McSeem

BTW, the hex endless sustain driver is still alive! I'm working on it. This what I played right now with a couple of simple chords and a hex sustain pedal. http://antigrain.com/hexatune/crap/sample01_driver_delays_01.mp3 Don't shoot me please, I'm not a player, it's just a sample of sound with a hex sustain driver and effects.

Well, I couldn't spend a lot of time on it, I was really busy at my primary job. But it's quite rewarding, now we are acquired by Autodesk, and I've got a pretty big bonus. As for the sustain, it's really not that simple, as I expected, it takes time to make it perfect. Robert didn't use it, because he would need some time to handle it. And I have another crazy idea how to drive the strings mechanically with a hexaphonic device on the bridge. The idea is to have a suspension on the bridge for each string, instead of a support. Then I can design drivers that work in a similar way that armature earphones work. Am I totally crazy?

Yeah, the problem is I'm on East Coast, you are in San Diego. But anyways, anybody is very welcome to visit my place and test it.

Hi, I had hard time at my main job, so, I didn't participate here. But still I kept working on my favorite hexaphonic project. A couple of days ago I invited a real guitar player, Robert. I have a micro-studio with 6 cheap Behringer active monitors, one for each string. I also can record a stereo-version of that sound. But in the beginning a player gets very confused, it sounds so unusual. The main thing is no inter-modulation. The sound can be heavily distorted, but still, a big chord remains clean. Next there are some samples with different distortions, octavers, reverbs, and delays. And, yes, the sustain driver is not used here. I can't post more than 2 media files, so, I just put direct links for your convenience. If it's strongly against the rules, feel free to ban me, I won't complain. http://antigrain.com/hexatune/robert/sample08robert_reverb01.mp3 http://antigrain.com/hexatune/robert/sample09_robert_delays01.mp3 - this one I like a lot. http://antigrain.com/hexatune/robert/sample10_robert_delays02.mp3 http://antigrain.com/hexatune/robert/sample11_robert_delays03.mp3 http://antigrain.com/hexatune/robert/sample13_robert_delays04.mp3 http://antigrain.com/hexatune/robert/sample14_robert_delays05.mp3 http://antigrain.com/hexatune/robert/sample16_robert_schoeder_reverb_slow_attack01.mp3 So, please, tell me if it all makes any sense? PS. I see big changes in the web design. It's nice to see that the projectguitar.com is alive and very active.

Absolutely. AFAIU, fuzz is just a matter of a proper transfer characteristic plus filtering. I can simulate any transfer with fancy math or just by interpolating a manually designed chart. For example, this function: double gloubi_boulga_sharper(double input) { double x = input * 0.686306; double a = 1 + exp (sqrt (fabs (x)) * -0.75); return (exp (x) - exp (-x * a)) / (exp (x) + exp (-x)); } It's VERY computationally expensive (takes about 5% of the time I can afford in the process call-back), but it sounds nice, especially combined with a Bezier-based transfer chart. http://antigrain.com/hex_project/sample_transfer01.png http://antigrain.com/hex_project/sample_transfer01.mp3 Well, I realize it's still not "kosher", but I'm in the very-very beginning of my way. Besides, big chords with fuzz sound very differently because there's no intermod. So, with hexaphonic processing (no matter, analog or digital) you won't achieve this authentic dirty grunge sound. It's not bad, it's not good, it's just different.

First, there's no way to use time multiplexing with a mono pickup/sensor; this part has to be polyphonic. Second, there's just straight physics: I tried to use pickup coils as the driver, it didn't work. The coils I use now for hex mag pickup have about 300 ohms DC resistance and produce up to 10 millivolts RMS, which is pretty low. They can theoretically work as drivers, but you need a lot of voltage. The driver coils have about 12 ohms and they are fine with about 0.5-1 volt of the signal. However, if you try to use these coils as sensors, they will barely provide you 10s of microvolts. Much lower than tape recorder pickups, which I remember was always a problem - to amplify it with low noise. So, my opinion is everything must be designed in a reasonable manner. The easiest way is to use a true hexaphonic loopback. If not possible -- at least a hexaphonic sensor with time multiplexing for the mono driver. And, of course, a separate signal pickup.

