Linear Tracking Turntable

[julianE]

I attached a couple wires to the small DC motor that controls the tone arm carriage, used a multimeter to measure the voltage going to the motor. More complicated than i expected, the voltage to the motor varies from nearly 7 volts to barely over 1 volt. the high voltage being used for manually moving the carriage to different tracks. The error control voltage while the record plays varies between 1 and 2 volts and the motor is at times off but it's a very short time, second or less, it's almost always on.

Not sure how to measure and record the motor voltage since there is the conversion time and storage time to be concerned about. I'm not sure I could get any meaningful data with the picaxe.

While writing this i'm listening to a record, the kenwood sounds very good and it's tracking a record well despite it being warped.

 

[papaof2]

That voltage might be better analyzed with an oscilloscope to see how and when it changes - the 'scope is much faster than a meter. That might give you some ideas on how to monitor or re-use a recorded sample. Maybe store the sequence in a large FRAM chip and be able to select the signal sequence by number?

 

[julianE]

That voltage might be better analyzed with an oscilloscope

will give that a try today.
having digital control of the motor might actually be a deservice to the design. seems to me that the current system is an analog computer which might be the best solution.

That voltage might be better analyzed with an oscilloscope to see how and when it changes - the 'scope is much faster than a meter. That might give you some ideas on how to monitor or re-use a recorded sample. Maybe store the sequence in a large FRAM chip and be able to select the signal sequence by number?

need to order a fram chip never used one yet. thanks for the suggestion.

 

[julianE]

Followed papaof2 advice and attached a scope to the motor leads. There is a pattern, usually an off time of a little less than a second followed by correction voltage. I have noted a difference in the correction signal depending on how loud the music passage is.
Here is the trace

 

[julianE]

Have not made much progress at building my own linear tracking mechanism, the part are in just need to find the time to work at it.
I have studied the revox linear tracking mechanism and it's a little different from technics and the rest, it too relies on a dial cord type of system to move the carriage. the motor driving the carriage is direct drive which adds to the reliability, it's likely made to the high standard of revox.

i have been reading the audiophile insanity on the web, people are very chagrined that mobile fidelity used a digital file in their vinyl production. It's a fiasco because the anti digital brigade had kind things to say about the pressings and now that the cat is out of the bag and they have been listening to digital files reproduced by vinyl the backtracking has begun. I have long lost my audiophile standing because I don't find digital offensive I enjoy vinyl for the quality and also the nostalgie factor.

 

[wapo54001]

By chance, over the weekend I acquired a castoff not-high-end Onkyo integrated amplifier -- A9555 -- which has a phono (MM) preamp built in. So, for jollies, I hooked it up to my backup system Kef LS50s to see how it sounded. The fact is, I have not played an LP in more than 30 years, they have been sitting in boxes and my Technics SL1300 has been collecting dust but this thread made me curious again so, I pulled out a totally random LP to play -- it was Deutsche Grammophon Vaughan Williams Concerto for Oboe -- and was astonished by how alive it sounded! Wow! I've never been a believer in $14,000 speaker cables nor the natural superiority of vinyl over digital but I'm definitely going to pull more records to see if there is a consistency here or whether this was just good luck in touching a particularly good recording.

 

[julianE]

and was astonished by how alive it sounded!

very cool that you got the turntable out. don't discount the onkyo, i have one of their amplifiers from late 90s. it's a very nice sounding amp, beautiful built quality, good components and a very nice power supply, i like it better than a harmon cardon amp i have.
i think what makes vinyl feel more real is that the stylus/cartridge act like a musical instrument.
While learning how linear tables work i played a few warped records and as i'm watching the stylus i could hear variations in pitch caused by warping and even greater wow and flutter from off center holes. one of the tables i bought from ebay is a light weight belt drive, when it starts you can hear it ramping up to speed, instead of seeing it as a flaw i see it more akin to musicians tuning their instruments before a performance.

As much money as I've spent on music equipment and recorded music I've spent far more on tickets for opera and symphony, I have never heard reproduced music that comes close to live music in a good sounding hall.

