Mono cartridge classification

Oooh, boy. This is a pretty complex area you're getting into. Google will be your friend. The wide range of contradictory information you find will be your enemy. I'm just learning about the world of mono myself, so take everything I say with a grain of salt. And I hope those more knowledgeable will double-check me. But here goes:

That symbol you're talking about is almost certainly the symbol for micron (also called a micrometer). The thing to remember is that 25.4 microns equal 1 mil. Generally, you will see today's typical elliptical stylus dimensions stated as .3 mil x .7 mil. These serve well for playing mono records. When you see a stylus specified in microns, just convert it.

Despite the fact that I said a .3 mil x .7 mil stylus is fine for mono records, many people maintain that it is best to use styli that are similar to those used at the time the recording was made. VERY GENERALLY speaking, records that are not labeled either "mono" or "stereo" are mono recordings. These, according to some, should generally be played with spherical (aka conical) styli of 1 mil (25.4 microns). If the record is labeled "mono," it was probably made during the early stereo era. Since the record grooves were narrowed at this time, it's GENERALLY best to play these records with spherical styli of .7 mil.

Modern high-end cartridge makers like Lyra are today making very expensive mono carts and maintain that variations of modern fine-line styli are best for playing mono records.

Also be aware that cartridges that are sold as mono carts actually do produce a mono signal (Denon DL-102, Grados). But some are called mono only because they have a bigger spherical/conical stylus appropriate for mono recordings——BUT their output is stereo (Ortofon D25M, I think). The signal must be summed by a mono switch on a preamp, by wiring the cart for mono, or by using a double-Y connector to sum the signals.

Keep in mind that in discussions of mono, the term "LP" is used to refer to 33-1/3 RPM records, as distinct from 78 RPM.

If this isn't confusing enough for you, I invite you to hit Google. A very good summary is offered here:

http://www.esotericsound.com/CartStyli.htm

There's also a mono forum at Lenco Heaven:

http://www.lencoheaven.net/forum/index.php?board=18.0

Hope this helps, but I'm guessing it might not!
-Bob

Sorry. The first sentence of my fourth paragraph, above, should read:

"Also be aware that SOME cartridges that are sold as mono carts actually do produce a mono signal (Denon DL-102, Grados)."

-Bob

Hesson11, I've posted comments on selecting stylus size relative to the records to be played here and elsewhere and thank you for your added descriptions. I've also read the suggestion that Lyra narrow profile styli are recommend for mono playback. But then I ask if the Lyra recommendation was for modern mono reissues (cut with current stereo cutter heads as apparently no mono cutters remain) as compared to original '50s monos cut with a wider groove? So far, I've not seen an answer to that.

Also, you include mention of Grado as an example of "mono carts (that) actually do produce a mono signal". My understanding is that a true mono cartridge will only pick up lateral motion, not vertical. Several sources have suggested that Grado mono cartridges are merely stereo designs that have been strapped internally for mono output. In other words, they still pick up vertical signals, thus would be more susceptible to noise. Have you found a confirmation one way or the other?

Lastly, I'm not aware of any manufacturer who claims a cartridge is mono simply because it has a conical stylus. Do you have an example? Many early stereo cartridges had conical styli, the current survivor being the Denon 103.

Thanks for checking me, Pryso. I need it! Still learning.

Here is a post by Jonathan Carr of Lyra that says Lyra listened to a wide range of mono recordings in developing their stylus. He says the records were both pristine and well-worn, but he doesn't cite the eras they represented. I assumed that by well-worn, he meant they listened to records from many eras, but he doesn't explicitly say that:

http://www.audioasylum.com/cgi/t.mpl?f=vinyl&m=418745

About Grado, I was careful to say that they produce a mono signal. As you said, I believe they are "mono carts" in that they are strapped to sum the L and R signals. Like you, I believe I've read that they do have vertical compliance, but I can't be sure. So they probably can't be considered TRUE mono carts like the Denon DL-102.

For your last question, the KAB website states that the KAB/Ortofon OM-1M is a stereo cart with a 1.1 mil stylus for mono playback. I believe this cart is the same as or similar to the Ortofon OM D25M, but I may be wrong about that. Do you know for sure?

I wish I had time to track down and post all the references I've drawn from——but I don't. So I hope others like you will continue to fact-check me. Not that we'll ever solve all the contradictions of mono! THANKS.
-Bob

Hesson11, thanks for the link to Carr's information. Nothing like going to the
horse's mouth! Here is information I posted on VA some time ago. Mr. Carr's
information seems to correct part of that -

"I believe you must first consider which records you will be playing before
buying a mono cartridge. From reading I've done, here are my conclusions.
Note this applies only to 33 LPs, not 78s. Dates refer to master cutting, not
performance date for reissues. This is a function of the groove shape created
by the cutter head.

Pre-stereo era monos (roughly '48-'57), select a 1.0 mil conical stylus.

Early stereo era monos (roughly '58-'68), select a 0.7 mil conical stylus.

Recent mono reissues (mid '90s to present), select a mono cartridge with a
modern narrow stylus profile.

Lyra may have been the first to promote narrow profile stylus tips for better
performance in mono cartridges. I suggest this may be true for playback of
the many mono reissues, but not as good for older originals. I've heard that
mono cutter heads are no longer available so reissue monos are now cut with
stereo heads, but with lateral motion only. This is not to say a mono cartridge
with a narrow profile stylus would not sound OK on earlier pressings, it
simply would not be optimal."

I've since purchased a mono Denon 102 but installation awaits the
completion of a new plinth for a two-arm table.

I'm not familiar with Ortofon cartridges so no help from me there.

If you think there are lots of contradictions with mono lps, start doing some
research on 78s! I have a 4-record 78 album of Louis Armstrong and the All
Stars at Town Hall, a very famous concert from 1947. I began researching 78
cartridges and that is where the waters really become muddy, and deep.
You've got to add speed and EQ variations to the various tip dimensions. At
least the situation was a little more standardized by the late '40s for my
album.