Just reporting... So far there's no much progress with fancy "totally-in-control" sustain, but my project is not only about the sustainers, it's mostly about hexaphonic in general. Next step will be a fast reliable pitch detection, synchronization and controllable phase shift. It's still a long way to go. However, I'm gradually handling sound processing and having a lot of fun when I have spare time. Recently I have implemented formant filters used for vocoders, and applied them to the guitar sound. The result is interesting. The formant filters take spectral rich signal, such as saw or square and produce more or less realistically sounding vowels, o,i,a,u,e. But applied to the pickup signal it sounds very differently. I also implemented an oscillating filter that interpolates the parameters between different vowels at low frequency. It sounds like a Leslie speaker, which I didn't expect. Well, it actually sounds like 6 Leslie speakers connected to the respective strings. So, this is a sample of pure formant signal: http://antigrain.com/hex_project/sample_os...ant_filters.mp3 But it sounds too fat, so, I decided to mix the result with the undistorted input: http://antigrain.com/hex_project/sample_os...mant_mixed1.mp3 Yes, there's a hex sustain too, I feed the coils with the filtered formant signal. The next is taken from piezo saddles, with NO SUSTAN, but with huge formant input gain and distortion. The bridge saddles are so sensitive that with these parameters you can hear some noise at the end. The noise is produced by my heartbeat. Really! It's not a joke. http://antigrain.com/hex_project/sample_os...mant_mixed2.mp3 Different parameters, with mostly magnetic hex, and with a bit of piezo mix (also no sustain at all): http://antigrain.com/hex_project/sample_os...mant_mixed3.mp3 With a simple slight noise gate and a lot of sustain: http://antigrain.com/hex_project/sample_os...mant_mixed4.mp3 Some single notes with heavier noise gate and also a lot of uncontrolled sustain: http://antigrain.com/hex_project/sample_os...mant_mixed5.mp3 Sorry for non-artistic playing. But note all is processed in REAL TIME, with very low latency, less than 10 milliseconds. So, my point is. After some initial efforts I can easily implement a lot of fancy effects in software and it's going to be all hexaphonic. The effects are so simple to implement and there's a plenty of algorithms, thousands of them.

Hmm, it doesnt look simple either. You probably will use analog switches to connect different filters. Besides, what happens in case there's a signal from two or more strings? Just connect two filters in parallel? In my opinion it's not that hard to build a true hex system. You can order pickup coils from Paul Rubinstein, for example, and use 3 minimal-circuit stereo power amps, such as LM4952, which has a DC gain control. Not sure about namely this one, but I'm sure there's a simple and compact IC solution. No analog switches, just different filters for different channels and a single-pole sustain pot. Well, plus maybe 6 single FET preamps. But anyways, it's nothing compared to that monster circuity Moog guitar. I was truly impressed by that.

I only found this one, it's still in the "experimental" status: http://www.ffado.org/?q=node/862 So far I use Win7. It's OK for experiments, but it's not a real-time system and can't be used for any live performance or even recording. So, in future I'll probably switch to Linux. Hideki, thanks for the info. It looks like they use something like Pulse-width modulation, at least, at the first sight. Anyways, the processing is very complex there and the circuit board looks like a monster. I'm trying to experiment with different software approaches, which is much simpler and takes much less time for prototyping.

It's hard to tell, mostly because of very different spectrums. But I noticed, for best fundamental frequency sustain there must be different phase shift between mag and piezo. So, when I adjust the phase for piezo and then switch to mag, I have to adjust the phase differently. I haven't yet done enough experiments, but the mix definitely affects sustain. I can't estimate it in terms of versatility or balance, but the sustain spectrum definitely differs. In my design hex and piezo channels are mixed in the Graphtech preamps with two 6-pole volume pots. So, in the guitar I have only 6 channels. To experiment with different sustain source and inputs I would have to use 12 channels, which would be a total overkill. I simply don't have so many inputs in my audio interface. The signal goes through the in-interface, software, out-interface, power amps, and back to the sustainer. I already use a 24-pin dual link DVI cable. There only 14 wires that can be used for the audio signal (it has 7 separately shielded pairs). I use 7 for the pickups signal and 6 for the driver (the 7th is the neck HB). So, plus one wire for the preamp power, and I only have 4 wires left for the future on-body controls. 5 pins are used for shielding. BTW, the new interface, Saffire Pro 40 seems to be absolutely stable. It's cheaper, better, and has more ins and outs than this shitty MOTU 8pre. And their preams sound is very good. So, just a note: MOTU 8pre is totally incompatible with PC and Windows (I suspect it's only because of absolutely buggy software drivers). It can simply damage your power amp, speakers and even your ears. Sometimes it produces a huge wild burst of noise: http://antigrain.com/hex_project/motu_noise.mp3 (I recorded it with a USB mic from headphones). Other people also complain about it: http://forum.recordingreview.com/f93/motu-...te-noise-22921/ Although, with the OSX there were no any complains, so MOTU must be fine with Mac DAWs.

