"David Looser" wrote in message
...
"Iain Churches" wrote in message
ti.fi...



But the Decca PPM as such had an Ernest Turner
meter with the red segment starting at +8dBm.
IIRC It had a rise time of 10mS and a slow decay
(2 secs) They was also a later faster
version with the peak level marked at +12dBm.


Is the Decca PPM actually marked in dBm, rather than just dB?.


It's 28 years since I saw one, but yes I am sure they
were calibrated in dBm I may have some photos of the Neves
in Studio II, and at Tollington Park, and the Decca mixer in
Studio III. I will try to find them. The meters in copying
and cutting rooms had a red line at +8dBm, but other
versions had a red segment from +8dBm and the later
faster meters in Remix II had the red segment starting
at +12dBm.

There must have been many hundreds of these meters
in use at Decca.

Iain

"Iain Churches" wrote in message
ti.fi...


"David Looser" wrote in message
...
"Iain Churches" wrote in message
ti.fi...



But the Decca PPM as such had an Ernest Turner
meter with the red segment starting at +8dBm.
IIRC It had a rise time of 10mS and a slow decay
(2 secs) They was also a later faster
version with the peak level marked at +12dBm.


Is the Decca PPM actually marked in dBm, rather than just dB?.


It's 28 years since I saw one, but yes I am sure they
were calibrated in dBm I may have some photos of the Neves
in Studio II, and at Tollington Park, and the Decca mixer in
Studio III. I will try to find them. The meters in copying
and cutting rooms had a red line at +8dBm, but other
versions had a red segment from +8dBm and the later
faster meters in Remix II had the red segment starting
at +12dBm.

There must have been many hundreds of these meters
in use at Decca.


Then this is yet another example of the audio industry's notorious
sloppiness with the use of the term "dBm". I'm sure that if a line-up tone
indicated "0dBm" on the meter an rms voltage of 0.7748V (0.7748V rms
dissipates 1mW in 600 ohm) was present at the line-out of the mixer. But
that doesn't mean that the meter was actually reading dBm with music signals
(rather than tone) or if the impedance presented to the mixer line-out was
other than exactly 600 ohm.

I would have expected better of Decca.

David.

David Looser wrote:

"Iain Churches" wrote in message
"David Looser" wrote in message
"Iain Churches" wrote in message


But the Decca PPM as such had an Ernest Turner
meter with the red segment starting at +8dBm.
IIRC It had a rise time of 10mS and a slow decay
(2 secs) They was also a later faster
version with the peak level marked at +12dBm.


Is the Decca PPM actually marked in dBm, rather than just dB?.


It's 28 years since I saw one, but yes I am sure they
were calibrated in dBm I may have some photos of the Neves
in Studio II, and at Tollington Park, and the Decca mixer in
Studio III. I will try to find them. The meters in copying
and cutting rooms had a red line at +8dBm, but other
versions had a red segment from +8dBm and the later
faster meters in Remix II had the red segment starting
at +12dBm.

There must have been many hundreds of these meters
in use at Decca.


Then this is yet another example of the audio industry's notorious
sloppiness with the use of the term "dBm". I'm sure that if a line-up tone
indicated "0dBm" on the meter an rms voltage of 0.7748V (0.7748V rms
dissipates 1mW in 600 ohm) was present at the line-out of the mixer. But
that doesn't mean that the meter was actually reading dBm with music signals
(rather than tone) or if the impedance presented to the mixer line-out was
other than exactly 600 ohm.

I would have expected better of Decca.

You mean dBu of course ! ;~)

Graham

"Eeyore" wrote in message
...


David Looser wrote:


Then this is yet another example of the audio industry's notorious
sloppiness with the use of the term "dBm". I'm sure that if a line-up
tone
indicated "0dBm" on the meter an rms voltage of 0.7748V (0.7748V rms
dissipates 1mW in 600 ohm) was present at the line-out of the mixer. But
that doesn't mean that the meter was actually reading dBm with music
signals
(rather than tone) or if the impedance presented to the mixer line-out
was
other than exactly 600 ohm.

I would have expected better of Decca.

