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| Parallax Forums > Public Forums > Propeller Chip > PROJECT: OpenStomp(TM) Coyote-1 (Guitar Effects Pedal) | Forum Quick Jump
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epmoyer
Music maker, dreamer of dreams
      
Date Joined Apr 2007
Total Posts : 314
|  Posted 2/25/2008 1:24 AM (GMT -7) |   | | | |
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Graham Stabler
Registered Member
Date Joined Jul 2006
Total Posts : 2124
| Posted 2/25/2008 4:59 PM (GMT -7) | | | | |
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Bob Lawrence (VE1RLL)
Registered Member
Date Joined Aug 2007
Total Posts : 506
| Posted 2/25/2008 5:03 PM (GMT -7) | | Try this: (I moved it over from the other thread)
epmoyer
Music maker, dreamer of dreams
Email Address Not AvailablePersonal Homepage Not AvailableSend a Private Message to epmoyerAIM Not AvailableICQ Not AvailableY! Not AvailableMSN Not Available
Date Joined Apr 2007
Total Posts : 248
Posted 11/22/2007 9:16 PM (GMT -8) Quote This PostIgnore Posts From epmoyer.Alert An Admin About This Post.
OK, here’s the first demo recording I did. The file’s only 80kbps, but that's the best I could do given the file size limitations on this forum. The background guitar uses the Chorus effect. The three main parts of the song have a second guitar with the tremolo, followed by the delay, followed by the distortion. All tracks were recorded using the same guitar with the exactly the same knob settings so that the operation of the effects was not masked by other changes (other than the distortion, for which I cranked up my guitar’s built in compressor so that I would get more sustain). I would normally have used some reverb but I haven’t written one yet and I didn’t want to add any effects that weren’t coming from the pedal.
Distortion normally uses some filtering to affect which frequency ranges get distorted. This one doesn’t yet, so it’s a little rough. I also didn't have these effects written to use the knobs for parameter alteration at the time, so I had to dial in the delay time by iteratively changing my constants and recompiling; It’s not quite matched to the song tempo, but pretty close. Chorus usually uses some sample interpolation to avoid the noise of sliding the delay line tap point back and forth at discrete sample steps. The current version doesn't, but the noise is not very noticeable in this recording. If I play harder it becomes more evident.
Aka: CosmicBobPost Edited (Bob Lawrence (VE1RLL)) : 2/26/2008 12:13:44 AM GMT
File Attachment :
Howler.zip 1.79Mb (application/x-zip-compressed)This file has been downloaded 357 time(s). | | Back to Top | | |
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epmoyer
Music maker, dreamer of dreams
Date Joined Apr 2007
Total Posts : 314
| Posted 2/25/2008 5:08 PM (GMT -7) | | Good question! The strength of the Howler is that it is programmable. Its purpose is to facilitate a community of users who create and share new and interesting effects of their own design. In a lot of ways it is like the first Apple II, in that it is a platform on which cool things can be done, and they will come over time.
At the outset, there are a number of cool things which it will do out of the box. One is a "KT Tunstall" type delay loop which one can layer multiple passes onto "live", and which has a very long loop length by guitar pedal standards (almost 8 seconds at 24 bit resolution, and around 12 if you go to 16 bit).
As for the price point, its on the high side because it's a "boutique" pedal with a rather specific target audience and low production volume. If it was the kind of thing you could sell 4,000 a month of then the price point could be brought way down by paying for extrusion tooling and manufacturing it off-shore. The Hydra plays in the same market space in a way; it costs as much as a WII and doesn't compare from a performance standpoint, but It's worth the cost because it's so unique and fun (which is why I have one). That said, I also have a WII, and as guitar pedals go I also have a Line6 PodXT Live which I adore and wouldn't dare get rid of. If you're looking for the most guitar-effect performance and commercial versatility for your buck, you'd go get something like the PodXT (which is why I have one :), but If you're lucky enough to be able to put some disposable income toward a unique tool with all the coolness the propeller has to offer, then the Howler is the ticket.
