To upsample or not to upsample

Same goes for the creator of HQPlayer. Claims his filters sound better than Chords and the tap talk is mostly marketing.

I haven’t bothered to test this myself but I suppose at some point I could. It would just be comparing Hugo 2 internal upsampling vs HQPlayer xtr 768k.

Yes absolutely. But I haven’t pointed to anything HQP’s Dev has said :slight_smile:

There is no way to completely bypass Hugo2’s internal up-sampling, only the 1st stage (WTA1)…

By up-sampling to PCM768kHz in HQP, you are bypassing WTA1 in Qutest/Hugo2/TT2/Dave… just like M-Scaler does but with different algorithm obviously.

Rob still has WTA2 which takes PCM768kHz to ~90 MHz, as mentioned earlier…

I personally can’t be bothered with HQP with my Hugo2… I use HQP and enjoy it with other DACs…

I merely responded to the post by @iamoneagain in which he mentioned Rob Watts’ recommendation of using source sample rate and ideally not MQA, to which I pointed out that a small amount of my listening is MQA by virtue of being a TIDAL HiFi customer. I never said MQA was upsampling.

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Yeah, re-understood.

As it turns out you were right about Qutest upsampling, too.

The point of MQA was that it’s not the original source file. It’s been altered to sound best with MQA rendering for the final stage. Chords was designed to work best with original cd quality.

About Chord and upsampling and M-Scaler…

When Chord released the M-Scaler some people (including me) were distracted by the term “upscaling”. The $5,000 M-Scaler upscales 44k to 705k and feeds that into Chord’s DACs, but Roon already does upscaling (for $0 including VAT) so why do I want the M-Scaler? And much as I admire Rob Watts’s work, and his openness in lectures and writings, I fear his explanations in this area drown us in detail and are not helpful.

I read up on it, stubbornly, and I think I understand (and I eventually bought one). And with characteristic hubris, I think I can explain what it does better than Rob can. Sometimes knowing less helps…

A few years ago, people used to say that DACs perfectly recreate the original sound because Nyquist said so. If you believe that, I have a 1982 Sony CD player I can sell you for $20,000, a bargain price for perfect sound, no? “Ok, those early devices were flawed but today DACs are perfect because Nyquist said so.” Where in Nyquist’s paper does he mention 2019? “But the paper says perfect recreation, are you saying Nyquist is wrong, do you claim to know better than Nyquist?”

Poor Nyquist never said anything of the sort. Nyquist and Shannon did math, not engineering, they never claimed that their solutions are physically realizable. “But math is the foundation for engineering!” Yes, but math does not have a problem with solutions that involve infinite numbers. Infinite is awkward in engineering, because the cost is infinite, and energy consumption, and latency. And size and weight of the equipment, and there is the black hole problem, and destroying the universe. And note that Moore’s law doesn’t help with infinite.

“But we can get close to Nyquist’s perfect.” Maybe, but like most math results, Nyquist’s theorem does not address how close to the solution you get with an incomplete implementation. That’s an engineering question,

This is what Rob Watts addressed. Looking at the infinite sinc function that is used in Nyquist’s perfection, he figured out how much computation he needed to reduce the residual error below a specific threshold. When he first did this, the requisite computation wasn’t feasible, so they made the best implementation they could, and gradually improved it, and they now claim the M-Scaler has achieved that goal. So this is not just the usual incremental improvement that the industry (including Chord) does: “this year’s model is better than last year’s model”. Specifically, he says the error (distortion) is below 16 bit, which is 96 dB or 0.0016%. This is where the million taps comes in: the previous devices have increased the tap length as they could afford to, but the million taps threshold was always there, given the target error threshold of 16 bits.

And as this approximation of Nyquist’s perfection within a specific error margin was really the objective, I believe the upsampling is incidental. The calculation delivers its results to the DAC in upscaled form, because that is the way the calculation engine can cooperate with the DAC. Why? How does this two-stage processing work? I don’t know—there is a lot of discussion on the internet if you care, but I consider that secondary. Why is the million-tap scaler a separate box and not built into the DAC? I don’t know, business reasons?

