Hybrid mixing dither question

I am starting to get into hybrid mixing.

I’m using a Steinberg UR824 (24 bit) interface and Cubase using an effects loop to go through a Warm Audio 1176 and WA2A (LA2A clone).

I’m working in Cubase at 32 bit float so I presume I should dither before the output to the effects loop? Is there any way around this problem. I understand that if I set the project bit depth to 24 bit, Cubase is still processing those files internally at 32 bit float - it’s just the sound files are recorded at 24 bit depth. If that’s the case then presumably, I still should be dithering each time I use the external effects loop. Is that correct?
Many thanks

No. The only time you need to dither is when you render audio to a lower bit depth.
The confusion here lies in the difference between the project bit depth vs Cubase’s internal audio engine.
This can be turned into a massive topic, so I’ll just keep it real simple.
The project bit depth (and sample rate) is what your audio interface uses as well as recorded audio, virtual instruments and plugins.
Internally Cubase’s mix engine can handle audio in a much higher bit depth. This provides benefits in mixing and processing audio but is transparent to any other components (such as plugins and your interface). I.e. your audio interface’s AD/DA converters are still converting 24 bit audio regardless of the bit depth of Cubase’s internal mix engine.

Sorry, that is actually not fully correct. The project bit depth affects the audio files that are recorded and generated (in the case of e.g. render in place, freeze, DOP). It does not affect instruments and plugins, those operate either in 32bit float or 64bit float (depending on the mix engine settings and whether they support 64bit processing).

The interesting question for me is whether converting from 32bit float to 24 int (which is what happens when you send data to your audio interface) actually is a reduction in bit depth. I think I once read that 32f and 24i have the same precision as the mantissa of the float is 24bit in size. That would mean that there is no truncation happening when converting and no dithering would be needed, but I am definitely not knowledgeable enough to really understand the intricacies of DSP programming and whatnot :wink:
The other question is whether anyone actually could hear the difference between dithered and non-dithered 24bit… but I won’t go there ::upside_down_face:

To the OP: in case of doubt, test it with and without dithering and see whether you can hear a difference. My hunch is that any millimeter of knob movement on your hardware will have a bigger impact on the sound.

Dithering is only useful when intentionally lowering the bit depth of an audio file, for example when converting your mastered file from 96 kHz/24 bit to 44,1 kHz/16 bit.
If you do that without dithering, all the samples will abruptly snap to the closest bit value.
That will effectively alter the audio and change the waveform shape, introducing unwanted distortion/artifacts.

There’s actually no need to dither when going 32 to 24. The resolution is already high enough at 24 and the distortion will be exceedingly low and completely negligible.

However it is highly recommended when going 24 to 16, because 24 bits has 16,777,216 possible values, and 16 bits only has 65,536 possible values, which is 255 times less.
It means that when going 24 to 16 without dither, the distortion would be 255 times higher than when going 32 to 24 without dither.

Cubase (or plugins) internal resolution (32 or 64 bit float) only serves for internal calculations when the audio is processed. It can be anything, gain faders, panners, effects, etc.
Let’s say your recording is in 16 bit, and Cubase is in 64 bit float.
The 16 bit audio goes through an EQ.
When you tweak the EQ bands, all the internal mathematics will happen on the 64 bit range, and the resulting values will be rounded to the closest 16 bit values.
This causes no distortion at all, and needs no dithering, because it is only related to the internal processing, not to the actual audio resolution.

It is a total myth thinking that plugins will increase the actual bit depth on input, then lower it back to original on output.
Audio Processing and audio Conversion are two completely different things.

To answer the OP original question :
No need to dither when sending the audio through external FX.
If your interface is set to 24 bit and your audio has also been recorded in 24 bit, then it will always stay in 24 bit.

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Basically, if you convert at 24 bits or above you should be ok.

Many thanks for your reply. That’s very helpful.

Many thanks for your reply. I’m most grateful to you.

Many thanks for your reply. That’s clearly answers my question and is most reassurring.

Many thanks. Cheers.

“When you tweak the EQ bands, all the internal mathematics will happen on the 64 bit range, and the resulting values will be rounded to the closest 16 bit values.”
“It is a total myth thinking that plugins will increase the actual bit depth on input, then lower it back to original on output.”

No. The math will happen in the 64 bit range, but the result will not be truncated to lower bit depth. The result will be outpus in 32 or 64 bit float format, depending on your Cubase setting. This is true for any audio processor, even if it is only a gain knob which is not at the neutral position.

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Well, if the plugin processes in 64bit float, but Cubase’s mix engine is set 32bit, strictly speaking there will of course be truncation and you will inevitably lose precision (whether that is relevant is of course another question, maybe one for the golden ears :wink: ).
But of course the important part, as you mentioned, is that through the whole mix engine the audio stays in 32 or 64 bit float, and any conversion to 16 or 24bit integer only happens on export, where you should dither, if only because it doesn’t hurt.

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