Godin xTSA review: the synth (plus Axon AX50 and Roland GI-20 and a zillion VSTis)

Part three.  Parts one, electric guitar, and two, acoustic, are also up.

In this section, I want to tackle two things about the Godin xSTA‘s synth section and then compare the Roland GI-20 Synth controller to the Axon AX50 controller.  I’ll show how the guitar and the controller together make up an expressive unit that effects the sound profoundly before it ever gets to the synth part of your setup.  But first, I am going to complain about a flaw in this expressive unit, why no one addresses it, and a workaround.  Keep in mind that although I am complaining, this is not, as Liz Lemon would say, a dealbreaker.  It just means I had to settle:)  The problem with an expressive unit that is made by two different companies is that when something is wrong, each can point the finger to the other and say the problem lies over there.

guitar synth signal flow
guitar synth signal flow, with hum

The first task is to map out how the guitar synth makes sound. The bridge of the xSTA connects to a hardware synth controller via a thirteen pin plug.  What’s so hexaphonic you ask?  Instead of one output, it has a separate output for each of the 6 (=hex) strings.  Instead of outputting a single weak audio voltage, it presents you with six, so each string sends its own signal, making chords much easier to pick out than with software, but also meaning you can set each string to its own synth if you want.  The box you plug it into — either the Roland or the Axon — then transforms pile of voltage signals that into a stream of midi signals and sends it on via USB to your computer and from thence to whatever you are using to turn midi into sounds, the synth proper.  Both Roland and Axon make controllers that have built in synths for double to quadruple  the price, but I loves my vsts and saved the money and got the cheaper controllers that just transform the voltage to midi for me to mangle myself.  For the most part, the pre-built synth sounds are cheesy, both Roland’s and Axon’s.  That includes the resource hog NI Kontact Player softsynths included with the AX50.  I’d rather roll my own and have more control over the tweaking and so forth.

guit synth
The guitar synth "expressive unit" -- no hum

The one big problem with the “expressive unit”  arises from a ground loop hum when you use the USB midi/audio interface on either the Roland or the Axon controller.  The details of the hum are in the original post I made, and it is a problem well known on the Roland and Axon, forums, and to Godin (the latter via me at least).  Because the problem appears on both synths, and it seems that it is particular to Godin guitars, the problem would seem to lie in the xSTA.  My theory is that guitar synth setups are still designed for a hardware rather than a software synthesizer producing the actual sound, and with the expectation that a guitarist will not only use an outboard synth but a separate hardware amp or two for the electric and acoustic signals.  If you try to send the (non-synth) audio signals and the synth signals to the same device  (to treat the signals on your laptop rather than through an amp and effects boxes as discussed in a zillion other articles here), a shared ground sets up a feedback loop which in turn produces the hum.  The problem is in the wiring of the thirteen pins.  To get rid of the hum, send the acoustic and electric guitar signals through their own cables to the sound card in of the computer, skip the USB portion of the controller altogether, and send your output to a separate midi input device (I use an M-Audio midi-sport 2×2 for example).  No hum, but then you cannot use the software patch editors for either unit while you are playing, or the built in internal midi ports they create.  If you want to set up and store patches, you have to do it along with the hum, then unhook the USB to play.  It is not a problem until you start running everything into the laptop, but now that it is an option to do so, and a good one, Godin should really rewire the plugs to get rid of the ground loop.  A response from someone at Godin would be especially welcome here. When I contacted tech support, they said take it in for service, but this seems from the forums to be a problem with all of them, a design flaw rather than a defect with my particular guitar.  But because the source is easy to push off , and there is a workaround, Godin has more or less ignored the problem.