 

[wapo54001]

As much money as I've spent on music equipment and recorded music I've spent far more on tickets for opera and symphony, I have never heard reproduced music that comes close to live music in a good sounding hall.

I think it's like a soccer game -- you can go to the stadium and enjoy the ambiance and the crowd's energy while watching the game from 50 yards up in the stands, or you can sit in your living room and see the critical replay and Messi's expression close-up on screen when he misses a shot. It's a tradeoff but I like watching the details from close up, and I prefer a comfortable front-and-center seat in my LR over a hit-and-miss seat somewhere in a sea of people. My favorite music is solo guitar, and being amazed by the performer's hands moving across the instrument is part of the magic.

 

[papaof2]

"being amazed by the performer's hands moving across the instrument is part of the magic "

Amen!

 

[erco]

My favorite music is solo guitar, and being amazed by the performer's hands moving across the instrument is part of the magic.

Amen. I won tickets to a Prince concert many moons ago. Wasn't a fan but went anyway. He put on a GREAT show with an amazing but the best part was him solo. Very talented performer.

 

[julianE]

I got one of the ebay turntables (panasonic) together to be moved to the garage. To verify operation I played a record with plenty sustained piano notes. the wow was very pronounced. Took everything apart and pulled out the motor assembly to test on the bench. the capacitors are over 30 years old so i unsoldered one and tested it, tests great. since i had it out i might as well put a brand one in. tested the speed and wow and flutter and wow is still there. i cleaned the area the platter runs near, no luck. i'm thinking i'll replace the belt or get a new motor. as a last check i ran my finger around the plastic housing the platter sits in and found a tiny section where plastic was proud, sanded it down and the wow dropped from .31% to .14%
good enough. it's rated for even lower but it's over 30 years old and the belt is new.

i'm not sure how the turntable regulates speed i don't see a hall effect or a light sensor or anything on the motor. the motor is a DC motor with two leads so there isn't a tachometer built in. the speed is spot on and the manual says it has DC Servo Control. I have no idea how they are regulating the speed, every example of servo motor i've found has an encoder built into the motor housing, the one in my turntable is a plain DC motor.

the turntable does have two pots to set the 45 and 33.3 rpm speed. i prefer direct drive quartz locked turntables but this is an early model that's belt drive. audiophiles prefer belt drive because it supposedly has better isolation and freedom from cogging motor issues. my cynical side thinks the preference for belt drive is the simplicity and greater profits for the audiophile manufacturers.

with the help from this forum i made an led strobe to test the speed of turntables and now i'm thinking of making a simple tachometer to display the speed.

 

[julianE]

I'm still tinkering with linear tracking turntables and am also learning 3D printing in order to make my own tracking arm.
just in case others are interested here is a video showing how record mastering is done at abbey road studios, very good presentation.


Abbey

 

[erco]

I'm still tinkering with linear tracking turntables and am also learning 3D printing in order to make my own tracking arm.
just in case others are interested here is a video showing how record mastering is done at abbey road studios, very good presentation.


Abbey

Cool video, TYVM!

 

[dennis]

I am not an audiophile and my hearing is poor but I was wondering ....
Do you notice a difference in quality between outer and innermost tracks ? There is after all a considerable linear speed difference.

Maybe the next scheme to update the concept (and make a market for more hardware) would be variable rotational speed to maintain a constant stylus speed along the groove . Variable speed could allow much more music to be stored on the same diameter disc or be used to even out or improve quality. Of course the new deck would require new records but could easily be made compatible with existing vinyl by incorporating a fixed speed mode.
If a linear tracking set up was also included then both of the inherent advantages of the, admittedly cumbersome to store, wax cylinder set up would be achieved

Could be a fine Picaxe and mechanical design challenge

 

[julianE]

would be variable rotational speed to maintain a constant stylus speed along the groove

i think i can tell a difference between the inner grove and the outer but it's impossible to AB test since you'd have to record same material on different tracks. the best audiophile grade vinyl records are being pressed at 45 RPM increasing the resolution but shortening time.

right before the collapse of vinyl there were DBX encoded records, i have a couple and a decoder, it sounds glorious, it went nowhere. if there truly was a vinyl resurgence things like variable rotational speed would be implemented. what we have is a profitable fad, people buying cheap turntables to be "cool". i believe people that buy the very high quality equipment that there is something magical about vinyl, i hear it every time i play a well made record. i also don't find digital recordings fatiguing and have a large collection.
as an aside i've seen turntables in a number of current movies and in one movie the conductor laments that her recordings are not being made direct to disk analog.

