Three speed automatic turntable replacement

Are you sure it's a BSR ? IIRC they used a piece of flat stamped metal on t= he bottom which was lightly sprung away, and then the "velocitrip" was righ= t on the main drive gear right under the platter. If there was a piece of p= lastic at the end of it, that would not require a complete teardown.=20

What kind of unit is this in ? If you're looking for a dropin I assume this= unit is what used to be called a "mahogany monster". The BSRa were only us= ed in a couple of brands, Zenith had their own, Magnavoxes used a Colarro o= r something like that and then there were a few others. I think there were = about five major types in all.=20

Those cheapo dropin replacements were not satisfactory as far as I am conce= rned. All plastic and in a word - junk.=20

The real question here is whether this is THE complaint or not. You say the= customer won't pay, well then he has a fine manual turntable if the rest o= f it works alright. If he doesn't understand what it take which is likely t= o require you to cut and grind because you aee not going to get the part, I= guess you will have to make him understand.=20

Actually when confronted with this situation and a really unusable turntabl= e someties I sold an upgrade. You could get like a Dual 1218 or something u= sed, get the automatic spindle for it and everyhing. Even a magnetic cartri= dge and a preamp. But then no tightwad wants that, or people who want to ma= intaain the integrity of an antique. Of course a dropin is not for them eit= her. And sawing up their turntable cutout ? It's like when they put those g= odawful 22" tires on a nice old Oldsmobile from the 1960s. I would like to = shoot those people but alas it is illegal. Can't do it in public.

If the guy is cheap, what is wrong with a manual turntable ? On the other h= and if this is a "restoration" job, he should know not to be cheap.

J

How many cases of them do you want? Google USB turntable. Geek.com had them on special this week for $29.95.

It's also likely that the rubber parts are going bad on anything that old.

I have one I picked up at Costco for about $75. The big problem is finding replacement needles. Check for availability before buying. Also, make sure that it will play 33.3, 45, and 78 rpm disks. The one I bought only does 33.3 and 45.

However, such turntables are boring. Sell the customer one of these:

Only $150,000.

or maybe this 400 lb monster:

But those use a stylus. Modern turntables use a laser:

Only $9,000 to $12,000.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

The laser ones actually don't do that good a job. There are a *lot* of mechanical "errors" in a needle-in-groove system that are "automatically" taken care of by stylus reproducers, in a system that has been refined by "cut and try" over a period of years and has no real spec. Basically, the cutter "pre-distorts" the groove so that when the reproducer adds its own distortion, things sort of come out even -- sort of. If you use a laser to read the groove, then you have to do all those things some other way, and the list of them is long and isn't well defined.

Isaac

One plays a vendor supplied calibration record on the turntable to calibrate it for those distortions and anomalies. For example, they record a clean low distortion sine wave at various frequencies using the standard record cutting lathe. When played back on a laser turntable, the processor look for distortion products (harmonics) and tweak a DSP to compensate. Resonances can be taken out via a freqency sweep.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Not really. Pre-distortion requires a specific technique, first (and last) used by RCA in the early 60s.

Someone did a master's degree thesis about 10 years ago on writing a program that would read a photo scan on a desktop scanner of an LP and convert it to audio files.

It worked within the limitations of resolution and size of the scanner, and computer processing ability available to him.

10 years later, it would be possible to do a much better job, but no one seems to interested in doing it. Oh well.

The distortion is not a big deal. One just has to find a few master tapes (or films) and the corresponding records, digitize and compare them to come up with a "correction".

We may even be lucky enough that someone could build a library of them, and be able to trace a recording to the specific lathe used to master it.

Geoff.

Geoff.

--
Geoffrey S. Mendelson,  N3OWJ/4X1GM/KBUH7245/KBUW5379

This was known and done 50 years ago -- qv, Dynagroove.

Which, as it turns out, died a quick and well-deserved death. There's a good reason why it was abandoned by RCA and never adopted by any other recording company. It sounded terrible.