The second problem with the setup from the guitar angle is that the thirteen pin connection is spotty, even with a brand new cable (update: It was the cable.  Another new cable sorted this out).  Both the Roland and the Axon have an onboard tuner, and I recommend you use it each time you plug the cables in because often one string won’t output any signal until you remove and reseat the cable plug in the guitar.  Once it is working it seems to be pretty solid, but this is not a guitar for Pete Townshend acolytes (although I suppose Pete has mellowed enough to play it by now).    This second problem just makes it one more thing to check and double check before a live gig.  Doing a live gig with a guitar and laptop setup is still a pretty brave move, because a dozen things can be unplugged, switched off, or in need of a jiggle whether electronic or physical.

That is the end of my problem with the guitar, and as I said, all this is something I’ve learned to live with that is more than made up for by the sounds I can concoct on this setup.


I’ve been interested in guitar synthesis for eons, but it was always priced out of my reach until the arrival of VSTi synths.  Even then, the software-only solution I used had a major weakness. The biggest technical difficulty for guitar synthesis is something called tracking. That is the ability, or lack thereof, of software or hardware to turn an audio signal into a midi note.

I tried a couple of all-software ways to convert guitar notes to midi with mixed results.  That method uses a freestanding program like the discontinued g-tune or a vst plugin like widi to analyze the audio input and produce midi output.  I’ve described the sound (and the method of getting it) elsewhere as being like playing with a drunken Thelonius Monk wannabe.  The notes come out, but they are a little late and often a little bit askew, and all the velocity information is lost.  the note is either on or off.  This can actually be charming on occasion, and making synth sounds with slow attacks and long releases is a pretty good way of adapting to the all-software methods, as in this rreplay song.  If you are holding off on going synth because of $$, this is a cheap way to get started and opens up lots of tonal vistas.  Ultimately, whether it is hardware or software, the converter has to deal with the same thing, so I think that tracking will eventually move out of the controller box (i.e. the Roland or Axon) and back into the software.  Optimizing what comes out of the guitar will still help better the process though, so the specialized synth pickups on the Godin will probably stay.  Software solutions to hexaphonic output are limited by soundcard input at this point, which does not have the right connectors, and except for semi-pro and pro sound cards, does not have enough channels to deal with all the sounds coming from something like the xSTA.  For the foreseeable future the outboard controller box is still a necessity, but not for any really good reason other than nobody has moved it onboard a sound card and developed the necessary software yet.    Maybe Gibson’s firewire cabling scheme  will catch on –it is a step in the right direction — but it remains to be seen, and at a little shy of 4 grand for the guitar, I won’t be seeing it!

I finally took the dive and got the xSTA (less than a grand)  and started out with a Roland GI-20, then switched to an Axon AX50 synth controller interface.  This requires a bit of explanation.  The xSTA and other Godin guitars are known for having state of the art tracking.  Not having the budget to go out and buy a bunch of synth ready guitars, I’ll have to take their word for it.

The biggest challenge for tracking is the bass register of the guitar.  The lower the note, the more time between wave peaks in the sound signal.  Most voltage-to-midi converters need at least one wave cycle of the note, usually more, to determine what to output. To make things worse, the initial moment of striking a guitar with a pick or finger creates a noisy stretch before the note stabilizes, called a transient.  As a result, there is a slight delay before the note can be calculated from the signal, and the lower the note, the longer it takes to calculate because a wavelength takes longer to happen, so the worse tracking gets. One solution is to just turn the octave setting down a few notches and play your bass using higher notes on the guitar.  I just have a hard time getting the feel of a bass when I am playing on a wambly little G, B, or E string.

The xSTA’s job is to get the cleanest signal for each note to the midi controller and from there the controller takes over, so we need to divide the issue up and separate the xSTA’s job from the midi box’s job.  That said, the tracking from the xSTA is twenty times better than the software tracking solutions, which it damn well better be because it is also twenty time the price!  There really is not much more to say about the guitar part of the synthesis chain, so with that, we need to turn from the guitar to the midi controller hardware, and compare the Roland to the Axon.

