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PROJECT: OpenStomp(TM) Coyote-1 (Guitar Effects Pedal) - Page 4 — Parallax Forums

PROJECT: OpenStomp(TM) Coyote-1 (Guitar Effects Pedal)

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Comments

  • J. A. StreichJ. A. Streich Posts: 158
    edited 2008-07-18 21:25
    Gordon, any effects pedal can be used for other electric instruments... Some aren't as good for certian instruments (i.e. some Guitar distortion pedals can be a bit heavy for violin distortion), but with the open nature of this pedal, I'm sure you can get whatever your looking for to go with your instrument in question. What instrument you have in mind?
  • Gordon CharltonGordon Charlton Posts: 3
    edited 2008-07-19 08:05
    J. A. Streich said...
    What instrument you have in mind?

    The theremin.

    Most theremins provide line level audio out, which causes undesirable distortion on some of my guitar effects pedals that are designed for instrument level audio. Consistent use of the word "guitar" in describing an effects pedal can be a warning sign that it is not happy with line level.

    Also - it seems I'm going to be either installing Windows on my MacBook or buying a Windows machine - am I correct in presuming that the associated software is not terribly processor intensive so I can get away with buying a cheap PC with low specs? I don't anticipate using it for any other purpose.

    (Incidentally I am not sure that epmoyer is correct in assuming that Windows has a market share of 92% amongst his target audience. Microsoft totally owns the business sector, but I have seen more musicians with Macs than PCs.)

    Post Edited (Gordon Charlton) : 7/19/2008 8:11:08 AM GMT
  • epmoyerepmoyer Posts: 314
    edited 2008-07-23 16:49
    Gordon,

    You're correct; in general guitar pedals are typically designed to have an input impedance of around 1M Ohm (i.e. very high). Line level input impedance is typically 10-20K or so. In general you can use a "direct box" to match a line level signal to a high impedance input.
    The input impedance of the CODEC in the Coyote-1 is 12K Ohms but there is a pre-amp in front of it who's sole purpose it is to create a 1M Ohm input impedance at the jack. Bypassing the preamp in hardware would be pretty trivial if someone wanted to modify the pedal to accept a line level input.

    I'm actually doing some tweaking in that area right now and trying to resolve the final shipping configuration, so I can't tell you exactly what the final shipping input impedance will be, but 1M is the target. I ran into an odd situation where it hadn't occurred to me that all of my test guitars actually have pre-amps in them and that I'd gone all this time without testing the pedal with a "standard" pre-amp-less electric guitar! Now I'm tweaking the input to make sure it handles standard guitars.

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    The World's First Open Source Guitar Pedal:··http://www.OpenStomp.com
  • epmoyerepmoyer Posts: 314
    edited 2008-08-01 02:32
    MILESTONE: First 9 up and running

    Here's a shot of the first nine units up and running. I can't say for sure when they'll be ready to ship; possibly as early as this Monday if the weekend goes well. I'm still wrapping up the material for the release CD. I'll be contacting the early mailing list subscribers very shortly to dole out the first 9, and more will follow later. I'm almost sad to see them go; they look so cool all lined up on my table like that [noparse];)[/noparse]

    first_9.jpg

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    The World's First Open Source Guitar Pedal:··http://www.OpenStomp.com
  • Bob Lawrence (VE1RLL)Bob Lawrence (VE1RLL) Posts: 1,718
    edited 2008-08-01 03:03
    Congratulation! They look great. That's a cool.gif picture.

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    Aka: CosmicBob
  • Gordon CharltonGordon Charlton Posts: 3
    edited 2008-08-01 07:24
    epmoyer said...
    Bypassing the preamp in hardware would be pretty trivial if someone wanted to modify the pedal to accept a line level input.

    That is excellent news. Without openstomp the only option really available to me to create the effects I want would be Max/MSP - and I don't want to get into taking a laptop to gigs.

