Onkyo uses a patented circuit to remove noise from the DAC output. They give it a fancy name, "VLSC - Vector Linear Shaping Circuitry" and provide some unhelpful sales-patter to explain how it works.
The original patent (US 6697002) is pedantically titled "Low pass filter" Apparently the device works something like this:
I would upload the patent, its quite interesting, but at 1.5 MB its too fat for diyaudio. You'll have to settle for the main figure referenced by the abstract above.
Anyone with more smarts than me care to comment? Reading the patent it looks like Onkyo are serious about it, but what it actually is, and how different it is from what's been put forward before, is beyond my skillz.
/Richard
Conventional D/A conversion methods reduce digital pulse noise at the conversion stage but can't remove it completely. VLSC employs a unique D/A conversion circuit to overcome this problem. Data is converted between sampling points and these points are joined with analog vectors in real time to produce a smooth output wave form. The result—a virtually noiseless, smooth, analog signal based on the digital source that brings out even the most subtle of nuances in music sources (including DVD-Audio and Super Audio CD), DVD Video sources (including high-definition), broadcasts, digital music files such as MP3s, and gaming content.
The original patent (US 6697002) is pedantically titled "Low pass filter" Apparently the device works something like this:
A low-pass filter (700) includes a differential operation circuit (2), a voltage-current conversion circuit (3), and a capacitor (C1). The voltage-current conversion circuit (3) and the capacitor (C1) form a filter circuit (700), and therefore the low-pass filter can remove a high frequency component. The differential operation circuit (2) outputs a differential signal (.phi.C) for the difference between an analog signal (.phi.A) and an output signal (.phi.B). Therefore, with the differential operation circuit (2), a necessary frequency band is not attenuated. The phase level of the output signal (.phi.B) output from the low-pass filter (700) can be substantially equal to that of the analog signal (.phi.A) by the differential operation circuit (2). Therefore, the low-pass filter have a higher attenuation ratio for a high frequency component.
I would upload the patent, its quite interesting, but at 1.5 MB its too fat for diyaudio. You'll have to settle for the main figure referenced by the abstract above.
Anyone with more smarts than me care to comment? Reading the patent it looks like Onkyo are serious about it, but what it actually is, and how different it is from what's been put forward before, is beyond my skillz.
/Richard