seeking HW advice for new SW project

[raybert]

Hi,

I'm interested in using my Linux laptop with my guitar amp, preferably in the FX loop but perhaps out front. My current amp is a Marshall JVM 410H but I imagine this question could pertain to any amp. I'm looking for some advice on HW interfaces.

I have a Focusrite Scarlett 2i2 USB interface that works great with my (Fedora) laptop and it can take input from my amp loop and guitar as well as speaker sims, emulated direct outputs (as on my 410h) just fine. The problem comes when trying to put the output back into the amp (again, front input or FX loop return). The Scarlett only has a headphone out and the amps I've tried it on don't seem to like it. I've shopped around for other interfaces but have not found any that appear to solve this problem.

I know generally about levels and impedance matching but I don't understand these well enough to diagnose the issue. My suspicion is impedance, however, seeing as the headphone out has a level control but it doesn't really help. I have not tried using a pedal as a buffer (I'm away from home at the moment but I plan to try that when I get back).

The reason I'm doing this, BTW, is that I'm considering developing an app for guitar effects processing. I've bounced back and forth between rack processors and pedal boards over the years and I'm somewhat tired of both. I've devised a plan for an app that would work a little differently from both while (hopefully) providing the best of both without the downsides. For me (as a professional developer), the SW side is relatively easy but I'm not sure how to get over the HW hurdle. So any help would be greatly appreciated. (Incidentally, if anyone wants to hear more about my design ideas I'd be happy to elaborate.)

Anyway, I'm wondering if anyone has any advice or knows of a device that will essentially allow me to put my laptop in my amp's loop.

Thanks in advance...

~ray

[apathity]

I don't have any hardware advice but keep us updated about that application for sure

[peter]

I do not exactly understand the problem, because the scarlett has a line output besides the headphone out.
But among the solutions are:
use a DI interface to split the signal behind the scarlett.
use a line splitter to split the signal behind the scarlett.
use a foot-switch (like the switchblade+ ) to split the signal
use a second audiocard as output. (needs some software adjustments, can be flaky)

I myself use a 4 channel headphone mixer to split the output of my interface among 2 sets of monitors and a headphone. This works great if the amp can accept that output.

success.

[gimmeapill]

Agree, you should use 1 of the Line outs (Mono) on the back of the unit, not the headphones out.

[ssj71]

Hi Ray!

I know generally about levels and impedance matching but I don't understand these well enough to diagnose the issue. My suspicion is impedance, however, seeing as the headphone out has a level control but it doesn't really help. I have not tried using a pedal as a buffer (I'm away from home at the moment but I plan to try that when I get back).

level control won't change the impedance, but you are on the right track since guitars are high impedance and headphones are low impedance, so headphone out to guitar in isn't matched. A DI box used backwards I think will work (but look it up first, I've never tried and people usually are going the other way).

The reason I'm doing this, BTW, is that I'm considering developing an app for guitar effects processing. I've bounced back and forth between rack processors and pedal boards over the years and I'm somewhat tired of both. I've devised a plan for an app that would work a little differently from both while (hopefully) providing the best of both without the downsides. For me (as a professional developer), the SW side is relatively easy but I'm not sure how to get over the HW hurdle. So any help would be greatly appreciated. (Incidentally, if anyone wants to hear more about my design ideas I'd be happy to elaborate.)

I'm not going to tell you what to do, but I can say, we are always in need of developers in the community, but we already have 2 pretty well established guitar programs in linux that could both use more programmers. Do you think your ideas could be incorporated into rakarrack or guitarix? It would be great to have as much collaboration as possible rather than efforts be put into another separate program. Regardless of what you decide in that respect though I'd really like to hear what your ideas are!

[glowrak guy]

Hi,
I'm interested in using my Linux laptop with my guitar amp,

Two related solutions.

1. If you don't have a windows/mac setup, One of the several
Fender Mustang V1 usb amps simplifies recording by using
direct usb support, and shows up in qjackctl, without futzing.

An app called Plug allows full editing and saving of sound presets to the
amps main selector dial, 24 on Mustang 1 and II, or 100 on the III, IV, V, and Floor.

It's sound quality has been proven in double-blind tests
with tube equivalents, and sending a clean signal to amp-sims
like Guitarix, or Amplitube, and effects like Rakarrack, and Calf,
is both rewarding and trivial.

