Three speed automatic turntable replacement

[klem kedidelhopper]

I got an old, (what looks like a BSR) three speed automatic turntable
in for repair. It doesn't work on auto because the plastic trip pawl
is worn. I can't get to the trip pawl without doing a semi major strip
down. And this guy isn't going to go for that. I would like to replace
the turntable with an equivalent inexpensive BSR type for him. I used
to be able to buy these from my parts suppliers for about 20 bucks
about 100 or so years ago but I haven't looked into this for a long
time. Is it still possible to find something like this, a basic
general replacement type idler driven mechanical turntable with a
cheapo ceramic cartridge? Thanks, Lenny

 

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

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 used in a couple of brands, Zenith had their own, Magnavoxes used a Colarro or something like that and then there were a few others. I think there were about five major types in all.

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

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 of it works alright. If he doesn't understand what it take which is likely to require you to cut and grind because you aee not going to get the part, I guess you will have to make him understand.

Actually when confronted with this situation and a really unusable turntable someties I sold an upgrade. You could get like a Dual 1218 or something used, get the automatic spindle for it and everyhing. Even a magnetic cartridge and a preamp. But then no tightwad wants that, or people who want to maintaain the integrity of an antique. Of course a dropin is not for them either. And sawing up their turntable cutout ? It's like when they put those godawful 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 hand if this is a "restoration" job, he should know not to be cheap.

J

 

[Klaatu]

"klem kedidelhopper" <captainvideo462009@gmail.com> wrote in message
news:94a40af6-2e0b-4c39-b866-a3bd1e6f2543@l10g2000yqo.googlegroups.com...

I got an old, (what looks like a BSR) three speed automatic turntable
in for repair. It doesn't work on auto because the plastic trip pawl
is worn. I can't get to the trip pawl without doing a semi major strip
down. And this guy isn't going to go for that. I would like to replace
the turntable with an equivalent inexpensive BSR type for him. I used
to be able to buy these from my parts suppliers for about 20 bucks
about 100 or so years ago but I haven't looked into this for a long
time. Is it still possible to find something like this, a basic
general replacement type idler driven mechanical turntable with a
cheapo ceramic cartridge? Thanks, Lenny

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

 

[Jeff Liebermann]

On Sun, 12 Aug 2012 11:23:23 -0700 (PDT), klem kedidelhopper
<captainvideo462009@gmail.com> wrote:

I got an old, (what looks like a BSR) three speed automatic turntable
in for repair. It doesn't work on auto because the plastic trip pawl
is worn. I can't get to the trip pawl without doing a semi major strip
down. And this guy isn't going to go for that.

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

I would like to replace
the turntable with an equivalent inexpensive BSR type for him. I used
to be able to buy these from my parts suppliers for about 20 bucks
about 100 or so years ago but I haven't looked into this for a long
time. Is it still possible to find something like this, a basic
general replacement type idler driven mechanical turntable with a
cheapo ceramic cartridge? Thanks, Lenny

<https://www.google.com/#q=usb+turntable&hl=en&tbm=shop>
<http://www.shopping.com/usb-turntable/products?CLT=SCH&KW=usb+turntable>
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:
<https://www.google.com/search?q=ultimate+turntable&hl=en&tbm=isch>
Only $150,000.
<http://www.onedof.com>
or maybe this 400 lb monster:
<http://goodwinshighend.com/manufacturers/basis/work_of_art.htm>
But those use a stylus. Modern turntables use a laser:
<http://www.elpj.com>
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

 

[isw]

In article <a71h289obn9nhjkda06b1tthmcqmg9node@4ax.com>,
Jeff Liebermann <jeffl@cruzio.com> wrote:

On Sun, 12 Aug 2012 11:23:23 -0700 (PDT), klem kedidelhopper
captainvideo462009@gmail.com> wrote:

I got an old, (what looks like a BSR) three speed automatic turntable
in for repair. It doesn't work on auto because the plastic trip pawl
is worn. I can't get to the trip pawl without doing a semi major strip
down. And this guy isn't going to go for that.

