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SD 664 Meter Callibration


Werner Althaus

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I just took posession of a 664 and am a bit confused about the menu options. In the 442 and 552 that I use I have the option to calibrate the tone level (defaults to 0dBu for reasons unkown to me) AND the meter reference level (also defauts to 0dBu=0VU).I set all our mixers to tonelevel =+4dBu, meter reference level 0VU=+4dBu.

With the 664 this seems impossible. The tech support person @ SD didn't really underrstand my concerns so I was wondering how to best deal with this.

Recalibrate all out SD mixers to 0dBu = tone= 0VU?

I know the output of the 552 is a max of +20dBu but we've never had any issues with the output limiters set to +17 dBu (honestly I thought they were kicking in at +17VU which would be +21dBu in our setup)

 

Again, in my world -20dBFS = 0VU = +4dBu = 1.23Volts

Edited by Werner Althaus
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Heard back from Matt@ Sound Devices.

"Let me step through a few things on the 664:-The maximum analog output level is +20dBu.

-This corresponds to 0dBFS, and is not adjustable.

-This of course implies that -20dBFS = 0dBu.

Because of this, it is not possible for -20dBFS to correspond to +4dBu; this would imply a maximum analog output level of +24dBu, which is beyond what the voltage rails of the 664 will allow.

We have for quite some time now shipped all of our units with defaults of 0dBu = 0VU, as this was requested over and over again from customers. It somewhat flies in the face of convention from years ago of having 0VU = +4dBu or +8dBu, but then again, as electronics have gotten quieter in real world situations this arbitrary reference has become less relevant".

 

 

Not sure I like what I hear but at least I know what's going on. Also asked about the 0dB pan-law and got this:

 

"The panning really comes from how most of our customers use the product. Most are not recording music, and don't use the pans like "real" pans - rather they hard pan L, C, or R simply as a bus assign really. In those situations, it is easier for them to deal with the gain not changing as they pan."

Makes me wonder why they didn't just use a routing switch (LCR) and sae on real estate.

Other than that it a fabulous mixer. I took it out for a 6 microphone multicamera shoot yesterday and the results were great, really like the preamps, huge improvement over 442, and the unit is so intuitive it hurts:)

 

Edited by Werner Althaus
typo
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I think you *might* be confusing the numerical layout on the screen. I believe the meters on the 664, though it is a digital recorder, are in analog dBu, not dBFs. Does that make any sense with regard to your issue?

No, it doesn't.

The 664 meters use an analog scale with 0VU = -20dBfs. They should have done 2 things, IMO. They should have designed the I/O to handle +24dBu at minimum and they should allow the digital reference to be selectable (at least include -18dBfs as an option)

A VU style meter doesn't show dBu, it shows dB relative to a reference level with 0VU =reference . That reference level used to be -10dBv for consumer gear and, +4dBu or +8dBu for prolevel gear, then Mackie and some others started this 0dBu=0VU thing years ago. It might be a costcutting measure since it brings the requirements on the analog I/O closer to the range of consumer gear. In the end it makes sense to preserve 20dB of "headroom" by moving the reference level to a point that's 20dB below the maximum analog output but then it's not really a reference level anymore, I mean, why not use -6dBu as =0VU on an XLR output?  I used to not even consider equipment purchases where, at +4dBu, the analog I/O doesn't equal or exceed the artificial digital headroom set by the agreed upon digital reference of -20dBfs (-18dBfs in Europe) but my guess is that those days are over.

Edited by Werner Althaus
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