i'm preparing to flatten/tweak my system soon. i'm wondering if i should be doing it from 0db, or +10db? does having the deck's gain on overdrive introduce any kind of distortion?

also, how does loudness work? isnt it that it boosts bass at low volume? but as you get to higher volumes, it eventually goes to a 0db boost? i ask because if i tweak the gain for my sub so there's no clipping w/ 0db loudness, and i decide to go w/ +14db loudness, will i introduce clipping to my sub at maximum volume (0db or +10db, whichever was suggested above).

I thought that anything above 0db was supposedly going to cause clipping, but im not sure.

Sean

As I understand overdrive, it causes clipping if the file in play reaches 0 dB while the player is in overdrive. As long as the resulting digital level after applying overdrive does not go beyond 0 dB at any time during playback, the waveform from the player will not be clipped.

Stu

Remember that the volume setting is only one of the items in the overall DSP equation. The EQ and loudness settings also come into play. Hence my recommendation about cutting instead of boosting your EQ levels here.

Forgot about that. I don't boost any of the levels (EQ and loudness) except for volume on "quiet" songs on mine anyway. If only the output could be 20 or 24 bits, we would have much more headroom for adjustments.

Stu

so basically you're saying that even using the loudness will so this is what i'm going to do. i'm not gonna use loudness anymore, tweak my amp gain for clipping, then flatten using the eq.

so basically you're saying that even using the loudness will introduce clipping and distortion. so this is what i'm going to do. i'm not gonna use loudness anymore, tweak my amp gain for clipping, then flatten using the eq.

so basically you're saying that even using the loudness will introduce clipping and distortion

No.

I'm saying that any waveform in a digital signal processor that tries to go past 0db will clip, in digital form, before it reaches the output stage.

That doesn't mean that turning up the loudness will make it clip. Only if the audio source material has a low bass waveform that is very loud (close to 0db) and you have the volume turned all the way up to 0db and you have boosted the bass frequencies, only then will it clip.

It'd be nice if the visuals could be post DSP. Then we could see what the effects of the DSP were.

Actually, from my kernel work, and from reading the DSP specs, I think that you're wrong here...Of course, part of this is guess work as I've never signed an NDA to be able to see the programming info for the DSP.

dB is a relative unit, and has no meaning without a reference level. In the case of an analogue signal, we could state that our reference was eg 1V, and then -3dB would be 0.5V, and +3dB would be 1.5V. In the digital domain, once all of the bits are 1, you cannot get any higher, so if you did state that this level was your 0dB reference point, then only negative dB values make sense, and any signal that attempted to exceed this value would indeed clip, as you have alluded to.

In the case of the empeg, 0dB in the player domain does not *appear* to be the maximum volume level that the DACs can handle - but near the point where the THD in the DACs is lowest.

Interesting.

I've played sine wave files from a CD through an oscilloscope connected to the outputs of my head unit and outboard equalizer before, it was a very cool way to see how far you could go before the signal distorted.

Could the same be done for the empeg? Rip a sine wave?

(PS, I didn't leave the gains maxed, in fact I normally set all of mine all the way down and only up what is necessary to get a pre-EQ balanced sound. Also - I notice at 0db on the empeg, that it's a perfect match when switching sources on my CD player / head unit. That is, going from tuner to CD to empeg, etc. all have the same relative volume. so for me, odb is perfect.)

is there any way we can have an indicator of when the output signal is clipped... ie, if at any time the output becomes clipped (eg you just twirled the loudness to +12db, or pumped up the 50hz band up a couple of dB) an icon flashes in the top corner or something... as an indicator... is this even possible? just as a general guide.

my soundstream amplifier usefully has output monitor LED's that light on clipping, and im sure other brands of amps do that too? so i was wondering if something similar is possible for our empegs.

also, something else i have noticed with my empeg - there is a puzzling shift of volume from 'centered' over to the left hand side, whenever i shift my Q of any frequency down to 0.01 - in fact, if you sit still and twirl the Q setting up and down you can hear the midrange output (mainly from vocals to the highs) shift over to the left. the right channel still outputs sound but at a markedly lower volume output. ive played merry-go-rounds with the RCA jacks and what not and it is definitelty not a problem at my amp stage or further, it is the signal coming out of the empeg. has anyone noticed this happening to their unit?

to test, play something with constant vocal range output (just for interests sake, i used Portishead's 'Cowboys' track, its a good constantly noisy track, and the range it uses is the range that is most affected by the shift), use the flat EQ setting, and go thru each EQ bar and shift the 'Q' down from 0.55 (thats the default from memory?) to 0.01 - when i do this i can hear the vocals shift from the center, off to one side. swapping the RCAs makes it jump to the other side of course.

i was pulling my hair out trying to figure this one out until i realised it was the Q setting that was shifting my image. i am not using the time alignment features, and balance is set to center, etc.

anyway, just wondering if any one else can recreate this problem. or explain/solve it for me

thanks guys

Could the same be done for the empeg? Rip a sine wave?

The empeg can play WAV files now, so I just create my sine waves in CoolEdit and send them to the empeg. Works fine. It's part of what I do when I mess with the RTA stuff.

also, something else i have noticed with my empeg - there is a puzzling shift of volume from 'centered' over to the left hand side, whenever i shift my Q of any frequency down to 0.01 - in fact, if you sit still and twirl the Q setting up and down you can hear the midrange output (mainly from vocals to the highs) shift over to the left.

This is a known bug in 2.0 beta 11. If you mess with the Q in the 2.0 beta 11 equalizer, it's only working on one of the two channels. The other channel gets its Q set to some arbitrary value (either minimum or maximum I don't remember). This will be fixed in the next release.

Note: 1.03 does not have this problem, and there is no problem in 2.0b11 if you use the auto Q. Also, if you set the left and right channels independently, it works correctly. This is only in locked L+R mode and only when you independently adjust the Q.

In reply to:

---

dB is a relative unit, and has no meaning without a reference level. In the case of an analogue signal, we could state that our reference was eg 1V, and then -3dB would be 0.5V, and +3dB would be 1.5V. In the digital domain, once all of the bits are 1, you cannot get any higher, so if you did state that this level was your 0dB reference point, then only negative dB values make sense, and any signal that attempted to exceed this value would indeed clip, as you have alluded to.

---

I haven't read the DSP specs or anything, but having positive dB values still makes sense to me. The dB value represents the gain (the output amplitude relative to the input amplitude) of a given stage (e.g. the volume control). 0dB is the point at which the signal is neither attenuated or amplified, so that if the input signal uses the full digital range (i.e. goes to all bits 1) then it will pass through cleanly. You can add in amplification (i.e. +ve dB values) and clipping will occur if the generated output signal exceeds the full digital range. e.g. If you double the amplitude of the signal, clipping will occur on any input signal that uses more than 50% of the full range. For signals smaller than this, it will be fine.

If you use only attenuation at all stages (volume, eq, etc) then even an input signal that uses the full range will not be clipped, hence the advice to eq using attenuation (-ve dB values).