@racebit
IMO, the latest HQPlayer 4.2.0 'poly-sinc-long-lp' enters the realm where it is indistinguishable(*) from WTA1. It's now available (on HQPlayer website) for any HMS owner to download and test using USB for A/B comparison (A: set PCM Mode, DAC bits=24, filter=poly-sinc-long-lp, dither=none, rate=768k (HMS does pass-through) or B: set filter=none so HMS does the upsampling ). If you run the test on a x64 CPU then Jussi uses 80-bit extended precision floating point. The SQ is unlike anything else.
When you say "indistinguishable from WTA1" I assume you mean mscaler WTA1. Because if I understand correctly all Chord DACs have a WTA1, and mscaler is just a (better) replacement WTA1.
In fact when we feed any Chord DAC with 705.6K we are disabling the DAC WTA1, replacing it with another upscaler which may be better, but may also be worse.
Looking strictly to number of taps, do you know the number of taps of the poly-sinc-long-lp?
My concern is that as Jussi states many taps are not required, his filter may have much less taps than even Chord DAC WTA1, which we are replacing. So it could be a downgrade instead of an upgrade.
Of course more important of all is how it sounds in the end. So back to the beginning it seems you say HQPlayer matches mscaler WTA1, so much better than Chord DAC WTA1.
I am in the process of testing HQPlayer myself, but unfortunately I could only get 352.8K to work. Setting 705.6K does play but with a clicking digital noise.
My desktop is a 10 year old dual core i3 with intel integrated graphics. Soon I will get a new 8 core 7nm Ryzen, and will test 705.6K again.
As expected any output rate not multiple of input rate (even 48K or 32K output rate) gets me CPU overload and will not work, while 352.8K being multiple of 44.1K works fine.
No GPU needed. It seems GPU is only required for DSD (Vade retro Satan!!)