I think most people use HQPlayer with Roon for its up-sampling and sigma-delta modulation (“PCM->DSD Conversion”) capabilities.
There’s a 99% chance that your DAC is performing some sort of over-sampling internally–this is pretty much the case unless you went out of your way to buy a NOS (No Over Sampling) DAC.
There is also a very high likelihood that at some point during the source material->analog process, your signal is being digitally transformed from PCM (pulse code modulation at a low sampling rate and high (16+) bit depth) into an SDM (sigma delta modulation, high sampling rate, low (1-5) bit depth) signal inside the DAC chip before being converted into an analog signal.
There are good reasons why it is done this way. The performance/$ is higher, and SDM architecture escapes some pesky analog domain noise-floor issues inherent in building DACs that handle many (18+) bits directly. Virtually all of the popular dac-on-a-chip solutions today (ESS Sabre, Burr Brown, …) do something like this.
There are some issues to consider with this approach:
- The MIPS budget of the DSP in most DAC chips isn’t very high, so quality compromises are likely during the upsampling/sdm process
- Putting a hard-working DSP right next to the delicate analog bits within the same chip isn’t the best for analog-domain performance
- The DSP within your DAC does not change or evolve much after you’ve purchased the product.
HQPlayer addresses all three issues:
- It lets you use your computer’s CPU to perform the upsampling/sdm, so your MIPS budget is only limited by the amount of hardware you want to pay for.
- By performing upsampling/sdm outside of the DAC chip to the maximum input rate that the chip supports, you’re taking a load off of the internal DSP, which reduces its influence on the delicate analog bits sitting a few mm away.
- You can continue to benefit from upgrades to the DSP processes as Jussi makes HQPlayer better, and you upgrade your computer.
If you look at the list of recommended hardware for HQPlayer, you’ll see a pattern: it’s mostly focused on less expensive DACs that don’t have their own discrete DSPs. This isn’t an accident–HQPlayer is ~$100 way to make the digital portion of your $500 DAC behave more like a $5000 DAC.
If you already have an expensive DAC with a discrete DSP implemented on FPGA or similar (dCS, Linn, PS Audio, Meridian, Ayre, MSB, and many others), then they’ve already put some space between the DSP and the analog bits, and the device probably has an ample enough MIPS budget to do an excellent job at up-sampling the signal internally. HQPlayer will make much less of a difference with these.
The biggest drawback of HQPlayer is the overall UX and the technical nature of setting it up. I’d love to see a tighter integration with Roon that gets us past the “player stacked on top of player” stuff and lets us treat HQPlayer as more of a DSP plugin. At the moment, it isn’t built to be used that way, so we went with a more direct integration.