A difficult LP reproduction question

Johnnatais has answered the variable speed questions about the Lenco.

As for why this is necessary, here is a section from a page on 78 RPM disc playback.

      By no means all 78s were actually recorded at 78 RPM. Even in the late 1920s English Columbia was still using 80 RPM, and prior to about 1921 speeds were widely variable. Some of the audio tracks included in the Music hall section of this site were transferred at speeds as low as 74 RPM, and I have come across records where the speed was as low as 68 or as high as 84 RPM.

As to a turntable capable of coping with these speeds, that is yet another problem. Few turntables have more than a tiny variation (usually 2 or 3 per cent, which is nowhere near enough); but electronically controlled turntables may be modifiable. You need a speed range of 72 to 82 to cover most records. I'm using a Goldring-Lenco turntable which has a mechanical system for continuously varying the speed from about 32 to about 84 RPM, but it's not available any more - indeed I have had mine since 1963

Exactly why I think it's a valid choice for 78 RPM playback and still deliver good performance on modern LP.

Eldartford, the speed variations caused by belt reaction falls beneath the radar, so to speak, happening too fast to be captured by a strobe. This is why certain 'tables measure superbly averaged over a minute, yet don't hold up sonically (audibly) under pressure. But it is audible as confusion, loss of focus, orchestra melding into a single monstrous violin, loss of attack, and so on. And yes, it is far more difficult to design and properly set up an idler wheel drive than a belt drive, which is why belt drives won the war: a matter of price and profit margins. Fortunately there are the Lencos, whose simplicity in execution and design (a closed system of silent high-torque motor, perfect idler wheel and high-mass flywheel/balanced platter in which groove modulations have no effect) makes optimization much easier. The models I recommend were built from the late '60s to the mid-'70s, when many of the problems you cited were identified, understood and eliminated. I had never actually thought about the effect of stylus pressure, and you're right, lower tracking force would go some way towards mitigating this effect in belt drives, but with the Shure stylus profile (which digs deeply) the problem is increased, probably balancing out in the end. Yet one more thing I will have to experiment with!

Another deck, unfortunately more rare (particularly outside UK) that would be excellent for 78rpm replay is the Strathclyde Transcription Developments Ltd STD305D. This, sadly no longer available, deck is belt drive (using a DC motor) and has an electronic speed control unit complete with digital readout which can be varied electronically over quite a wide range. Check it out on my STD site:

http://members.lycos.co.uk/willbewill/

regards
willbewill

Johnnantais...A massive turntable will prevent high frequency speed variations. If you know the stylus drag force variation, and the angular inertia of the platter you can calculate speed variation, even neglecting any tendency of the motor to smooth things out.

I think that the stylus drag probably correlates with "Trackability", a parameter where Shure pickups excel. What do you use nowadays for stylus downforce for 78's? In the old days, when 78's were new, downforce of 5 to 10 grams was used, and this would certainly cause a lot more drag.

Eldartford, do you know I never actually tried to play 78s on my Lencos? I stumbled on them entirely by accident one day, and that particular model being defective, I simply threw out everything which was not directly connected to the drive system, thus accidentally modding it and being blown away by the sound. From there, hooked, I pursued the idler wheel grail. But from perusal of various 78 and mono stylii, I believe these can be tracked today from as low as 2 grams and up to 5. Others with hands-on experience will know more.

While it's true that high mass platters overcome belt reaction to a certain degree, what is actually happening, since physics cannnot simply be banished, is that this mass lowers the frequency of the reaction, as the belt reaction must overcome greater mass/inertia, thus reacting continually, but at a slower pace. This is why high-mass decks sound less lively than lower-mass decks (their bass rhythms messed up by low-frequency reaction), which major in PRaT, versus the information retrieval of high-mass decks which overcomes high-frequency belt reactions. I used to have one of the highest mass platters in the business on my Maplenoll, a 40-pound lead platter. Yes, there was greater retrieval of information, but it also sacrificed the famed Maplenoll liveliness. I eventually went back to the lower-mass Maplenoll Athena, which is far more musical. Thus is the high-mass/low-mass phenomenon exposed, as the human ear is still the best measuring instrument we have, with respect to music. Once I had a good idler wheel properly set-up, I was forced to seek the causes of the great increase in detail, attack, bass, imaging, and so on. So, having experience of both high-mass (Maplenoll Ariadne) and low-mass (Ariston, AR-XA modded, Maplenoll Athena) belt-drive 'tables, I came up with the above theory, which seems to fit the facts. A recent review of the Origin Live Aurora Gold turntable in Stereo Times had the following to say: "The heart of music is time and timing: music unfolds in its own created universe of time, divided into smaller sections placed within that fluid time scheme, divided further down to the individual note. Each individual note begins with silence, rises to its intended volume and then decays. Identifying that note, the instrument playing it and the physical location of it are all based on an exact sequence in time. It wouldn’t be too false a metaphor to understand music as an emotional language based on intervals of tone and time."

And what has better speed stability than an idler-wheel drive with perfect wheel, incredible cogless 4-pole 1800-rpm motor, and massive balanced flywheel platter which creates a closed system (groove modulations and stylus drag? what's that?) in which the platter smooths out the motor's revolutions while the motor carries the platter relentlessly? And yes, you're right, this extemely high-torque design is an accident of being designed for high stylus pressures - 5 to 10 grams - in the old days. But properly designed and implemented (a heavy, non-resonant plinth), the extreme speed stability regardless of groove modulations and stylus pressure is entirely audible at 33 1/3 rpm, even compared to the best of belt-drives. Again from the same review: "Since accurate tracking of the timing of a note - it’s loudness, attack, flowering and decay is also the perceptual mechanism behind reproducing a coherent stereo image, it’s no surprise that the I/AG is as adept at reproducing the stereo illusion as it is with the music unfolding within that illusion." And here speed stability must be the reason my Lenco with Rega arm clearly out-images and out-soundstages my parallel-tracking Maplenoll (the precursor of the E-T tonearms, the Maplenoll having been designed in part by Bruce Thigpen). To conlude, it's not for nothing that I flipped over the Lencos. A series of accidents beginning with a 'table which was designed to combat extreme stylus drag in the days of 78s, and ending with a lad who already owned a Maplenoll Ariadne and Audiomeca turntable, but in a foreign land needing a table cheap and picking an idler-wheel 'table he had never heard of at a flea market.