How to resample a single cycle waveform
In this tutorial, we're going to create a complex, phase modulated (similar to FM) waveform, take a sample of this by resampling the ER-301, and set it up to be played back with pitch control. The process for sampling a single cycle waveform from an external piece of gear or module is very similar, so we'll point out the differences as we go.
You will need to make two cable connections to get started. We'll use channel 1 for this:
- Patch OUT1 to your mixer or sound card.
- Patch your incoming V/Oct to A1
For more information about which inputs are appropriate for various signal types, see Front Panel Inputs.
Creating the complex waveform sample
In this first section, we will create the complex, phase modulated waveform that we want to sample. We will modulate the phase of one sine wave oscillator with another that is tuned to an even multiple of the carrier sine wave's frequency. If you wanted to sample an external module, you could skip these steps and proceed to the next section. But it may be easier to follow this re-sample tutorial all the way through your first time.
(1) Begin on channel 1 with an empty chain. Insert a Sin Osc unit.
(4) Once inside the phase subchain, move your selection cursor to the insertion point, and insert another Sin Osc unit. Let's set it's frequency (f0) to an exact multiple of the carrier's frequency to get a nice, harmonic result. 130.8 * 4 = 523.2. You may need to press the FINE button to switch to fine resolution to adjust this control more accurately. You can hold down the SHIFT button in fine mode while turning the encoder to get even smaller increments. In this case, I have settled for 523.3. You will not yet hear any difference in the sound yet, but you have set the "phase modulation ratio", or just "ratio" for short.
(5) Press the UP key twice until your screen looks like this. We will now adjust the amount of gain for this subchain. Press the S2 button to select the subchain gain if it is not already selected. This will be the amount by which the subchain influences the phase. In phase modulation, this is called the "modulation index" or "index of modulation", or just "index" for short. You should hear the timbre of the sound change as you change the gain amount. A gain of 0.36 sounds nice to my ears, so let's choose that.
Sampling the Waveform
In the preceeding section, we created a complex, phase modulated signal to sample. If you wanted to sample a single cycle waveform generated by some other external module, you could set the input for this chain to be one of the audio inputs (INx), and continue with the steps below to sample the waveform.
(2) Insert a Dub Looper unit here. The Dub Looper is capable of recording any signal (audio or CV) fed into it's input. Since our complex waveform generator is being fed in, this is what we'll record. In order for the Dub Looper to work, we must first create and assign a buffer to record to. Focus press the Dub Looper's unit header.
(4) Since we only need to sample a single cycle of a repeating waveform, the buffer can be very short. 100ms should be plenty sufficient here. Notice in the lower display, the amount of RAM required for this buffer automatically calculates as you change the target buffer size. Select 100ms, and press Enter. This will create the new buffer, and assign it to the Dub Looper.
(5) The Dub Looper's play head is initially in a stopped state. We need to start it by Engaging it. Press M3 to select the Engage control. Then press S3 to fire a trigger to it. The engage control defaults to a toggle style control (you can change this in the unit menu), so pressing fire will toggle Engage on, and the play head will cycling through the buffer in a 100ms loop.
(6) The play head is moving, but the Dub Looper is not currently recording anything. Press the M4 button to select the punch control. Press the S3 button to start recording. Make sure to wait at least 1/10th of a second (100ms), and then press S3 again. This will stop the recording. You should still be hearing the timbre of your complex waveform, though it may sound a little glitchy at this point. We will fix this in the next section as we prepare the sample for playback. If you like, you can mute/unmute channel 1 by pressing the SHIFT + Channel 1 buttons together.
Prepare the Sample for Playback
Congratulations! You've created a complex waveform, sampled it, and saved it to your SD card! Now let's do something useful with this sample. Let's set it up so that it plays back perfectly with no glitching, and set it up so that it's pitch can be controlled by an external V/Oct input.
(1) Press the M button underneath the Dub Looper's header to select it. Now press the S3 button - "Replace". The unit selection menu will appear. Choose the Variable Speed Player.
(2) When you replace a unit with another, the ER-301 intelligently keeps what settings it can from the unit that you replaced. In this case, since we replaced a Dub Looper with a Variable Speed Player, and they both use a sample buffer, the Variable Speed Player will inherit the sample buffer from the Dub Looper. In other words, the sample we recorded above is already in place. Smart, huh? Note that Variable Speed Player does not have a unit input connected, and will block any sound or signal being fed into it. Next, focus press the Variable Speed Player's header to enter the unit menu.
(6) Make sure the COARSE LED is lit. If not, press the FINE/COARSE once button to change to COARSE. Now hold the FINE/COARSE button down while turning the encoder to the right. This will zoom in horizontally on the waveform, with your cursor being the center point. Zoom in until the view looks about like it does above. Now we will insert two slices - one at the beginning and end of a single iteration of this repeating waveform.
(7) To insert the slices, position your cursor at the points shown above. You are targeting the places where the waveform crosses the zero line. When your cursor is as close as you can get it, press M5 to go to the zero crossing. The ER-301 will assist you by moving the cursor a few samples in either direction, if needed, so that it's exactly on the zero crossing point. Next press the M3 (+ Slice) button to add a slice. Repeat this process to put another slice at the end of the cycle.
(8) Press the S3 button to switch from cursor mode to slice mode. In the lower display, you can confirm that you have made two slices, and their times. Turning the encoder now will jump to the different slices. This can be very handy for deleting slices (- Slice). But you may want to return to cursor mode to insert new ones. Once you're happy with your two slice points, press UP to return to the unit.
(11) Since we have a single cycle waveform, press M5 to change this to "repeat". This will cause the sample or slice to continuously play back, jumping back to the beginning of the slice or sample when it reaches the end. The Play Extent defaults to "slice". Since we only want to repeat the one slice we just created and not the entire sample, this is the correct setting.
(13) The unit is now looping the first slice, which actually is not the portion of the sample we carefully trimmed out using slices. Select the slice control and set it to 0.32. Since we are in index mode (per the Playback Options), which slice is selected for playback is controlled using this slice control. You may notice the sound hasn't changed yet. We need to retrigger the player to get it to move to slice indicated by the slice control.
(15) Now use the M button to select the Variable Speed Player's header, and press the S1 button to bypass the unit. Since we still have our original sound generator in this chain, bypassing the Variable Speed Player will allow us to hear the original signal. You may notice the sound is very similar, but it's not quite exactly the same. Hmm....
(17)Select the fade control of the Variable Speed Player. It defaults to 5ms crossfade at the beginning and end of the sample. This can be useful with other types of samples, but here, we have trimmed our sample to exactly one cycle, and we don't need any crossfade. Set it to zero by pressing SHIFT + Zero. Now try bypassing and un-bypassing the Variable Speed Player again a few times to A/B compare our sample with the original. We have an exact matching sound!
(18) If you like, focus press the Variable Speed Player's header, and go back into the slice dialogue. Here you can see the play head moving and resetting across the middle part of the sample - between our two slice points. This is just a confirmation step to help visualize the result of selecting the slice.
(20) Now let's assign a V/Oct from an external keyboard or sequencer to the V/Oct control of the Variable Speed Player. Press the M button underneath V/Oct to select it, and press S1 to enter it's subchain. At the beginning of the tutorial, we connected our external V/Oct signal to input A1, so assign A1 to the V/Oct, as covered in previous tutorials.
Your keyboard, sequencer, or other V/Oct source should now be controlling the pitch of this sampled, complex waveform. And it should sound perfect. Happy sampling!