Latency of the system

A digital system always has some latency. On a forum, someone questioned the use of digital mixing desks because of the latency that is added by the system. Although my experience tells me that the latency is really small, it is always a good idea to measure it.

For this test, I downloaded the 'test tone generator' software an ran this from the tablet. The headphone-output of the tablet is split to two XLRs: one going in the IDR32, the other going in a two channel USB pre-amp. Then, a cable is connected between output 1 of the IDR32 and the second input of the USB pre-amp. Using Audacity, it is possible to capture the exact delay added by the IDR32.


The latency turns out to be 1.2 ms (or 53 samples at 44100 samples a second). This is equivalent to time it takes sound to travel 41 cm through the air. I think this latency is very acceptable for live sound, but things might be different when using in ear monitoring.


(BTW, the gain of the pre-amp was not matched, this is only a test on timing).

PL10 working

I tested the PL10 device, and it works brilliantly. Using the 8 rotary knobs, you can control the levels of your channels, the aux sends for each channel etc. The 16 push knobs at the top allow you to select different scenes. For now, just a picture showing the levels for the first 8 channels on the tablet and on the PL10.

One problem I found was that when the tablet is unplugged, the PL10 stops responding for almost a minute. This is a problem since I planned to use the PL10 as backup in case the tablet has some problem. I've been told that A&H is aware of this problem and is working really hard on fixing it.

Soon, I'll do some digging around on the network protocols to see what is actually happening on the cables.

Poor man's multitrack

A while ago, I wanted the ability to practice mixing without a band present. Normally you would buy a nice multi-output for your computer (or go digitally, for example with MADI) and connect that to your mixing desk. There are many expensive solutions for this, and I settled for a very cheap one.

Buying two cheap USB 5.1 channel sound devices, I now have 12 outputs (14 including the outputs of my macbook pro). These outputs are minijack, so using minijack to 2x XLR I can connect to the mixing desk.

Very cheap USB 5.1 Audio Devices

Minijack to 2x XLR

Combining the two usb devices in one aggregated device

In Mac OS X, there is a nice feature called aggregate devices (in Audio MIDI setup). An aggregate devices allows you to tie multiple sound devices together. Using this, I create a virtual sound device with 4 inputs and 12 outputs.




Next I installed Ardour and Jackpilot. This open source 'digital audio workstation' allows me to load my tracks and play them to the different outputs I have. With this, I have my poor man's multitrack output for less than 100 euro's. Such a system is unsuitable for real use, but allows me to play around with the IDR32 without a band present.

Jack Pilot

Ardour

The complete setup

It works!

IDR32 and PL10 arrived

Today the IDR32 and PL10 arrived!

The tablet and IDR32 work!

First test is connecting the tablet to the IDR32 with a network cable. The process is fairly simple: connect the tablet to the IDR32 with the network cable, set the IP address of the tablet to 192.168.1.10 (netmask 255.255.255.0) and run the ilive editor.

Some problems did occur. First, I had to update the firmware of the IDR32 to match the editor (V1.70). Second, when I connected the system said something about a connection error. There were no problems at the next try, but this is something to keep an eye on in the future. Finally, it seems that the pad is turned on default for the input channels. When connecting my SM58, I had to turn up the gain significantly to get any signal and the resulting background-noise was terrible. Of course, when I figured out the pad was turned on the problem was solved.

Now we have a nice system and can start playing with wireless, the PL10, multitrack, etc!

The firmware needs updating

Updating the firmware is simple

First connection attempt failed

Second attempt succeeded

Don't forget to turn of the PAD!

IDR32 and PL10 are on its way

We have ordered the IDR32 and PL10 @ TMaudio, and they will arrive tomorrow or the day after! We are really looking forward to testing this system, the tablet is already in place and we also have some poor-mans multi-track playback system.

Dell Latitude XT tablet

This weekend, we bought a second hand Dell Latitude XT tablet! We will be using this as primary device for running the ilive editor. The tablet has a intel core2duo 1.33ghz processor and 3 gigs of ram. The screen is 12.1" with a resolution of 1280x800. The idea is to run linux with the editor on this.

So the first thing I did was install Ubuntu 10.4 (Lucid) on this, by using UNetbootin. I created a LVM partition of 40 gig with 32 gig for root and 6 gig swap (the complete hard disk is 120 gig). A minimal installation was chosen, so I could add only the packages we really need, keeping it nice and clean.

To install the X server, I install the following packages: xserver-xorg-input-wacom xinit lxde chromium-browser cellwriter. However, there are some additional things we need, for example some support for wireless lan. For this I installed the network-manager, bcmwl-modaliases and bcmwl-kernel-source packages. Then, there is a bug in the wpa_supplicant (version 0.6.9), so I installed the debian packages for 0.6.10 using gdebi and the AMD64 .deb files from http://packages.debian.org/sid/wpasupplicant http://packages.debian.org/sid/libpcsclite1 and http://packages.debian.org/sid/libssl0.9.8.
wireless-tools.

To install the ilive editor, I first installed libc-i386 and default-jre. Next, the editor is downloaded from the ilive-digital site and installed. Now we have a working ilive editor on a minimal linux configuration. But, it turns out that the linux version only supports online with surfaces!

So in the end, I installed windows 7 on the remaining disk space and it works like a charm. Hopefully, linux support for only mix racks will be added, so I can switch back to the linux version.

ilive IDR32, tablet, ipad, T112 demo

On Wednesday, Gijs and me traveled to Utrecht to meet Martijn from TMAudio. He responded to my e-mails inquiring about the possibilities of using a mixrack and tablet by inviting us over to play with the system. In three hours time, we learned a lot about the system and the possibilities.

Martijn is showing Gijs the ipad app

I must say, the ilive system sounds incredible and has real good potential. Martijn started of by showing us the T112 surface in combination with the IDR32 mixrack. All processing is handled by the mixrack and the surface is just one very big remote with many nice and shiny buttons and faders. Another way to control the mixrack is using a laptop or tablet using the ilive editor software. Also, there is an app for the iphone (iTweak) that has the ability to change basic channel levels and EQ. Finally, there will be a nice ipad application that has the ability to perform many of the editor functions. You want to use the ipad over the tablet because it has multi-input, which allows you to change the levels of multiple channels simultaneously. Martijn is working closely with Allen & Heath of the development of this app and therefor has a beta version of this app, allowing us to actually try it out. When the app is released (in 2 month time), it will be a really nice way of controlling the mixrack!

T112

The control of the mixrack is performed using a computer network connection. This means that you can also use a wireless router that connects to the mixrack and use your ipad and tablet from anywhere in the room or stage. The ilive surfaces are also connected using a cat5 network cable to the mixrack, but use a different protocol (ACE) which combines the control with some channels of audio. These audio channels allow the surface to receive the PFL and allows some local input/output (at the back of the surface). These audio channels are not possible when using the ipad or tablet.

In three hours time, Martijn showed us a lot about the system and we were able to make a basic mix on the T112, the tablet and the ipad using the multitrack we brought with us. It is a bit slower to build a mix from scratch then using a normal surface with faders and such. However, when the basic mix is made, the control is more then adequate to mix the rest of the show. In our case, we will need to perform a sound-check once (and spend much time on that to make it right), save it, and recall it whenever we need it.

We ordered the IDR32 with the PL10, which is a small controller you can connect directly to the mixrack. This controller gives us direct access to all channel levels and aux sends, in case something goes wrong.

I'll write much more information when we receive the IDR32!