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karimko 2010-11-29 10:05

[Request] Guitar Amplification
Alright, so here's the deal.

Imagine hooking up your electrical guitar to your n900 and playing with distortion, reverb, and all the amp effects you want right through the speakers or earphones. That would be cool, since the solution would be portable with no amps or hardware to carry.

In order to achieve this, we need to:
  • Understand microphone latency on the n900
  • Find a good open source signal processing engine
  • Find out if the n900 hardware (CPU etc...) can handle the signal processing demand
  • Have the right libraries to create an application like this

I'm not an expert but I think these are the basic building blocks on which we can build our argument from.

Some searching on signal processing for linux gave the following interesting links:
What do you think? Possible? Any experts who can chip in?

ju-maha 2010-11-29 10:34

Re: [Request] Guitar Amplification
Really nice idea!!!

I would like to use that with my electric violin. :)

I would like to help you, but no skills for that.

TiagoTiago 2010-11-29 10:56

Re: [Request] Guitar Amplification
There probably won't be much amplifying going on considering how low the N900 is (i mean at least not by the N900 itself, if you hook it to a speaker with builtin amplifier or a standalone amplifier box or somthing obviouslly you will get amplification)

ossipena 2010-11-29 11:09

Re: [Request] Guitar Amplification

Originally Posted by TiagoTiago (Post 885471)
There probably won't be much amplifying going on considering how low the N900 is (i mean at least not by the N900 itself, if you hook it to a speaker with builtin amplifier or a standalone amplifier box or somthing obviouslly you will get amplification)

there should be enough juice for earphones at least. but if the resolution of mic input just isn't enough, it probably will be really distorted by default....

TiagoTiago 2010-11-29 11:28

Re: [Request] Guitar Amplification
Also, what will be providing power for the guitar itself? I wouldn't expect the N900's headset plug to offer anywhere near as much juice as a regular electric guitar needs, you might need to make a custom amplifier that will give the guitar power, amplifythe signal received and convert it to the format the N900 expects (current, voltage, impedance etc)

karimko 2010-11-29 12:33

Re: [Request] Guitar Amplification
Well let's separate both microphone signal amplification and output amplification. I think the former one is the one we should focus on.

@TiagoTiago: The guitar doesn't need power. What happens is that the guitar's pickups carry the signal to the wire coming out of it, similar to a microphone that singers use. So the basic concept is amplifying the guitar signal (like you would a normal voice through the mic), and then apply some audio processing on it.

I use GuitarRig [URL][/URI] for that. And what i do is, I plug the end of my guitar to the mic input of my pc, then start up guitarrig which does what i stated above. If i want to amplify the output i simply plug my pc to a speaker box, otherwise headphones would do.

I think the first step to solve this microphone amp business is to connect the guitar input to the microphone section of the 3.5 inch jack. And see if the microphone catches some guitar tones (using recoreder app for example) Won't have time to do this anytime soon due to work, uni, and some traveling but if someone wants to chip in on this it would be awsome :cool:

nubsis 2010-11-29 12:47

Re: [Request] Guitar Amplification
This is an absolutely awesome idea! I'd love to see this happen!

karimko 2010-12-01 09:34

Re: [Request] Guitar Amplification
2 people showing interest
2 people showing doubts
That's good!
More than 360 views with only 6 posts!
That's bad! :)

Come on peeps can't do this on my own, anyone interested to help out? :)

mr id 2010-12-01 09:49

Re: [Request] Guitar Amplification
Okay some comments then. :)

I've been trying for many weeks to find a splitter for the headphone/mic input with no success - any pointers are welcome. My understanding is that the ones that are available for iPhones are a different pole order (happy to be corrected).

In general the userspace applications and audio processing I have played with (mostly gstreamer) are quite laggy - this doesn't mean it's a no-go just sub-optimal. There are other audio paths to try but gst is the path of least resistance for me.

Audio processing is pretty processor intense and in userspace I'm not sure if much (if anything at all) is offloaded onto the DSP.

We do not currently have any of LAPSDA plugins compiled or available for arm/maemo. The gst plugins available are fine (echo, volume, panorama, filters, limiter/expander etc) but aren't the sexy ones for guitar players (crunchy distortions, hi gain, big delays etc).

In short there looks to be a lot of work to do. I'd be really happy to be corrected on any of this.

Still, all said and done I'm by no means ruling it out completely. Just reiterating your 4 point challenge and suggesting that we don't have any quick wins on the list as far as I can see.


[Edit] Forgot to add that I'd had a quick attempt to see if I could get some usb input devices working with host mode. Mixed results and all short of a resounding success.
Zoom H4 enumerates but doesn't get hooked up by hid.
Alesis GuuitarLink (usd to jack adc built in) gets enumerated, recognized, hooked by hid but isn't exposed as a device through gstreamer. (incidently this is already quite laggy on my desktop machine where it does work).
In short the USB sode of things is great from a host mode perspective but taht's as far as it goes.

James_Littler 2010-12-01 09:59

Re: [Request] Guitar Amplification
Ok I'm interested in this after seeing it on an iPad commercial, it made me realize it's use.

I'm sat in the studio at work with a set of mics, a ton of xlr cables and some 3.5mm jack converters, so I can try this right now using a mic.

I'll try with recorder and post back with my results.

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