"keithr" <keithr@[EMAIL PROTECTED]
> wrote in message
news:482bc7ca$1@[EMAIL PROTECTED]
>
> "Iain Churches" <IainNG@[EMAIL PROTECTED]
> wrote in message
> news:0cGWj.949$_03.116@[EMAIL PROTECTED]
>>
>>
>> I have no idea what came before the VU, but I do remember
>> seeing tube driven VU meters at Decca. There was a shelf full
>> of them in what we called the Redundancy Store. In retrospect,
>> Aladin's Cave might have been a better name:-) The buffer amp
>> was just a simple cathode follower 12AU7. I used to own an
>> Ampex 351-2 tape machine with VUs but I cannot recall how
>> the metering was done. But I do know that the meter units for
>> European tape machines like the Studer C37 and J37, had a
>> tube buffer amp just like the one I describe.
>
> Heres a question to you Iain as a member if the recording industry.
> Whenever I see footage of recording and radio studios, it always seems
> like the VU meters are slamming into the red with alarming frequency, so
> why do you have the things when it seems like the engineers ignore them
> anyway?
Actually, one does not ignore them, but learn to
"interpret" them:-) Compared with any peak reading
analogue meter, the VU has a slow rise time of 300mS.
One of my first jobs when I started my training with
Decca in the UK was the duplication of safety masters
of Rolling Stones material, which had been recorded
at Bell Sound in New York. It was an interesting
experience..... The transfer console had PPM meters,
but the tape machines had VUs. After the white leader,
the meter whacked over to the end-stop +3 VU, and
stayed there, hardly fluctuating for the duration of the
title, and then slowly returned to the left-hand end stop
while the second leader passed, and then, whack over
to the end-stop again. This happened on every title.
My tutor, Alec Rosner, gave an excellent demonstration
of the VU characteristics. He recorded a long section of
1kHz tone at 0VU (+4dB) on analogue quarter-inch tape,
and then cut it into sections of 38cms, 19cms, 13cms,
10cms, 5cms, 2cms and 1cm etc etc all separated by 38cms
of leader.
The first segment caused the meter to rise to 0VU, likewise the
second (half-second) segment. On each subsequent segment the
durations of which were decreasing, the meter showed a lower and
lower reading as the duration oif the signal was shorter than the
rise-time of the The final segment was so short (but was still recorded
at +4dB) that it hardly caused the needle to flicker.
> In my limited experience of recording ( a friend and I used to record
> local rock groups at college) we were always extremely careful to
insure
> the the levels never went into the red.
Analogue tape distortion is actually quite benign, but nevertheless
just like you, we were taught to strictly observe peak levels. At
Decca the standard was +8dB and monitored on PPMs. You
were required to write the peak level on the tape box. No one
expected it to deviate > +/-1dB. Each tape also had a frequency
alignment run, 3pips left. 4 pips right, 1kHz, 15kHz (azimuth)
12kHz (HF) etc going down in steps to 5kHz (MF) and then
down to 100Hz (LF) with 50Hz and 20Hz at the lower end.
I visited the BBC frequently when I lived in the UK, but by
that time they were using their own excellent analogue PPM.
They were meticulous about peak levels sent to the
transmitter. Heavy compression and peak limiting in
broadcasting was not common then as it is today.
There is renewed interest in the VU meter now, escpecially
in CD mastering where it makes an interesting addition to the
ubiquitous digital peak meter. The peak meter gives one no
idea at all of the amount of compression being used, but,
accurately interpreted the VU can tell you a lot. It's an
interesting meter because it gives you an indication of
"perceived loudness" to the ear.
I am currently putting the fini****ng touches to a tube-
driven VU meter unit. The final unit is now complete
except for top and bottom panels, and as soon as I
have these I will post a link to this project.
Regards to all
Iain
|