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

I would like to replace
the turntable with an equivalent inexpensive BSR type for him. I used
to be able to buy these from my parts suppliers for about 20 bucks
about 100 or so years ago but I haven't looked into this for a long
time. Is it still possible to find something like this, a basic
general replacement type idler driven mechanical turntable with a
cheapo ceramic cartridge? Thanks, Lenny

https://www.google.com/#q=usb+turntable&hl=en&tbm=shop
http://www.shopping.com/usb-turntable/products?CLT=SCH&KW=usb+turntable
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:
https://www.google.com/search?q=ultimate+turntable&hl=en&tbm=isch
Only $150,000.
http://www.onedof.com
or maybe this 400 lb monster:
http://goodwinshighend.com/manufacturers/basis/work_of_art.htm
But those use a stylus. Modern turntables use a laser:
http://www.elpj.com
Only $9,000 to $12,000.

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

 

[Jeff Liebermann]

On Sun, 12 Aug 2012 22:37:59 -0700, isw <isw@witzend.com> wrote:

In article <a71h289obn9nhjkda06b1tthmcqmg9node@4ax.com>,
Jeff Liebermann <jeffl@cruzio.com> wrote:

On Sun, 12 Aug 2012 11:23:23 -0700 (PDT), klem kedidelhopper
captainvideo462009@gmail.com> wrote:

I got an old, (what looks like a BSR) three speed automatic turntable
in for repair. It doesn't work on auto because the plastic trip pawl
is worn. I can't get to the trip pawl without doing a semi major strip
down. And this guy isn't going to go for that.

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

I would like to replace
the turntable with an equivalent inexpensive BSR type for him. I used
to be able to buy these from my parts suppliers for about 20 bucks
about 100 or so years ago but I haven't looked into this for a long
time. Is it still possible to find something like this, a basic
general replacement type idler driven mechanical turntable with a
cheapo ceramic cartridge? Thanks, Lenny

https://www.google.com/#q=usb+turntable&hl=en&tbm=shop
http://www.shopping.com/usb-turntable/products?CLT=SCH&KW=usb+turntable
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:
https://www.google.com/search?q=ultimate+turntable&hl=en&tbm=isch
Only $150,000.
http://www.onedof.com
or maybe this 400 lb monster:
http://goodwinshighend.com/manufacturers/basis/work_of_art.htm
But those use a stylus. Modern turntables use a laser:
http://www.elpj.com
Only $9,000 to $12,000.

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.
<http://www.elpj.com/about/howitworks.php>

--
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

 

[William Sommerwerck]

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.

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

 

[William Sommerwerck]

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".

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

 

[Geoffrey S. Mendelson]

isw wrote:

In article <a71h289obn9nhjkda06b1tthmcqmg9node@4ax.com>,

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.

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

 

[isw]

In article <k0ai07$1he$1@dont-email.me>,
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote:

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".

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

 

[isw]

In article <k0agkd$qmo$1@dont-email.me>,
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote:

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.

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

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

 

Boy this is a useful group. Get a USB turntable. Sure, now where the fuck do I plug it into this 1968 Magnavox mahogany monster ? LOL

Or a laser can read those grooves, just buy the interface and a PC to feed the tape input (if any) of the mahogany masterpiece.

Fucking amazing how people actually live. I mean not starve to death. To cook dinner, right click the desktop and go down to food. In the categories there choose from meat, veggie, fish, poultry etc. Click on the category you want and then read (OH NO) the contents of the window that opens. Then choose side dishes.

Make your selection and allow autocomplete to give the pizza guy your life history and access to all your money and wait for the bell to ring. Note if you live in a hi-rise apartment, death may occur from starvation.

We apologize for any inconvenience.

J

 

[spamtrap1888]

On Aug 13, 10:32 pm, jurb6...@gmail.com wrote:

Boy this is a useful group. Get a USB turntable. Sure, now where the fuck do I plug it into this 1968 Magnavox mahogany monster ? LOL

Or a laser can read those grooves, just buy the interface and a PC to feed the tape input (if any) of the mahogany masterpiece.

Fucking amazing how people actually live. I mean not starve to death. To cook dinner, right click the desktop and go down to food. In the categories there choose from meat, veggie, fish, poultry etc. Click on the category you want and then read (OH NO) the contents of the window that opens. Then choose side dishes.

Make your selection and allow autocomplete to give the pizza guy your life history and access to all your money and wait for the bell to ring. Note if you live in a hi-rise apartment, death may occur from starvation.

We apologize for any inconvenience.

You don't think it's a bit quixotic to demand a drop-in replacement
for a half-century old consumer apparatus? In the 1960s were you still
trying to keep your 1918 Maxwell running? My mom used to be a Victor
Comptometer operator. Do you think she could get that kind of work
today?

