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Gear / Technical Help => Battery Boxes, Preamps, Mixers, ADCs, and Processors => Topic started by: balou2 on June 21, 2006, 03:03:11 AM
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Still on my learning quest....
How many folks out there do an actual analog input alignment? For the all-in-one boxes (e.g. v3, ua5) I guess this would not be necessary, but for those running pre>ADC, who is actually doing this? If I understand this right, the analog input levels need to be aligned using a 1 kHz sinewave fed from a +'X' dB balanced source.
A couple of questions:
- How necessary is this procedure?
- I don't have a digital peak meter. Is there another way to calibrate this?
- What are the possible ramifications of NOT aligning my analog outpu?
In my case, I'm running v3 > ad2K+, and hopefully looking to upgrade to v3 > mytek 192. The Mytek has trim pots that are adjustable in 10-turn increments, running from mute to +4dB. According to the Mytek technical specs, +4dB = -6dbFS, which is pretty sensitive. Regardless, the trim pots allow for the manual alignment, but does anyone know how this would be done with the AD2K+?
I remember a couple years ago (seriously) there was a thread about calibrating ADCs to a pre. I don't recall if it was the same thing, but I'm assuming it was probably close.
Thanks in advance for the dialog.
Mike
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If I remember correctly there was some info about this on the sonicsense website. I remember glancing over it once or twice awuikle ago. I'm not sure if it's still there, I'll check and see.
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here is the page. I'm not sure if it is exactly waht your looking for but it might help
http://web.archive.org/web/20020815073321/sonicsense.com/calpage.htm
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Yeh...that's the right info, but not for the AD2K. I'm pretty sure I cannot do the analog input alignment without the gain pots. I was just hoping someone knew a trick that I was not aware of.
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I believe the technique you're speaking of demands that the ADC have some sort of adjustable trim/gain...a la ADC-20, Mytek etc. The AD2K cannot be "aligned" in this nature to the best of my knowledge.
As for the ramifications, they'll only be as severe as the equipment will dictate. If you're running high-end equipment, you will notice little to no difference in the subtle db-variation resulting from NOT calibrating your analog input. As long as the V3 stabalizes your mic inputs, you'll be fine.
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yeah, using that gear, i wouldnt worry about it, when i ran v3>modsbm1, i just calibrated the modsbm1 output to where the v3 would clip w/ the ansr on, so thatw ay instead of glancing at the modsbm1 all the time, i could just glance at the v3's peak hold and know the modsbm1 wasnt going over ;)
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According to the ad2k manual, "The “Input Level” switch should be set so that the AD2402-96 will clip 3 to 6 dB before the
microphone preamplifier.
I usually set it at +22 and run the V2 pretty damn hot (a fair amount of red flashing, but not out of hand) and use the trim pots, just a little, to fine tune the levels. The red lights on the V2 come on at +16 and it clips at +26 so I think what I am doing is pretty close to gain matching or input alignment.
Also, per manual, "For example, if your microphone preamp has a maximum output level
of +24 dBu, then set the switch to “+20”. This will reserve 4 dB of headroom in the preamplifier.
If too much headroom is allowed in the microphone preamplifier, noise from the preamp may
reduce the dynamic range of your recording. If no headroom is provided, the microphone
preamp may add distortion to your recording."
Hope that helps - if I am talking out of my ass someone please step up ;D
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That's EXACTLY what I was looking for. Much grass.
+t
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...blip...
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iirc
V3 is +25dB max output
V2 is +27dB max output
lowest sensitivity on AD2K is +24dB = 0dbFS, it should always be set to +24dB with these preamps
then you use the (excellent) meters on the AD2K
when the AD2K clips at 0dB (which of course you dont want to do, and really shouldnt ever need to, as it has great peak hold and lights at -5. -4. -3, -2 and -1), you still have 1 dB of headroom on a V3 or 3 dB of headroom on a V2
so really in *any* case its impossible to clip a grace pre before you clip an ad2k, but by setting it at +24 it allows you to run the hottest signal you possibly can into it for the best noise performance
the Ad2k is in the -110s and both the lunatecs are in the -120s on EIN.
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iirc
V3 is +25dB max output
V2 is +27dB max output
lowest sensitivity on AD2K is +24dB = 0dbFS, it should always be set to +24dB with these preamps
then you use the (excellent) meters on the AD2K
when the AD2K clips at 0dB (which of course you dont want to do, and really shouldnt ever need to, as it has great peak hold and lights at -5. -4. -3, -2 and -1), you still have 1 dB of headroom on a V3 or 3 dB of headroom on a V2
so really in *any* case its impossible to clip a grace pre before you clip an ad2k, but by setting it at +24 it allows you to run the hottest signal you possibly can into it for the best noise performance
the Ad2k is in the -110s and both the lunatecs are in the -120s on EIN.
^
Thank you very much for the information!!
:coolguy: