User briel just sent me a message on the use of Ableton as a control voltage source for the Slim Phatty. Here is the original video:

briel asked:

… I can’t seem to figure out where the automation that you’re using in the video is. I’m assuming it’s some sort of audio effect. Do you think you could go step by step of what you did?

This is actually a lot simpler than it comes off in the video.

First off I am not using any audio effect (in the strict traditional sense). Only Volume automation. Back to that in a minute…

Volume “changes” is what the Slim Phatty translates into CV instructions. Think of it this way, the Slim Phatty is listening to the volume of your line level signal. Normally some action applied to the volume changes the level of the signal from nothing to max. In this case Ableton (or any DAW / similar program) will change the volume for you via automation (an instruction set) . So the Slim Phatty is ‘listening’ to the loudness of the modulated and now incoming (to the Slim Phatty) CV signal aka volume.

I know it sounds weird, but using a broad stroke explanation -- CV and volume are the same.  Speakers move via a modulation of voltage (passed into an electromagnetic system). Loud speakers need an amplifier. The amp takes the weak and wimpy Line Level Voltage and adds more juice to the signal (amplifies). This line level voltage is how volume is expressed in an (non-amplified) analog system (such as loud speakers). This is the same voltage used for the Slim Phatty CV inputs.

This is generally an industry standard and  is also why headphones and audio players all operate the same and can be swapped as needed. So your Denon Mixer will provide the same output signal (voltage and modulation) as my Echo Audio interface for Ableton -- they are all Line Level!

I am moving fast and sloppy on Line Level signal. Please go over to this Wikipedia post on Line Level to learn more and see how far I wandered.

The expected incoming CV signal should be between 0 (zero) and 5 volt (DC for the record). At 0 (zero) there is no volume on the outbound audio, at 5 volts you have full volume on the outbound audio. Outbound audio is the signal coming out of your audio interface connected to Ableton.

Ableton Master Volume

Taking the above paragraph a little further, if you were to change the master volume fader in Ableton (image to the right)  you would in turn change the audible volume and actually change voltage applied to the outbound signal. So 50% volume is 2.5 volts, 100% volume is 5 volts (not that simple in reality, but close enough for the point to be made).

So the trick is volume automation -- this can come from any number of sources. The master fader, the channel fader, arrangement automation, a switch or potentiometer in the analog audio signal, or clip envelopes.

I use clip envelopes. Here’s the fast walk through for a wave file. These steps are almost identical for MIDI, synth, VSTi’s:

• Click on a “cell” aka audio clip in session view

  • 

    One Audio Clip Selected

• View the clip wave form (shift+tab is the shortcut to toggle the 2 views)

  • 

    Clip Details

• Click on the “E” to access the envelope properties of the clip.

  • 

    Envelope Properties

• Select “Clip” then “Volume”from the drop downs

  • 

    Clip->Volume

• Modulate the envelope as you wish (pen tool or normal tool, each has pros and cons)

  • 

    Envelope Modulation

• Route the track now modulated to the correct output to use as Control Voltage

  • 

    Route to CV input

That is it.

The envelope modulation will change the volume aka voltage in the outbound audio signal following the clip envelope instructions. Clip envelopes are used because they are easy to trigger from Ableton and allow you to manipulate much information in a simple encapsulated unit.

Some important tips!

Don’t get fancy. Get this dialed in using a solid noisy over driven wave form. Then apply the envelope. This will allow you to hear and feel the cause and effect cycle of this exercise. If you use wimpy samples (quiet) or want to use natural dynamics wait until you get the VERY LOUD ENVELOPE MODULATION UNDER CONTROL!

Don’t waste time on effects. They don’t have the impact here like you may be used to. They will only effect the volume in the scope of the Slim Fatty. I am not saying NO to effects, but there is little need to stress your CPU for CV (generally)

Make your early attempts SIMPLE! Seriously -- there is a lot of silly things you can do wrong that will make this fail. Once you “get it” you will never forget!

Work with Pitch or Filter CV inputs first. They are the most easy to hear in the system. Get the basics under control first. Understand your levels, know your gear.

YES! You will need one channel per CV output! In my example(video above) channel 1 and 2 are the Left/Right stereo mix. Output channel 3 is the CV signal (a wave file with clip envelopes applied)

Hope that helps!

Link to example file/project (Ableton 8.2, good back to 8.1.3)

--Marc