In the end I'm really not looking to make a salary off this thing. I've just wanted someone else to make an open-source pedal for 5 years now and nobody has stepped up to the plate so I found I had to do it myself. Since I'm bothering to do it I'm going to do it right, and make it commercially available so that anyone who wants to come along for the ride is welcome to join me. I'm absolutely thrilled that Andre' did it with the Hydra; that's one less thing I have to make myself ;)Post Edited (epmoyer) : 2/26/2008 4:03:24 PM GMT | | Back to Top | | |
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mosquito56
Registered Member
Date Joined Dec 2007
Total Posts : 387
| Posted 2/26/2008 11:16 AM (GMT -7) | | Listened to your file AWSOME effects.
I think you hit someting if you can make the interface easy enough for a non programmer to use.
1.Add a drum accoup.
2. Add a chorus?
3. Add a second guitar that is an octave above or below?
4. With the prop you could make guitar sound like anything like the keyboards do.
4. Metronome
I was thinking maybe you could sell it as a kit and cut labor costs and sales costs. Look forward to your progress.
"What do you mean, it doesn't have any tubes?"
"No such thing as a dumb question" unless it's on the internet
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Clemens
Registered Member
Date Joined May 2007
Total Posts : 219
| Posted 2/26/2008 11:59 AM (GMT -7) | | I sure wish, the OS of my Roland MC 909 Grovebox was open source like this one! The machine is cool hardware but the software has some unresolved bugs.
I think your Pedal is a really cool idea. Sorry for the remark about the name, I definitely did not want to be the party pooper. 
Wouldn't it be cool to put an acceleration/tilt sensor inside the guitar and connect the input to the pedal, so people can control effects like wah-wah just by waving the instrument around? That way all these poser-gestures like spinning the guitar around ones neck could lead to interesting sound effects... LOL, just a thought. | | Back to Top | | |
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mikestefoy
Registered Member
Date Joined Feb 2008
Total Posts : 84
| Posted 2/27/2008 1:04 AM (GMT -7) | | I would be perfectly happy with a kit, and solder the SMD parts etc.
any idea of price yet ?
Mike | | Back to Top | | |
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epmoyer
Music maker, dreamer of dreams
Date Joined Apr 2007
Total Posts : 314
| Posted 2/28/2008 12:15 AM (GMT -7) | | | | |
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epmoyer
Music maker, dreamer of dreams
Date Joined Apr 2007
Total Posts : 314
| Posted 3/3/2008 8:51 AM (GMT -7) | | Somebody asked me about the software tools I used for the chassis design, and the company I used for fabrication. I thought the answers might be of interest to other forum members so I'll post them here.
I used SolidWorks for the 3D modeling, and I used a local company in Anaheim for the manufacturing (Executive Tool Inc).
I've been designing electronics boxes of one kind or another in my "real job" for a long time, so my choice of tools, methods, and manufacturer had a lot to do with the resources already available to me. I'm going to assume you don't have any previous experience in chassis design and give you the best advice I can:
1) SolidWorks is just fabulously awesome if you can get it, but it is very expensive. They don't even print the price on their website. If you call them and tell them who you are and what you're doing you can probably get a better rate than the corporate one. I also think they do some very low cost or free deals for "educational" use, so if you can get in under that umbrella that might work for you.
2) There is a fair amount of stuff to understand about how sheet metal can be worked and what kind of fasteners are available for putting it all together. I learned all of that from working in an industry where the people working for me knew it, and I picked it up along the way. I'm sure if you troll the web you can find some good info so you'll have to educate yourself on that as best as possible.
3) You should know about PEM fasteners and about McMasterCarr. PEM is the "big" name in sheet metal fasteners (though many companies make knock off products), and McMasterCarr is a great on-line distributor for screws, washers, nuts, rubber feet, studs, PEM fasteners, etc. I get all my hardware there.
