After complaining about the shoddy overdrive sounds coming out of my Behringer GDI21 pedal in another post I did a bit of homework on where my guitar sound is going wrong.
I checked through my effects chain usinf DFX RMS Buddy http://destroyfx.org/extras/ and found that the extra input volume I get from the pedal means that I occasionaly hit over 0db between effects. My soundcard input and effects chain output are both well below 0db.
Is it possible that I'm wrongly blaming the pedal and that I'm actually getting a crap sound because of digital clipping between effects?
Clipping inside an FX chain
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- KVRist
- 39 posts since 17 Apr, 2005 from Sydney Australia
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- KVRAF
- 6937 posts since 4 Jun, 2004 from Utrecht, Holland
It is very well possible that you're feeding a signal that's ust too hot. In case the fx return has no trimming pot, you can fix that with a volume pedal after the overdrive before it returns back into effect return. Also not so expensively avaliable from Behringer 
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We are the KVR collective. Resistance is futile. You will be assimilated.
We are the KVR collective. Resistance is futile. You will be assimilated.
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- KVRist
- Topic Starter
- 39 posts since 17 Apr, 2005 from Sydney Australia
My input is around -10db, and I keep my output well below 0db (attenuating at or near the end of the chain using one of the effect output levels). So I'm not clipping on the way in or out. Maybe it's in between.
For example if I used TLs Saturated Driver the output from that would be 0db ...
then if go into an eq and the sum of my cut and boosts lets through the occasional 1db ...
then I pull the level down with a compressor to say -6db.
My start and finish are under clipping level but at the EQ I stepped over the line.
Should I get audible digital clipping/distortion even though my soundcard level never actually hits above 0db?
For example if I used TLs Saturated Driver the output from that would be 0db ...
then if go into an eq and the sum of my cut and boosts lets through the occasional 1db ...
then I pull the level down with a compressor to say -6db.
My start and finish are under clipping level but at the EQ I stepped over the line.
Should I get audible digital clipping/distortion even though my soundcard level never actually hits above 0db?
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- KVRAF
- 6937 posts since 4 Jun, 2004 from Utrecht, Holland
I think I did not understand it correctly. I was under the impression you had a clean recorded guitar, going thru an effects loop (outside the PC) through a Behringer foot pedal distortion/overdrive, back into the PC again.
If you are keeping the effects signal chain comletely inside the VST realm, then internally there is no clipping ever (unless an effect developer has coded it on purpose.)
Maybe I should look up this previous thread of yours...
If you are keeping the effects signal chain comletely inside the VST realm, then internally there is no clipping ever (unless an effect developer has coded it on purpose.)
Maybe I should look up this previous thread of yours...
My MusicCalc is temporary offline.
We are the KVR collective. Resistance is futile. You will be assimilated.
We are the KVR collective. Resistance is futile. You will be assimilated.
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- KVRist
- Topic Starter
- 39 posts since 17 Apr, 2005 from Sydney Australia
Not much in the previous thread, just me saying I think the amp sims in the pedal suck and Lunch Money having a different opinion ... http://www.kvraudio.com/forum/viewtopic ... 3&start=30
I guess what I'm really trying to work out is if digital clipping/distortion happens ONLY when something over 0db hits the soundcard or if it can happen at some point during an effects chain, even though that sound never exists in the real world.
I expect at least one reply from somebody which includes this emoticon ...
I guess what I'm really trying to work out is if digital clipping/distortion happens ONLY when something over 0db hits the soundcard or if it can happen at some point during an effects chain, even though that sound never exists in the real world.
I expect at least one reply from somebody which includes this emoticon ...
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- KVRAF
- 6937 posts since 4 Jun, 2004 from Utrecht, Holland
Ok, Looking for a bass amp sim it was...
Firstly, recording a guitar with pedal-boxes directly into the PC is a tricky business. You might miss the things that a real amp & speakers do to the sound: cut away transients above 15kHz. This is what most amp & cabinet sims should take care of.
And then there is the problem with getting a proper signal level & impedance, since the high-impedance guitar signal (which also comes out of most stomp boxes) must be transformed to either mic or line level.
So what exactly your problem is, is hard to tell without hearing what you have recorded, and how it sounds on your effects chain. Maybe you're only missing a chorus effect to fatten it, or have not found a right EQ setting yet.
Firstly, recording a guitar with pedal-boxes directly into the PC is a tricky business. You might miss the things that a real amp & speakers do to the sound: cut away transients above 15kHz. This is what most amp & cabinet sims should take care of.
And then there is the problem with getting a proper signal level & impedance, since the high-impedance guitar signal (which also comes out of most stomp boxes) must be transformed to either mic or line level.
So what exactly your problem is, is hard to tell without hearing what you have recorded, and how it sounds on your effects chain. Maybe you're only missing a chorus effect to fatten it, or have not found a right EQ setting yet.