One suggestion: When my late grandfather decided there was no more use
in maintaining his seven-year-old monochrome TV, just about that same
time, he disposed of the guts and turned the fine woodworking case
into a curio cabinet.

 

[William Sommerwerck]

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".

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.

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.

 

[William Sommerwerck]

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,

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.)

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)

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

treble boost to account for loss of HF due to the cutter being heated
to reduce noise)

Not a form of distortion.

corrections because the cutter traverses the disk radially and the
playback stylus does not

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

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.

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.

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*.

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.

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.

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.

 

[Jeff Liebermann]

On Mon, 13 Aug 2012 22:32:29 -0700 (PDT), jurb6006@gmail.com wrote:

Get a USB turntable. Sure, now where the fuck
do I plug it into this 1968 Magnavox mahogany monster ? LOL

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.

To cook dinner, right click the desktop and go down to food.

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.

In the categories there choose from meat, veggie, fish, poultry
etc. Click on the category you want and then read (OH NO)
the contents of the window that opens. Then choose side dishes.

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.

Make your selection and allow autocomplete to give the pizza
guy your life history and access to all your money and wait for
the bell to ring. Note if you live in a hi-rise apartment, death
may occur from starvation.

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:
<http://news.cnet.com/8301-1023_3-57489629-93/instacart-aims-to-be-the-amazon-prime-of-grocery-delivery/>

We apologize for any inconvenience.

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

 

[boardjunkie1]

On Aug 13, 12:37 am, "Klaatu" <which...@today.org> wrote:

"klem kedidelhopper" <captainvideo462...@gmail.com> wrote in message

news:94a40af6-2e0b-4c39-b866-a3bd1e6f2543@l10g2000yqo.googlegroups.com...

I got an old, (what looks like a BSR) three speed automatic turntable
in for repair. It doesn't work on auto because the plastic trip pawl
is worn. I can't get to the trip pawl without doing a semi major strip
down. And this guy isn't going to go for that. I would like to replace
the turntable with an equivalent inexpensive BSR type for him. I used
to be able to buy these from my parts suppliers for about 20 bucks
about 100 or so years ago but I haven't looked into this for a long
time. Is it still possible to find something like this, a basic
general replacement type idler driven mechanical turntable with a
cheapo ceramic cartridge? Thanks, Lenny

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

USB turntables are plastic junk....

 

"Use the MaggotBox for firewood and replace it something
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" much money on it lol.

Really though some people do like those, at one shop where I worked on a few of them they were clearing estimates for near $300. Still want that weenie 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 turntable and just hook it up to the existing speakers. It depends on the "purism" of the customer. In fact my Uncle BUILT a mahogany monster a long time ago. Copied a MacIntosh Williamson push pull design and built a pair of monoblock amps, dug up a preamp and tuner and mounted them, put in an Elac Miracord 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 would be worth quite a bit - to the right person (read fanatic) of course. In fact 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 cabinets. It was the cost of the new table model TV which we had to choose of course, plus about $250 labor. If a combo we would wire the TV sound to go through 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 ! Plus about ˝ the people I've ever known. Amazing how many ideas I had, and now 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,
we take dried soybean curd, add flavoring, modify the texture,
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 seems CBS is very stingy with them.

"There are numerous supermarket delivery services"

Yes but some of these high security buildings are ridiculous. Sign this, stand here for the photo, show ID. Next the TSA will be there doing cavity searches.

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 recoding. 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 concievably cancel out no ?

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

"IN THEORY it should work"

If you have never heard that one raise your hand.

J

 

[isw]

In article <k0d6br$guc$1@dont-email.me>,
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote:

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,

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.)

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.

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)

It was a component of Dynagroove

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

-- the only one that actually worked.

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

treble boost to account for loss of HF due to the cutter being heated
to reduce noise)

Not a form of distortion.


corrections because the cutter traverses the disk radially and the
playback stylus does not

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

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.

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.

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.

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

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.

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.

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.

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

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

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.

On that, we can absolutely agree.

Isaac

 

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

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

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 faceplate 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 to 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 them. This made HISS. Since the high frequency waves ARE actually smaller, they 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 and therefore to the master tapes made to record music. Hiss upon hiss. Think AM was bad ?

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 capacitors per channel achieve this. It matches because they match the "time constants" of the opposite network applied to the signal when it was recorded.

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 the 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 there 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 only thing.

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

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

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

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

Is it that good ? Well CD quality has been quite surpassed by certain DVD audio 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.

J