DSD Recording Level - Does It Matter?


#1

Hi,

Does recording level matter in DSD as it does in PCM?

In PCM, we want the highest level possible without going over 0, to use the maximum number of bits for the best resolution.

DSD is 1-bit (essentially). Does a higher recording level lead to “better” sound quality in DSD (other than improved S/N ratio, I suppose)? I do know that overs in DSD are especially horrifying :wink:

The reason I am asking is I am ripping vinyl to DSD and often I like to use the phono preamp in my Luxman integrated. I send the recording output from the Lux to the Analog Input of the Phono Converter. There is no gain adjustment there, and no gain adjustment in the Vinyl Studio software (you just set it to 100).

So it records at whatever level is coming from the turntable, which generally shows into the 30s on Vinyl Studio’s record level indicator and thus the DSD file plays back at pretty much the same level the LP does. It sounds great.

But I’m curious if there would be a reason to just always use the NPC phono preamp, where I can increase the gain, maybe getting it into the 60s or 70s in Vinyl Studio. (Using the NPC’s phono preamp section rather than the Luxman’s, I can increase the gain in the analogue domain prior to digital conversion which I cannot do using the NPC’s analogue input).

It’s a bit difficult to listen and compare b/c volume matching is a bit tough with what I have to hand.

Thanks!

-James


#2

Are you referring to the analog level to the ADC? If so, the requirements for both are identical. Maintaining a high enough level of the analog signal, without exceeding 100, is important only to take full advantage of the dynamic range available and to keep the music from being buried in the background noise on low level passages. Once you achieve that, whether it is then converted to PCM or DSD matters not - both conversion to digital enjoy the same benefits from proper level.

But if your question is the level of the PCM vs. DSD signal, then I don’t know the answer - and I am not sure it matters for either. It should only matter for the analog coming into the ADC - and the ADC is built in on the NPC.


#3
Muso said In PCM, we want the highest level possible without going over 0, to use the maximum number of bits for the best resolution.
This approach is a holdover from the days of recording onto analog tape, where we indeed wanted to record at the highest possible level as the noise floor was high on tape and we hoped that the lowest level signals would not be buried in noise. Additionally, many like the sound of tape compression, it is gentle and warm, and thus levels over analog 0dB were no problem.

With digital, 24-bit resolution easily exceeds the S/N ratio available in the analog side of the recording chain. The quiescent noise of our mic preamps, ADC, amps - everything - will allow 20-bit resolution at the very best, often less. Additionally, ADCs, plug-ins, etc. all have a sweet spot which tends to be around -20dBFS to -25dBFS. Thus, most engineers record digital with the absolute peaks at around -12dBFS.

If one wants a hotter digital level for the final product it is trivial to normalize the peaks to -0.3dBFS or your level of choice. (I strongly suggest never normalizing the peaks to 0dBFS as some DACs and CD players do not handle intersample overs well and will clip them. A lower peak level avoids this.)

DSD is 1-bit (essentially). Does a higher recording level lead to "better" sound quality in DSD (other than improved S/N ratio, I suppose)? I do know that overs in DSD are especially horrifying
All of the above applies to DSD, although intersample overs are not an issue, there are no DSD plug-ins, and DSD ADCs do not appear in my experience to have a sweet spot to the same degree.

Getting a “higher level” in Vinyl studio will make absolutely no difference. All it is doing is capturing the digital stream. The level that matters is the level of the analog signal the ADC sees and converts to digital.

Exceeding 0dBFS in any digital format is excruciatingly awful.


#4

Hi, thanks for the replies.

My recording chains are:

Turntable --> Amp Phono Input --> Amp Record Out --> NPC Analogue Input --> USB --> Vinyl Studio (DSD 64)(gain maxed @100)

That results in a recording level in the lower third of the scale. (when recording in DSD, Vinyl Studio does not make gain adjustments and they say to set it at 100)

If I run it so:

Turntable --> NPC Phono Input (set cartridge gain higher) --> USB --> Vinyl Studio (DSD 64)(gain maxed @100)

This way, I can adjust the cartridge gain in the NPC to get the recording level much higher. Thus, I get a hotter analogue signal into the ADC. So that’s what I was wondering about.

In PCM, a higher level yields more bits of resolution (higher resolution) as I understand it (and I could be wrong). E.g. if I record PCM at some level that peaks at 18 bits out of a 24-bit word (262,144 levels) vs. a lower level that may use only 14 bits (16,384 levels).

As I understand DSD (and again, I could be wrong), it doesn’t use discrete slices of volume levels that way. It uses 1 bit to direct “volume up” and “volume down” 2,822,400 times per second (a bit more complex, but that’s sort of the basic idea).

So, in DSD, is the resolution similarly higher at a higher recording level, or is it just better S/N ratio? I would think it’s not, but maybe I’m missing something.

I guess it’s a weird question - I hope I’m asking it right :slight_smile:

-James


#5

Tho perhaps not directly answering your question:

DSD has some head room above 0dBFS - or put another way you can’t get to all 1’s or all 0’s in DSD so they define a lower level as the nominal 0dB point. With SACDs this is 50% of the rails. With DSD converters in chips the 0dB level may be higher. Anyway going too far above 0dBFS in DSD may compress the sound a little on peaks, but unless you pushed it really hard it will recover when the level lowers. With SACDs peaks sometime (often?) go to around +3dB. You can think of DSD as more tape like than PCM since when you pass 0dBFS on PCM at best you get a hard limit and at worst PCM may wrap around.

The bottom line is that you should always attempt to get the peaks as close to the 0dBFS when recording for the best S/N, but if you go over now and then with DSD it’s more benign.

As Elk mentioned if you lose a bit or two off of the top it’s not the end of the world unless your A/D has an abnormally high noise floor. 20 bits is more than you need in practice (after all, how bad are CD’s really with only 16 bits.)