I started with the Roland GI-20.  It was a hundred or two $$ less than the Axon AX50 and offered some features the Axon did not have (see below). The tracking is much better than software solutions, but not good enough to play a complex rhythm on a bass line and keep the nuances.  You can hear it drift around a bit in this piece, which is the acoustic section played with the synth on and the midi transposed down an octave and sent to a bass synth vst plugin.  The bass should be playing the same notes as the guitar part an octave down, but as you can hear, they don’t exactly, giving the not unpleasant illusion in this case of two players playing slightly different things.  Not drunk Monk, but forget funk or even punk. Its still thunk thunk.  Sorry, had to do that 🙂

Ultimately, two factors made me retire the Roland and go for the AX50.  One is size (because as I mentioned, I am traveling a lot) and the other is the tracking.  It has been a tradeoff though, as the Roland is better for some things, especially if you have some room to spread out (anyone want a good deal on a barely used GI-20? seriously, if you do, contact me!).

The Axon is pitched as a tracking monster.  Instead of waiting for a whole wavelength, the folks at Axon studied the transient part of a guitar picker’s attack, the very first moments during and after hitting the string but before the signal has stabilized to produce whatever frequency it is going to produce.  They figured out how to accurately predict the note to follow from the transient, in theory doing away with our tracking problems.  It works really well, if not quite perfectly.

In the musical example, the first time through I play the electric guitar section only on the left channel, so you can hear what I am trying to play.  Next comes the guitar on the left with a bass synth on the right powered by the xSTA and the AX50 run through Cakewalk’s Dimension with the “electric fingered 1” bass patch.  The third time, just so you can hear the difference from software solution tracking, I used widi, an audio to midi vst plugin, fed into nuSofting’s marimka, emphasizing the attack so you can hear how slow the tracking is on the software solution.  Its not bad, but a little off.

tracking bass -close
tracking bass -close

If you look closely at the image files, you will see that the green lines, which mark the onsets of notes in the guitar only signal, come a little before the bass notes in the left (lower) channel.  In the closeup image, it becomes clear that this lag is right at the edges of perception, in the ten to twenty millisecond range.  Thus playing it doesn’t sound like a lag so much as it feels a little slow. (n.b.:  the green lines are generated by a software onset detector that uses the whole signal, thus not real time, and not subject to the problems above, but also not useful for live playing)

Once you set the AX50 up to your playing style, it tracks any cleanly played notes with very little mis-tracking (playing notes other than what you played).  Some of the subtleties of a bass line will still get lost, as is obvious from the gaps in the first picture for the left channel, but the tracking is just shy of instant.  I have found that you can get a pretty expressive bass sound by mixing in some of the acoustic guitar signal into the octave-down synth mix to get the sound of the strings and the transients in there with zero lag and then plastering on whatever bass tone you choose so that the acoustic transients cover for the lag.

GI-20 vs. AX50

The GI-20 has some features I like that the AX50 lacks.    It is massively flexible.  You can program the switches on the xSTA to send either octave up and down messages, great if you want to switch quickly to a bass guitar register, or it can be set to send patch change messages (which by the way, can also be programmed to set the octave, sort of rendering the first choice a bit redundant).  The volume control for the synth can be set to any midi control (cc) message rather than just controlling volume, so for example, you could use it to sweep a filter instead of controlling volume  (losing the volume control in the process however).  Where the GI-20 is most remarkable in this regard is when you hook up both the optional foot controllers, one being a two button footswitch and the other an expression pedal.  The GI-20 gives you lots more options than just sending CC mesages, though it does that to.

