Clarification of cartridge output voltage?

[jrebman]

I saw this statement on the Eros product page and need some clarification:

Because of the varying levels of phono cartridges, a S/N ratio figure cannot necessarily
tell you how the preamp will behave in your system. The Eros was designed to have
10dB more gain than our Seduction kit, and it may be more suitable for high output
moving coil cartridges and moving magnet cartridges with an output level lower than
2.5 mV.

So what would be the downside of using a cart with a 3.5 mv output?

I'm still not sure if I'm going to get back into the whole licorice pizza thing, but I'm seriously considering it and the cart I'm looking at is rated at 3.5 mv (Clearaudio Maestro wood).

Thanks,

Jim

 

[Paul Joppa]

3.5mV is fine, and should give excellent performance. Today I would estimate that the sweet spot for Eros is 1.5 to 5mV, and for Seduction 3 to 10mV - but tomorrow I may say something different.

Even though I wrote the white paper (posted under "Community") on signal to noise ratio, the whole subject still frustrates me. Now that we've been working on an MC stepup device to replace transformers, I am diving into the question again. There are quite a lot of data and even more opinions - and that's just in the peer-reviewed academic papers. The papers are not very consistent with each other, and even less consistent with our experience. Internet claims naturally cover an even wide range.

Here's the basic example: our first phono product was the Seduction, still in production after 9+ years. Good solid product, with 40dB midband gain when the C4S is installed. The math works really well - a 3.5mV cartridge makes a nominal 350mV, very close to the unbalanced consumer level of -10dBv or 315mV. Assuming the normal headroom of 14dB for tape and vinyl, that's a peak output of 1.75v, which is very close to the CD standard of 2.0v peak. So you would expect vinyl and CD to be equally loud. But almost everyone who has a Seduction has noticed that the phono is significantly quieter that CDs and they have to turn the gain up, usually by 6 to 9dB (2 or 3 clicks of the Foreplay level control). Clearly, either the levels or the headroom assumptions are not typical of the recordings that people are listening to! Incidentally, this is the reason Eros has more gain - when theory does not match our customer's reality, a good engineer accepts the reality. A good scientist of course looks for a better theory, which is what I am also trying to do.

It gets worse. Shure published a lot of work on peak levels back in the day, and claimed that peaks can be more than 20dB greater than the nominal (maximum VU). For the Eros, that corresponds to a 10v peak output with a 3.5mV cartridge. Eros can handle it, it runs out of steam somewhere above 20v. But if that were really happening then the downstream amplifier would be clipping severely unless the preamp is turned way, way down - which nobody does in practice because you can't hear the music then. I can only conclude that such high recorded levels are extremely rare and unusual.

That's where it stands today, to the best of my knowledge.

 

[jrebman]

Thanks, Paul, especially for the detailed explanation.  Yes, it certainly is yet another of those perplexing questions that no matter how much you try to predict with engineering, the real world just seems to let you know that there's more to it than meets the eye.

That said, I'm still very much on the fence about the whole vinyl thing -- I would be starting from scratch, have no LPs left anymore, and I've put a lot of effort and money into my digital rig and it easily bests lower cost TT options, but I empasize that it was not inexpensive and was not exactly plug and play, and there are still more upgrades waiting for me to try them once I get my new speakers.

BTW, this not a slam against vinyl at all, and if I had a collection of music on LPs, I certainly wouldn't hesitate.

And then there's that dangling carrot in the form of a pair of balanced HD-800s that I would probably get far more use from.

Thanks again,

Jim

 

[jrebman]

Ok, so after a number of attempts to find a Thorens TD-124 that was in reasonable condition, had a decent arm, didn't cost too much, and was not a "project" table, I threw in the towel and went back to my other, well-researched choice, a Clearaudio Concept TT -- which I found a very lightly used one for a good price.  Also found a essentially new old stock Clearaudio Aurum Beta S wood for a fine price, so looks like the Eros will be next.  The Beta S is very close in voltage to the Maestro, so if and when I end up upgrading, there won't be any issues.

Just decided to get a decent, modern table that requires very little in the way of setup and adjustment and as a bonus, can run on the same quality battery power supply that my Mac Mini uses, which is said to give a nice performance upgrade to the stock poer supply.

So, the first jump into the land of vinyl (or re-jump as the case may be) is done, now just need to order and build an Eros -- soon...

-- Jim