Three speed automatic turntable replacement

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 ?=20

If you are really interested i have a lucky recording. The surface noise of the vinyl disc, the residual FM broadcast noise, and the residual NAB tape hiss of a nice Ampex AX-300 semipro open reel tape deck are all = about the same level. If you know how to listen to you can hear the three different noises clearly.

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.=20

some

dbx

To

=46ine. Dbx systems included dynamic compressors, like A-law and u-Law telephony systems. Provided better dynamic range and other nice properties at the cost of more processing, see also SACD.

?-)

--snip --

He was chief engineer for several recording companies. What are your qualifications?

Yeah ... I didn't think you knew.

Isaac

Of the signal "modifications" applied prior to cutting -- to prevent slope, displacement, and curvature overload, stylus tilt correction, distortion of the groove so the output of a spherical (or elliptical) stylus will better approximate the original signal, LF vertical limiting to guarantee there always will be a groove to track, ..., a number are not reversible during playback even in theory. I don't see how those can be called anything except "distortions".

And, FWIW, John Eargle refers to the things done to the audio to make it suitable for making vinyl disks as "distortions" ...

Nope. Just a retired EE and a long-time student of the audio recording and reproduction process, with some experience in a recording studio and at running a cutting lathe. And a serious pragmatist, when it comes to what is necessary and sufficient for good *domestic* audio reproduction.

Of course I don't object to them; they are necessary to get even the not-very-good reproduction that the analog media you mention are capable of.

The bass is cut to minimize stylus excursion at low frequencies; that would be a problem no matter what the disk was made of.

I have designed low noise/low distortion RIAA preamps; the better ones have three breakpoints (3180 µs, 318 µs, and 75 µs), plus a fourth HF rolloff to keep the loop gain from dropping too low in the ultrasonic range (improves stability), and sometimes a fifth to keep the sub-20 Hz stuff from messing with the speakers.

Well, except for the unilaterally applied radial EQ (the cutting amp boosts the highs towards the inner grooves -- the corresponding playback cut is neither specified nor controlled; it just happens because the groove "wiggles" get closer together there.

Preemphasis was included in the CD spec, and was used at first, but it is rarely used today; hasn't been for a long while.

For CDs, the dither signal is rarely white noise; other spectra are more useful.

All this info is in the Eargle book I mentioned earlier.

Isaac

The only compression used was dynamic-range compression, which was (badly) needed for 8-bit (!!!) digital recording. As you said, you could make audio-only recordings. Pioneer produced a machine that could record 24 hours on a single two-hour video tape, using six passes. (Pioneer's presenter at the SCES remarked sarcasticly that some people could put their entire LP collection on a single tape!)

A good live broadcast on FM has far better sound that most CDs. 15kHz is hardly a meaningful limitation.

Agreed! (I have it, too.)]

Normal mode is 44.056 kHz, 14-bit. 16-bit recording gains two bits by weakening the error correction, making uncorrectable errors more likely. (I never had problems with 16 bit.)

separates the positive and negative, then it is further compressed down to eight bit words. Additionally there is a Dolby-like noise suppression scheme. That is not quite high fidelity, yathink?

If you're talking about CDs, that's mostly wrong. The CD format is linear. There is no "Dolby-like noise suppression scheme" of ANY sort. EFM means "eight to fourteen modulation", which maps eight bits of each 16-bit data word into a 14-bit "space". This reduces read and pressing errors, and makes it easier to correct those that do occur.

The PCM-F1 is essentially identical to CD. Both are 16-bit, and their sample rates differ only by 0.1%.

You're confusing the PCM-F1, CD, and DAT. DAT has 48kHz sampling (plus 44.1 and 32). The others don't. NONE of these systems use lossy compression. And they're all "real" 16-bit.

Most systems of theatrical digital sound use some form of lossy compression. But I believe non-lossy compression is beginning to appear. (Someone fill me in, please.)

The original Red Book standards defined a four-channel disk that ran at double speed (halving the playback time). Unfortunately, the idiots at Philips neglected any provision requiring two-channel-only CD players to be compatible with four-channel disks.

As long as we're on it... The Philips idiots also missed the opportunity to double the playback time for mono recordings.

To quote Alexander Pope: "A >>little

I know what I'm talking about. Does Mr Eargle?

I didn't say John Eargle was wrong. I said I was right, and that if his views (which I don't know in detail) were different, then he's wrong. I stand by that.

what

the

like.

