And likely the same for GPU’s trying to do the work of DSP’s too. They maybe quicker than a CPU at this task, but nothing like a true DSP. Give them a the workload of a graphics card or an AI problem and they’ll do better 
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One of the FPGA design houses in Europe (QBayLogic) has a every effective visual on this 
;
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Thanks for all the answers and links folks, very interesting reading! The AudiophileStyle forum post was particularly useful as it seems the author of HQplayer is active there and there is a lot more information there than on the Signalyst website.
It’s still not clear to me how HQplayer is manipulating the calculations to enable GPUs to share the heavy lifting. According to the author of PGGB there is little to be gained, which is consistent with my very basic understanding. However now I have asked the HQplayer author directly. Will report back if he answers.
Still curious to hear if anybody has done any direct comparisons between offline upsampled material and Vivaldi Upsampler (or any other dCS upsampler for that matter) per @Gibraltar 's question to @oldmustang above. Anything to report there Steve?
Very snappy response from Jussi, author of HQPlayer:
Interesting stuff!
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Hi Jeff,
I did compare PGGB to the Upsampler. What I hear is the Upsampler always improves sound quality, whether streaming content or local files. Not always dramatically but most often worth keeping the Upsampler in my system. It never has made perceived sound quality worse. So I currently keep the Upsampler set at DXD Lock and DSD Pass Through.
On the other hand, I cannot say that PGGB always improves sound quality. Sometimes it does, and markedly so improve SQ. But other times as I’ve posted it sounds overly sterile, thin, or tipped up.
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No persuasion necessary – the author is perfectly happy to re-authorize a license to a new machine. No loss of investment.
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And I should re-emphasize that my improve/disimprove comments regarding PGGB are strictly in relation to my own sonic priorities and in the context of my system. What you hear and its relative importance and signficance to your listening pleasure might certainly be different than my experience. There are many PGGB users out there that like it and evidently don’t experience the caveats I’ve mentioned.
So I would urge anyone considering PGGB, HQP or a dCS Upsampler try them all (tough I know for the Upsampler) before committing. I would certainly not choose one over the other based on some theoretical superiority of one method over another. The proof is in the listening since IMHO this should be about “My FI” and enjoyment of music rather than passing some kind of technical purity test.
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PGGB ?
I stick to my widely acclaimed professional mastering tools from Weiss Engineering
(https://www.weiss.ch), Weiss Saracon (https://weiss.ch/products/pro-audio/saracon/) / Softube (https://www.softube.com/weiss-complete-collection).
They have been the standard in virtually every mastering studio in the world for more than three decades (founded in 1985).
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