Cycfi

Thanks! I'm quite pleased in fact. I'll try 1000 turns or lower next for comparison.

Here are some (mp3) wave samples of the initial prototype of the pickup along with some FFT graphs of the harmonic spectrum taken from the uncompressed, raw (aiff) samples. Stratocaster and Les Paul samples are also provided for comparison.

Indeed. I wish my DSP knowledge were advanced enough to participate in this more. While I have built a 24bit 96KHz ADC in the past, it was really nothing more than joining a bunch of IC datasheets/application notes together, and it has been a long time since I've done any serious electronics work at this level. I'd really want everyone to be able to hack on this. My goal is to make everything modular such that one can simply connect things like they do with stomp boxes. And, for the bare-metal hackers out there, there's the source code and schematics to play with. PS> There's a parallel discussion about the Hex-pickup project at the Seven-string.org forum. I'll be cross posting to both forums. I'm pretty sure cross-pollination would be very welcome. I have the same reply to something similar there :-)

USB was going to be my other suggestion, although it would limit you to only being able to use the instrument with a PC/Mac. Then again, maybe this shouldn't be considered a limiting factor? No, I don't think so. It is easy to build a USB board with DACs for each channel for those who want to get the raw (unprocessed) audio. Another idea is to use the Raspberry PI, as a stand-alone audio processor. Its 700 MHz core is pretty capable and with Linux as the underying OS makes it quite easy to program with. Also, I have a hunch that its GPU can be repurposed as a DSP processor (I'm pretty sure you've heard about GPU computing). Oh, that is pretty cool! Thanks for the link! I've been keeping a keen eye on XMOS. They're pretty much focused on audio and a lot of their clients are actually audio related (e.g. Sennheiser). Anyway, at the moment, I am looking at the lower-end. I've got this new stuff from digikey which includes the C5000, ultra-low-power DSP Booster Pack from TI. Its TMS320C5535 fixed-point DSP chip with two multiply-accumulate (MAC) units capable of up to 200 Million Multiply-Accumulates per Second (MMACS) and a tightly-Coupled FFT Hardware Accelerator. At $10 a piece (per 100 at Digikey), these DSP elves are very capable. There's a lot you can do at that price point already.

Yes! Yes and yes! That's what I'm talking about :-) No 1/4 plugs and sockets here, for sure. At any rate, some folks might find the just the pickup usable as-is. I'm inclined to agree! In as much as wireless is a sexy proposition, and I'm often lured into looking into the current state of the art every once in a while :-), I think that a wired connection is still the way to go. A means for wireless transmission should be just an option. I'll look more into Dante. Serial bitstream is cool! A bit related to that, lately I'm interested with this idea of using class D amplifiers for sending differential analog: Inexpensive analog isolation using a digital isolator. That said, the easiest solution I can see right now is to simply send through USB. That means ADCs on-board plus a microcontroller at the minimum. USB can provide the power just fine. USB has sufficient data rate and is getting better all the time. Plus, you can connect to any computer without additional hardware. Nod. Agreed!

That's more in line with what I am thinking of. I wouldn't even think of (nor afford :-) ), six amplifiers and effects chains. It seems obvious to me early on that DI and digital signal processing is the way to go with hex processing in mind. There's no other practical way. Of course it is still possible to route the mono-mix back a guitar amp, but hmmm...

That's certainly a neat idea! I'd say cross the bridge when we get there. For now I'll start with a wired connection. As you say, there's finite time. There are lots of things to work on still. My strategy is to make it work as quickly as possible. Refine, rinse repeat Indeed. My observation is that in general guitar players are conservative when it comes to guitar sound. I think that is the reason why digital emulations of amps cabs, pickups, guitars, etc., are quite popular, for example. Take the Roland VG guitar. You see emulations of the strat, the les paul, acoustics, all sorts of amp and cab emulations, all sorts of pickup emulations (single coil, double coil), effects emulations, etc. The same can be said of all the current generation of plugin effects available for computer based recordists. My opinion? We've stagnated! Emulations are good, but they are, ehm... emulations. If I want to have a strat sound, I'll get a strat. If I want a marshall JCM800, well, nothing beats the real thing. But what's sad is that we always tend to go back to the same tried-and-true path. The les pauls, the strats, the marshalls, the 50s style humbuckers and single coils. Bottom line is: we all sound the same! There's nothing new these days that gives me the OOHHH that is new! Like, I would imagine, what people thought when they first heard Jimi play a soaring riff through an overdriven marshall. What I really want is to explore new sounds. Not the tried and true. Not the strat, Not the Les Paul. Not the Marshall. Something totally different with a totally unique signature. For example, I'd really love to have complete control over attack, decay and sustain. I'd die for cello or violin like expressivity, dynamics and sustain without resorting to distortion and without sounding like a synth. IMO, expressivity (through sustain) is the very reason why the fuzz, overdrive and distortion were invented. I'd like to traverse different avenue for exploration with that same goal in mind. For the test bed, I resurrected an old strat copy to start with. I'll probably incorporate the results later in another prototype of the bamboo/carbon guitar.

