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DJM900 to CDJ 3000 maximum quality connection

Hello everybody

A question for understanding.

I will buy two CDJ 3000s shortly. I would like to use this in combination with the DJM900 NXS2. Now it is important to me that the 32-bit conversion of the CDJ-3000 is also transferred and output in this way on the DJM.

I assume the best quality can be achieved via the digital coax cable, right?

If I connect the CDJ to the djm via cinch, then I only have 24 bits, right?


Martin Muffler Con risposta

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Hey Martin,

Yes - the digital coax connection would be how this is achieved, but remember the mixer you use must also support a digital input of that bit depth.

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"If I connect the CDJ to the djm via cinch, then I only have 24 bits, right?"

Never seen the term 'cinch' used for SPDIF before.  That a European term?

You're correct that SPDIF goes up to 24 bit in linear PCM and the CDJ-3000 is advertised as processing at 32 bit float, but since your files are mostly 16 bit, it's just adding a bunch of zeros and then taking some of them off prior to the SPDIF.  32 bit float is just common now in audio processing because it's cheap, ubiquitous code to buy due to being used in many different fields besides audio (like RF processing and theoretical physics) and mostly doesn't hurt anything. 

The scaling of floating point math does provide additional audio processing headroom, but other than speed changing and key changing, DJ media players usually don't have much effects or multitrack summing that would increase volume much like you might see in a DAW.  You need to pad the processed audio anyway prior to the SPDIF and DACs to prevent clipping, so usually you just halve the level of any audio file by -6dB from its normalized commercial levels, process it, then convert it from float to fixed point prior to the output stages.  32 bit hypothetically gives you slightly better precision both for these attenuations and with rare implementations of certain high/narrow Q filters, but the latter probably aren't even used on the players.  Float math can do weird stuff around DC zero crossings in audio, but that's also very rare cases.

As Pulse said, use SPDIF.  Don't worry about the bit depth on this gear.  On older CDJs you had a choice of 16 or 24, but that was for SPDIF compatibility with outboard gear.  If your mixer supported 24 bit, you put the CDJ at 24 bit even if your files were mostly 16 bit just in case you played the odd 20 or 24 bit file, because processing or transmitting 16 bit audio in 24 bit format is harmless.  If you tried to send 24 bit SPDIF to gear that could only deal with 16 bit, then you had a problem.  While bit depth conversions are a real thing, that's applicable when being forced to convert, for instance, a 24 bit audio file to 16 bit, and doesn't apply in your case.  Sample rate is actually a more relevant discussion and where you start to get into alterations of the audio due to interpolation and conversion, but that's separate from what you're asking about.

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