So, I added a simple software dynamic range compressor and there's some non-distorted acoustic sound with hex sustain. First is just a plain feedback. http://antigrain.com/hex_project/sample_su...pahse_shift.mp3 The second is with a phase shifting at random speed for different strings. You will hear some digital noise there. It's normal and expectable. It's just because I do the phase shifting without care, that is, without any interpolation between frames. The cure for that is plain simple, it's just not done yet. http://antigrain.com/hex_project/sample_sus_pahse_shift.mp3

Absolutely. I'm in the very beginning, and I said that before: That is, the first step is ONLY reproduce a simplest solution and prepare the ground for further experiments.

I have already provided a "clean" sample: http://antigrain.com/hex_project/sample_sus_linear.mp3 In the auto-excitation mode, with a significant gain it's very unstable and tends to tear off the strings. As I expected.. So, at least a heavy DR compression is a must. So far the distortion plays role of a "dirty compression". al s., yes, it sounds nice when playing chords, but single notes don't sound that nice. To be nice it requires a noise gate, compression, and automatic phase adjustment. As for the progress... I also have to fight with Win7, task and IO priorities, and so on. With the normal, regular settings and with small buffers, it clicks and pops as soon as you move any window. So, Win7 by default is very unfriendly to pro audio streams. I spent some time with the Win7 multimedia API, but made it perfectly, solid-rock stable, even with other tasks running that load all CPUs 100%.

Psw, you will hear it. All in good time :-) The reason is, in my initial experiments I just want to hear what I put to the driver coils. Then. The non-linear voltage tranfer characteristic is the simplest thing that provides some degree of low coil power plus stability at the same time. In my previous experiments, the direct signal, combined with a high-Q resonance system (which guitar strings are) just goes wild. That's OK, just as planned. I have a suspition that in mono systems, there's just a natural power restrictrion - the 9v battery simply cannot provide so much power, and that's why a simple battery-powered sustain is getting stable. Works like a "natural dynamic range compressor". In my case I have no power restrictions, I can easily melt the coils and break the strings. And, BTW, the sound is not completely saturated. It's not like square, it has almost perfectly round peaks. However, the fronts and backs of the waves are almost vertical, which also sounds harsh and saturated. Anyways, I am a "nut scientist", I'm just trying to experiment with different crazy ideas. But I'm not totally nut, if I fail, I'll admit it. Also, there's a big frustration about MOTU 8pre audio interface. It's total crap, I'm totally disappoined with it. I ordered another device, Saffire PRO 40, which is inexpensive and has very good responses. It's time to look at the "traditional quality from England" :-) Well, the best one seems to be "the Germans" RME Fireface 800 (nom-nom-nom), but it's sooo overpriced.

Well, I'm not quite sure what am I shooting for. Basically, so far, just experiments, new sounds, new expressions. Tonight I tried a random phase shift in dynamics. It's not actually random, but just the rotation speed is random for each string. There's nothing very interesting, but now I'm sure with the dynamic phase shifting you can do a lot. Here's an example with a couple of chords, in the self-excitation sustain mode: http://antigrain.com/hex_project/sample_ra...phase_shift.mp3 So, when I achieve some results with the "best phase conditions" by default for each string and each fret, I can add a pedal that shifts the phase. Or, as I mentioned before, you can control it even with dedicated strings. I admit musicions, in particular, are looking for some fancy things that are tricky to handle, like ebow. Well, I'm thinking about it too. Not ebow, of course, but something else - strings plus pedals puls other controls. We will see. Maybe it's all about nothing, but I feel a lot of potentials in this area of engineering. So far it's pretty exciting.