Figured out a source of clicks when recording buffer to buffer

Elektron Gear Octatrack
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EDIT: This ended up being a very long thread, so I thought I’d summarize the key findings we uncovered here in the first post.

My key goal was to use the Octatrack for “sound on sound” type looping in which I leave the recording buffer always overdubbing audio. That could be a track onto itself or a track onto another track, both potentially with external audio coming in. That took some dialing in.

  1. Some of the effects (filter, for example) will cause issues. Best to switch them off. In my experience, EQ and Lo-fi are ok.
  2. I think some care needs to be taken with the other settings on the Octatrack such as various volumes, time stretch, etc. See how I set it in post 34.
  3. Clicks are often introduced when the playback trig restarts the buffer. Only some combinations of tempo and record buffer length eliminate these. I posted a spreadsheet and the math behind it in post 83.

(Back to the original post)

This is probably common knowledge, but it took me a while to figure it out. I do a lot of live audio looping with long loops. For example, I’ll have a 32 step buffer on T1 that starts on 1 and a 32 step buffer on T2 that starts on 33. T2 records T1 as it plays back, T1 records T2 as it plays back. In principle, if you don’t change anything then it should be an infinite delay line.

But I was getting intermittent clicks when the handover happened. I did all the standard stuff of tweaking FIN, attack, decay, etc,

The culprit was the filter that is inserted by default. Once I removed that, clickless looping bliss.

Probably common knowledge, but figuring that out really unleashed some of the capability I was seeking from the Octatrack. You can loop long sustaining sounds with no concern.

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2

great catch and I discovered the same thing last night when recording my new jomox to tx-6 mixer.

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Isn’t the default filter and delay ?

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Exactly what I was about to say.

Anyway, glad the OP solved the puzzle.

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Doh. Yes. The default filter was the culprit. Fixed the original post.

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Here is an example of a long loop that would normally cause clicks when the two tracks transition from one to another. But I think I’ve sorted it out …

Edited to add that I also make sure all of the stuff in the SRC menu is switched off.

Further edit to state that I think the BPM on this one was 120.

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The amount of droning sounds I’ve listened to today is ridiculous. I did run into an issue where the sound gradually increased in volume over time. That was with the default loop recording behavior (+12 dB, volume on Amp page set to 0). I’ve had better luck setting the recording to record at 0 dB and then setting the Amp page volume to +63. That seems to perfectly replicate the input audio.

My typical use case is to then adjust the Volume control (it is serving as a “feedback” control on the loop).

I’ll report back as I learn more.

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Are you using OT mk1 or mk2?

I enjoyed your other OT tracks on Soundcloud. What OT machines are you using? Just mic’s running directly into OT?

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Mk 2. I’m just a few weeks into it, so I’m really geeking out with it.

I’m almost exclusively using flex machines on the OT.

Sources are either microphones on acoustic instruments, direct Moog, or electric guitar amp (DI and then through a speaker sim). Everything interfaces through Logic, then to the OT, and back to Logic. All the testing today was either the Moog or electric guitar.

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Dang, one of my biggest gripes with the OT was the random clicks that happened. Ultimately limited the utility of it for me.

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The clicks were my first big annoyance with the OT when learning to record to a Flex track. It is such a flexible way of recording audio, but seemed to have an Achilles heel at the loop point. For sounds that go across bar lines (sustained notes, reverb tails, or whatever), it was going to cause me a lot of annoyance.

If the Pickup machine weren’t so limited, I doubt I’d have dug into this as deeply as I did.

Bonus tip: modulating the Vol on the amp page (I think of it as the feedback control for the long delay line) is a fun way to make live loops dynamic. You can do a similar thing with modulating the Gain control on the Pickup machine … except the Pickup machine repeats the audio once before applying the modulation.

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I’ll add if you do overdub with Flex and Filter it becomes very muddy after several passes.
Some fx like comb filters (flanger and lofi maybe) add a DC offset than can be problematic…

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Thanks! So many subtleties in this instrument.

One strategy I’m using is to have two Flex tracks that are “pristine” that handle the always-recording audio buffer. I think I’ve worked out the issues so it has no clicks and the gain is at unity. I send this to Main and Cue as needed.

If I want to seriously mangle that sound I have additional Flex tracks that sample from Cue. From there I can do all the fun Octatrack stuff. It was getting that first pair of Flex tracks dialed in that was surprisingly challenging.

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Update: For the most part, this works exactly how I want. But occasionally I get a click when the buffers switch. Frustratingly, when the click sneaks in it won’t be every buffer switch. More like every third or fourth.

Any Octatrack experts have suggestions for other things I might try to completely eliminate this?

I have a loop running right now … not a click to be found. So I know it is possible, but sometimes the OT misbehaves.

Maybe a power issue? Something weird with the master clock?

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Nope.

Zero crossings.
Bet you any money.

Cant say I have any click issues myself, but then I hide everything with fx and LFOs anyway.

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16

Thanks for the filter tip.

I’m getting random clicks on Pickups but NOT at the loop point

Wasn’t always this way

I’ve eliminated other gear as source of clicks, but I found there has to be some signal. I haven’t noticed it on silent recordings

&not sure if I get it on internal sampling

Thinking it may be my CF card gone bad (it’s the Kingston one that came with it 10 years ago)

The problem seemed to go away after I formatted it, but has crept back in after a just few MBs on there

A CF card is a boring thing to spend £ on, but if others think it’s the likely cause, I wiil. Pickups are great

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It is certainly at an area that can have a discontinuity - the start of the loop. But something is causing the discontinuity since it doesn’t happen every single time. Even when it does happen, it is only every third or fourth loop point.

My intuition is that the timing has drifted enough that the OT slightly shifts the start of the samples.

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I had uploaded a clip that Soundcloud then flagged as a copyright violation. Ridiculous.

Edit - they restored the recording.

In the clip, you can hear the clicks sneak in at 0:22, 0:39, 0:56, 1:18, 1:35, 1:58. Not regular and not every time the loop is resampled.

And — critically — these clicks do not end up in the loop. They are just in the playback.

Further edited to add that the BPM on this one was 85, hence the clicks.

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19

Some more experiments tonight. I’ve learned the clicks are dependent on the tempo. I have no clicks at 120, 100, or 75 bpm. 85, 86, 87, and 95 do. 95 is particularly bad. Yet 96 is click free.

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I went a bit overboard and started documenting tempos that behave well with long loops (clickless in my testing) and those that don’t.

Good: 56, 60, 63, 64, 72, 75, 96, 100, 108, 112, 120, 125, 126, 135, 144

Bad: 55, 61, 62, 65, 66, 67, 85, 86, 87, 95, 97, 110, 122, 123, 124, 127, 128, 129, 130, 131, 132, 134

Not an exhaustive list, but I’m searching for the underlying pattern …

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