You mean dBu of course ! ;~)


Oh Indeed!, dBu was invented to be the thing that audio engineers had long
pretended dBm was, but wasn't. The silly thing is that had Decca simply
marked the scale "dB", it would have been correct, as it was they added the
"m" to make it wrong. Why?

David.

In article ,
David Looser wrote:
Oh Indeed!, dBu was invented to be the thing that audio engineers had
long pretended dBm was, but wasn't. The silly thing is that had Decca
simply marked the scale "dB", it would have been correct, as it was
they added the "m" to make it wrong. Why?

No real need to mark it with anything. The BBC PPM doesn't - simply 1-7.
Or ABCD 1-7 if anyone remembers those. ;-)
A PPM is an operational tool, in essence, for the use of a sound mixer -
not a laboratory standard measuring device.

--
*The problem with the gene pool is that there is no lifeguard *

Dave Plowman London SW
To e-mail, change noise into sound.

On Wed, 06 Feb 2008 23:20:39 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
David Looser wrote:
Oh Indeed!, dBu was invented to be the thing that audio engineers had
long pretended dBm was, but wasn't. The silly thing is that had Decca
simply marked the scale "dB", it would have been correct, as it was
they added the "m" to make it wrong. Why?

No real need to mark it with anything. The BBC PPM doesn't - simply 1-7.
Or ABCD 1-7 if anyone remembers those. ;-)
A PPM is an operational tool, in essence, for the use of a sound mixer -
not a laboratory standard measuring device.

Don't forget 1 - 2 - 3 - TEST - 5 - 6 - 7 where TEST would correspond
to 0VU on a VU meter.

d

--
Pearce Consulting
http://www.pearce.uk.com

In article ,
Don Pearce wrote:
Don't forget 1 - 2 - 3 - TEST - 5 - 6 - 7 where TEST would correspond
to 0VU on a VU meter.

[Sharp intake of breath]
What a VU should read at 'zero level' is the source of many a debate. ;-)

--
*It IS as bad as you think, and they ARE out to get you.

Dave Plowman London SW
To e-mail, change noise into sound.

David Looser wrote:

"Eeyore" wrote
David Looser wrote:

Then this is yet another example of the audio industry's notorious
sloppiness with the use of the term "dBm". I'm sure that if a line-up
tone
indicated "0dBm" on the meter an rms voltage of 0.7748V (0.7748V rms
dissipates 1mW in 600 ohm) was present at the line-out of the mixer. But
that doesn't mean that the meter was actually reading dBm with music
signals
(rather than tone) or if the impedance presented to the mixer line-out
was
other than exactly 600 ohm.

I would have expected better of Decca.

You mean dBu of course ! ;~)

Oh Indeed!, dBu was invented to be the thing that audio engineers had long
pretended dBm was, but wasn't.

Exactly.


The silly thing is that had Decca simply
marked the scale "dB", it would have been correct, as it was they added the
"m" to make it wrong. Why?

Habit perhaps ?

I know people who still use dBm incorrectly today from force of habit.

Graham

"Dave Plowman (News)" wrote:

Don Pearce wrote:

Don't forget 1 - 2 - 3 - TEST - 5 - 6 - 7 where TEST would correspond
to 0VU on a VU meter.

[Sharp intake of breath]
What a VU should read at 'zero level' is the source of many a debate. ;-)

Is it ?

It reads '0' with a 1.228 V input and loads the circuit with 7.5 kohms.

Graham

--
Iain
Aural perception is a skill that requires study and careful development over
along period of time. Few have it as a natural gift.
"Eeyore" wrote in message
...


"Dave Plowman (News)" wrote:

Don Pearce wrote:

Don't forget 1 - 2 - 3 - TEST - 5 - 6 - 7 where TEST would correspond
to 0VU on a VU meter.

[Sharp intake of breath]
What a VU should read at 'zero level' is the source of many a debate. ;-)

Is it ?

It reads '0' with a 1.228 V input and loads the circuit with 7.5 kohms.

Indeed. And has done so since May 1939:-)

VU meter characteristics were precisely defined by
ANSI specification "Volume Measurements of
Electrical Speech and Program waves" C16.5-1942
(which is now incorporated into IEC 60268-17).

Iain