I traced the Volca Beats, schematic/layout + some new mods

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Dimitree
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I traced the Volca Beats, schematic/layout + some new mods

Post by Dimitree »

hi everyone,
I had some spare time to waste in tracing the Volca Beats and then analyzing the circuit.
So I'm uploading here the schematic, a component layout and some mods that I've done to make it sound more like a TR808.
it is all explained in the attached pdf

I'm not a drum machine expert (this is my only drum machine) and don't have a superior hear, I'm sure this can get better, so please don't bang on me :lol:
For example, the hats are not really similar to TR808 but I still prefer them now rather then the original on the Volca.
Also, with the schematic/layout should be easier to implement mods like individual out or adjusting the mix levels.

here is a quick comparison between my mods with TR808:
https://soundcloud.com/user-32380672/vo ... s-vs-tr808

sorry for my english,
I hope you find it usefull. I always get huge helps in this forum, so I hope this is a little way to thank you all.
Attachments
Volca Beast Dimitree mods.pdf
(2.49 MiB) Downloaded 1908 times
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CeeJay
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Post by CeeJay »

Wow, thanks!
That‘s a lot of work you have done!
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minisystem
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Post by minisystem »

Cool. Looking forward to digging into this. I traced just the Beats snare a while back: http://system79.com/volca_beats_sch.pdf
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minisystem
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Post by minisystem »

That PCB layout artwork is something else! :hail:
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Post by spacedumpster »

awesome! so hesitant to crack open gear i've spent any amount of money on but i am tempted.
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555x555
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Post by 555x555 »

Oh, wow. Thanks! This will save me a lot of time...
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brawnywynn
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Post by brawnywynn »

Amazing work Dimitree! Thanks!! :yay: 8-)
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Post by funky catsmell »

incredible! now for a trigger input mod :nana:
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Post by funky catsmell »

Image
built this real fast. it doesn't work, but it does cause the kick to only trigger when gate is high. not the goal but nothing blew up. ideas?
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Dimitree
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Post by Dimitree »

I'm afraid you can't just do that to trigger a drum sound.
The Volca uses a pair of signals: a short trigger (0V to 3.3V, 15mS) to excite the bridged t-network, but then it also provides an envelope to each VCA following the corresponding sound generator (Q10-A for the kick, for example).

So you also need to open the VCA (and keep it open as long as you like) when you send the trigger.

Also, you can't trigger the hats and the pcm sounds.
Maybe you'd be better to use MIDI.

I guess Korg added the VCAs so you can control the "part level", and also because without them the decay of the bridged t-network would be too long, so they cut it out digitally (just try to listen the sounds before the VCAs and you'll notice that they take really long time to actually decay)
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Post by PWM »

Dimitree wrote:also because without them the decay of the bridged t-network would be too long, so they cut it out digitally (just try to listen the sounds before the VCAs and you'll notice that they take really long time to actually decay)
Don't be daft, no bass drum is too long! ;)

Great work reverse engineering the schematics!
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tito_tunes
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Post by tito_tunes »

Do you know if it’s possible to defeat the gating of the kick? I don’t like how the decay envelope cuts off abruptly. Also do you know if it’s possiboe to replace the hat metal sound with white noise? Thanks!
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Volca Beats play button

Post by noiseygear »

Dimitree

Hey Dimitree! Thanks for all your work on the Volca Beats.

I would like to install a foot switch jack to start/stop the Beats. Do you know where I should wire it to trigger the play button? Thanks!
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Re: Volca Beats play button

Post by Sparkey »

noiseygear wrote:Dimitree

Hey Dimitree! Thanks for all your work on the Volca Beats.

I would like to install a foot switch jack to start/stop the Beats. Do you know where I should wire it to trigger the play button? Thanks!
Can you wire something to connect to the sync-in jack socket, or are you using that to actually sync?

The sequencer is "paused" when there's a jack in the sync input (so you hit play and it lights up, but just sits there). If the correct pads on the jack socket were connected to a cable, you should be able to simulate a jack being inserted and then removed (switched off) to start playback with a footswitch.

It looks like something that bridged gnd and the jack side of R87 would do it - or maybe "PAD-6" whatever that is.

I've used the method of keeping a jack inserted in the sync socket while setting my Volcas up, and pressed play on all of them. Then I can pull the jack out of the sync socket on the first Volca, and they all start playing together.
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THANKS!

