Resurrecting Record Turntable

I noticed that this was a moving magnet stylus amplifier. Hopefully that is what you have in the turntable. One question is why not buy a whole pre-amp/amplifier rather than just the standalone preamp? I would be bothered by the potential injection of noise from the cheap external power supply (60Hz and harmonics). With a complete pre-amp/amp, this has already been solved with one power supply designed to remove audio hum.

I have an old NAD 3140 that has a failing power stage, but I keep it just for the phono pre-amp and send the pre-amp output to a Rotel Amp. Works great, but makes me aware that I have to live with record noise again.

 

Patrick, good choice, good price!
I too have been slowly transferring many of my thousand plus album collection into my car Ipod!
To that end I found a nice direct drive turntable on eBay, and found a new Audio Technia cartridge at a great price, and preamp, online, and it works great!
I am at the point where I have 10 days worth of music on the Ipod, and another 6 days worth to transcribe!
But it's gonna sound great!!!
Well worth the effort!!
Rock on!!!

And I keep back up DVD's of the files.....

 

Some of us young'uns have record players too. I have one of these (attached to an ableton live setup):



But a Technics 1200 would be awesome.

 

I heard a rumor that those flat discs came in different speeds... and some required plastic inserts to work.

I'm too young to remember that, of course *LOL*

 

I've seen those in museums, but it's not at all clear to me how the laser reads the groove and turns it into music. And they're huge! CD players weren't really that big way back when, were they?

 

Im a youngin' with a real old turntable that works just fine. Problem is that in my climate those magic black plastic spinning disk things warp and bubble if left out of the sleeve for too long. We have to keep them in a sleeve and compressed on the book shelf so they dont self destruct, including our autographed Thriller album

 

laserdisks anyone?

 

How much do you love your record collection? Do you love it enough to justify the purchase of a $10,000 turntable? If you have valuable records, consider investing in a laser turntable from ELP, a Japanese manufacturer of high-end products for audiophiles. For those on a budget, we'd recommend that you convert your LPs into a digital format and call it a day. But for you "purists" who demand nothing but the analog sound from a turntable, preserve those records by playing them in this machine. Unlike a traditional turntable, the record is never touched when it's loaded into what looks like a Laserdisc player. There's no needle involved; instead, five laser beams are used to "read" the record. There's also no digitization of the audio, so you'll hear the analog recording "as close as possible to when the master tape was recorded," according to ELP. The company also says the Laser Turntable "even allows you to play records that have been severely warped or damaged over years of wear and tear." More info about how the player works is available at ELP's Web site.
ELP recently announced a price drop. The entry model, the LT-1LRC, starts at $9,900 (originally $15,000). The LT-1LRC has speeds of 33 and 45 revolutions per minute (rpm) and can accommodate 7-, 10-, and 12-inch records.


Be careful what you wish for....for 10k it can be yours!!

 

It is digital. The laser is at the very least, pulsed so it can measure distance. That puts it in discrete time, digital. It doesnt matter, digital as long as its double the max frequency of the record reproduces the original 100%. Analogue is going to sound wonky and different everytime, which is generally what people like, but not accurate and not audiophile-like.

 

There is no inherent reason requiring it to be digital. There are analog methods of doing this too, and the website emphatically declares that it uses analog, no digitization.

That is a necessary but not sufficient requirement to get 'original 100%'. And in normal practice, it won't get great fidelity without incredibly expensive analog filters.

 

Im curious as to what analogue-only-method can be used to measure distance from an optical reflection?

 

Before the flat circular discs, music came on cylinders.

 

One easy method is to fire the laser at the top reflective surface at an angle, and find where the reflection lands.

Given more than five seconds of thought, I'm sure we could figure out more methods.

 

Ok, but lets take that.

Where it reflects would be any area over the disk or way farther from it. Then you would need extremely accurate light sensors over a large area. This player definately doesnt do that. And you would need like a 1m CCD sensor for something like that.

I am aware there are methods that can read distance analoguely via optics, however none that I am aware of that would read vinyl media in an enclosure of the size pictured.

 

It only needs to maintain the flying playback head a fixed distance above the record surface. Bounce a narrow beam off the flat reflective surface (between grooves) at an angle, and use servo control to keep the center of the return spot at a particular sensor location. When the spot drifts one way or the other, raise or lower the head to bring the return spot back to the desired location. The only 'distance' the system knows is too close, too far, or just right.

There are plenty of us analog electrical engineers who can still do this, and have not yet fully retired.

Beyond this, the product description promises only that the signal path, i.e. lasers #3 and #4, are purely analog. The playback head height is maintained by laser #5, which is not part of the signal path, therefore we don't know for certain whether is uses analog or digital methods.

 

Ah, I was thinking fixed head... This is the reason you ask. Engineers learn from others, and as a n00b in both fields obviously there are things that escape you.

**but could one not argue then that the servo keeping position has a digital resolution for the PWM signal being given to it? Would you not need to know the exact angle and position of the source beam as well as the exact reception point of the reflected beam to measure the distance? And if one of those variables is digitally controlled, then the resultion of the whole system is off no?

**So assuming the servo controlled position is known to N bits accuracy, and always keeps the receiving beam at location A, adjusting its position based on the feedback of "too far" or "too close", "right on" will have a margin where it is neither "too far" nor "too close", yet "not right".

And to actually recover the data, since the location is fixed, you would need to vary the beam itself correct? So maybe a sine wave at a fixed frequency, measure the amplitude of what was received vs. what was sent, and find the phase shift... I am not sure if this is what you are suggesting. I am curious and want to learn, I guess the engineering curse.

Analogue was never my strong point, though.

**EDIT: Just realized an error on my part. If the sensor's active area was greater than the digital margin of errors, then it would make no difference... Gotcha.

 

I simplified things a bit. To keep the control loop stable, the 'too close' - 'too far' signal would be made approximately proportional to distance, and kept as linear as possible in the immediate region around the desired set point. The loop drives to maintain that set point. No PWM needed. However, they could have gone to such methods without breaking the 'analog only' signal path romise.

As for data recovery, the groove will modulate the reflected beam in different directions, so a lens and sensor in a fixed location will see a varying signal. It shouldn't take much accuracy at all to get a recognizable signal. Getting high fidelity would take more design work, beyond the scope of this thread.