    Also good to see the first batch all lined up and waiting for shipping. I hope some of the early recipients will share their impressions of the pedal here.
  • steve_bsteve_b Posts: 1,563
    edited 2008-08-01 15:31
    I've been watching this thread and am quite excited/impressed with the "adventure"!
    I'm hoping I'm one of the early subscribers!! hehe

    Great work and am planning no getting one and putting it through the paces!!

    About the only thing I'd suggest, can't remember if it's in the thread already, is a tuning setup. Would have been nice to have a red LED for being in tune, but I suppose the LCD would suffice at this point in the design!
    [noparse];)[/noparse] Further with the tuning is a tuning teacher that would tell you which direction you need to tune each string if you wanted DADGAD or Open G etc...

    Cheers

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    <FONT>Steve



    What's the best thing to do in a lightning storm? "take a one iron out the bag and hold it straight up above your head, even God cant hit a one iron!"
    Lee Travino after the second time being hit by lightning!
  • epmoyerepmoyer Posts: 314
    edited 2008-08-04 06:24
    MILESTONE: Final issues resolved

    Well my friends, it's been a busy weekend but I have arrived at a final hardware shipping configuration. Here's what I've been wrestling with:

    1) Expansion port termination
    I tweaked the resistor values on the expansion port to get optimum signal quality on the interface lines.

    2) Headphone volume
    I've been working with the headphone volume for about a week now, since I made the discovery that a pure sinusoid at max DAC output range was much louder to the ear than a guitar which was peaking at max range. I ended up making the rather difficult decision to cut the headphone amp gain down considerably. The practical upshot is that most users will find the headphone output volume lower than they would normally prefer for their own guitar playing. The reason I chose to do that is because if I'd left it where it was it was capable of producing EXTREMELY loud sounds if, say, you encountered a bug in some effect code you (or someone else) wrote. I know from experience that coding errors in digital effects can produce some very obnoxious sounds, and even with the new volume reduction I still recommend NOT doing code development with headphones on. Anyway, it seemed prudent that since this is a development pedal I err on the side of safety and make sure nobody's ears get blasted.

    3) Input impedance
    This was the big one. As I said in an earlier post, I went for quite a long time on this project without realizing that every guitar/bass I own today contains a pre-amp of one kind or another. There are two occasions in which other guitarist's have plugged their gear into my pedal in in at least one of those cases they were also running though a preamp. I just can't remember what the setup was for the second case, but it's very possible that we had some other stomp box in front of mine in the signal chain, which would have acted as a pre-amp. What's the big deal? Electric guitars have pretty high output impedances, which is to say that they are weak line drivers. That's shouldn't be too surprising when you consider that all the energy they output is generated by the string vibrating through the magnetic field of the guitar's coil. What's more, electric guitars have lower output impedances at low frequencies, and higher impedances at higher frequencies. That means that if you take a regular Fender Strat and plug it into an audio DAC with a 12K input impedance, you end up loosing all the high frequency components and the sound gets all muddy (the highs run around 100K on an electric guitar, so at 100K into a 10K load the high frequencies get cut down to less than 10% of what they started at). Now, if your guitar has a pre-amp built into it (i.e. if it contains a battery (or is otherwise powered) and actively drives the output signal), the preamp will have a very low output impedance across the whole audio frequency range and will no problem driving a 12K load. That's what was happening to me. All my guitars sounded great and I got very close to shipping before I realized I hadn't tested with a "normal" guitar!

    The solution was to put an impedance buffering preamp into the pedal, which is basically an emitter follower transistor with about a 1M ohm input impedance (typical for guitar pedals). Now, the problem with that is that once you have a high impedance input it means you can be driven by extremely weak signals, which is great if a guitar is plugged in, but kind of stinks when the line is unplugged because you end up very easily coupling any noise around the circuit. It turns out that the circuit and wires which drive the pots for the control knobs are close enough to the audio circuits that you can get a decent amount of buzzing if you don't have anything plugged into the input. I did some things to reduce that noise as much as possible, and in the end the unplugged case is not a huge deal and the preamp is an absolute necessity to support "standard" guitars, so it's going in.

