Analogue audio chain technical standards (no yawning please)

[Mark Wright]

Just trawling through various random clips of classic BBC TV pres from the 70s-90s on YouTube and it's interesting how noisy and compressed the audio often is. I can remember as a viewer (and anorak) at the time noticing occasional distant whirs and hums when the announcer's mic was live, or the odd "nngggg" audio artefact when there were certain bright dominant colours on screen (e.g. Pages from Ceefax) but not the rumble of a processor/limiter dragging up the silence as exhibited here:

https://www.youtube.com/watch?v=y66ETrIzyak
https://www.youtube.com/watch?v=44NLgOOp91Q

So I'm wondering, was the audio chain really this noisy on broadcast? Clearly there's processing on the con mic (hence you can hear the "air" in the room along with the various clunks) and limiting on the output, all normal practice. Perhaps what I'm hearing is the result of a video recorder's "auto gain" feature, in much the same way as sync splats are accentuated in clips sourced from VHS? Poor tuning/signal might account for all the buzzing and humming, exaggerated by the AGC. I realise that sound quality will have suffered as part of the transfer/encoding process too, but I'm farily certain what I'm referring to is part of the source material.

And while I may have answered my own question here (sorry everyone) I'm still curious as to what went into the audio chain between pres and transmitter in the analogue days.

[Bernie]

No, no compression leaving us, just straight audio - levels set on the PPM. I think transmitters had some kind of top limiter but we would never be near that.

Any crackle and noise is downstream, as is level pumping. In the second clip you can hear background air con and the sound of faders and cut buttons behind Andy Cartledge, but that's it.

B