Death of the pre-amp and HQPlayer digital gain?

[jussi_laako (Jussi Laako (Signalyst))]

So my question - is this really possible? Is it the way to get un-coloured sound that isn’t slightly degraded by a pre, as any component you add to the chain is going to affect the sound (signal loss through interconnects, circuitry of the pre, etc.).

Yes, it works well. But as I warn in the manual, it requires one to be extra careful to avoid nasty surprises. Because there’s always danger that for example some application like the OS itself accidentally blasts “bling you have new email” sound or something similar to the DAC at full volume.

It is also generally best if the gain matching is such that the power amp doesn’t have so much gain that you would need to use a lot of attenuation. Because regardless of type of the volume control, doing first lot of attenuation followed by lot of gain is sort of counter-productive.

Some power amps like Benchmark AHB2 have a low-gain mode especially designed/suited for this kind of use.

can you elaborate on which filtering / dithering algorithms are better suited to digital gain? Is digital gain perhaps more destructive to the signal than using a reference quality pre?

Main rule is that if you output PCM, you need to use some type of dither. There are some recommendations in the manual, but for 24-bit output even industry standard TPDF dither is good choice across the board. At higher PCM rates, one use noise shaping instead to gain extra dynamic range in audio band.

Rough rule of thumb is also that is preferable to have at least 2x upsampling when using digital volume control, especially when output is DSD. So for example if input is DSD64, then preferably output DSD128 when using digital volume control. Or if output is PCM, then use at least 88.2k output rate if input is 44.1k.

The errors of digital volume control are much lower than distortion and thermal noise in analog components. Good DAC has a low noise and low impedance analog stage and output. Adding resistor-based analog volume control on the path increases intermediate impedance (typically at least by 10x) and thus level of thermal noise too. If there are active stages in the pre-amp too as there usually need to be, those also add their own distortion.

Do I have a preamp? In some cases yes, other cases no. In my listening room I have so many DACs (and new upcoming LP player) that I need source selection. Some power amps have two switchable analog inputs and such may be perfect for this kind of setup in their own way.