    It's still going to take me a night or two to get these last couple changes into the first nine units. I'm going to wait until everything's boxed and ready to ship before I take the orders; again, these are going out to early mailing list subscribers and I'll contact them directly. The first large production run has been on hold waiting for resolution of the issues above, I'll cut that loose this week.

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    The World's First Open Source Guitar Pedal:··http://www.OpenStomp.com
  • epmoyerepmoyer Posts: 314
    edited 2008-08-06 05:59
    I just finished putting the fixes into the first 9 units and testing them. The audio sounds just fabulous with standard guitars and bases now! I'm extremely pleased.

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    The World's First Open Source Guitar Pedal:··http://www.OpenStomp.com
  • HatredmanHatredman Posts: 1
    edited 2008-08-06 15:08
    Hi Eric

    I have just discovered you project (via Wikipedia) and really liked it.

    As it is an Open Source project I wanted to participate, not only in the electronics design thing but also in developing a Linux version of the software.

    I know, on the software part I'm on square one and all, but I really wanted to try.

    Anyway: if it's an OpenSource project, where are the schematics? Where's the source code? I couldn't find them on the official website.
  • epmoyerepmoyer Posts: 314
    edited 2008-08-08 03:07
    Hatredman said...

    Hi Eric

    I have just discovered you project (via Wikipedia) and really liked it.
    As it is an Open Source project I wanted to participate, not only in the electronics design thing but also in developing a Linux version of the software.
    I know, on the software part I'm on square one and all, but I really wanted to try.
    Anyway: if it's an OpenSource project, where are the schematics? Where's the source code? I couldn't find them on the official website.

    Thanks!

    The electronics design is now complete (see my next post) smilewinkgrin.gif
    The OpenStomp(TM) Workbench application source is not being released at this time.
    Yes, the project is open source (schematics, O/S code, and module code) but source code and hardware documentation is being provided to pedal owners via the distribution CD. Different pieces of the project are licensed differently and I'll post a summary of all the licensing arrangements to the web site once I've gotten the full production run cranking. In short, the O/S and module code is released under GPL3, and everything else is under copyright with regard to redistribution.

    The reason this project is open source is to put in the hands of pedal owners everything they need to fully understand the pedal, modify/enhance/expand/rewrite any piece of pedal code, and to share those modifications. The licensing arrangement is designed to accomplish that.

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    The World's First Open Source Guitar Pedal:··http://www.OpenStomp.com
  • epmoyerepmoyer Posts: 314
    edited 2008-08-08 03:10
    SHIPPING!

    I have sent notification to the earliest mailing list subscribers making the first lot of production units available for sale, so if you think that might include you go check your mailbox smile.gif
    Orders completed by 2PM Pacific will ship out tomorrow (Friday).

    Wooooohoooo!

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    The World's First Open Source Guitar Pedal:··http://www.OpenStomp.com
  • KeeblerKeebler Posts: 58
    edited 2008-08-10 00:49
    epmoyer said...
    SHIPPING!

    I have sent notification to the earliest mailing list subscribers making the first lot of production units available for sale, so if you think that might include you go check your mailbox smile.gif
    Orders completed by 2PM Pacific will ship out tomorrow (Friday).

    Wooooohoooo!

