Author Topic: Check levels  (Read 551 times)

petewilson

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Check levels
« on: July 09, 2019, 12:49:16 am »
Simple situation which I think I understand but would appreciate confirmation:

1. The scale 0-100 of the indicated input volume (seen when checking levels and recording) is a simple linear scale, where 0 is 0 and 100 is the largest number available, and negative incoming values are 'rectified' to positive, yes?

So if I record with 16 bit precision, 100 corresponds to 64K; at 24 bits it corresponds to about 8M. In any case, it's linear and covers the complete possible input range.

2. I'm recording from a NAD M12 'digital preamp', which (grrrr though it's good for recording) has just fixed level digital outputs, converts any analogue input signal to your chosen bit-depth and sample rate, but has no way of scaling the A/D conversion. I set it to 96KHz and 24 bits.

It shows up with peak values in the 10-13 range from a typical LP.

If it were 12.5, I'd be recording at 1/8th full scale. Goodbye about 3 bits of precision. Since the "24 bit" A/D probably only does 19 or 20 bits of real conversion, and I've just lost 3 bits of precision, looks like I'm recording 15 or 16 bits.

Not good.

Is my analysis (on the data given) correct as far as VinylStudio is concerned?

(I'm going to contact NAD, who have claimed that the rhe A/D is auto ranging, to see if there is actually a way of changing the scaling. Else it's back to the PS Audio preamp, which is manually adjustable. Sigh...)

Thanks much!

Paul Sanders (AlpineSoft)

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Re: Check levels
« Reply #1 on: July 09, 2019, 12:56:27 pm »
Yes, I'd agree with all of that, except perhaps the assumption that the preamp is limited to 20 bits or so internally.  You could ask NAD about that.