Vintage DD turntables. Are we living dangerously?

Regards Lewm:

Retrieved from JVC literature:

Both the TT81 and 101 utilize a servo system operating in both positive and negative directions. A disc with either (dependent on model) 180 or 90 slits is opposed to a circuit board with the corresponding number of printed-coil elements. A phase comparator circuit reconciles the signal from a quartz frequency generator with the one built into the motor.

If my math is correct, for the TT101 at 33.3 RPM, speed is sampled and corrected every 0.003 seconds. This second "negative" servo system is absent in the TT71.

Speed deviation for the 101 & 81 is given as 0.002%
Drift stated as 0.00004%/hr.for the 101 & 81. 0.0002%/hr. for the 71.

From this source:

http://audio-database.com/PIONEER-EXCLUSIVE/player/p3-e.html

"Linear torque scheme of a slotless and a coreless structure by Quartz PLL is adopted as a phone motor and a bearing structure. Furthermore, by the conventional measuring method, the impossible rotation performance of 0.001% of less (---) rotation unevenness 0.003% (WRMS, the FG method) a rotational frequency precision is realized."

http://audio-database.com/PIONEER-EXCLUSIVE/player/p10-e.html

"Rotation unevenness, 0.007% (WRMS, the FG method) 0.015% (WRMS, the Japanese-Industrial-Standard record method)."

http://audio-database.com/PIONEER-EXCLUSIVE/player/pl-70lii-e.html

"Rotational frequency deflection 0.002% or less. Time drift : 0.00008%/h."

Again relating to the OP (and I'd not wish to put it to the test) by all references Pioneer is committed to service components bearing the "eXclusive" badge.

Apparently my "IIRC" function is somewhat out of phase. Apologies were offered in advance. In view of maintaining accurate information your comments are entirely appropriate.

Peace,

Throw away those specs. The real units don't meet them. They are pure craziness. they are about as good as amplifier specs of the day.

Wow! I am overwhelmed. But nowhere in your many quotations do I see the words "eddy current", so is it fair to guess that you agree with me? Also, and I have no dog in this fight, nor is it a fight, I had been led to believe from my own internet reading that the TT81 differs from the TT101 principally in the fact that it does not employ a "bidirectional" servo (Victor's parlance). But I always could be wrong. I believe I got that idea from Vintage Knob. (Where else?) The main reason I targeted the TT101 when I needed another tt like I need another... (name anything useless to have two of), was that coreless motor. I think it is key to what I like about the L07D, wanted to know whether that is a general property of coreless motors or some other magic of the L07D.

The earlier Denons with induction motors: did they employ servo feedback as well? It is hard to imagine how that would work well. Did DP6000 use induction motor?

I have more than five times the expense invested in my TT-101 over the TT-81....and would love to say that the performance difference is worth the cost....?
Unfortunately (or fortunately)...that is not the case and I can honestly say that I can hear no differences between them.

Thanks for the honesty, Halcro; in the same situation, I probably couldn't bear to write those same sentences.

...according to the JVC flyer that timeltel linked to, there is no "significant difference" between the ql8 and the ql10, except the digital counter. So, you may be on to something in your comparative assessment?

It does seem odd though to cram all the added circuitry of the 101 just for the sake of the readout. And to expect people to pay nearly $1k more for it in 1977. That was the going entry fee for digital, I guess.

Lewm: "The earlier Denons with induction motors: did they employ servo feedback as well? It is hard to imagine how that would work well. Did DP6000 use induction motor?"

The one I'm know for sure uses induction motor was a DP-755, an old table without quartz lock that I used to own and saw the gut myself. In the Amp8 website there's no picture of the DP-6000 motor but there's a similar looking DP-3000 that uses an induction motor. I believe all the 4 digit series tables have induction motor and they all use a tapehead reader for servo. The later 2 digit series such as DP-75, DP-80, etc... went back to motor with magnet but retained the tapehead servo system.

Halcro: "HiHo, Your interest in the Victor motors seem to have been ignited by your experiences with the TT-71.....is that correct?"

Long story. I can say it is one of the tables that got me interested in JVC products and DD genre again. Technics SP10Mk2 was my table for the longest time, over 10 years before the DD revival. Always got laughed at by my audiophile friends for not using an "audiophile approved" table a la Linn. But I ignored the noise. Then there was a period I didn't work so I had all the free time to experiment. For whatever reason I didn't use the SP10 and started exploring belt drive and got into the Empire 208, still an excellent table. I just missed the conciseness of the DD and low noise so I decided to give DD another try. I bought a bunch of DD tables for experiment, TT71 was one of them, also included models from brands like Pioneer, Denon, Kenwood, Sony, Technics, JVC, etc... Up to that point I hadn't encountered any table with coreless motor and then one day I got to listen to a dirt cheap Pioneer PL-300 and it had a smooth quality that reminds me of belt drive so I gutted it out and discovered it had a coreless motor. Ever since I started looking for tables with coreless motor and they always have that smoothness I crave for. There are some non coreless exceptions, of course, such as Sony PS-8750 and Denon DP-60. You can call this smooth quality euphony or distortion or whatever. All I know it has a sound I enjoy -- neutral or not, I couldn't care less. It was then I relistened to the Technics models, SP10Mk2, SP25, SP15, SL12000mk2, SLM3, SLM2, etc.... none satisfied me. (Although the sleeper in Technics is really the SP15.) When I started with the SP10mk2 -- college days? -- I was deeply into punk rock and the bass dynamic and tightness is perfect for that musical genre. Playing The Clash's "Police and Thieves"was great way to show off the Technics. But as my musical taste expanded, it no longer could satisfy me in other music, that often criticized sterile sound is true for me. Technics does not represent the best of DD tables, there are many options. It's unfortunate many people dismissed the DD genre just because they didn't like the Technics without thinking there are at least half dozen worthy brands out there.You just have to be open-minded about it. So, that's the gist of it.

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Some of the quoted specs Timeltel provided were from Pioneer P3 and P10 and had nothing to do with JVC. Wrong links!

It appears the prose was written using Google Translate program with very awkward phrases.

Happy Listening,