    Wow, congrats.· That's quite a milestone!
  • steve_bsteve_b Posts: 1,563
    edited 2008-08-13 17:33
    I see mine is on the way to Windsor, ON....just has to get through customs and I hope to see it by Friday!! woo hoo!!
    Now I just have to get the wife a day spa treatment so I can play all day! [noparse]:D[/noparse]

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    <FONT>Steve



    What's the best thing to do in a lightning storm? "take a one iron out the bag and hold it straight up above your head, even God cant hit a one iron!"
    Lee Travino after the second time being hit by lightning!
  • BradCBradC Posts: 2,601
    edited 2008-08-14 18:15
    If you can make it sound like an AC30 at full noise I'm _so_ there [noparse]:)[/noparse]

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    Pull my finger!
  • epmoyerepmoyer Posts: 314
    edited 2008-08-14 19:12
    Great sounding distortions include a lot of subtle analog behaviors. I think that distortions on the Coyote-1 are going to play around in the "look I created something different and cool" space for a while before they get into "look I made it sound just like a <guitar pedal X>" territory.

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    The World's First Open Source Guitar Pedal:··http://www.OpenStomp.com
  • kelvin jameskelvin james Posts: 531
    edited 2008-08-16 17:28
    Awsome, i just got mine, and all i can say is Eric has some serious talent happening here. A very professionally designed product, with like software and documentation in one package. At this point i am going to read up on the operation, and understand how to use it before i fire it up. Looks like a winner to me.
  • unigamerunigamer Posts: 1
    edited 2008-08-17 08:40
    I was wondering if there are any sound clips available? Also, I live in the UK and am trying to persuade myself to buy one so when they are available in the EU I think I'll want one!
  • steve_bsteve_b Posts: 1,563
    edited 2008-08-17 12:20
    I got mine on Friday and have been playing with it all weekend.
    To be honest, there are some usable effects right out of the box....I had been avoiding learning the Propellor, as I didn't have any one project that was interesting enough to me to bust my arse and learn it. Well, I'm a guitar player....I love this thing and know a few other people that would love the ideas of being able to program a "sets" worth of effects in to one guitar pedal.

    I tell ya, there was nothing more of a pain then rigging up a pedal board (a platform with multiple guitar pedals) as you had to power each one with either a battery or wall-wart! Sure enough the batteries would be lacking more often than not....luckily, the Coyote-1 doesn't use a battery and only requires one wall-wart! So benefits for sure!

    Cheers

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    <FONT>Steve



    What's the best thing to do in a lightning storm? "take a one iron out the bag and hold it straight up above your head, even God cant hit a one iron!"
    Lee Travino after the second time being hit by lightning!
  • Bob Lawrence (VE1RLL)Bob Lawrence (VE1RLL) Posts: 1,718
    edited 2008-08-21 10:19
    CIRCUIT CELLAR- Issue 218 September
    page 78 said...
    Photo 2—One step closer in the quest for tone, courtesy of the Coyote-1 stompbox
    and plenty of Parallax Propeller multicore MIPS. The Coyote-1 serves as an openended
    platform for a virtually unlimited repertoire of programmable effects
    (www.openstomp.com).

    cool.gif

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    Aka: CosmicBob

  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,090
    edited 2008-08-21 16:31
    @Eric:

    Congrats on being posted on the Parallax homepage!
    How about some more sound samples for us non-guitar guys? Propeller Album?

    OBC

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    New to the Propeller?

    Getting started with a Propeller Protoboard?
    Check out: Introduction to the Proboard & Propeller Cookbook 1.4
    Updates to the Cookbook are now posted to: Propeller.warrantyvoid.us
    Got an SD card connected? - PropDOS
  • epmoyerepmoyer Posts: 314
    edited 2008-08-23 17:45
    Bob,

    Thanks for the sighting! Circuit Cellar had contacted me a few months back asking for a high-res photo, but I wasn't sure when/if the picture would run. I'll have to go grab a copy [noparse];)[/noparse]

    OBC,

    I am going to be posting audio clips in the OpenStomp forums accompanying the effect posts. The first is up now in the Chorus thread here: www.openstomp.com/phpbb/viewtopic.php?f=6&t=6

    Unigamer,

    There is the audio clip mentioned above, and there are a few others earlier in this thread and on the propeller audio page here: www.parallax.com/tabid/645/Default.aspx

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    The World's First Open Source Guitar Pedal:··http://www.OpenStomp.com
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