Sample Rate Conversion with Mojo

Hello all,
Does it make sense to activate the Sample Rate Conversion (Max PCM rate) when I am using a Chord Mojo DAC? In theory the Mojo should take care of the upsampling itself, shouldn’t it? I do hear a difference but I cannot put my finger on it.
Thanks for your help!

Hi Robin,

When an upsampling DAC receives a signal that is already upsampled then it bypasses the internal upsampling to that rate and sends the signal directly to the next stage. That may be further upsampling if the signal is not yet at the rate which feeds the internal DAC stage, or it could be directly to the DAC stage.

Sometimes external upsampling can be advantageous, especially if the design/processing constraints within the DAC limit what can be achieved by internal upsampling. This is the philosophy behind HQ Player.

Other times the internal upsampling may yield a better result than external upsampling. This can happen when the maximum input to the DAC is not the rate feeding the internal DAC stage, meaning that another upsampling operation is required. If that later stage is badly implemented compared to the earlier upsampling then the internal DAC upsampling may be preferable. It can also happen if the DAC just has a better upsampling implementation than the external program.

So I’m afraid it’s not one of those questions with a simple yes/no answer. You now have a choice as to where the upsampling occurs and you can decide which one you prefer, based on your own listening environment, program material and perception. No one can say you are wrong, whichever you choose. Some people like external upsampling to Max PCM, some prefer Max PCM (power of 2), others like external upsampling to DSD, others still may prefer the internal upsampling to any of those. I’d suggest trying them out and sticking with the one that sounds best to you.

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I have tried upsampling (max PCM and max PCM power of 2) to both Mojo and 2Qute. I did detect a difference (perhaps a wider stage), but in the end preferred turning DSP off. Enabling DSP, at least on these Chord DACs and in my system, reduced detail and precision.

Per Rob Watts when asked if the Mojo upsamples and if so what does it upsample up to?
“Yes all my DAC’s up-sample to 2048 times that is at least 16 times
more than typical. What does this do? Well its not just about up-
sampling but filtering out the RF noise that is present on a digital
signal. Its essential to do this, as it gets you closer to the original
analogue signal in the ADC (and this is the DAC’s job to recover the
analogue signal not the digital data). This extensive filtering reduces
jitter sensitivity by a factor of 64, and allows the DAC to eliminate
noise floor modulation. Now this is a very important problem, as it
makes the DAC sound hard and less smooth and is a major problem with
DACs - all other DACs have very large noise floor modulation, Mojo has
zero measurable noise floor modulation (I have plots at home proving
this). This is a major reason why Mojo sounds so smooth and natural.”


Thanks for the answer! I just saw it. May I ask how one upsamples to DSD? Merci :slight_smile: