Pal Analogue Audio level

[Bob Zelin]

They have a new invention – it’s called a MIXER ! There are lots of American brands (like Mackie) and even British brands (like Soundcraft and Allen Heath). But seriously, I too have noticed that the default output of the I/O is NOT +4dBu. I never setup ANY system without an audio mixer.

Bob Zelin

[Darren Mostyn]

Thanks Bob for the quick response. I have a mixer (spirit folio), but all this will do is take a now overmodulated signal and reduce it in my mixer -this is surely not the way to keep audio levels best quality.
So, I presume there is still no way to reduce this level from the IO box.
Best Regards
Darren.

[Bob Zelin]

you state –
I have a mixer (spirit folio), but all this will do is take a now overmodulated signal and reduce it in my mixer

Sir – you take the +4dB analog source (your Beta VTR, etc.) and send this into the mixer. You can then ATTENUATE (drop) the level of the analog signal before it goes into your AJA I/O box. No overmodulation – no distortion.

Ready now to finish your job and dump back to your VTR? Take the output of your AJA I/O and send it into your mixer. Send the output of the mixer into your VTR. You can now use the mixer to easily set the levels of the VTR, by simply moving the faders on your mixer. The Soundcraft Spirit Folio easily can handle a +4dBu signal (it can handle a lot more than that without distortion).

bob Zelin

[Darren Mostyn]

Bob, Hi.
I understand what you are saying, and of course that would work. My point was that even if I reduce my levels (as you rightly suggest) to compensate for the Aja box then I am reducing quality. Basically, the level in does not equal the level out on the Aja IO box. I can ‘compensate’ for this in my mixer but I will be losing quality by reducing the level available (ie, the full level) to allow Aja to add not 4, but more like 8 or 9 dB on the output. (PPM diference between 4 and 6 is 8dB).
I will try this out and see anyway. I am also reducing the output level in FCP so we’ll see if this sounds good.
BTW – Tested the box for frame accurate insert editing and it worked a treat. All seems great with it except this issue. Is this a PAL only thing..? Surely it is an easy firmware fix..?
Thanks again,
Darren Mostyn.

[Ed Dooley]

Darren’s point is that the signal coming *out* from FCP through his IO is hotter than +4db. Sure his mixer can handle +4db, but that’s not his problem. The problem/question is it’s getting more than +6db. Again, his point is that he’s forced to lower a hot signal, not whether he needs a mixer.
Darren, I haven’t noticed this on my IO LA here in NTSC land. I’ll check it as soon as I get onto a system.
Ed

[Bob Zelin] “you state –
I have a mixer (spirit folio), but all this will do is take a now overmodulated signal and reduce it in my mixer

Sir – you take the +4dB analog source (your Beta VTR, etc.) and send this into the mixer. You can then ATTENUATE (drop) the level of the analog signal before it goes into your AJA I/O box. No overmodulation – no distortion.

Ready now to finish your job and dump back to your VTR? Take the output of your AJA I/O and send it into your mixer. Send the output of the mixer into your VTR. You can now use the mixer to easily set the levels of the VTR, by simply moving the faders on your mixer. The Soundcraft Spirit Folio easily can handle a +4dBu signal (it can handle a lot more than that without distortion).”

[Darren],/B>
“Just got FCP 5 and an Aja IO box today. Upon checking the Inputs and Outputs I have noticed that the audio level out from a -18dB (Pal) test tone generated in FCP out of the IO straight to a set of PPM’s reads over 6. This should read 4. There is no way of controlling the analogue output of the IO as far as I can tell. Does anyone have a solution for this?”

[Bob Zelin]

Darren –
Attenuation (dropping the level of a signal) does not reduce the quality of a signal. Amplification (increasing the level) is what add’s noise. But modern mixers from companies like Mackie and Soundcraft have noise floors of -90db, so a small increase in amplification would be insignificant. Believe me, analog Beta machines are not that quiet to begin with – that is why the world switched to digital audio !

Bob Zelin

[Darren Mostyn]

Thanks Ed. Would be interested to know (not that I can suddenly start editing in NTSC of course!!!).

[Darren Mostyn]

If I drop my analogue signal -6dB to go into the system to compensate for it coming out 6dB higher (at least) I WILL be losing some quality. As you say it can reduce by -90dB but this is an exponential curve we are talking about. An initial reduction of 6dB to my signal gives me much less of a signal to mix and add effects etc. in FCP. Any other system I have worked on (Avid, Pinnacle, Sony Xpri, ES-3) allows me to set and fine tune audio reference/attenuation for the hardware. I would love to work with SDI or AES/EBU audio all the time and remedy this situation but whilst some of my clients still hand me Beta SP tapes and I do not have a spare

[Dave Jenkins]

Darren, We run through a mixer but what we are seeing is:
when we capture at -12db on the FCP meters it plays back at -6db in FCP after capture.
I’m not sure if that’s what your seeing as you were taking about output and we see it on input.
This is NTSC.

Dajen Productions
Santa Barbara, CA
G5 Dual 2 Gig – AJA IO & LA
Huge 1.2 Raid
FCP 5-OS X 10.4.1-QT 7

[Darren Mostyn]

Hi Dave,
Appreciate the feedback (no pun intended!),
Will try this out on Saturday when I return to UK and compare notes. Seems like a bit of a mis-match going on somewhere down the chain. Away on a job at the moment.
Darren.