As for cost a Mustang 1 Version 1 will cost $50-$70 used, and the other models
a bit more accordingly. The V is a head-only beast, easily found used for $200

2. If you have mac/pc access, new Version 2 Mustangs
start at $120, and their Fuse amp-editing gui can be used to populate the amp with presets.
And you get a warranty, a downloadable light version of Amplitube Fender, (it's gear can be
integrated within the free Amplitube Custom Shop that works via wine) and an Ableton-light
frisbee/download.
The V2 have a few more amps/effects than V1 models, but Plug was not updated to work
correctly with V2 Mustangs.

I would describe setup/use in linux as 'no-brainer', perfect for my attenshun span

Try setting Periods/Buffer to 3 with usb Mustangs.

[raybert]

I do not exactly understand the problem, because the scarlett has a line output besides the headphone out.

Hi. Thanks for the response and sorry for not following-up sooner. I was away from home when I first posted and I've been playing catch-up since getting home.

You reminded me that I forgot to mention the line out. I did try it but was unable to get it to work. Trying to remember what I did, I think I was having some trouble getting any sound at all and then figured out that the SW was not configured correctly *after* switching to the headphone output. I think I may have forgotten to go back and try the line out again (doh!). I haven't really had time recently to revisit this but I've clearly got a few things to try.

Thanks again for you help!

[raybert]

I know generally about levels and impedance matching but I don't understand these well enough to diagnose the issue...

level control won't change the impedance...

FWIW, I wasn't expecting to change the impedance with the level control; I was just trying to adjust the headphone level to something that would work, but couldn't. Hence, I concluded there must *also* be an impedance issue. I don't think I described that clearly enough. Thanks for confirming the impedance issue.

The reason I'm doing this, BTW, is that I'm considering developing an app for guitar effects processing...

I'm not going to tell you what to do, but I can say, we are always in need of developers in the community, but we already have 2 pretty well established guitar programs in linux that could both use more programmers. Do you think your ideas could be incorporated into rakarrack or guitarix? It would be gret to have as much collaboration as possible rather than efforts be put into another separate program.

At the moment, I don't think I can achieve what I'd like to do in those apps. However, I plan to spend some time with them once I get the HW sorted out, so we'll see.

Regardless of what you decide in that respect though I'd really like to hear what your ideas are!

What I want to do with this app is basically to create a virtual pedal board. I've used rack effects for years and got really tired of programming patches for everything. I now use a pedal board and I enjoy the spontaneity but I hate dealing with velcro, audio cables, power cables, knobs getting spun during transport, it weighs a ton and did I mention velcro? It's also a pain when you need to remember specific pedal settings for certain songs. It occurred to me one day that I could leverage all the plugins that are available and create a "soft" pedal board that could save specific effects settings and allow me to activate effects on a whim (using a midi pedal).

I've found a couple of apps for os/x & ios that do something similar (but I haven't looked too closely at them since I'm not an Apple guy). I've also found (and bought!) one guitar device that is very similar to what I want. It's the M13 Stompbox Modeler from Line 6. It's still more limited than what I want though.

My basic design consists of an effects library and banks of "effects chains". You start out by creating individual effects where you choose a plugin, set the parameters for it, give it a name and save it. You can create as many effects as you want like this, including multiple of the same type. Next, you assign one or more effects from your library to an "effects chain" in some bank. You can then toggle effects chains on/off with CC messages. Doing so will activate all the individual effects in that chain. You activate as many chains as you like simultaneouly (depending on the horsepower in your computer) in any combination (like a pedal board!). Chains have only references to the assigned effects in the library so you can assign each effect to as many chains as you like and if you edit an effect in the library it will also update automatically in every chain that it is assigned to. (If you want a variation on the effect you just create a new one; something like a Save As operation.) You'll be able to switch banks with PC messages and there will likely be more midi options. In general though I plan to keep it very simple at first so there probably won't be too many 'extra' features to start with. I have the perfect midi pedal for this design, a Rocktron All Access, and my design was developed with this in mind. I can have as many as 15 dedicated CC buttons and still change banks (with PCs).

From what I've seen of rakarrack and guitarx they seem to emulate traditional rack processors and therefore have a limited set of effects per 'patch'. So I don't think they will work very well for what I want to do. I don't think rakarrack even supports plugins (IIRC).

So anyway, that's it. Would love to hear what you think and (especially!) if you know of something like this that already exists.

Thanks again...

[raybert]

Two related solutions.

1. If you don't have a windows/mac setup, One of the several
Fender Mustang V1 usb amps simplifies recording by using
direct usb support, and shows up in qjackctl, without futzing.
...

