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Re: 0db or -8db



I've seen the original post and the several responses to the Nagra tape signal
level question.

I handle a lot of location 1/4" tapes all recorded on Nagra IV machines and in
the UK all the Nagra's are lined up to give a line-up tone at 8db below peak
level.    We all work with peak programme meters here and I can not be sure of
the equivalent on a VU meter,  but I remember it being about -4 on steady tone
on a VU meter.   ( To be more confusing,  it shows -40 on a Nagra "T" meter.)  I
shall check with the experts on the levels recorded on tape.

Some of the tapes I get from US recordists have a line-up and recording level
much higher than this so I'm not sure if Nagra's in the US are lined up to a
record a much higher signal on tape.

We normally transfer into a hard disk recorder and we have to keep a careful
check when using Nagra location tapes.    We set the Nagra line-up tone to -18
on the digital scale and this works well for the majority of recordings,  but if
the location recordist is working with no recording limiter on the Nagra it is
possible to get digital distortion since the Nagra repro amps have a headroom of
+18db above peak.    On occasion this can give some peculiar results,
especially with strong male voices, where they are apparently peaking well
within the dynamic range on PPM's,  but the very short term transients are way
above peak level and causing distorion in the digital equipment.    In cases
like this,  we have to lower the recording level into the hard diak recorder and
enclose a warning for dubbing editors and mixers.   This is one of the reasons
that a lot of location recordists still prefer the Nagra.    When using DAT on
location,  some recordists resort to working in twin track mono and recording
the right hand track 10db down so that there is a fair chance of avoidiing
distortion when the dynamic range of the DAT cannot handle peak and transient
distortion.

Jim Guthrie
Sprocket & Bytes Ltd.,
Bristol/Denham.  UK  

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  E-mail from: Jim Guthrie, 29-Jun-1996