[Audio Empire]

On Mon, 3 Sep 2012 07:54:49 -0700, Arny Krueger wrote
(in article ):

"Audio Empire" wrote in message
...

You've brought-up a good point. When recording digitally, you just don't
want to come too close to that MSB.

This is an audiophile myth, just as surely as the idea that having extensive
unused power reserves makes power amps sound better.

I'll tell you what you do, overmodulate PCM so that you're trying to use
more bits than you have and watch what happens!

Craftsmanship suggests that you don't want to clip, but actual listening
reveals that a few short overages will escape even the most critical ear.

In analog that's true. Especially on a good pro tape recorder at 15 ips.
I've had recorders (like my old Otari MX2020) where you could bang the
needles against their pins momentarily with no APPARENT audible effect
(although I'm sure you could measure it at greater than 3%, you just can't
hear it) In digital recording, that kind of laissez-faire attitude toward
100% modulation is a distinct no-no.

While a pro analog tape machine can go
over the 0 Vu mark occasionally with little or no consequences, you never
want to do so in digital.

That's primarily because the position of the 0 dB mark on analog tape
recorders is almost always a judgement call.

It shouldn't be a judgement call. There is an ANSI spec for reel-ro-reel
tape. It's supposed to be: 0 VU = +4dBu = 1.23 V AC RMS or a fluxivity of 320
nWb/m. I used to always calibrate my tape recorders to that standard. Now, it
is true that with most CONSUMER tape recorders, that spec is reduced to *10dB
= 100% modulation or "0 Vu" or 200 nWb/m of fluxivity. That. BTW, is what
Dolby B was calibrated at for reel-to-reel tape but the Dolby "A" calibration
tape was 320 nWb/m at 400 Hz, however. The original Bell Labs spec called for
this spec to be adhered to at 1KHz, but the NAB used 700 Hz and a lot of pro
recorders used 400 or 500 Hz as the reference. In reality, the difference
between 400, 500, 700, or 1KHz is negligible as any pro recorder worth it's
salt is going to be ruler flat at any of those frequencies.

In some people's minds 0 dB was supposed to represent 1 % THD or 3% THD at
400 Hz or 1 KHz, but in reality things were never stable enough to make
those points stable, repeatible, or even necessarily audibly meaningful.

0 Vu or 100% modulation is not defined by the distortion in the ANSI or NAB
spec, it is merely defined as a voltage level or more usefully, a coercivity
spec. However a rule of thumb in a properly calibrated pro analog tape
recorder is that 0 Vu = 1% distortion and +3dB = 3%. But again, that's based
on a combination of characteristics including head and tape saturation levels
at a given frequency as well as the linearity of the recorder's electronics
and the amount of distortion present in the bias signal.

I used to know a guy who recorded on an Ampex 350 transport fitted with the
latest design sintered ferrous heads from Nortronics with some custom tubed
electronics that he built using the high-end audiophile practices of the day.
He took the standard Ampex record/playback electronics and rebuilt them using
simplified circuitry with metal film resistors replacing the carbon variety
and "WonderCaps" polypropylene capacitors replacing the original paper
capacitors for the larger stuff and polystyrene caps replacing the mica and
ceramic capacitors for the smaller values. The recordings he made were the
cleanest reel-to-reel tape recordings I've ever heard. He let the needles
bang the pin so hard that they often looked like they were stuck there during
orchestral crescendi! But on playback, one never heard the slightest soupcon
of audible distortion. Amazing.

Don't know what happened to him, but he did produce a couple of records for
the Musical Heritage Society while he was doing that.

In contrast, digital FS is a stable, reliable, well-defined point. As a rule
its the same at every frequency in the audio band.

Yes, thank whatever gods there may be, that we don't have to sit for hours in
front of a tape recorder before a session, calibrating, first the playback
using a standard calibration tape, and then the recording bias and eq using
an oscillator to make sure that the round-trip response was flat to at least
15 KHz. And that's the drill if you WEREN'T using Dolby A or DBX!

Digital recording has put all that in the past and frankly, good riddance!