The paragraph reads: "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."

Do you know the difference between velocity and constant-amplitude recording? If a recording approximates constant-amplitude, then the groove waveform will approximate the original waveform. Right? RIGHT?

Why don't you just google on his name and decide for yourself?

Nope. Not even close.

An electrical generator (a magnetic cartridge) provides a constant voltage in response to a constant velocity. To get a more-or-less square wave, the groove is a triangle wave. The slopes equate to the flat top and bottom, and the inflection points to the rising and falling edges.

Isaac

groove

It's dead-on.

There are non-magnetic electrical generators. You meant a /velocity/ device.

Only if it's a velocity generator.

Yes -- out of an UNEQUALIZED magnetic pickup.

Do I have to explain it all over again? Seems so.

When you cut a phonograph record with an electromagnetic head, you get a constant-velocity recording. That is, groove modulation is huge for low frequencies, teensy for high frequencies.

There two basic problems with this. The extreme low-frequency excursions require a very wide groove pitch (reducing playing time) and the high frequencies are "down in the dirt" (making the sound noisier than we might like).

The solution adopted by the recording industry was to cut the bass and boost the treble to produce an approximation of constant-amplitude recording. I say an "approximation", because a huge amount of boost and cut would be needed to get constant amplitude from (say) 50Hz to 20kHz (about 50dB). In practice, the bass cut stops at about 500Hz and the treble boost begins at about 2kHz (which needs only about 30dB).

The result is a recording that's much closer to constant amplitude. If one looks at a constant-amplitude recording under a microscope, it will resemble the original acoustic waveform -- not the temporally integrated waveform produced by an un-EQ'd magnetic cutter head..

When recording using RIAA (or other) EQ is played back with a constant-amplitude pickup, the output is essentially flat, exactly what we want in a cheap phonograph. When played with a magnetic (velocity) pickup, the constant-amplitude waveform is differentiated, requiring integrating equalization in the amplifier. Which is what phono preamps provide.

I realize this can be confusing, but the preceding is correct. You need to think it through.

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If you don't count quantizing error and aliasing effects.

kes

And kindly describe another kind of electromagnetic generator?

In fact, I did not "think it through" until I happened to actually LOOK AT THE GROOVE of the "square wave" track of a test record. Then I thought "well, that's odd ..." and then I realized what must be going on.

Isaac

Quantization is nicely taken care of by the dither, and aliasing by the oddly named "anti-aliasing low-pass filter" which is an integral (and mandatory) part of the process.

Isaac

I still have my CBS Labs test LPs, and don't even need to look at the square-wave disk to know that the groove doesn't resemble a triangle waveform. IT CAN'T, because an LP cut with RIAA equalization comes much closer to being constant-amplitude than constant-velocity.

-----------------

After writing that, I decided to pull out the STR 112 test disk. It turns out it //does// have triangle waveforms. Here's what the liner notes say...

"Two groups of four 1000 Hz square-wave [sic] test bands are provided on the STR-112, Side A, at the outer and inner radii of the disc. ... The actual modulation excursion, as viewed under a microscope, is a triangle wave. Therefore, playback with an ideal velocity responsive [sic] pickup will yield a square wave."

In other words... This is NOT a constant-amplitude recording, and it is to be used //without// RIAA equalization.

"The square wave modulation allows rapid appraisal of stylus-tip mass, damping, and tracking."

But the disk doesn't have "square wave modulation".

If the conclusion isn't clear, I'll beat it into the ground with a sledge hammer. This disk DOES NOT test what it claims to test. You cannot test the "square wave" response of a pickup by applying a grossly different stimulus!

What the disk actually tests is the response to a triangle wave. The fact that a (nominal) square wave pops out of a velocity-responding pickup is beside the point -- especially because an LP mastered with RIAA EQ //would// have a groove displacement that looked a lot like a square wave -- the pickup's response to which is what we're supposed to be testing.