4) I only used Executive Tool because they are local and because I know the guys over there and speak to them regularly on projects for my "real job". There are metal houses all over the place so I would recommend finding one close to you if possible. I find I always end up needing to meet face to face a couple times on a project, usually at least once on the front end to go over drawings and at least once on the back end to put the first parts together. Add more meetings if things go wrong (but of course they never do :) ).
5) Creating 2D manufacturing drawings is something of an art form in itself. Again, you'll have to use the web to educate yourself on what they look like and how to dimension things for a manufacturer. Your metal shop may be helpful in working with you to get your drawings to the point where they are in a format which gives them everything they need to know. The reason I LOVE SolidWorks so much is that you can build a 2D drawing from a 3D drawing, and when you change a dimension on the 3D model the 2D drawing updates automatically.
6) Manufacturing is expensive. If you design for cost you can get the per-piece price down quite low (the Howler chassis is down around $16 unpainted in 100 piece quantities), but you will always need to pay a "setup charge" when you run a batch. For this project I pay one to the laser cutter guys who make the blanks ($200) and another to the metal shop which bends the parts up and installs the press-in PEM fasteners (you need a hydraulic press to do that) ($200). Add to that the cost of your first couple prototypes and raw materials, and your in for about $500 to do your first prototype run; and that's "on the cheap" in my opinion.
7) There is a company on the web called "emachineshop.com". I haven't used them myself but they have some kind of free 3D tool which can be used to design parts, and then you can order them directly through the tool. I don't know what their costs are but if you're designing something in small quantities and you don't have access to a tool like SolidWorks then they may be a good solution for you.
8) The original chassis design for the Howler used a commercial aluminum enclosure from Hammond (purchased through DigiKey). It was about $16 and it would have cost me about $15 to get it drilled the way I wanted. I went down the custom sheet metal path because the per-unit price was better in moderate quantities (50 or more) than drilling out the Hammond boxes, but Hammond is a great way to go if your volumes are small or you can't afford the setup charges associated with developing a custom chassis.
9) The most important lesson I have learned in my engineering career is how (and when) to mock things up. If you're working for yourself then your time is free, and manufacturing is not, so it's worth it to double-check your design in every way possible so that you pay once for manufacturing and get it right. Paper models are one tool down that path, which is why I made several paper models (printed from SolidWorks) to verify the Howler dimensions. Another tool is to model everything you can in as much detail as possible in your 3D tool. All the Howler cards, connectors, buttons, etc. are modelled in 3D so that I could get as much confidence as possible in the metal, then once I modeled them I printed them out to verify that the models matched the boards and connectors. Model, check, model, check, model, check, check, check, sleep on it, check, take a deep breath, pay.
Best of luck to any chassis designers out there. Its a long hard road but there's just nothing quite like holding a (good) finished part in your hand.
The World's First Open Source Guitar Pedal: http://www.OpenStomp.comPost Edited (epmoyer) : 6/30/2008 12:29:47 AM GMT | | Back to Top | | |
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yerpa58
Registered Member
Date Joined Nov 2006
Total Posts : 25
| Posted 3/3/2008 11:31 AM (GMT -7) | | epmoyer,
Thanks for the interesting rundown on mechanical design. I use a version of IronCad that I got for nearly free when they were new, and I upgraded it for a fraction of the cost of a new seat. It also does associative dimensioning between the 3-D model and 2-d shop drawings. At my "real job" we design a lot of one-off products and I have learned to bend and punch simple boxes from 1/10" aluminum sheet. PEM makes some fasteners that can be pounded in with a simple hammer and anvil.
Having built some guitar DSPs in the past, I am following your project with great interest. It looks like it will be very solidly built, like some old Mutron pedals, or the Fender Blender. Those things were built to take a beating.
Do you have any approaches in mind to implement filters, such as wah or envelope modulated? I am still concerned by the propellor's lack of of a multiplier-accumulator.
