Re: [LAD] [LAU] Ardour MIDI tracer
On Sun, 17 Aug 2014, Will Godfrey wrote: > On Sun, 17 Aug 2014 16:15:58 + > Fons Adriaensen wrote: >> On Sun, Aug 17, 2014 at 08:24:38AM -0700, Len Ovens wrote: >>> So Allen & Heath uses 127 levels on their top end digital control surfaces, How do they do it? Well they have two different scales: - fader: ((Gain+54)/64)*7f - also used for sends >>> - Gain: ((Gain-10)/55)*7f - this is preamp gain >> Suppose you have *real* faders which have a range of 127 mm. >> That's not far from a typical size on a pro mixer. >> Would you ever adjust them by half a millimeter ? >> 127 steps, provided they are mapped well, and zipper noise >> is avoided by interpolation or filtering, should be enough. >> The real problem is that many SW mixers >> * don't use a good mapping, >> * and don't have any other gain controls. >> The latter may force you to use the fader in a range >> where it has bigger steps. > Well that got me thinking! > Presumably this should be set up as a proper log law, so even if the steps > represent (say) 0.5dB that still gives a control range of over 60dB I forgot to add: I would think ((Gain+54)/64)*7f uses a lot less CPU time than a real (proper) log. Think 8 fingers (plus thumbs?) fading around 80 steps in a small time. Remember that this calculation has to be done at both ends too and the receiving end also has to deal with doing more calculation on as many as 64 tracks of low latency audio at the same time (amongst other things). Also remember, this is only of use if you are building a control surface (I am) and not buying one where "you get what you get". Add to that, even if you are building your own control surface, do you want to use Yet Another standard that you then have to make middle-ware for so that the SW you are talking to will understand? A&H does supply middle-ware (for OSX) that takes the above values and converts them (both ways) so that their control surface looks to the sw like a Mackie (just about put Wackie) control surface. Talk about lot of computations in you music box! -- Len Ovens www.ovenwerks.net ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] [LAU] Ardour MIDI tracer
On Sun, 17 Aug 2014, Will Godfrey wrote: On Sun, 17 Aug 2014 16:15:58 + Fons Adriaensen wrote: On Sun, Aug 17, 2014 at 08:24:38AM -0700, Len Ovens wrote: So Allen & Heath uses 127 levels on their top end digital control surfaces, How do they do it? Well they have two different scales: - fader: ((Gain+54)/64)*7f - also used for sends - Gain: ((Gain-10)/55)*7f - this is preamp gain Suppose you have *real* faders which have a range of 127 mm. That's not far from a typical size on a pro mixer. Would you ever adjust them by half a millimeter ? 127 steps, provided they are mapped well, and zipper noise is avoided by interpolation or filtering, should be enough. The real problem is that many SW mixers * don't use a good mapping, * and don't have any other gain controls. The latter may force you to use the fader in a range where it has bigger steps. Well that got me thinking! Presumably this should be set up as a proper log law, so even if the steps represent (say) 0.5dB that still gives a control range of over 60dB Actually, I got the idea that we should not only do that, but that we should use a gain or trim to put the signal in the area (level wise) where we have the smallest gain steps. On a DAW, we sort of do this already by recording using the fader (and audio device gain) for trim and then mixing down using the fader for fine tuning. However, as I commented earlier, sometimes a harsh effect can introduce the need to: - re-record the track - add a gain section after the effect(s) before the fader. This may be as simple as using the output level the effect already has. -- Len Ovens www.ovenwerks.net ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] [LAU] Ardour MIDI tracer
On Sun, 17 Aug 2014 16:15:58 + Fons Adriaensen wrote: > On Sun, Aug 17, 2014 at 08:24:38AM -0700, Len Ovens wrote: > > > So Allen & Heath uses 127 levels on their top end digital control > > surfaces, How do they do it? Well they have two different scales: > > - fader: ((Gain+54)/64)*7f - also used for sends > > - Gain: ((Gain-10)/55)*7f - this is preamp gain > > Suppose you have *real* faders which have a range of 127 mm. > That's not far from a typical size on a pro mixer. > Would you ever adjust them by half a millimeter ? > > 127 steps, provided they are mapped well, and zipper noise > is avoided by interpolation or filtering, should be enough. > > The real problem is that many SW mixers > > * don't use a good mapping, > * and don't have any other gain controls. > > The latter may force you to use the fader in a range > where it has bigger steps. > > Ciao, > Well that got me thinking! Presumably this should be set up as a proper log law, so even if the steps represent (say) 0.5dB that still gives a control range of over 60dB -- Will J Godfrey http://www.musically.me.uk Say you have a poem and I have a tune. Exchange them and we can both have a poem, a tune, and a song. ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] [LAU] Ardour MIDI tracer
On Sun, Aug 17, 2014 at 08:24:38AM -0700, Len Ovens wrote: > So Allen & Heath uses 127 levels on their top end digital control > surfaces, How do they do it? Well they have two different scales: > - fader: ((Gain+54)/64)*7f - also used for sends > - Gain: ((Gain-10)/55)*7f - this is preamp gain Suppose you have *real* faders which have a range of 127 mm. That's not far from a typical size on a pro mixer. Would you ever adjust them by half a millimeter ? 127 steps, provided they are mapped well, and zipper noise is avoided by interpolation or filtering, should be enough. The real problem is that many SW mixers * don't use a good mapping, * and don't have any other gain controls. The latter may force you to use the fader in a range where it has bigger steps. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] [LAU] Ardour MIDI tracer
