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[MerlinWerks]

Hi All,

I'm thinking about eliminating the preamp from my audio chain and using either MC or my souncard (RME Digi96/8 PAD) app for volume control.  

Before I do though I'm trying to get a better understanding of how digital signal processing in general and in MC specifically works.  For starters, how much attenuation can I expect before the processing starts to eat away at signal bits and begins to negatively affect sound quality?  

Assuming a 16 bit source, ASIO drivers, no Windows controls (volume, mixer, etc) and the only MC DSP being the volume control, my understanding would be:

MC internally processes audio at 32 bits, so with a 16 bit source there are 16 bits left over for DSP. I should get ~ -96db of digital attenuation (6.02 * 16 bits) before affecting the actual program material.  Am I on track here??

If I add  Replay Gain how does this figure in to the equation?  I would think the RPG processing would occurr before the volume control.  If for a given song the RPG value = -9db I would assume ~1.5 bits are used and 14.5 bits are leftover for additional DSP such as volume control.  

What would I need to take into consideration to determine if it's better to do the volume control from within MC or in the sound card?

Any help would be greatly appreciated!!

[Matt]

If you output with ASIO at 24 or 32 bits, you lose no precision to speak of.

For example:

Full volume PCM codes: 7, -4, 3
MC 10% volume PCM codes: 0.7, -0.4, 0.3

This is a lossless transformation since you can undo it fully.  That means no precision or bits are lost.  In real life, you may lose a bit to precision rounding issues (i.e. 1/3*3 = 9.999...) but you're still left with 31 bits which is complete overkill.

So with an ASIO connection, MC does everything as well as possible.  The only unknown is your amp, which of cource, MC can't control.

[MerlinWerks]

Thanks Matt!

What  happens to the "bit overhead" when I start to include additional processing?  Replay Gain would be the first candidate and possibly some sort of DirectX EQ plugin.  

[Matt]

Thanks Matt!

What  happens to the "bit overhead" when I start to include additional processing?  Replay Gain would be the first candidate and possibly some sort of DirectX EQ plugin.  

There's a lot of spare elbow-room with 32-bits so there's essentially no bit overhead with a properly implemented DSP.

I think my ears can only hear out to about 14 or 15 bits in a quiet room with Sennheiser 600's on.  32-bits has like 100,000+ times more precision than that, so I wouldn't worry about the "bit overhead" of things.

My question is: with a good amp, will the two SPDIF streams I described above have the same noise level?

[MerlinWerks]

Which two streams are you referring to?

[Matt]

Full volume PCM codes: 7, -4, 3
MC 10% volume PCM codes: 0.7, -0.4, 0.3