Isaac

There were lots of sorts of pre-distortion used in the vinyl recording process: noise reduction EQ (the RIAA curve), radial EQ (poorer HF response on inner grooves), bass mixing to reduce groove cut-through, stylus shape pre-distortion because the cutter is flat and the playback stylus is a cone or an ellipse (and they need different treatment during recording) (this is NOT Dynagroove), treble boost to account for loss of HF due to the cutter being heated to reduce noise), corrections because the cutter traverses the disk radially and the playback stylus does not, several others.

If you think it's easy, here's a nice thought experiment:

If the waveform you want out of the phono preamp is a square wave (or near enough), what path must the groove cause the stylus to trace to produce that? (Hint: it's *not* a square wave). Once you figure out what the groove looks like for a square wave output, you'll realize that the groove *never* really "looks like" the waveform of the "sound", and that the conversion from one waveshape to the other is yet another compromise, though not so much as the recording process. It is, in fact, quite difficult to analyze the shape of the groove and determine "analytically" what the resulting sound waves should look like.

A mechanical playback method takes care of all that "automatically" because the recording process is arranged so as to minimize the *system* distortion, *assuming the reproduction is going to be by means of a stylus in the groove*. Any other playback process must perform all those things explicitly in order to get good results -- i.e. it must simulate the behavior of a stylus in the groove -- and that's not so easy.

Isaac

I knew I shouldn't have said anything about Dynagroove.

The Dynagroove system was intended to make recordings "sound good" on cheap playback systems. It abandoned the concept of fidelity to the original sound, producing recordings that sounded worse the better the quality of the playback system. Almost everything about it was aesthetically invalid or technically dubious.

ALMOST everything. The one thing Dynagroove "got right" was the pre-distortion of the groove, to compensate for the finite radius of the playback stylus.

End of story, case closed.

None of these are forms of pre-distortion, because the effects they compensate for are linear -- they are not distortion. (I'm going to insist on this, because "distortion" has a clear, specific meaning.)

It was a component of Dynagroove -- the only one that actually worked.

Not a form of distortion.

This is a form of distortion, but it's not compensated for during recording, because there is no standardized playback-arm geometry.

Actually, it's quite simple, because we know how cutting systems were designed. In the electrical era, cutter heads were velocity devices, with EQ applied to produce what the record label considered a practical approximation of constant-amplitude recording.

No, it isn't. If distortion in one part of the system cancels out distortion in another part, it's either dumb luck, or because somebody "fiddled" with things. This was particularly true in the days of acoustic recording, when recordings were intended to be played back on the reproducing equipment made by the record manufacturer.

Please read what Western Electric said about its system of electrical disk recording -- it was intended that each element of it be as perfect as technology then allowed, without errors in one part of the system being compensated for in another part. This allowed for continual improvement without having to periodically re-design everything.

Sure it is. The math to do this existed long before any of us was born.

In general, mechanical analog recording stinks, and mechanical analog playback is even worse. There's nothing inherently "correct" about it. It's amazing that phonograph records were as good as they (sometimes) were.

You don't. Use the MaggotBox for firewood and replace it something more modern. With streaming audio, I have more than a few customers that use computahs as front ends for their music systems. However, if that's too much for your limited imagination, there are conventional turntables still available with phono outputs that will work with your antique.

In the mid 1970's, I worked part of kitchen automation system that would have done exactly that. I thought it was a good idea, but none of the average housewife wouldn't touch it. We didn't have a mouse, but the elastometric keyboard looked very much like Windoze 8 Metro or a banking machine.

You've been watching too much old Star Trek episodes. These days, we take dried soybean curd, add flavoring, modify the texture, heat, and serve. Welcome to the space age. It's highly likely that your next hydrocarbon meal will originate in a coal mine.

Not really. There are numerous supermarket delivery services. Webvan is dead, but Safeway.com, delivery.com, etc are still merrilyl delivering to high-rises, where a trip to the market is a major expedition:

We understand.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

had

USB turntables are plastic junk....

"Use the MaggotBox for firewood and replace it something=20 more modern" (My dear old Dad used to call them that :....)

