Leedh Processing ?

[matthias]

Leedh Processing, the "lossless" digital volume control, has been implemented into Soulution DACs and there are rumours that Audirvana will get it as well.

Are there any news about this topic?

 

Matt

[mansr]

Is there anything to suggest it's not just a standard digital attenuator wrapped in technobabble and deep-fried in snake oil?

[matthias]

17 minutes ago, mansr said:

Is there anything to suggest it's not just a standard digital attenuator wrapped in technobabble and deep-fried in snake oil?

 

According to this review there seem to be advantages:

 

http://www.6moons.com/industryfeatures/munich2018/9.html

 

Matt

[mansr]

9 minutes ago, matthias said:

According to this review there seem to be advantages:

 

http://www.6moons.com/industryfeatures/munich2018/9.html

I'd expect nothing less from 6moons. The trouble with these claims is that no matter what you do, the result of the processing must ultimately be sent to a DAC chip as, at best, 32-bit integer samples, only about 21 of which actually matter due to unavoidable noise. If the signal level is reduced by half, the topmost bit will go unused, or in other words, the softest details will be lost below the noise. There is no way around mathematics.

[alec_eiffel]

Here's the patent

 

interesting but somehow disappointing. 

[Patatorz]

A link to give perhaps more insights to a disappointing patent : https://www.processing-leedh.com

Soulution (yes yes Soulution), Lumin, 3dlab : who’s next ?

[matthias]

2 hours ago, Patatorz said:

A link to give perhaps more insights to a disappointing patent : https://www.processing-leedh.com

Soulution (yes yes Soulution), Lumin, 3dlab : who’s next ?

 

The conclusion from the second paper:

 

So the Leedh Processing Volume offers perfectly lossless performance down to -30dB for 16 bits digital signal with a 24 bits DAC and more than -30dB with a minimized level of loss by truncation.

 

Matt

[matthias]

So if I understand the papers correctly there must be a headroom of at least 8 bits, that means a 24bit DAC works with 16bits only or a 32bit DAC works with 24bits only and the Leedh VC is NOT lossless when the attenuation is more than 30dB.

 

Matt

[alec_eiffel]

@matthias, yes

The trick of the Leedh processing is to only allow volume gains leading to a "lossless" representation the signal over a 30dB range, even with only 8 bits of "room of manoeuver" (use case : 16bit CD quality source, 24bits DAC). It's clever and also very efficient against more advanced techniques involving complex dithering.

I struggle to see the interest for 32bit DAC though, when "room of manoeuver" is 16bits, for example using software DSP such as in Roon or HQPLayer :

16 bits --> 64bit float --> reduction of XX dB --> conversion to 32 bit --> DAC 32bits

It should sound identical to Leedh volume control even for large XX values, especially with good dithering techniques TPDF or other noise shapers.

If you convert 16 bits to 64 bit float, apply 30db reduction, convert to 32 bits, convert to 64bit float, apply 30dB gain, convert to 16bits, you'll get the source signal bitperfect, no information is lost, no "need" for the trick of the LP.