to SUT or not to SUT- that is the question

[kip.duff]

My Lyra Skala cartridge has 0.5mV output and 5.4 ohm impedance.  Will be running into Eros 2 > BeePre > Paramount 1.1 300B monoblocs > Altec A7 Voice of the Theater speakers (efficient).  So there may be enough gain without SUTs.

Usually, in an audio circuit, less is more.  However, is this a case where insertion on a component (SUT) can improve sound quality even if there is enough gain/db speaker output without them?  I ask this question not because I'm trying to save money by not buying an SUT. 

General pricing on SUTs is not bad at all- and I already have some Lundahl LL9226 1:10 SUTs.  Also, Sowters are affordable and I really like the neat, clean install provisions on the Eros chassis plate.  But then of course there's the fly in the ointment: other brands like Bob's devices claim to be significantly better- but don't have a neat install and are big $.  Any feedback or advice appreciated.....

[Paul Birkeland]

  So there may be enough gain without SUTs.

There will be waaaay too much noise (tube rush) though!

Also, Sowters are affordable and I really like the neat, clean install provisions on the Eros chassis plate. 

Yes, this is the way to go.  The Sowters aren't particularly expensive and they have a good selection and a clear explanation about what to use where with a reasonable amount of detail about their products.

But then of course there's the fly in the ointment: other brands like Bob's devices claim to be significantly better- but don't have a neat install and are big $.

Bob's Devices uses Cinemag transformers.  The Cinemag CM-1254 with the threaded bushing option will mount to the Eros plate and is their TOTL step-up transformer that costs about $180 each. 

I tend to favor Sowter at the moment because of the currency exchange rate.

[grufti]

The numbers for your Lyra don't lend themselves for just one perfect SUT match. You would want a 1:10 SUT (20dB gain) to get just about 5mV for the Eros 2. That gets you a reflected load from the 47kOhm input impedance of 470R. That's right around 90 times the cartridge impedance of 5.4R. It's not ideal.

[kip.duff]

Well the discussion of loading is still not totally clear to me.  This is made somewhat easier by the fact that Lyra (and most cart manufacturers) say "tune loading to taste" (a bit tedious).  Attached are Lyra's specs on the Skala.  I used the K & K / Lundahl Excel calculator to do some preliminary specs (attached).  I think I will remove the existing 47.5k stock resistor in the Eros 2 and use single (non parallel) Rs as I experiment.  There is also the discussion of possible use of caps here for Zobel network.  I have to go to work, otherwise I would have made this post a little more detailed.  Would love to hear some opinions on this... Thanks for great responses......

[Paul Birkeland]

Those numbers seem reasonable. 

[grufti]

The Zobel network / cap is where it all gets complicated. You would need to verify the results with a frequency generator and scope. Your cartridge already sees capacitive loading from the EF86 tube. I can't tell you how much in the Eros 2 circuit. It could be the perfect amount or not. In a perfect world the Zobel network eliminates most of the ringing after a step response / square wave.

[Paul Birkeland]

I can't tell you how much in the Eros 2 circuit.

It's almost nothing, like 4pF or so.

[kip.duff]

Getting ready to order SUT.  Setting the issue of price difference aside,  does anyone have any experience, feedback, or opinions  on Cinemag vs Sowter?  Considering the investment we have in our hi-fi systems, I’m not going to quibble about the price difference if I have reason to believe that I would be happier with Cinemag.   I know that Doc mentioned Sowter so that means to me that you are familiar with their use in the phono stage. That is a good reason right there for me to go with the Sowter.

Thanks.....

[Paul Birkeland]

I would also recommend Sowter for this application.

[kip.duff]

I would also recommend Sowter for this application.

Thanks.  They have OCC silver option so I'm seeing if that takes too much extra time.

[DesignTaylor]

Hope I don't offend anyone piggybacking onto this thread but seems to be the closest to my query.

I've got an original Eros (which I love and have dialed in with all my favorite tubes) but in the past when I've tried running MC carts I found that I would need to crank the system up to the point where I became too aware of background noise. I settled on a high output MC cart (Denon DL-110) but I'd really love to give the DL-301ii a try. I've been reading a lot about SUTs / step-ups and trying to figure out the right amount of loading or the best boost ratio.

How much do I need to bump things up to avoid having to overly amplify the output from the Eros? Am I even on the right track here?

Thanks!

[Paul Birkeland]

How much do I need to bump things up to avoid having to overly amplify the output from the Eros? Am I even on the right track here?

I would aim for 5-6mV.  The DL301 is in a weird spot because it's slightly high at 0.4mV, but a suitable 1:10 will get you in listening range.  This is part of the reason why I gravitate toward the Ortofon offerings, as they are a bit more flexible.

[DesignTaylor]

Thanks for the feedback! I've heard good things about the Ortofon MC Quintet Blue as well but that one is trickier to get in my price range.