THe AX50 has no inputs or dials.  no footswitches or pedals.  just an LED with a simple display and a power switch and a little tuning button on the front.  Everything gets done via the program banks controlled from the tail-most switch on the Godin, which you set up in software (with the USB hooked up).  What is extraordinary about the setup is that because of the transient sensitivity, the  unit can tell where on the guitar you are picking, whether closer to the neck or the bridge, with enough accuracy that you can assign a midi controller to it so that you can for example run a filter sweep  (like on a wahwah pedal) by changing the picking location.  This maneuver without the synth is already part of any expressive guitar player’s repertoire — it changes the tone drastically — so hooking it up to midi is a natural feeling extension of what you can do with the tone.  This is a great feature and I love it a lot.  You can divide the picking area and the fretboard into zones and assign each by string to a different sound, so that if you play an “A” on the seventh fret of the  D string,  it can play a different instrument than if you play it on the twelfth fret of the A string!  I have not had the chance to experiment with this much yet, but I like the idea.  What this does is keeps the expressive potential on the guitar.  No feet are involved and the hands never have to leave the guitar.  Now if I can only get the tilt sensor to the wiimote hooked up and attach it somewhere…oh wait a minute, maybe this not-so-free freeplayer thingie will work for another chunk of change….

Anyway, the bottom line is that you can get a tremendous variety of tonal wonderment out of the mixture of electric, acoustic, and synth sounds that the xSTA makes accessible, and the whole package of guitar and controller costs around the price of a nice mid-level guitar.  I opted for the Axon for the tracking and having a simpler smaller setup, but the Roland has its neat features too.  The whole setup is a blast most of the time, and I am still, after a year, finding new tones and new ways of making and mixing sounds every day, which is what it is about for me.  I’ll keep writing about the software setup, but I think I’ve pretty much covered what I have to say about the hardware.  Any comments?

Finally, if you made it this far, please take a little more time and listen to some of the great music on way net if you haven’t already.  Anything I’ve recorded in the past year and a half or so has been on the xSTA and either the Roland or the Axon.

Godin xTSA review: the “acoustic” part

Yesterday, I reviewed the Godin xTSA strictly as an electric guitar.  Of course, alone, that would miss the point, seeing as it also has a piezo pickup that doubles as an acoustic guitar emulator and a synth pickup.  Today, I’ll focus on the acoustic sounds you can get from the instrument.

Godin xTSA piezo EQ
Godin xTSA piezo EQ

Here is an mp3 that demonstrates the sounds I get out of the piezo.  You might want to leave it open in the background to refer back to.

The first thing to note is that the “acoustic” sound does not really sound much like an acoustic guitar out of the box.  It sounds more like a solid body guitar played without amplification and miked, which is a bit like what is actually happening.  The pickup itself is part of the bridge, and as I understand it, picks up the vibrations of the each string directly from the string’s contact with the saddle.  That signal is then routed through a small preamp with volume and a three band equalizer.


The EQ is quite responsive, and jacking or cutting the mids in particular completely changes the tone.  The result is a jangly sound with mids cut a little and a cutting sound with the mids punched.  It still does not sound very acoustic, but it could be useful to adding some definition to an electric sound, particularly on the attack portion.

the convoluted part

I mess with this basic tone to give it a more realistic acoustic flavor.  First I run it through Voxengo’s Perfect Space, a convolution reverb plugin I got with Cakewalk’s Sonar.  They also sell it separately as a plugin called Pristine Space.  Convolution is the process of combining your signal with the sound of some real or imagined acoustic environment.  In this case, I mixed the piezo sound of the guitar with the characteristics of an actual acoustic.  The sound file that Perfect Space needs to do this is called an impulse response, because it is a recording of the sound of something as close to an impulse as possible, often a balloon popping.  In this case, the author of the IR tapped a ceramic spoon against the bridge of his acoustic guitar.  I used the “near” version of the acoustic guitar IR from Noise Vault.  They have a great selection of acoustic instrument responses, speaker cabinet responses, and various hardware.  It is a great resource.  If you need a freeby convolution plugin, you might try freeverb3 but it is hard to set up and a resource hog.  There used to be one called revolverb, also less than perfect, but that’s gone it seems.  If you want to drop a few bucks,  Elevayta’s ConvoBoy is good, as is Voxengo’s previously mentioned Pristine Space. Both are reasonable and worth the money.  Voxengo is a little less resource hungry, but ConvoBoy lets you load a different IR in each channel of your stereo output, which is kind of neat.  Since most of the guitar’s sound comes from the strings, the convolution is kept down in the mix, a flavor rather than the substance.    This gives the sound a “woodier” feel, but the resonance gets a little obnoxious if the mids on the eq are turned to high.