I don't have the figures right now, but I seem to recall seeing strong overtones from the 10KHZ..20KHZ range at the attack transients, when hitting the strings hard (e.g. slap bass). Not quite sure though. But you might want to check it out. About ADCs, my electronics and C++ friend shared this article about Multi-channel ADC choices (specifically delta-sigma or SAR). He has very good points about SAR.

Update: I forgot to mention this technology: BlueGiga 12MBPS module. So... there's still hope I wonder about the range though since it's listed as class-2 BT (10 meters). Class-1 (100 meters) would have been better. But the lower power is very welcome.

Indeed! I've heard accounts that the BT module I linked to can only go up to 700+kbps in practice, at best. I also don't have a good experience with BT audio devices, for example, headsets. Move a few meters away and you get a choppy signal. As for the dynamic range, I see no problem in scaling down before transmission (then a corresponding gain after, and prior to the amp). In the end, it's the resolution that matters and that there's enough to capture the transients. 16 bits (or even 24 bits) is pretty good enough. What am I missing?

Those are interesting ideas! No, the op-amp debate is not set in stone yet.

It's cool you asked. I've been looking into wireless options sometime last month. I haven't yet found something suitable yet (e.g. BT 3.0). There are a couple of modules for BT 2.0, but as you now, the bandwidth is not sufficient (though they can theoretically go to up to 1382400 baud; Asynchronous: 2.1Mbps(Max) / 160 kbps, Synchronous: 1Mbps/1Mbps). Link: http://tinyurl.com/9sd596j. Another option is TI's pure-path: http://tinyurl.com/d9v6g74, but that is for 2-3 channels uncompressed and 4 channels compressed. There's also the NRF24L01 module which can (theoretically) go up to 2Mbit/s: http://tinyurl.com/9s8kc7h. So bottom-line, I have no good leads on that matter yet.

Re: size. Yes, It's very compact. I'll post some pictures soon for the first prototype. The coils + PCB + SMD Op Amps is just tad under 10 mm. The distance from the pickguard to the strings of a Strat type guitar is something like 5mm. I'm not sure what you mean by WAL-like full-width coil. Could you explain a bit? Do you mean having 2 coils for humbucking purposes? For prototyping, we are molding our own bobbins using a CNC'd mold and casting urethane, but I am also in contact with some manufacturers for mass producing them (expensive!). I've searched everywhere, but couldn't find off-the-shelf bobbins like these. So, yes, some aspects of the design (such as the bobbins) are already committed. However, I am pondering on having some flexibility. For instance, I can imagine 7-string or 8-string, or even bass guitar applications. For that matter, I am also considering single units complete with active preamps. I can imagine crazy ideas for combining and using such things.

Sounds cool. I tried that, but it seems I am not allowed to have URLs in my signature. Anyway, I donated to the site. Perhaps I'll be allowed as soon :-) Thanks, Carl!

Thank you, Prostheta! This is indeed a nice forum. Thanks for inviting me. I've just started reading through the posts. I see the looonnnggg thread about the "Sustainer Ideas" dating back from 2004. Wow! Anyway, reading through the posts, I believe I have some new ideas to share on the subject. For instance, I intend to use high-efficiency, low-power class D drivers (instead of linear amplifiers) and do digital signal processing (DSP chips are very affordable now!) on each string to have full control over attack, decay and sustain level. Again, as I said, I wish to share all the designs to the community.

Thank you, Chris. I'm glad you enjoyed the site. Building innovative stuff is my passion.

Hi! I designed and built the carbon-fiber-bamboo guitar. Currently, I use DiMarzio Injector pickups. On my next iteration of the prototype, I would like to experiment on hexaphonic pickups for hex processing. The Cycfi Six Pack Project is an ongoing Open Source Hardware project for the development of an active hexaphonic pickup system designed for hex processing. The pickup has six low impedance coils. The hex pickup is active with six differential low-noise, low-power pre-amplifiers —one for each coil. It has the same footprint as the ubiquitous Strat single coil, with a very low profile: 8mm (0.3 inch). Eventually, the goal is to have hexaphonic sustain drivers as well. That, and with extensive processing for each string, will give us musicians full control over the dynamics of the guitar. I know hexaphonic sustain has been done in the past with the Moog guitar, but that was a very expensive gear. I want something more affordable. And I want a system that can be adapted to just about any guitar. This IMO is the holy grail and I know this is very difficult to do right, but every journey starts with the first step. As an Open Source Hardware project, all the designs (schematics, PCB layout, software, bill of materials, CAD drawings and source code) will be freely shared, 100% free. I would very much love to hear your thoughts and gather ideas while the project evolves!