QED. Case closed.

somehow compressed. Not the data but the music. the texchnique was = developed for the 8mm Sony digital audio format which ran on the same = tapes as the camcorder. It would record IIRC 12 tracks, like an old eight= track. You could switch tracks but to get back to the beginning unless = you rewind the tape.=20

sectors. The 8mm system had integral flying erase heads, just as PAL had= an integral COMB filter. You COULD change tracks with ease, if the tape = position was near.=20

find out a few things. First of all it's LIMITATIONS are that of an FM = broadcast. Well two, in tandem to give you two channels. But you are only= getting 15Khz.=20

worked. But I have in my posession the full manual on the PCM-F1 which = explains it's operation in more detail than anyone could ever want. It = has the normal mode which is 44,100 siteen bit. Your CDs are not that. = The 16 bit audio is cropped down by EFM which separates the positive and = negative, then it is further compressed down to eight bit words. = Additionally there is a Dolby like noise suppression scheme. That is not = quite high fidelity, yathink ?=20

if tha isn't good enough, it has a 48Khz mode, which is what the big = movie theaters etc. use. And there is no compression at all. Well they do= use it but they have REAL sisxteen bit, CDs do not.=20

the ubiquitous CD is capable of four channel discrete sound. (reference a= book called "Principles Of Digital Audio" circa 1990 or so for that)

stopped before the "you know what you are talking about" part.=20

You are incorrect on some points. =20

CDs are true 44100 samples per second, 16 bits per channel, stereo. Any compression is applied before translation to disc; that does not mean = that there isn't any, it is just not in the process from audio stream (analog or digital) to disc to what comes out of a standard player.

=46rom what you say you have no idea what EFM is or does. Let alone how = it is used in making CDs.

?-)

turns

say...

the

actual

to

sledge

the

stimulus!

Wrong. Oh and BTW the velocity of the track IS (approximately) a square wave. Think that through.

fact

//would//

And you really missed a lot. The output of the cartridge is a = approximate square wave for that track, if you run that through RIAA playback equalization you get a very different signal.

?-)

They're commonly found in cheap turntables, especially of the USB ilk.

Yes, of course. That's simple calculus, which I took in high school almost

50 years ago.

First of all, the issue has nothing whatever to do with whether amplitude-responding pickups exist, ever have existed, or ever could exist. We are talking about a manufacturer claiming that a test record shows how a pickup responds to (mechanical) square-wave modulation, when the disk doesn't have such modulation.

Piezoelectric transducers are basically amplitude-sensitive. Crystal and ceramic pickups were manufactured for decades, but gradually disappeared as magnetic pickups grew less expensive and tracked at lower forces. There have been "good" ceramic pickups (Sonotone and Weathers, for example), but they were rare. However, you can still find ceramic pickups in cheap turntables.

(The author's claim that anti-skating is an absolute necessity is debatable, to say the least.)

If you want to get super-ultra picky about it, many ceramic pickups are mechanically equalized to compensate for the ~12dB shelf in response when playing RIAA LPs. This doesn't change the fact that the pickup is, fundamentally, an amplitude-responding device.

It appears that we are equally annoyed by the spread of misinformation.

I seriously doubt that. Those pickups are either magnetic or piezoelectric, both velocity response.

almost

exist.

how a

But it IS a square wave in velocity. Also, is there any cutter that you can imagine that cut a square wave in amplitude or a stylus that can = track it?

as

have

they

turntables.

debatable,

There are plenty of other techniques have equivalent geometry to the cutting lathe to be sure.

when

If you get a strain sensor pickup they are amplitude responding. Rare = and very expensive. Also there are laser types that are "amplitude" responding; even more expensive.

it is

of

(1997)

are

RJ-45

have

Sorry, piezo pickups are amplitude-responding. Where did you ever get the idea they were velocity-responding? If you have any doubts, get a ouija board and contact Pierre Curie.

I detest "appealing to authority", but here are six (technically, five)...

(This article is 54 years old.)

(Note, in particular, the response curves.)

These are among the top listings when Googling "ceramic pickup amplitude response" (sans quotes). Note that in the fifth one, the writer shows a fundamental misunderstanding of why recording EQ is used and how it is implemented.

Anti-skating has nothing to do with matching the geometry of the cutting lathe's path. However, there have been numerous attempts at tone arms that either track linearly, or which have zero tracking error. Unfortunately, there's never been one on an $80 hunk-o'-plastic.

See preceding.

Linear tracking doesn't work out well in practice in any case, because the signal sent to the cutter is distorted (or pre-altered, or modified, or call-it-what-you-will), to benefit playback with a pickup traversing the disk in an arc.

Isaac

This is absolutely untrue. If it were true -- what would the point of linear tracking?

It is theoretically possible (in much the same way that Dynagroove distorted the groove to compensate for the finite diameter of the stylus) to do this, but it would require a standard for the tracking error -- that is, every arm would have to have "mis-track" in the same way.

There is no such standard, and never has been.