Next in the chain is the best fifteen bucks I have spent in a long while, G-Sonique’s FSQ1964 vitalizer/exciter.  It grabs the transients…just the part of the signal we are most concerned with in getting a realistic sound — and makes them sound wonderful.  After that comes a touch of reverb, then out.  I experimented with light chorusing, but ultimately realized whenever I could hear the chorusing it was too much and let it go.

12 string

Not content to have an acoustic, I wanted to see if I could get a twelve string sound out of the piezos.  I split the input signal, before all the other effects mentioned above, and ran the unaffected signal in one side and sent the other side first to a very short delay with no feedback to emulate the space between the strings when you pick a twelve string, and to articulate the higher note just a little clearer.  Then the delayed signal goes to a pitch shifter set to raise the pitch one octave.  The delayed, raised note then gets fed back in with the slightly earlier unmodified note before coming out the convolution “body.”  It is not exactly accurate, as the high E and B strings on a real twelve string are not an octave higher like the lower four strings are, but it still sounds neat.  As the sound file makes clear, it is not perfect.  It warbles a little as an artifact of the pitch-shifting effect, but when it is mixed back a little and accompanied by other instruments, it passes reasonably well.  Take a listen to Be Miner for an example.  The rhythm part is all on the “12-string.”

Conclusion of acoustic part

Obviously, I like the processed sound a lot and have spent some time to get it as good as I can.  If I really need acoustics on a recording, I’ll go with fresh strings and an XY arrangement of a matched pair of mics on a real acoustic, like in Bomb the Beach.  But having an acoustic-sounding guitar that you can mix in with your electric and synthesized sounds as you are playing is a blast.  A couple of things I like to do are to chop the attack off a distorted electric guitar and replace it with the acoustic attack, or have one delayed a beat or portion of a beat behind the other.  It is also really nice to be able to put an analog, human touch sound into a synthesized one, opening up lots of new textures and spaces, which is what I am all about musically.

Well that is it on the acoustic portion of the xSTA.  Two down, with the synth section yet to go.  Even without the synth, this is a blast of a guitar.

Finally, If you didn’t get a chance the other day, give a listen to the four new tracks from rreplay and let me know what you think!

Godin guitar synth

godin guitar and case

n.b., update June 23, 2010: in depth review of Godin xTSA, part 1: as electric guitar.  Part 2: as acoustic. Part 3: as guitar synth with Roland GI-20 and Axon AX50

I decided to get a new guitar for traveling so I would not have to subject my ancient SG and pre-cbs jaguar to airport bumps and tosses.  If you just want to hear what the new Godin xTSA sounds like, here are a quick one, strange attractors, and recession era dreamscape 17, all showing off the synth and acoustic capabilities.

I have been eying up Godin guitars for some time now, and played a neat one with two humbuckers and a single coil in the middle with a little twist…there was also an onboard piezo pickup to emulate an acoustic sound.  The one I played was in Honolulu, at Easy Music Center, and a good deal, but I decided to forgo it and wait til I got to Los Angeles to buy anything, thus saving one leg of travel.  Plus I figured there might be more guitars in LA than in Honolulu.  I sent some emails out inquiring and got back a response from Jon Bingham at West LA Music on Santa Monica Blvd saying he could get the Godin for me.  He got me a great deal.  Go see him for yr guitars!  When we got around to details, it turns out that Godin has stopped making this particular guitar but makes the exact same one with a guitar synth built in as well, the xtSA.