Anyway, with this understanding, we see that the M-Scaler doesn’t necessarily have anything to do with Roon’s upsampling, or upsampling in any other device (my Meridian digital speakers upsample to 705k). What is central is the algorithm, how it does the calculation to bring the error down.

(How fabulous is it? This is a technology discussion, not a product review, I’m not going to gush over how it was like removing a veil and how it opened up the sound stage and how it was just like vinyl and how the backgrounds were blacker and how the cymbals shimmered…)

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I already hinted at the reason above… it’s an RF nightmare.

This is one of the benefits of M-Scaler - not just the million taps, but taking a lot of the heavy DSP outside of the DAC housing, away from analogue electronics (as I already mentioned above…).

Even with same number of taps, there is improved measured performance with a 2-box solution. Rob has confirmed 2 cascaded Dave’s (via DX connections) has some improved performance, even with same number of taps…

dCS have had 2-box solution since the 90’s. Ted Smith will be moving to a 2-box solution with his next DAC.

HQPlayer users have been using the same 2-box philosophy for years…

Rob Watts:

"The RF noise that the FPGA generates is a nightmare; it’s 12A of correlated current with large amounts of 2GHz noise. In the long term I would like to integrate an M scaler with a DAC; but I have not been able to figure out how to do it without it compromising sound quality."

https://www.head-fi.org/threads/hugo-tt-2-by-chord-electronics-the-official-thread.879425/page-89#post-14376430

I have an i3 Nuc and no DSD - so HQP is out of the picture for me. But am very pleased with what Roon does to the sound in my livingroom.

Sounds reasonable, but that wasn’t really the point.
The point was about the secondary role of upsampling.

As far as to upsample or not really depends on the dac and whether you use roon upsampling or HQPlayer. Also helps if you have a dac that allows you to completely bypass their internal upsampling.

If your dac uses off the shelf chips for upsampling then HQPlayer would most likely sound better. I found certain settings to sound more realistic from HQPlayer than roon. My testing was with an ifi idsd micro. Have not bothered with external upsampling and the Chord dacs.

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You said:

“Why is the million-tap scaler a separate box and not built into the DAC? I don’t know”

That’s why…

The point, in reply to the OP question To upsample or not to upsample, was that Chord’s solution is about the algorithm approximating an infinite solution. The upsampling is incidental. Upsampling with another algorithm would not have relevance to Chord’s approach.

Btw, The Absolute Sound just published an article on the TT2/M-Scaler, where they discuss the same thing I describe. Although they do gush: I neglected “slack-jawed”.

I was sharing some insight that might help, with your own comment:

“Why is the million-tap scaler a separate box and not built into the DAC? I don’t know”

My original reply to you quoted just that part… that you wrote… unless by saying “the point…” you imply there was no point to what you wrote :grin:

The other stuff your wrote, related to the topic, was already discussed…

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My Audioquest Dragonfly Cobalt can do 24/96. Should I have Roon upsample 16/44.1 to 24/88.2? It sounds good, but I don’t know if it’s real or my imagination.

Do whatever sounds best to you. It doesn’t matter if it’s real or imagination.

Thanks. I’m not sure. I’ll just try it for a while, then turn it off for a while.

I turned it off. I don’t hear any benefit.

I played around with it a little but ultimately decided to turn it off. I also deactivated Roon’s equalizer profile for my SR-009s and now just listen to the raw file without any sort of DSP. Maybe I’ll change my mind later but for now it sounds excellent.

My take is this HAS to be DAC specific. I didn’t hear any difference with my W4S DAC2 so I decided to take a load off the network and not upsample. Leave more bandwidth for the fortnite games my kids won’t stop playing.

Can anyone remember where the DSP and Upsampling menus are in Roon? I saw them earlier this year but can’t find them now despite my best efforts.