Karplus strong

Is it possible with the er-301?
Someone can share how it sound?

i haven’t tried it, but the tools are there to create a burst of noise, delay it, filter it, and then feed it back into itself.

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I’m looking forward to trying this out too, when I get my 301 (the day is coming soon :slight_smile: ).

One really nice thing is with the sample players, your choice of exciter/impulse is pretty much limitless.

I do think this particular application would be enhanced a lot when/if more filter types (specifically BPF) are added. I think the original Karplus Strong was based on a LPF, but a lot of modern adaptations use a series of high Q BPFs to really tune the harmonic response, don’t they?

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Great idea - I must try this - cheers :robot:

Interesting point Joe, Elements is an exciter section followed by “a modal filter bank – an ensemble of 64 tuned band-pass filters simulating the response of various resonant structures (plates, strings, tubes…) with adjustable brightness and damping.”

I keep meaning to write my own custom set of exciter signals for Elements, the ER-301 may well provide a nice way to test these out a little bit before going the full monty! Apparently it took Olivier a very long time to tune those 64 filters to all the different settings! If ever there was an argument for digital synthesis this is it!

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I gave it a go…


Many thanks!

Nice job on this one Neil!

Nice one, but i’d really love to know how to properly map the pitch to a V/Oct keyboard.

Maths!!! :slight_smile:

not my strong point, this might help:



Of course one day I will provide a 1V/oct to 1V * oct converter but for now how about:

1V/oct -> Sine Osc (1V/oct) -> Period-o-meter -> Variable Delay (delay time)

A simpler setup can be obtained if you use the Clocked Delay:

1V/oct -> Sine Osc (1V/oct) -> Clocked Delay (clock input)

You even get all the integer ratios for free (i.e. just intonation).


Im not that smart, :crazy_face: and can’t make the V/oct works, anyone tried and succeeded?

I was never able to get it to track to 1 V/Oct.

Ah…the newer version of the TapTempo object which is used in all the clocked delay units has a 2ms hysteresis filter on the output period measurement because it is designed for measuring and locking on to periods typical in rhythm. I can add an option that disables the hysteresis.


I’m not sure when that changed, but I’m pretty sure I tried your suggestion soon after you posted it, and couldn’t get it to track then either.

Anyone succeeded? Really need this!

I’ve added a unit called Octave per Volt to the testlib:

testlib-v0.3.18.zip (4.7 KB)

Create a folder called testlib in ER-301/libs and unzip the contents of the archive into this folder. When you mount the card again you will see this new Octave per Volt unit in your unit selection menu (under the Experimental category). Just place inside the delay time sub-chain and set the source of the sub-chain to your V/oct signal.


Don’t forget to set the delay modulation gain to 1.0 and the bias to 0.0.


For those who care, this unit calculates:

OUT = p0 * pow(2, -1 * (IN + tune))


Amazing! can’t wait to test it tonight!!! Thanks @odevices!

Can’t see the unit :face_with_raised_eyebrow:

I need more info to help! What did you do with the testlib.zip?

By the way, here is my silly test using this in a Karplus-Strong patch:

(ER-101 + ER-301 only, one stereo track, no treatment)

The stereo chain preset used to create the demo track.
karplus.lua (55.6 KB)


Oh wait. I told you the wrong folder. You should put the contents of the testlib archive into ER-301/libs Sorry!

I’ve fixed the original post.