A4 teardown (and infrared pics)

void · 2013-09-28T14:30:32.000Z

""Toumal"":

These effects are most likely done in the digital world, don’t you agree?

Well, of course they are. What I meant is that the main audio signal from the 4 voices is not converted to digital and then back to analog, interrupting the analog signal chain, as you wrote:

""Toumal"":

…after which the four channels are converted back to analog for output.

I think this is not the case.
Imo, the ADC/DAC is used to tap the individual voices just for the FX sends, and then to convert the stereo FX signal to analog so it can be mixed into the main stereo signal.

pinkbabyhead · 2013-09-28T14:46:04.000Z

love it. thanks for posting this.

Toumal · 2013-09-28T17:18:22.000Z

[quote=“” void""]

[quote=“Toumal”]These effects are most likely done in the digital world, don’t you agree?
[/quote]

Well, of course they are. What I meant is that the main audio signal from the 4 voices is not converted to digital and then back to analog, interrupting the analog signal chain, as you wrote:

""Toumal"":

…after which the four channels are converted back to analog for output.

I think this is not the case.
Imo, the ADC/DAC is used to tap the individual voices just for the FX sends, and then to convert the stereo FX signal to analog so it can be mixed into the main stereo signal.[/quote]
Hmm well according to the official site you are right!

[i]Both oscillators of each voice are analog, with all their elaborate waveshaping completely analog, and with their pitches controlled digitally. The noise generator is digital. The two filters, and the overdrive circuit between them, of each voice are fully analog. The amplifiers are analog. The envelopes and LFOs are digital. Their design allow them to go well into audio range.

The signal path from the oscillators to the audio outputs is completely analog. The signal path from the external inputs to the audio outputs is also fully analog. The digital send effects are parallel to the main audio path, and the wet signals from the digital send effects are mixed with the dry analog signal before the main output stage.[/i]

Somehow I had it in my mind that you had to go THROUGH the effects processing, rather than mixing in with the original audio. BUT, this also means that the more “wet” your effects mix is, the less of the “true” analog sound remains.

The envelopes and LFOs being digital kinda explains the peculiar amount of logic ICs on the board. I bet the FPGA does a lot of that stuff as well. I doubt it’s being used to drive the display or do any of the UI input stuff.

What fascinates me is how SMALL a single voice section is in that thing. I bet you could easily modularize the whole thing and make it expandable to more voices. Heck, you could even start a new, modular kind of synth that offers slot-in expansions with different synthesis types, kinda like a Buchla but with each expansion adding one “voice” instead of requiring you to patch stuff like a telephone operator only to get a few bleeps and squeaks.

Just think about it, you could mix and match voices, you could slide in two digital sampler voices from an octatrack and three analog voices from the A4, or do all kinds of combinations.

Mmmm… daydreams…

Anigbrowl · 2013-09-28T19:33:47.000Z

""Toumal"":

P.S.: Give us a bigger display next time. Maybe an OLED screen? Oh and… pads for the sequencer buttons would be nice. Perhaps even with force detection. And it should whiten our teeth while we sleep. Thanks

What an awesome analysis. As for your feature request, I invite you to perform a similar analysis on a DSI tempest…min eshould be here on Monday and I’m looking forward to connecting it to the OT and A4 (which will be sending CV to the Tempest to overcome its lack of free-running LFOs).

plusn · 2013-09-28T20:11:42.000Z

Wow, thank you for the “inside job”. Excellent findings!

MX · 2013-09-29T10:52:18.000Z

Wow! Amazing analysis

switchbox · 2013-09-30T10:35:32.000Z

great…what is the j1 25 pole connector all about?..just for programming the fpga?..or for upgrading something? …maybe like a +drive?

jgb · 2013-09-30T11:16:24.000Z

Thanks! Interesting read, and lovely pictures.

jaalmadakan · 2013-09-30T11:30:07.000Z

"what is the j1 25 pole connector all about?..just for programming the fpga?..or for upgrading something? "

FPGAs are not “programmed” per se. The chip reads its configuration from a non-volatile memory chip at startup and reconfigures itself according to that. Kind of like a CPU program that would be loaded in RAM at startup.

The jumper is most likely used to load the configuration binary file in the memory and/or for functional testing during production… nothing really interesting for modding (unless you are willing to re-design the FPGA program from scratch).

Cocker · 2013-11-13T14:51:19.000Z

Wow. Unreal. Not really sure what I’m looking at for most of this but is there anything there that hints at future upgradeability / expansion ?

avantronica · 2013-11-13T14:57:02.000Z

[quote=“” Cocker""]
Wow. Unreal. Not really sure what I’m looking at for most of this but is there anything there that hints at future upgradeability / expansion ?
[/quote]

…"Next to that we have a Micron 256 SDRam chip (2WG22) and a Toshiba flash memory chip. My guess is it’s a 2GB chip but I couldn’t find the datasheet to verify. "…

make of this what you will ! ? 2GB, potentially ? hmm, room for all sorts in there, we can but hope

void · 2013-11-13T15:28:34.000Z

yea wondering what this is for… strange!

udenjoe · 2015-04-29T13:30:23.000Z

My guess is the larger memory is for the +drive, the next smaller is for your saved content that isn’t in the +drive. Then the other memory is for storing your changes constantly, your sandbox, undos, parameter changes, etc.
Just my blind guess.

vos · 2015-04-29T15:26:57.000Z

Very interesting - even if this is allmost Chinese to me - Thanx.
I allways had this feeling with Elektron instruments - they’re developed with passion and love - I wish I understood electronics - must be so interesting. Well it’s never to late to lurn I guess.
Great info Guys ! I’m very happy about the quality of the long - term memoty ( Hey !! I understood somethig !! )

Greatings

TrabanT · 2015-04-29T15:46:50.000Z

awesome thread! thanks for the work OP !!!

henning · 2020-02-19T21:19:58.090Z

Even today cool and interesting! Too bad the virus pics are not working anymore, probably they updated their forum?

It’s an interesting observation how Elektron builds quality hardware, and hopefully this is still true for current devices. But I assume it’s worth to invest in the more expensive devices, as surely there’s not much benefit for a company to make even the cheapest model:samples (that I got as my first Elektron) for 300€ as robust that it will last for 10 or even 20 years or more.

(found this while researching a bit for this discussion: Firmware + overlay = new machine?!)

Toumal · 2020-02-20T23:01:52.528Z

Sorry the Virus pics don’t work anymore, unfortunately I used imageshack which wiped everything.
I fully agree with Elektron hardware being built to last. Every button just oozes ruggedness. And the fact that they chose a long-lasting long term flash storage is awesome too. No leaky batteries.

swiss · 2020-02-21T00:30:43.470Z

Coolaudio is owned by behringer right ?

plusn · 2020-02-21T07:03:58.142Z

Yes

Noumenaut · 2021-12-15T05:05:07.213Z

Was just thinking today how it would be cool to see the innards of an A4 without opening up my own. Forum delivers again! Great post.