Thanks for the suggestion but I don't want to do this for recording. I want to use it in a live setting for effects only (I use my amp for overdrive, etc.). I have a Yamaha THR-10 if I want to do something like you describe and it works really well.

[peter]

Yes, this is done before.
Search the forum for jackrack to get idea's how to configure such a setup.
Jackrack can be controlled by midi. https://www.youtube.com/watch?v=MSD1csGHW40
If you want to control a lot of settings at once (your preset) you need something like mididings or even seq24.
This is mentioned in http://linuxmusicians.com/viewtopic.php?f=18&t=11476

success, and let us know what you did

[ssj71]

You are right that guitarix and rakarrack are both straight rack effects processors, but there are several programs that are close but I'm not sure if they will do exactly what you want:

Carla is a great patch-anything anywhere plugin host, but it lacks the preset functionality you are looking for (though I understand its on the TODO). You can drag and drop mutli-plugin presets (called projects) into carla to load them, but not through midi (you might check out what I did for rkr lv2's presets (github.com/ssj71/rkrlv2) which ported rakarracks preset banks to carla project files.
Ingen, has exactly the sort of individual preset/ chain preset sort of patching you mention. In fact that is the backend being used by the MOD system (see moddevices.com) I'm not sure how ingen is for changing presets by midi though. Maybe its already there. Ingen seems to have some bugs, but if you find them and report it helps everybody or patch requests are always welcome.
MOD's software is open source too, I haven't used it yet.
And jackrack as mentioned, though IIRC that only hosts ladspa.
Ardour is another powerful plugin host, but obviously was created for quite a different use case. I'm pretty confident that you'd be able to do what you want midi wise though.

Of these I think Ingen/MOD is the closest to what you want, and Carla will eventually be. I think both programs are great and could use additional developers.

[tramp]

guitarix clearly is a rack processor, but, without limits, on cor, and, full, really full, midi controllable.

[raybert]

Yes, this is done before.
Search the forum for jackrack to get idea's how to configure such a setup. ...

Hi Peter,

Thanks for the info. I do know about jack-rack, in fact, it's what I've been using to test my HW set-up. I wasn't aware of it's midi capabilities. Even with that though I don't think it'll suffice for what I ultimately want to achieve. For one thing, jack-rack's UI is not something I'd want to try to negotiate on a dark stage! The UI for this project is actually just as important to me as the sound quality! In fact, I plan to build the UI first (hopefully soon!). I'll post more info once I get something worth showing (unfortunately, been too busy lately to do much with this -- although I did sketch-out a save file format -- I also got side-tracked grooming a brand new Arch install on my laptop (Arch first-timer)).

[raybert]

You are right that guitarix and rakarrack are both straight rack effects processors, but there are several programs that are close but I'm not sure if they will do exactly what you want:
...
Of these I think Ingen/MOD is the closest to what you want, and Carla will eventually be. I think both programs are great and could use additional developers.

Thanks for the suggestions. I have heard of the MOD device (in fact, I considered buying one) but I haven't checked out their SW. I have not heard of Ingen; will check it out. I do know something about Carla but I was under the impression that it was more a code library for managing plugins as opposed to a stand-alone app. In fact, Carla's currently at the top of my list to use as the backend to handle the plugins in my app (along with jack for the audio/midi). I will definitely be checking it out further.

[raybert]

Thanks again for all the input everyone.

I've decided to buy a new audio interface for this project, one that also supports midi (my Scarlett doesn't) so I can minimize the number of devices I need to have on stage. I'm wondering if anyone has any suggestions.

I made a (sorta) quick scan of devices on Amazon the other day; these are the ones that made my short list:

Code: Select all

Tascam US-144MKII USB Audio Interface
Behringer UMC204 Audio Interface
Presonus AudioBox 22VSL 24-Bit/96 kHz 2x2 USB 2.0 Audio Interface
Akai Professional EIE Pro 24-bit Electromusic Interface Expander
Alesis IO2 Express 24-Bit USB Recording Interface
TASCAM US-2x2 USB Audio Interface
TASCAM US122 Audio/MIDI Interface
M-Audio M-Track Plus Two-Channel Portable USB Audio and MIDI Interface with Digital I/O
Steinberg UR22 2-Channel USB 2.0 Audio/MIDI Interface

I haven't researched any of these in-depth yet.

My minimum requirements are: at least one mono instrument input; midi in/out; at least one mono output (something that I can put back into my fx loop somehow); under $200; and, of course, Linux support.

Thanks again!