On Sun, 17 Aug 2014, Ralf Mardorf wrote: On Sat, 2014-08-16 at 09:45 -0700, Len Ovens wrote: A quick thought on fineness of control. It is true that 127 levels tends to "zipper". However, 127 levels is more than enough for static levels. I disagree. I never heard zipper noise, when I fade in or out or when using MIDI panning. Usually those steps aren't audible when fading or panning, but I often missed steps for static levels. Speaking for synth from the 80th and 90th, for the panning synth usually didn't use all 128 values, but 128 steps usually are used for the volume. I don't remember audible steps when fading, but I remember that there were not enough steps for optimal mixing. YMMV! I don't know if it matters, but was that a linear fade or log? Right now with 1024 steps in the range around 0 where we would be doing most of our mixing (0 on the fader, about -4 signal?) it is 4 steps to go from -0.1 to -0.0, That is 0.025 of a db. Does that kind of fineness really need to be used for mixing? The problem is that the faders are linear, so with 127 levels, by the time you are down -20 you are 1 click per db instead .1db with 1024. So if you are mixing a hot level, for example, I often record my guitar raw and then add effects later which really adds to the level, so I may be mixing it in quite low, I have bigger steps in my control range. So Allen & Heath uses 127 levels on their top end digital control surfaces, How do they do it? Well they have two different scales: - fader: ((Gain+54)/64)*7f - also used for sends - Gain: ((Gain-10)/55)*7f - this is preamp gain I think in both cases only the 7f is hex (their chart is colour coded and hex numbers are blue, decimal are black). SO the fader has two clicks per db from -45 to +10 and the gain value seems to be 9 steps for 4 DB on the bottom (+10 to +22) and slowly increases towards +65 at the top where there are 12 steps for 5db. This means they are starting out with a linear value from the motorized fader (pot or encoder - if it was me it would be an encoder) and prescale it from a higher resolution, or they start with a log pot or encoder in the first place. The fact that they post the formula leads me to believe they do the former (though I think if it was me, I might have an encoder made with that built in). So the problem with 127 levels is not that it is too little so much as how those levels are applied. SO far as I know, all control surfaces on keyboards have linear CC values. The upside of using 127 levels is a lot less MIDI noise. Even though most interfaces not longer go at 30khz, most are 100meg or gig networks, bandwidth for a large number of channels still counts. (plus I think they run audio on there as well) It gets away from using pitchbend for faders with it's built in limit of 16. The upside of using 1024 (or more) levels: It is easy, no need to compute a level. Just like 192 samples/second, it makes for good advertizing. At some levels, it does give finer control... of course by the time you get to -40 or so, you have less resolution than scaled 127 level control. Pots vs. encoders: My preference for encoders is two fold. One, they have a very direct built in relationship between location and value. A pot will be different from one to the next and need to be callibrated once in a while (the Mackie controller has instructions for doing this). Two, there is no wear in the read area as a pot has with a wiper (assuming an optical encoder). They are expensive, but in a $25K control surface, I expect that kind of quality. A rotary encoder with 1024 pulses per rotation is about $50 in singles, One with 8 bits out and 256 states per rev is about $35. The ones used in most control surfaces with the push button are 24 clicks per rev and use mechanical contracts... but cost only $2.50 each, there are actually 96 clicks per rotation, but 4 clicks are required to sense direction (2 bit greycode) so it is possible to go for clicks for the first value and then assume the next click is the same direction from then on. The ones used in a mouse are even cheaper... -- Len Ovens www.ovenwerks.net ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
Re: [LAD] [LAU] Computer noise, was: Ardour MIDI tracer
On Sun, 17 Aug 2014 04:21:09 +0200 Ralf Mardorf wrote: > On Sat, 2014-08-16 at 20:17 +0200, Dennis Schulmeister wrote: > > On Sat, 16 Aug 2014 18:21:52 +0200 > > Ralf Mardorf wrote: > > > > > Increase the volume and you will hear digital noise from the analog IOs > > > of a card inside of the computer. Move the mouse and extra noise will be > > > audible, no MIDI is needed to get annoying noise. MIDI noise is very > > > silent compared to mouse noise, but there is some noise. > > > > That's exactly the noise I'm talking about. With ground-lift it goes > > away. At least it did for me. > > I'll keep it in mind and test it someday. The idea of a DI-box between > analog out from the sound card and input of the mixing console is > strange, but that's were the problem appears. Parasitic noise might > disappear, but transformers of a DI-box likely will have negative effect > to the sound quality. Is there a DI-box without negative effect to the > sound quality? You get what you pay for. An active DI with quality transformers can easily give a flat 20-20 response at up to +24dBu and with THD better than 0.1 %. I'm getting that at +10dBu with a home build using the the transformer makers recommended schematic, and was quite astonished to be able to reproduce a flat-topped square wave at 100Hz with no visible overshoot. -- Will J Godfrey http://www.musically.me.uk Say you have a poem and I have a tune. Exchange them and we can both have a poem, a tune, and a song. ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