 

[julianE]

I've been tinkering with my audio gear a lot of late. I'll be asking a lot of questions soon.
Bought some premium vinyl recordings from Japan. After months of critical listening I'm hearing the advantages of Linear tables but like everything there are negatives, I'm certain that Linear trackers are more sensitive to warped records, pitch change due to warping is more pronounced in Linear as opposed to pivot. I'm not certain why maybe there is a dampening effect on the pivot types where the arm is longer.

 

[erco]

Are there any ordinary turntables with a ridiculously long arm to reduce cartridge rotation?

 

[dennis]

Or maybe a platten with vacuum hold down to just eliminate the warp !

 

[wapo54001]

I've been tinkering with my audio gear a lot of late. I'll be asking a lot of questions soon.
Bought some premium vinyl recordings from Japan. After months of critical listening I'm hearing the advantages of Linear tables but like everything there are negatives, I'm certain that Linear trackers are more sensitive to warped records, pitch change due to warping is more pronounced in Linear as opposed to pivot. I'm not certain why maybe there is a dampening effect on the pivot types where the arm is longer.

Use one of the commercial or home-remedy techniques to reduce/remove warp from your records. Best solution, build your own Picaxe-managed temp & humidity controlled device to fix your LP warps -- easier/cheaper than finding a turntable to minimize the problem . . .

 

[julianE]

Use one of the commercial or home-remedy techniques to reduce/remove warp from your records. Best solution, build your own Picaxe-managed temp & humidity controlled device to fix your LP warps -- easier/cheaper than finding a turntable to minimize the problem . . .

I found source of my "warp" the rubber mat was slightly proud due to the tabs not lining up properly with the platter, pretty silly on my part for not seeing it earlier. i have a method of dewarping records, i bought turntable platters, some people part out turntable parts, i put the record between platters which are very flat and have a screw/bolt arrangement in the center hole, tighten to clamp and let sit overnight. i am considering adding heat to the mix, a box with an incandescent bulb for heat with a picaxe controlling the temperature.

btw, i've been buying records from europe, the quality is far better than the american pressings. listening to a Mutter violin concerto and it sounds as clean as digital, no clicks and pops or warping issues.

 

[erco]

I'm moving in the other direction as julianE, away from fidelity and embracing the charming scratchiness of old 78 RPM records. I have two vintage windup Victrolas (giant horn, needle tracking force in pounds) and a random collection of old records. You can buy old 78s for ~$1 each in lots on Ebay. It's more practical (and less wear & tear on records and machines) to play them on this little $20 player. Having a ball listening to these old disks.

I Like Mountain Music/Bill Mooney

youtube.com

You Are My Sunshine/Bill Mooney

youtube.com

 

[julianE]

Having a ball listening to these old disks.

It will pair nicely with your Corvair, put the gramophone in the back seat and take it to the lake, nothing like listening to music by moonlight

I haven't a single 78 but i do know they are critical of type of stylus used, if you decide to bump up the fidelity do buy a cartridge/stylus meant for 78.

 

[papaof2]

If memory serves, the groove on a 78 is about 3 times as wide as the groove on a 33 1/3. Lots of players were sold with a single needle for everything but some cartridges had a "dual stylus" where the needle had a lever arm to select between the two different size styli.

 

[erco]

People in the boonies were known to use cactus needles for a stylus!

 

[Buzby]

People in the boonies were known to use cactus needles for a stylus!

Well, I suppose they are much more environmently friendly. Totally organic and compostable, just what we need to save the planet !

 

[julianE]

cactus needles for a stylus

only for critical listening