Which HQP Filter are you using? [2015-2023]

Hi @jussi_laako - I am about to remeasure my main listening room again as I have changed some kits and so the filters from Theirry at Home Audio Fidelity now need updating. I have a couple of questions.

Previously, Thierry supplied 352.8kHz files for use in the pipeline set-up. He can supply files up to 768kHz, will these make much difference in terms of my ability to upscale to DSD 256? I currently use a i7 9700 overlclocked to 5gz. I currently upscale to DSD 256, Poly-sinc-ext2 with ASDM7EC modulator and I would like to do the same in the future.

I also noticed there are some differences in the pipeline setup, what do the new settings do (overlap-add, overlap save and expand hf)?

It doesn’t really make much practical difference if the filter is 352.8k or 768k. Convolution is performed at the source sampling rate. Except when source is DSD and output is PCM, then it will be performed after PCM conversion to 1/16th of the DSD rate. Thus the 768k filter could theoretically be useful if you play DSD256 sources converted to PCM, but from practical point of view doesn’t matter much.

Those have always been in the convolution engine setup, so due to requests also made available in the matrix pipeline setup.

Just seen this re R2R DAC. As youve read before, I use the Aqua La Scala Mkii Optoplogic DAC with the Gold Lion ecc81 tubes. the max sampling rate is PCM 384 and DSD128. I have set Hqplayer to output PCM 352.8/384.

So from your statement that NS9, NS5 and LNS15 would be the better options for an R2R, referring to the the above paragraph, which would be the option that would compliment my DAC/Sample rate?

Thanks for your time

You can try if you notice any sonic difference. LNS15 is newest thing, but the others perform well too, just different kind of noise shaping profile. Remember to set DAC Bits to 24 with your DAC. Since there are no linearity measurements available I don’t have exact figure. But I would also recommend trying to set DAC Bits to 20 which is likely closer to correct value.

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Thanks Jussi,

Also Try 20 bits under DAC Bits? Thats a new on me. Whats the thinking behind that, knowing that its either generally 16 or 24 bits…with a very small number that can do 32 bits

Whats then happening to 24 bit files if I set at 20 in hqplayer?

Thanks

Because none of the R2R DACs are actually linear to 24-bit. Point is to utilize only the linear range.

They are dithered and noise-shaped to 20-bit. But the resulting reconstruction accuracy is likely better and you are not loosing anything.

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Thank you…I had no idea, So looking at the website, it says here 24/384 for USB https://www.aquahifi.com/la_scala.html

So thats def not the case?

That is maximum resolution data it can take in technically. So for that reason just in case set DAC bits at most to 24. But that doesn’t tell about the actual conversion accuracy.

So you can safely set DAC Bits to 20 in HQPlayer and use one of those three noise shaped dithers and you are likely going to get better result than DAC Bits set to 24.

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What DAC has a resolution higher than 21 bits??

Pretty much none, but this is not as much about resolution directly. Above, 24-bit means that the DAC’s digital side understands 24-bit input, and it may even have conversion elements for 24-bit.

For choosing DAC bits the SNR resolution is not the determining factor, but instead linearity.

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Well there you go. Thank you for your help

20 is better than “default”?

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Very good question, I was wondering that myself, I thought the “default” option queries the DAC and the DAC provides the bit depth, now if HQP further internally reduces that to a “safe better linearity value” or if it uses the full depth only Jussi can answer. Good one Christopher

In this case likely yes. Default detects number of bits the digital device / driver interface can accept. Depending on the backend it may be more or less accurate, but it is always at least number of bits driver accepts.

You cannot exceed the detected number of bits with the manual setting, but you can go below it when you know better.

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Sweet, thanks.

I’ve really cooled my jets on the HQPlayer settings. Meaning, I’m not trying to do too much. I’ve settled on the ext2 filter, and I’m sticking with PCM at a max rate of 192khz. I don’t really need to stretch things to 768khz or convert to DSD or whatever. (Besides SACD’s, I don’t have any DSD files at this point.)

It sounds absolutely fabulous – no dropouts or other buffering weirdness – and the processor (mac mini) seems to prefer a less-ambitious configuration.

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I have now set to 20 rather than 24…but what is default setting. Is that “0”?

When I say 21 bits, I mean what DAC supports a dynamic range of more than 21 bits? Heck, most DACs today, even R2R DACs, do 24 bit math. So, 21 bits of resolution means 21 bits of linearity which means 21 bits of actual dynamic range.

After being away from HQPlayer for a couple of years, a series of unfortunate (or perhaps fortunate) events caused me to give HQP a second try. I lost my Chord HMS due to a busted power supply. One of my friends encouraged me to look at HQP for PCM up-sampling to Chord DAVE. I am using Sinc-M with max rate of 768kHz with auto rate family.

I have a Audio Linux i7 NUC server running Roon Core and HQP embedded (which I bought after just couple of days of trial, so thanks @jussi_laako as that is how long it took me to realize the potential). My current end point is a Pentium NUC also running AL.

PCM upsampling to 705/768kHz got me very close to what I am used to hearing from HMS + DAVE. PCM upsampling with HQP seems like a feather weight for the CPU. Both my NUCs are idling at 97% or more, not using CUDA or anything fancy.

Initially the infamous white noise issue reared it’s head on my right channel with 96kHz or higher source material, it was not very predictable but always happened. At that point I was running NAA on Euphony. Then I remembered reading Jussi suggesting it could be the end point not being able to keep up with the high sample rate especially with Chord DACs. I moved to AL NAA and things have been steady since.

To provide a subjective point of view (hopefully useful to someone) to the discussion, this is what I seem to prefer sonically after almost a week of extensive testing with Metrum Onyx R2R DAC over USB and coax (4-8x PCM upsampling, 20-32 DAC bits settings) in a headphone audio chain…

Filters:

  1. poly-sinc-ext2
  2. closed-form
  3. poly-sinc-short-lp

Dithers:

  1. LNS15
  2. NS5
  3. No dithering

Please note that poly-sinc-ext2 is a clear favourite of mine and somehow seems to synergize well with LNS15. That might be the primary reason why LNS15 pulled ahead. I would also point out that the majority of filters and even dithers included in HQPlayer were subjectively not to my liking, wouldnt use them on a long-term basis.

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The dropdown should have “default” as the default, first selection.

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