Dsp Modes [Archive] - Audio & Video Forums


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09-01-2004, 05:43 AM
I was trying out the DSP modes on my Denon 2805 yestreday, and I must say the sound level difference between "Virtual" vs. "Pure Direct" was crazy. The Virtual set up (2CH.) was way louder with alot more bass. I like to listen to music in Pure Direct mode but to get to good listening level I had to turn it up about a good 8-10db louder than that of the Virtual mode. Can anyone tell me why that is? THANKS!

09-01-2004, 09:58 AM
PureDirect is a different function from Virtual. PD is a way to turn you receiver into a reasonable facimile of a passive pre-amp; everything is shut down with the exception of the attenuator and the amps, except if you are using the internal DAC in which case it assigns 8 Analog Devices DACS/side in the processing. There is no manipulation of the output signal beyond the way it was intended to sound.

Virtual utilizes the AD SHARC dsp chip (separate from the previous DAC's) and is actually taking the signal and altering it to whatever parameters the designer had in mind. Therefore, it might be louder, might be quiter, who knows? I'm more of a purist so I think dsp processing sounds horrible, however there are many here that like it.

Hope that helps.

09-01-2004, 10:10 AM
I think TS covered it pretty well. What it really boils down to is that the direct mode is an analog bypass where the signal is sent directly from the analog input into the amplification section with no intervening digital conversions or processing. Often, the digital signal and analog signal differ in their nominal levels, and can vary from component to component. I doubt that you would get a level difference as significant as you'd noted if the source signal for both modes was digital. You might want to double check and see if the direct mode looks for an analog signal first, because typically the receiver looks for signal formats in a specific order.

On my system, the CD player's analog output is about 3 db lower than when I use the digital output, whereas with my DVD player, I only measured a 1 db difference in the levels between the analog and digital playback. The virtual mode might look for the digital signal first, which would explain the level difference with the direct mode.

Also, if the source signal is a 5.1 soundtrack like DD or DTS, there could very well be a noticeable difference in the levels between the direct and virtual modes because of how the signal mixdowns are done. Depending on how Denon implements the direct mode, the processor might be doing a 5.1-to-two-channel mixdown, which folds down all of the channels according to predesignated attenuation levels and eliminates the LFE track. Or if it's taking an analog output from the DVD player, then the mixdown is already done before it gets sent into the analog output. In the virtual mode, the processor is doing a lot more spatial processing and signal manipulation of the 5.1 source so that it creates an enhanced surround effect with two, three, four, or five speakers. Unlike the 5.1-to-two-channel mixdown, most virtual surround modes I've heard mix the LFE track into the main channel output. Typically, this results in a virtual mode playback that is significantly louder than a straight two-channel playback with 5.1 sources.