Post by quarterturn »

Dimitree, thanks for posting your schematic. It enabled me to have a PCM output I could wire up using the minijack switch. This way, when unplugged, PCM goes back to the main mix and out when unplugged.
R143 connects to a via just above the LM324 and a tiny bit to the left. I used an exacto knife to CAREFULLY cut the trace at the via. At R143 there is room to solder on an 0805 4.7uF SMT cap to R143 to block any DC offset and prevent loud POPS when plugging/unplugging.
A wire from the other side of the cap goes to 'tip', GND goes to 'ring', and the other wire on the jack goes to the via. I use solvent plastic cement glue to hold the wire in place. The jack just fits in the area between 'click; and 'high pitch' knobs if you trim away the lip from the panel plastic and you tilt the boards in so the jack goes between the PCBs.
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Re: I traced the Volca Beats, schematic/layout + some new mods

Post by Seten10 »

There are two types of people - those that trace an entire schematic and those that cant even use it once its been traced.

My volca beats wont power up and it gives me P. Er. 1 which I read means the main controller IC isnt getting power. Wheres the power section of the schematic? I looked for a very long time but I'm probably just not very experienced reading schems - I was just looking for a place where "9V" came into the circuit but I couldnt find it.
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Re: I traced the Volca Beats, schematic/layout + some new mods

Post by BillB »

Hi Dimitree

I registered on MuffWiggler just to be able to download your schematic. So thank you for your careful work on the Volca Beats and for so generously sharing. :yay:
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Re: I traced the Volca Beats, schematic/layout + some new mods

Post by ldezem »

I bought a beat-up beats. The pitch and decay of the snare don't work and the board is missing components. Thanks to the schematic I got values for most of the missing components! Having trouble with C91 which looks like a filter. Can anyone spot if there is capacitor on the board serving a similar function I could pull out to test? I'm thinking about pulling out C98 or C93, checking their values and use this as a starting point. I'll try to fix the device to full working order (before experimenting with mods).
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Re: I traced the Volca Beats, schematic/layout + some new mods

Post by bgreeves »

Wait this is amazing. Glad this got bumped so I could see it.
ldezem
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Re: I traced the Volca Beats, schematic/layout + some new mods

Post by ldezem »

Went for 100nF as I had a it handy which restored the pitch and decay control off the bat (also replaced other damaged/missing components).
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Re: I traced the Volca Beats, schematic/layout + some new mods

Post by mxzr »

Hey I got a beat up Volca Beats here that I'd like to resuscitate. With the help of your schematics and the Volca Bass service manual I was able to solve a problem with the PSU, essentially I'm feeding it 5V into where the 5V regulator is. Seems to work, no short, I can measure changing voltages when turning the knobs and I can hear a subtle noise when the headphones are plugged in, so I guess the analog parts could be working. However, the MCU doesn't seem to be on, I suspect it might be dead, but maybe it needs some kind of "switch on" pulse? Does anyone know something about it? Otherwise, if it's really dead, did anyone find out how to trigger the individual sounds are located? I tried to feed 3V3 triggers into the DT20 and DT21 as in the schematics to no avail. I might reuse at least the analog parts of the board and trigger it from Eurorack for example. Any hints are welcome!
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Radiance2021
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Re: I traced the Volca Beats, schematic/layout + some new mods

Post by Radiance2021 »

Very cool, thanks!
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Re: I traced the Volca Beats, schematic/layout + some new mods

Post by Andreso »

Hang on!

Thank you for uploading all these details - which has also highlighted something quite alarming ...

On the last page, looking at the component layout, it appears that there's a '1-bit-noise' component feeding a white generator, which then goes on to feed both the hats and the snare.

Does this mean that the noise portion of the hats and snare are both digital?

Also, this apparent quote from Korg doesn't sound very good either: "Control signals are generated digitally whilst the CPU has a 10-bit DAC giving incredible near-analogue resolution".

If anyone has any knowledge to share on these subjects please feel free.
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grenert
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Re: I traced the Volca Beats, schematic/layout + some new mods

Post by grenert »

Given that even vintage synthesizers like the Prophet 5 used digital noise sources, I don't think this is alarming.
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Re: I traced the Volca Beats, schematic/layout + some new mods

Post by LeFab »

Hey thanks for this, I am trying to fix my volca beats on which i accidentally pulled two pads off due to capacitor not wellplaced whan i closed the enclosure, now my snare has NO NOISE whatsoever i am freaking out.

I pulled R?134 (104) and R134 (103)
and i just noticed i also only have one pad left on the C78...

Is there a possibility to get some white noise back on the snare at least, bypass something.

I'm all ears. I dont know how i managed to do this , been doing all those mods for a few months no issues... then this...

anyone can point me to a solution i'd be really happy!
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