Optical Out Volume Q

SKiTLz · 12-15-2007, 06:10 PM

Just a qick question. If your passing your sound from your CarPC via Optical then you cannot controle volume on the carPC correct.

Does this mean you can no longer mix on the carpc. For instance GPS voice speaks over lowered volume music. Is everything passed from the carPC at the same volume?

Cheers

Lazyflip · 12-15-2007, 08:27 PM

I have an optical on a laptop and I can control volume via Windows.

SKiTLz · 12-15-2007, 09:15 PM

How is that possible? I thought you could only adjust an analog signal?

Lazyflip · 12-15-2007, 09:41 PM

I'm not really too sure. I have a Sound Blaster X-Fi for notebooks. I was curious to about the optical out feature so I got a 3.5mm to optical adapter and played a DVD. It outputs 5.1 DTS and the volume is adjustable within windows.

slinkytoy · 12-15-2007, 10:05 PM

It's and optical analog signal you can adjust it no problem. I have an creative labs laptop card that uses optical output and i can adjust the volume no problem

SKiTLz · 12-15-2007, 10:18 PM

Quote: Originally Posted by slinkytoy

It's and optical analog signal you can adjust it no problem. I have an creative labs laptop card that uses optical output and i can adjust the volume no problem

All soundcards are analog over optical?

pwntbypat · 12-16-2007, 10:23 AM

every optical source I've used (sound cards, car head units) have had the ability to adjust volume over optical.

pokki · 12-16-2007, 12:46 PM

Here goes.

Quote:

All soundcards are analog over optical?

No. All soundcards send a digital signal over optical.

If your PC is decoding audio to PCM then you can adjust the colume over optical.

If you PC is streaming compressed audio (DD or DTS) then volume cannont be adjusted.

However if you PC decodes DD/DTS to PCM adjusts the volume, then re-encodes to DD/DTS voluem adjustment over SPDIF (optical/digital co-ax) will still work.

SKiTLz · 12-16-2007, 01:41 PM

Im going to be outputting it into a Alping H701. Will i still be able to control volume from the PC? I don't know what happens to that PCM signal inside the H701

pokki · 12-16-2007, 02:38 PM

It doesn't matter what happens to the PCM inside the 701 as the PC can be considered the master volume. But for the record it takes the digital signal - does what ever processing you've setup, rund it through a DAC, and then through a pre-amp.

However be aware that controlling the volume in the digital domain requires "bit shaving" which if not executed correctly can reduce the quality of sound. Also if using PCM over optical you will be limited to 2 channels of audio between the PC and the 701.

Where as I expect the volume control within the 701 work in the analog domain in it's pre-amp section.

SKiTLz · 12-16-2007, 02:46 PM

Quote: Originally Posted by pokki

It doesn't matter what happens to the PCM inside the 701 as the PC can be considered the master volume. But for the record it takes the digital signal - does what ever processing you've setup, rund it through a DAC, and then through a pre-amp.

However be aware that controlling the volume in the digital domain requires "bit shaving" which if not executed correctly can reduce the quality of sound. Also if using PCM over optical you will be limited to 2 channels of audio between the PC and the 701.

Where as I expect the volume control within the 701 work in the analog domain in it's pre-amp section.

This is really good information. Thanks..

The 2 channel does not phaze me. Im running a 2-WAY front stage anyways. You said the bit shaving has to be done correctly. What controls this? The Soundcard? Im using a X-meridian for reference.

I would just run analog and be done with it but I've heard noise problems with the 701 and analog.

pokki · 12-16-2007, 02:52 PM

In a normal windows xp install I believe windows kmixer controlls the digital volume and thus the bit shaving.

If you're using ASIO audio then I believe you'd need an ASIO compatible volume control application/plugin in which case you bypass windows kmixer. This also allows a lot more choice in the volume reduction alogrithm used.

Personally i'd try it what every you have now, and compare the PC volume control to the 701s volume controll and if you can't notice a difference don't bother changing anything.

PS don't forget to set the 701 to max volume when using the PC to controll volume (PS that is presuming the 701 doesn;t clip the outputs at max)

SKiTLz · 12-16-2007, 08:18 PM

Thanks for all the info. I decided to go another route. I pulled the trigger on a AudioControl DQXS.

Running my X-Meridian Analog w/ LM4562 OPAMPS into the DQXS with a short 1ft run should be able to yield the quality/tweakability I need. We sha'll see.