My MusicCalc is temporary offline.
We are the KVR collective. Resistance is futile. You will be assimilated.
We are the KVR collective. Resistance is futile. You will be assimilated.
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- KVRist
- Topic Starter
- 39 posts since 17 Apr, 2005 from Sydney Australia
Thanks for the tips Cookie. I've re-arranged my effects chain and pulled down some levels and I don't hear the bad sounds anymore 
But I am still trying to work the clipping thing out for future reference. Perhaps I need to work on my posting technique to be clearer with my questions.
If this example happens:
*signal level entering the soundcard is minus 10db
*signal goes through a VST effect and the output signal from that effect hits occasional peaks of plus 4db
*the now 4db signal continues on its merry way to effect number two where the effect's volume dial gets turned way down and the output from the end of the chain is minus 10db ...
Will the +4db signal in the middle of this cause audible digital clipping? Or is it impossible for that to occur because the signal hitting the soundcard (at both ends) stayed well below 0db?
I hope I've explained it goodly enough this time.
But I am still trying to work the clipping thing out for future reference. Perhaps I need to work on my posting technique to be clearer with my questions.
If this example happens:
*signal level entering the soundcard is minus 10db
*signal goes through a VST effect and the output signal from that effect hits occasional peaks of plus 4db
*the now 4db signal continues on its merry way to effect number two where the effect's volume dial gets turned way down and the output from the end of the chain is minus 10db ...
Will the +4db signal in the middle of this cause audible digital clipping? Or is it impossible for that to occur because the signal hitting the soundcard (at both ends) stayed well below 0db?
I hope I've explained it goodly enough this time.
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- KVRAF
- 2582 posts since 24 Apr, 2003 from Canada
It shouldn't cause digital clipping. afaik how vst processes internally clipping isn't possible.
But in practice I'm not so sure. For example, when I use SIR sometimes I get digital clipping, regardless of whether there is a limiter or compressor after SIR. It seems if SIR clips internally, nothing after it in the fx chain will fix it.
But in practice I'm not so sure. For example, when I use SIR sometimes I get digital clipping, regardless of whether there is a limiter or compressor after SIR. It seems if SIR clips internally, nothing after it in the fx chain will fix it.
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- KVRist
- 85 posts since 7 Jan, 2005
I'm unfamiliar with how a VST host handles it's internal signals, but it is wrong to say there is no clipping. In any digital system clipping is possible. You simply run out of numbers to represent the waveform.
With 32bit floating piont, which I think most Native DAWs use, there are a lot of numbers, and therefore a huge dynamic range, but how each plugin determines its nominal level (i.e. the where 0dB is in relation to 0dBFS) i don't know. Which means that I am even more careful with digital gain structure than I am with analogue.
With 32bit floating piont, which I think most Native DAWs use, there are a lot of numbers, and therefore a huge dynamic range, but how each plugin determines its nominal level (i.e. the where 0dB is in relation to 0dBFS) i don't know. Which means that I am even more careful with digital gain structure than I am with analogue.
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- KVRAF
- 6323 posts since 30 Dec, 2004 from London uk
Possibly a badly behaved plug?
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- KVRist
- Topic Starter
- 39 posts since 17 Apr, 2005 from Sydney Australia
The part of the chain where it seemed to clip went TLs Saturated driver (out 0db) into Nyquist EQ (out hit occasional 1db peaks) then into Revolverb Lite where I pulled the volume back down to about -6db. When I moved the EQ to the slot before Saturdated driver I could no longer hear the clipping.
It seems that it is possible to have audible clipping within a chain. But then Revolverb is a convolution/impulse thingy and not a VST thingy (maybe?).
I guess I'll just assume that it does happen and pay more attention to volume levels within the chain, rather than just at the in and out.
Thanks to all for your help.
And Iain F ... your G-Phat amp rocks, keep it up. It makes me go like this when I play through it
but without the brick wall.
It seems that it is possible to have audible clipping within a chain. But then Revolverb is a convolution/impulse thingy and not a VST thingy (maybe?).
I guess I'll just assume that it does happen and pay more attention to volume levels within the chain, rather than just at the in and out.
Thanks to all for your help.
And Iain F ... your G-Phat amp rocks, keep it up. It makes me go like this when I play through it
but without the brick wall. -
- KVRist
- 382 posts since 6 Apr, 2005 from Fair NJ, the Garden State, US
VST fx can clip -- a bunch of mine have a 'clip' light, for instance. IainF is right to worry about gain structure, a concept that's completely lost in most digital signal chains but which remains as import as in analog. Just because we don't have to worry too much about noise floor doesn't mean we don't to get our gain structure right, yeah?
Grist for the glamour mill.