questions and thoughts

John posted Jun 14, 11:45:

Really interested in your project and will bill one in the next week but have some questions and some upgrade requests.

I have been playing Keyboards for 40 years and Midi guitar for the last 30 and would like to build your unit as a stomp box to use with my midi guitar rig.

First are the switches just standard momentary switches?

Second would like to have a 16X2 display saying patch name. This could be done two way either use the first 16 char of the subdirectory name or have a file in the patch folder with the name in it one line or two and and use a blinking cursor at the end of the line symbolising that it is loading and no cursor when it is loaded.

Third what midi codes does your software understand besides midi note on off events ? Program change This message sent when the patch number changes. Pitch Bend Change This message is sent to indicate a change in the pitch bender (wheel or lever, typically). The pitch bender is measured by a fourteen bit value. On a Midi guitar this happens when you bend the string. Main Volume as the controller on the guitar has a Volume knob to change the volume in real time value 1-127.

Fourth multiple samples being played at the same time or Combi Mode. I gave this some thought and read your other message on this topic. First can the Pi 2 handle playing multiple Samples on multiple Midi channels at the same time? If It can I would Have a toggle switch that shorts a pin that you can read that you are in combi mode and not shorted not in combi mode. if you are in combi mode look in the subdirectory after Combi/ in sample mode you look in Sample/ subdirectory. in the Combi subdirectory first you would have the combi number name directory just as you do for the samples subdirectory. then inside the combi directory (for example 01 Piano-Strings) your have all the samples with the same naming convention as you do now but with one change at the end of the name is a number corresponding with the midi channel that that sample is triggered by, so in this example all the piano sample would end with 01 and String samples end with 03 and all other Midi channels would be ignored. Use either subdirectory name for the name on the screen on line 2 output " loading "and then remove the the text when done. Don’t think the unit needs to build combi patches as that is better done on the studio computer system not live.

Fifth when you are loading a sample or a combi write the subdirectory out to a file so when you power up it will load the last sample or combi or when the combi toggle is activated or deactivated it load the last sample or cobi not to always start with the first one.

Six as I plan to put this in a metal slant case how much ventilation do I need and do I need a fan as it i will be running for up to 6 hours straight for a long night gig .

Seven the other mods I will make on the back of the case is 2 quarter inch jack outs and Two XLR Jacks outs.

And last I would not add any effects to the software as Reverb can kill cpu and just run the output jacks into what ever effects you need.

Don posted Jun 14, 16:20:

Your very last point about reverb. Without at least a little reverb isn't it going to sound rather dead and lifeless?

Is it really that hard on the CPU to do the reverb? I wonder if reverb can be done more effectively in hardware?

You seem to imply the existance of reverb boxes?

John posted Jun 14, 17:04:

Since the early days of the using Atari until now Macs a good reverb will Kill cpu processing the reason being is each reflection gets reprocess multiple times. So if your are having a small amount of reverb lets say 4 surfaces first you must use your algorithm for each of those surfaces then take figure out distance from source (large hall, small hall etc,) then add calculate the reverb again then merge the 2 together. Lexicon created a chip that does this. most pedales use a dedicated chip for just reverb.

I tend to either add a little on the samples themselves or run my samplers/synths thru a multi effect box or now a Pedal which is dedicated to creating reverbs or other effects so I can adjust it in real time.

But I dont know how powerful the RPI 2 processor is and If running multiple sounds then effects on top how the stability would be. Would rather have a stable Multiple sample play without effects. And just add an electro harmonix holy grail when I need reverb.

Don posted Jun 14, 19:00:

The RPi2 has a quad core processor running at 900 mhz with hardware floating point. It also has a dual core GPU that could probably be called into service for this kind of task. Quite a lot faster than any Atari.

I suspect that the samplerbox code, being in Python, only uses a single CPU. (I could be wrong about that as I have not read the code yet). So, lots of horses are available but riding those horses to give effects like reverb might be challenging...

Personally, I would like some built-in reverb because I plan to use samplerbox plus an amp and speakers as the only output for my project.

Sparky Lectric posted Aug 4, 19:19:

if you've got your heart set on reverb, here's a dedicated reverb module you can embed in any project - some amp manufacturers use this chipset for their products, I'm told.
Reverb Module - Accutronics Belton, Digi-Log, Mini, Horizontal

here's a link:

reverb can have a lot of parameters, that you can tweak to get the proper sound your after, so it really requires an interface of some kind, so you can adjust delay,room size, wet/dry etc. - Thats why an external reverb or fx processor is a better bet, you can find some low end pedals like the Danelectro Fab Echo (about 15$ plus shipping) to test out the sound.


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