2V, 2.5V, and 4.5V Line Levels? What are they?

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#21
PRR said:
The nominal "max" level was +18dBm without gross distortion (couple % THD). But there were no good affordable peak meters. On running program not to be repeated, 10dB headroom didn't sound dirty, so +8dBm was system maximum.
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+8dBm was never a system maximum though. It was actually a "nominal level". The fact that there were no affordable peak meters didn't mean that we didn't know that peaks landed between 8 and 10dB above a VU meter "average". Line amps intended to drive program lines had
PRR said:
For re-recording to film or tape, repeated "slightly distorted" becomes annoying so +4dBm is nominal meter level.
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Actually, with film and tape there were (are) specific modulation levels (optical), or fluxivity (in magnetic media) that established a reference level which corresponded to a point where distortion would not only be acceptable, but would not reduce if the level was lowered. The point of increased distorion depended on the medium and arbitrarily chosen headroom.
PRR said:
With modern notions of <0.1% clipping this needs a +20dBm line amp. This "fits" in a +/-15V opamp, just barely, no margin for slop or surprise or build-outs. So most +/-15V consoles use bridged pairs; also to get nominal "balanced" mode.
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+/- 15V opamp balanced outputs will go to +26dBu. In the days of 600 matched circuit studios and lines major equipment manufacturers (RCA, Gates, etc.) made equipment intended to drive program lines with maximum output levels at +30 to +32dBm so that "nominal" +8dBm could be used. You drove +8dBm into a program circuit to get over line noise and EQ losses.
 
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#24
ejp said:
This refers to post #6 which I wrote. I don't understand the question.
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The confusing was that a line output voltage was stated as part of the Red Book CD standard. It is not. The Red Book, now known as IEC 60908, covers the specifications of the disc, both 80mm and 120mm, it's data format, number of tracks, sample rate, bit depth, copy protection, etc. It has nothing to say about a player's output voltage at any dBFS level. IF 2Vrms or 300mV RMS are standads, they didn't come from IEC 60908.

This makes sense too because neither level applies to professional players at all. And that would imply that a pro player violates the Red Book standard. That's not true because Red Book, IEC 60908, doesn't cover players, it covers only the CD media.
 
#26
There is no norm and it doesn't matter. The German ARD uses 1.55V, the studios use 1.228V and old FM tuners use 300mV. A good amplifier is specified for 150mV so that it can deliver its full power e.g. 100W. Modern OP amp circuits are supplied with 15V. 10V would also be possible without THD.
 
#27
ejp said:
Well I suppose the answer to your question is 2VRMS = 0dBFS, but that should already have been clear from 'playing a full-scale sine wave'.

The 300mV mentioned later as a 'nominal' level is used by some preamp manufacturers to describe CD inputs, not as any kind of standard.
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316mv is consumer line level, and is an accepted standard. https://www.aes.org/par/d/#decibel see -10dbV , it also correlates to -14LUFS used by streaming services.
 
#28
Streaming service would not be concerned with an voltage output of a device, nor would they have any knowlege of it.

And they all used different target LUFS for normalization.

For exampe:
Spotify: -14LUFS
Apple: -16LUFS
Deezer: -13LUFS

316mV/-10dBV is an accepted standard reference voltage, but there's no correlation to any streaming level.

Ever stream a movie then pop over to YouTube...then dive for the volume control? Yeah. That. Same device, different streams.
 
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