Axiom Home Page Forums General Discussion Home Theater VLSC

JohnK or Chris, maybe you know, but how much audible benefit do you think comes from Onkyo's VLSC (Vector Linear Shaping Circuitry)? It's a feature on my Integra DTC-9.8, but not on my just-purchased, admittedly "mid-range" Onkyo TX-NR708. I'm simply curious if this is something that could give weight to the idea of not all receivers/processors sounding the same, or if its benefits are strictly theoretical, of no real consequence to the human ear.

I suppose there could be a little over-/under-shoot in the voltage levels that come out of a DAC. But modern DACs already produce waveforms with so little defects that it's beyond not only the human ear to detect, but even a lot of test equipment.

DACs output analog voltage (or current depending on their setup) levels. They don't instantly "snap" from one level to the next, there's ramping up or down from sample to sample. So they already produce a smooth, continuous form.

I'd be more worried that their shaping tech would remove actual high frequency information, because of delay in the feedback loop. Which would make the audio sound more "warm", as does anything that rolls off the highs.

Sweet. Thanks for the info, Chris.

Maybe I went too far with my comment about rolling off the highs. If they implemented it really well, it shouldn't have any real negative effect. But still the same positive effect.

If they really wanted to improve harmonic distortion (which is what their stair-stepped sine wave would measure as) and signal to noise, they should have stacked multiple DACs (or used all channels of an 8-channel DAC to drive one or two outputs (balanced or single-ended respectively)).

I'm not sure how that works. What does that stacking of DACs do, exactly? How many companies do that?

The SE Oppo did it for their dedicated stereo outputs.

Most DACs these days have eight single ended outputs (to cover the 7.1). Some gear that offers balanced outputs will use two DACs to cover all the channels, and use them in their balanced mode, which outputs an inverted signal from half the channels.

Some DACs offer a high quality (single ended) stereo mode that uses half the chip for one channel and half for the second. Those DACs usually also offer a mono, balanced mode so all eight channels are outputing the same signal or an inverse of it.

See what ESS shows how their dynamic range improves as more channels of the DAC are stacked: http://www.esstech.com/index.php?p=products_DAC It doesn't do anything for the harmonic distortion, but at -120 dB (about 0.0001%) there's not much left to do (note: there's no way to preserve that low level of distortion or even the dynamic range through the rest of the output stage).

Interesting stuff. Thanks again.

Working at a hospital, every time I see "DNR," I think, "Do Not Resuscitate."

It usually means Dynamic Noise Reduction (something you don't want applied universally), so I wish they had used another abbreviation.

Charles, the Onkyo blurb says "virtually noiseless". This should be interpreted to mean that even the most sensitive instruments can barely measure it. However, typical DACs(including chips costing less than $1 each)have been noiseless as far as our ears can tell for quite a few years now. The analog output has met the standards described in there without the need for any new circuitry.