I have been playing synthesized guitar for a while, using first G-tune, a tuning program with midi out, then the widi pitch tracking software.  This has been fun–but tracking is a problem.  Widi did a better job than g-tune (it should, it is made for the purpose while g-tune is primarily a most excellent tuner program), plus you could delimit the note range, taking some stray hits out of the picture.  Still, it was like having a slightly drunk Thelonious Monk wannabe playing something vaguely similar to what you played on guitar but a little later.  It is actually kind of cool sometimes, especially if used as an inexact wash kind of thing…check out rreplay’s round the perimeter, but the problem is something called tracking.  Turning guitar string vibrations into midi notes is computationally inexact and intensive, so the tracking was never more than an approximation.  Plus, neither captures any of the dynamics of your playing.  This is particularly a problem with widi…it would not take much to put in an envelope follower to track dynamics and map it onto a midi control change message…that should be built into the program.

So anyway, Jon said he could get me a sweet deal on the xtSA, basically getting it for the same price as the discontinued model without the synth, so I thought , ok.  Now last time I checked, guitar synths were always multi-thousand dollar affairs that locked you in to a particular set of synth hardware that did not sound so great.  I checked again and found the Roland GI-20, which was just what I needed, basically it just took the signal from the guitar and changed it into midi, which I could then run through my zillion plugins.

After a few mixups which delayed the guitar’s arrival, I got it, the GI-20, a road-worthy case, and the attendant cords and a cool strap.  The guitar is a beautiful flame maple top, black with lighter detailing in the wood.  I also like the cognac flam maple finish, but got the better deal on the black one.

Got it home and spent a week on the acoustic and electric pickups without doing the synth.  Very nice.  The combination of humbuckers and single coil is nice.  I have always played single coils, so it is nice to have that edgier sound available, and I figure when I get back to Honolulu, having something with humbuckers will add to the sonic palette.  The single coil is not so hot, outputting only about half the volume of the humbuckers, but with a nice fendery slinky kind of sound.  I am going to try raising it to see if I can get it to output a little hotter.  I like crunchy single coils a la p-90s, but I am not sure this one has it in it.  The pickup positions, selected via a strat-style 5 position switch are neck humbucker – humbucker/single coil – single coil bridge humbucker – and bridge.  I thought it might be nice if the humbuckers could be tapped, instead of mixing, and a couple of other Godins do that with two pickups, the the LGX-SA and the LGXT, but they are two to three times the price.

The acoustic section is cool sounding, though without some doctoring up, not really acoustic sounding.  It is more like the glassy 80’s Police/Andy Summer kind of tone that sounds really good chorused.  I am playing with running it through a convolution reverb with a guitar body impulse loaded to make it sound woodier, and also mixing it with an octave up signal and a light slow moving chorus to get a twelve string sound…hmm, maybe a delay would be better than a chorus to get that…I’ll have to try it. One down side is that the whammy bar is really microphonic when the piezo is on so usually you’ll want to swing that out of the way.

The guitar plays flawlessly.  It came set up right, and there are no dead spots or buzzes.  It has locking tuners, which I guess I don’t get the point of just yet.  They put on strings with no extra winds around the tuning peg, and I guess the lock is supposed to keep them in place and in tune, but mine slipped when I bent the strings, so I had to immediatrely restring.  Not a good pitch for the Godin strings that they recommend on the guitar.

Now on to the synth…this is where things get a little squicky.  The setup is to run an acoustic and electric analog out and a thirteen pin analog to midi cord to the Roland GI-20 midi box.  When I plugged the Roland into the USB, it gave a terrible whining noise through the electric pickups at 1000 hz, 2000 hz 3000 hz and so on (see image above).  I solved the problem by dispensing with the roland usb midi and running a midi cable out of the Roland and into an outboard USB midi port.  Another seeming problem is that the synth volume knob does not work until you program it to work on the roland, as I found out when I RTFM.  Once all that got sorted out, I was able to make some interesing music.  Check out a quick one first if you don’t have much time or patience.  It is the acoustic guitar played with a synth bass tracking the guitar sound.  Next comes strange attractors, and last and weirdest, but showing some of the interesting things that can be done with the synth, is recession era dreamscape 17.  All are recorded in one take in Plogue bidule.  Everything but the drums comes from the guitar.  As always, check out the rest of the music on way music.