice, would either the 9570 or 1990 be able to provide that?

Thanks!

[Paul Birkeland]

It would be nice for the cartridge to see a load of at least 400 ohms and the low output level calls for a 1:30 step-up transformer.  You could try the Sowter 1:30 with a loading resistor on the primary and an open secondary, but I'd lean a bit on PJ for further recommendations.  The issue with a 1:30 step-up is that it will step the impedance at the output down by 900x.  The 47K resistors from grid to ground become a 52 ohm load for your cartridge, which is too far from ideal.  Thankfully the Eros has extremely low input capacitance, so it is possible you could get away with the 1:30 but unless you are 1000% committed to that specific cartridge, you would be spending money on step-up devices that aren't going to work with the vast majority of what's on the market.

[ArtnShit]

Gotcha. I’m not married to the Sumiko, I was also looking at an Ortofon Quintet Black S ( https://www.ortofon.com/mc-quintet-black-s-p-549). Would this be easier to use with the 1990? I like the idea of being able to reconfigure it down the road.

Thanks!

[Paul Birkeland]

The Quintet Black would work happily on a 1990 setup as a 1:20. 

[ArtnShit]

Thanks! I am going with the quintet black and the 1990's. Are there any other resistors or components I should order in preparation for installing the transformers in the Eros circuit?

[Paul Birkeland]

I don't believe that would be necessary.

[joralieu]

Sounds like I should pony up for a quintet black if I want moving coil with eros. What would be an ideal cartridge for the eros if I decide go to mm or mi ?

[Paul Birkeland]

Most MM and MI cartridges are going to work well with the Eros, as they tend to have 4-6mV of output and are all approximately designed to work into a 47K load.