A4 MkI filter bug, looking for older OS

Elektron Gear Analog Keys/Four
#1

I’ll try to keep this short….

I’ve a MkI A4. The unit was returned to me by a buyer on Reverb because he said all the knobs were faulty. Turned out when you adjust the filter frequency, nothing happens for the first 1/3 turn of the knob, both directions. If you change to, say, Amp, the knob works normally from the get-go. All the other knobs work correctly. His buyer’s remorse aside, I’ve asked Elektron to help and sent them a video, but after some initial interest they aren’t replying further. It’s got the latest OS installed.

Does anyone have any thoughts on this or have older A4 OSs I can install and try? I can’t get them from Elektron unless they start replying to my emails.

Thanks for reading.

Tim

#2

What about hardware test mode (hold func while switching on) - does the encoder work as expected there?

#3

Yes it works fine. There’s nothing actually wrong with the knob; it’s a software issue.

#4

Had a feeling you’d say that.

Hopefully someone else has an older firmware to share. You could try searching for it via archive.org if I remember correctly there’s historic support pages from Elektron mirrored

#5

OS 1.12B: Elektronauts

#6

If you push-turn the knob for filter frequency, does it change the value more like you’d expect? Which knob (letter A, B, C, etc) is it?

I’ve found one or two knob-value combinations on A4 mk1 turn very, very slowly when they’re not press-turn. Like, it takes a half or whole rotation to increment/decrement by 1. I too think it’s a software issue, but I don’t know if it was any different on earlier OSes so I’ll be curious re: your findings.

#7

It may not be a bug in the firmware version itself but just that actual install on the machine, have you tried a reinstall of the current version yet?

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#8

Yes, if you push-turn it behaves normally. I’ve tried OS1.50A and 1.40 and they have the same weird behaviour as before.

Knobs A and F, on Filter F only, by the way.

#9

Sorry for slow reply. I’m thinking that if installs of two previous OSs give same weird result as current OS then this path of enquiry might be unproductive. But I’ll try it……nope, exactly the same going back from 1.40 to 1.51C

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Log in issue and zero response from support
#10

Clearly a hardware issue. If only one voice is affected then maybe one of the filter chip. If all 4 voices have the same weirdness then it can be a logic chip or a broken trace or similar.

#11

It’s all four voices, but not the FX or CV tracks. How do you know this above about the chipset?

#12

I’m just guessing.
Some info here:
A4 teardown (and infrared pics) - Elektron Gear / Analog Keys/Four - Elektronauts

There are common principles for analog polysynths building, like control signal path MCU -> DA -> multiplexer -> VCO/VCF/VCA
Elektron is protective about the schematic but more or less follows the principles.

#13

Here’s a video of what’s going on on my A4. It shows the lack of response to very very slow turning of the knob. This is actually present throughout the rotation range. Also visible is the “ghost” indicator going round the display’s dial, which is so weird.

Comments welcome.

#14

I think what you are showing is normal, but one of my least favorite aspects of the mk1’s. Certain parameters have more resolution than is shown in the numerical readout for the knob. When turning these params slowly, the “ghost” ring is showing fractions of a value (i.e. in your video you are sweeping the filter down from 127.00 thru, e.g. 126.73, etc.).

It should be pretty easy to confirm this by connecting the synth to the Overbridge app while adjusting knobs like this (the OB UI shows the full fractional value of e.g. the filter cutoff).

The feel of this sort of adjustment is greatly improved on the mk2.

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#15

Yeah. I noticed this too on my mk1 and reached out to support about getting my hardware looked at, but then I came to my own conclusion that this is software-related and not unique to my mk1.

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#16

This is probably normal behaviour.

The filters have a very high frequency resolution, which as ptomaselli mentioned, is much higher than that of the screen. When you turn the encoder slowly, the “ghost” animation indicates a fine adjustment.

Turning the encoder quickly should adjust the filter in a more conventional manner.
If it doesn’t, the encoder likely needs replacing.

Up around 127, the filter is cutting off around 20kHz, so I wouldn’t expect to hear a difference there, but in the midrange it should be audible.
The fine adjustment is indispensable when the filter(s) are self oscillating, and you want to dial in a specific pitch.

The oscillators have their dedicated fine tune parameter, so they don’t behave in the same way.

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