Keep us posted! | | Back to Top | | |
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computer guy
I have 4 propellers
Date Joined Jan 2007
Total Posts : 1066
| Posted 3/3/2008 1:51 PM (GMT -7) | | | | |
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epmoyer
Music maker, dreamer of dreams
Date Joined Apr 2007
Total Posts : 314
| Posted 3/9/2008 11:49 PM (GMT -7) | | Time for bed, but my initial results are hopeful.
This is the output from the C# app, with some code added to count multiplies (16x16 fixed point assumed), fetches (to prop RAM), puts (to prop RAM), and adds. There's certainly some "in between" code which runs in the middle of those actions, but since fetches and puts assume 8 cycles for cog sync those instructions can be done in the cracks if the code is written well.
App started.
Running FFT...
Stats Dump:
[samples] :1024
multiplies:24572
divides :0
fetches :22464
puts :22464
adds :32766
CYCLES :1178494
time(secs):0.0147
window interval(secs):0.02327
percentage: 63.2%
So, assuming a dedicated cog for FFT and another dedicated cog for inverse FFT I should be able to do a 1024 point FFT in fixed point math and keep up with a 44khz audio stream (that is, I think I can do a 1024 point FFT in about 14.7 msec, and at 44kHz it would have to be at least as fast as 23.3 msec to keep up) . The stats above were generated witht the FFT algorithm not yet optimized to elimiate the complex component of the input and output signals, so the utilization will actually get better. I kind of doubt that I'll get below 50%, but if I did then I could do the FFT and the inverse FFT in a single COG. If not, I'm hopeful that for frequency domain effects I can dedicate two cogs to the FFTs (one forward and one inverse), which leaves two cogs for processing effects (the Howler OS occupies 4 cogs).
The World's First Open Source Guitar Pedal: http://www.OpenStomp.comPost Edited (epmoyer) : 6/30/2008 12:30:17 AM GMT | | Back to Top | | |
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epmoyer
Music maker, dreamer of dreams
Date Joined Apr 2007
Total Posts : 314
| Posted 3/10/2008 1:43 PM (GMT -7) | | Bob,
I am going to try two different approaches to pitch detection. If you take the FFT approach then minor changes in pitch will cause two adjacent spectral components to alter in relative values. If you can pick the fundamental tone from the overtones by finding the strongest spectral "peak" and then determine the actual frequency with enough resolution by analyzing the relative heights of the two or three adjacent excited spectral components, then that should work. The downside is that it would take 1 or 2 cogs dedicated to FFT's so it's unlikely that you could run it while other effects are going (probably not a big downside anyway).
A different approach is to compare the signal to itself with a significant separation in time (about 200msec if I recall from running the numbers a week ago), "slide" the first sampled window against the second a sample at a time to find the best correlation, and compute frequency from that.
I'm not sure off the top of my head which will be less sensitive to the tone of the input signal, but I hate it when tuners are finicky about tone (or volume, but I'll fix that with a compression stage).
The other nice thing about the second method, if it works, is that it has the potential to be a cheap and dirty pitch detection mechanism for other purposes (without eating cogs). One thing I thought might be fun is to store some short sampled instruments (like wood blocks or something percussive) in the second EEPROM, load them to RAM at boot, and play them back based on pitch detection from the guitar. That way you could assign a couple different percussive sounds to a couple open strings and be able to play them with the guitar as a "controller". It's not going to replace anybody's MIDI guitar, but I just think it would be a fun trick.
The first release of the OS will leave the second EEPROM completely unmanaged, and users can do whatever they want with it. Later on I'll add O/S support for some kind of resource file system which will let chunks of data be saved/loaded from the second EEPROM easily by resource ID.
The World's First Open Source Guitar Pedal: http://www.OpenStomp.comPost Edited (epmoyer) : 6/30/2008 12:30:26 AM GMT | | Back to Top | | |
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