PCM to DSD low latency (<<50ms) conversion for live applications?

Some dCS products do PCM to DSD conversion (2.8MHz or 5.6MHz). The HQPlayer software allows you to use many options to do these operations but the processing latency is very high (>> 500ms), impossible to use in a live context (<< 50ms).

Are the dCS upsampler products (usable also with not-dCS hardware via DSD DoP) or the dCS DAC products compatible for a live context, to play a keyboard for example?

Best Regards,

I am assuming that you are talking about using a keyboard with MIDI output. This will not work with a dCS product as the MIDI file protocol will not be recognised. Further the connectivity of a dCS product is not necessarily compatible with the MIDI standards .

I also wonder what you are trying to achieve as upsampling adds no data to that produced originally. It does allow selection of some forms of digital filter which are broadly subtle in effect and more applicable to sound reproduction ( where elements like reproducing acoustic room decay are relevant) rather than with a signal directly from a MIDI interface. I would chance a guess that the MIDI source played directly and upsampled would sound identical to most listeners

Finally the housing of dCS components is a highly expensive, heavy and beautifully finished aluminium case unsuitable for the rigours of road/stage use if that is what is intended.

So my answer to your question is no . And I haven’t even touched on latency which is, of course, not immediately of relevance for the reproduction of commercial discs in the home environment. All it means in that context is that the resulting sound starts a fraction of a second later than pressing the play button.

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I’d 2nd Pete’s response. In the context of a live, presumably interactive, performance, there’s no benefit in exploring PCM-to-DSD. If it was a live broadcast maybe (like PrimeSeat), but then latency, even 500ms, is of no consequence.

Thanks for the replies. The MIDI keyboard is only for playing a virtual instrument with your fingers and through a PC-based sound system. I am talking about PCM digital audio at 44.1kHz / 24bit which I upsample on the fly to 176.4kHz (with a better resampler than the one integrated in the virtual instrument which generates a lot of aliasing) in order to be able to treat it with hardware / software DSP (for example passing simply the sound through the Pulteq EQP-1A is truly spectacular and of many implementations that of Universal Audio is the best).
It is true that oversampling does not bring an improvement in itself but using a DSP at a higher frequency can lead to a better and smoother result (many DSPs work internally with oversampling). Basically you can only process audio in PCM, with DSD you can do very little in real time.
Some DACs also work in upsampling, for example Crane Song professional audio products always upsample to 211kHz and use proprietary reconstruction filters for accurate time domain response. The dCS products also use DSP for upsampling (PCM-> PCM or PCM-> DSD as in the Scarlatti DAC or in other more recent models, perhaps Rossini).

More generally it depends on the context. How to say PCM generates sound differently than DSD but this also depends on the hardware implementation. You may like PCM or DSD more. It also depends on the type of digital conversion that is done and for this reason I mentioned HQPlayer which is very flexible in this.

Ultimately all this digital sound processing involves latency and the various delays are additive to the point that if you listen to a CD it makes no difference but if you have to play a musical instrument it can be impossible. From when you press a key to when you hear the sound it is best not to exceed 50ms.
I would hate to buy a dCS product and then not be able to use it for this low latency purpose …
Best Regards,

In fact, dCS has been using Digital Signal Processing from pretty much the very beginning with their 900 Series, including PCM upsampling and PCM<->DSD transcoding with the 972 as far back as the year 2000, not just the Scarlatti and newer.

You haven’t explained why you think you need a PCM-to-DSD conversion for a live keyboard performance as described in your original post. :man_shrugging:t2:

Thanks for the clarification. I don’t think that any of the ordinary members of this forum can answer your question about latency. It is not something that concerns us in our day to day use of the equipment to replay pre-recorded music. You need a dCS engineer to give this specific advice.

Unfortunately dCS retired from serving the studio equipment market several years ago and now only produce equipment intended for home use which has consequences both in regard to connectivity and physical housing.

I think that it may be best for you to email dCS directly with the question preferably in respect of a specific product.

Thanks for the contributions. I can measure with great precision (<1ms) the latency of a DSP or an external hardware component such as a dCS upsampler or dCS DAC, I will do some tests with some HiFi dealer in order to first check the sound and then the latency (which may change depending on how the hardware device is configured).

To conclude, the reason why it might be useful to switch from PCM (to process digital sound) to DSD lies in the fact that while in the digital domain we can work at an effective 24bit resolution (or even greater) in the analog domain 24bit they were a hypothetical resolution and this can make the speech less clear especially when playing softly.
dCS RingDAC will probably top the list of true 24 bits but in other cases the conversion to DSD could be smoother, more organic, more present, more alive, perhaps more real considering a wide dynamic from piano to forte. Obviously this is only a possibility to be evaluated and not a way that is absolutely valid!

The 24 bit delusion

“According to the experts that manufacture the finest DAC chips, resistors, and power regulators, there is theoretically no way to make electronics that are capable of discerning greater than a 20-bit resolution (120dB dynamic range). Any company that claims greater than 20-bit resolution from their DAC is simply full of shit. Oh they can decode 24-bits, because 24-bits does exist in software, but the output from their DAC has less than 20-bits of resolution and dynamic range.”