But the customer is in LUV with it ! Of course not enough to spend "too" mu= ch money on it lol.=20

Really though some people do like those, at one shop where I worked on a fe= w of them they were clearing estimates for near $300. Still want that weeni= e roast ? Another alternative is to replace ALL the guts. It takes a bit of= woodwork but you get a modest 25 WPC reciever from the 1970s, a regular tu= rntable and just hook it up to the existing speakers. It depends on the "pu= rism" of the customer. In fact my Uncle BUILT a mahogany monster a long tim= e ago. Copied a MacIntosh Williamson push pull design and built a pair of m= onoblock amps, dug up a preamp and tuner and mounted them, put in an Elac M= iracord turntable and built the speakers separate but in matching cabinets.= You couldn't buy something like this and I think if I had it today it woul= d be worth quite a bit - to the right person (read fanatic) of course. In f= act his son, my cousin also built his own amp and speakers, but of course = that was more modern having them thar newfangled transistors. Another thing= that brought in some money a while back was putting new TVs in old cabinet= s. It was the cost of the new table model TV which we had to choose of cour= se, plus about $250 labor. If a combo we would wire the TV sound to go thro= ugh the amp and speakers, for a small fee of course. People paid it.

" I thought it was a good idea, "

It seems I heard those words before, now where was that ? OH YEAH, ME ! Plu= s about =BD the people I've ever known. Amazing how many ideas I had, and n= ow tht I have spare parts to burn, PCB making supplies and a small machine = shop, I draw a blank. Well almost.

"You've been watching too much old Star Trek episodes. These days,=20 we take dried soybean curd, add flavoring, modify the texture,=20 heat, and serve."

Careful with a can of worms that big. I correspond internationally and just= joined Internations in fact. Get this, there are people who LEAVE AMERICA = because they can't stand the food. I shit you not.

By the way, I am having a very hard time getting any Star Trek online. It s= eems CBS is very stingy with them.=20

"There are numerous supermarket delivery services"

Yes but some of these high security buildings are ridiculous. Sign this, st= and here for the photo, show ID. Next the TSA will be there doing cavity se= arches.=20

Anyway this has been wonderful banter but I would lke to get on to this pre=

-distortion thing. I had a concept a while back having to do with tape reco= ding. As you all may know if a tape is underbiased, it loses some midrange = and lows, and has odd order distortion in the phase which extends the peaks= . An overbiased tape loses highs and has odd order distortion in the phase = which flattens the peaks. Now if one had a misbiased tape, and then copied = it misbiasing the tape to be recoded on the opposite way, that might concie= vably cancel out no ?=20

Of course it would be a PITA because then you have to determine the lavels.= But IN THEORY it should work.=20

"IN THEORY it should work"

If you have never heard that one raise your hand.

J

I would argue that any difference between the input to a system and its output would be "distortion" by definition.

One reason some early CDs sounded so bad is that they were made using the cutting masters intended for driving cutting lathes. Everything that was done to the master tapes to prepare them for making vinyls (and that is a hell of a lot) is distortion, in my definition.

It was also used long before (and after) Dynagroove came out, by many labels.

Which would explain why is was abandoned so soon after its introduction ...

For information on this, and some of your other statements, I strongly recommend that you get, and read, an earlier edition of John Eargle's "Handbook Of Recording Engineering" -- earlier (2nd. ed. for instance), because later ones make no mention of vinyl techniques, but they are well covered in early ones.

OK. It's simple. So what *does* the groove look like?

I've read it. Eargle's book is a lot more recent, and embodies a whole lot of knowledge and *practice* that was simply unknown at the time the Western Electric stuff was written.

And that is why vinyl recordings sound soo good ...

On that, we can absolutely agree.

Isaac

"I would argue that any difference between the input to a system and its=20 output would be "distortion" by definition. "

Well I would argue something else, in fact I will.=20

You may have made a blanket statement unknowing of certain aspects of hifi,= or you may be one of those purists that require the plastic for the facepl= ate to be grown in th...... nevermind.

That statement would mean then that you object to RIAA equalization as well= as NARTB. The reason RIAA equalization exists is because of the properties= of vinyl. Black vinyl is the toughest, and was produced by adding carbon t= o the material, just like many plastics and similar things. Before that the= laquer or whatever records (78s) that were CUT also had alot of grit in th= em. This made HISS. Since the high frequency waves ARE actually smaller, th= ey decided to crank them up on the recording side and do the EXACT opposite= on the playback side. It's like having to steer right when you have a flat= tire on the left.

Without what you erroneously call distorion everything you hear would sound= hissy, to the point maybe of unlistenability. This also applies to tapes a= nd therefore to the master tapes made to record music. Hiss upon hiss. Thin= k AM was bad ?=20

In an RIAA compliant phono preamp a calibrated EQ curve is applied. Actully= if you see the "curve" it is actually a tilt. Two resistors and two capaci= tors per channel achieve this. It matches because they match the "time cons= tants" of the opposite network applied to the signal when it was recorded.= =20

On tape the NARTB curve is THE standard, but for better results they do not= approach it separately. Very long ago they did, you could get an outboard = preamp and it would amplify your signal right from the tape heads, apply th= e requisite NARTB equalization and give you flat response at "line level", = which is all pretty much what a tuner put(s) out. However in a tape deck th= ere is so much equalization to do with the heads that the NARTB, as I said,= is not considered sepatrately, and neither is it in playback. HOWEVER for = compatibility between different decks, it must be adhered to, that is the o= nly thing.=20

You may not be aware but digital sound also has such schemes. Understand th= is (listen up y'all I ain't doing this twice).......

OK you got wonderful 16 bit sound, it is great right ? Well what happens wh= en you are at a piece of the music that is at -66dB ? It ain't 16 bit no mo= re, is it even 8 bit ? Just that very soft part of it, understand ?=20

Well the people who designed the system DID figure this out and as such the= re was a pre-emph signal on CDs from day one. When it got below a certin le= vel the preemph would kick in and the deemph on the playback side. This gav= e it more bits during the soft passages of the music.=20

This lack of bits situation is also abated by something called dither. Dith= er is white noise added to the program material to prevent these digital ar= tifacts from cropping up during the soft passages of you favorite jam.=20

Is it that good ? Well CD quality has been quite surpassed by certain DVD a= udio formats. In fact the Sony PCM-1 or PCM-F1 could take a DVDR or any VCR= and record better than a CD. Almost thirty years ago !

More later, this is long enough and I need to go eat. Cook and eat actualy.= =20

J

That's not correct usage. Any linear transformation of a system's I/O characteristics is, by definition, //not// distortion. Distortion is a non-linear transformation.

As far as I know, all the changes were linear changes, and were not distortion,

Name one.

I don't know how long it took RCA to abandon Dynagroove. My understanding is that RCA continued to use pre-distortion for some years. It was the only part of Dynagroove that was a technically and aesthetically legitimate improvement, and I doubt RCA wanted to immediately abandon the hardware for it.

If John Eargle's views differ from mine on these points, he is incorrect.

determine

Read the my preceding paragraph.

distortion

with

when

as

What does that have to do with the first paragraph of this section?

I don't know whether you're being ironic, but on the assumption you're not... About a year ago I sat down with a pile of audiophile LPs and sonically browsed them. Many had really nice sound -- highly listenable -- but little of it sounded as much like //live// sound as the best SACDs (and the rare CD). LPs can be highly euphonic -- but when push-pull comes to shove, they simply aren't that //accurate//. As only a few had performances I wanted to hang on to, I sold almost all my audiophile disks to Silver Platters, and got $600 in store credit.

It's

Yes, we don't have all day, Vince.

The pre-emphasis was optional, and was abandoned years ago. I believe some CD players have no way of compensating for it.

I don't think you know what you're talking about.

The PCM-F1 (and its Nakamichi equivalent, the DMP-100) could record at

14-bit or 16-bit resolution. That was its limit.

I own a DMP-100. 25 years ago I made parallel live recordings with the dbx

700, a processor using a system similar to Sony's Direct Stream Digital. To my ears, the dbx 700 was superior.