Repairing and debugging damaged Volca Beat

Symptoms: The unit will not power up.

Causes for incidents? Maybe some DC feedback while playing with PP… or external speakers back current… I still haven’t identified the cause for the damage…

I was trying some new different PP* (*=patchpoints) on my modded Volca beat from my standard mod.

I wanted to get back the Kick on the Main output that was lost when I added the individual output mod. The individual out was working great but I got tired of not having the Kick on the Main also. So I tried to apply a new PP,

Ahttps://modwiggler.com/forum/viewtopic.php?t=100831&start=25

I used the Kick inm Kick Diff, one phase only, and other as shown here:

Other PP on the back of the PCB are all the standard PP labeled for individual outs, included white noise, pink noise, and Kick+Tom out. When the unit shorted, I guess it has been for some sort of feedback while trying PP with the Kick, I was also playing with noise. All 16 PP are wired to a 4X4 dupont little patchbay accessible on the top of the unit, alongside all indivdual outputs, plus the speaker MONO output, when I damaged the unit.

I started debugging the unit from the PWR in and found all Vpp were shorted to GND. I removed the TP5 voltage controller and all components highlighted:

Then I removed all other parts that had a Vpp connection shorted to GND, following this schematic red and orange PP; downloaded here: https://modwiggler.com/forum/viewtopic.php?t=193238

I found IC 12 that was overheating by touch and removed it.

TPA2006D1 1.45-W MONO Filter-free Class-D Audio Power Amplifier with 1.8-V
Compatible Input Thresholds.

These are the Pin out and the Test schematic to determine if the IC is really damaged or not:

The PWR IC TP62112 schematic instead:

All parts removed were taped on a blank sheet of paper and labeled for the repair:

The PWR IC12 probably damaged need an alternative circuit to allow the unit to work again:

To remove the parts I used a twisted copper cable to run around the IC’s and heating all around:

So. Now I am going to try and test the power amplifier, see if it is really damaged or not. If it is, I will build an exact same circuit based on the schematics, if I can’t source the SMD, but even if I could, I have some alternative components that could do the job, without resorting to order from Digikey, that would set me back at least 25-50 eur…

Take care and extra caution if using those PP yourself., whilst I will attempt the repair…

Tchussy!

Volca mix Active buffered 8ch mixer upgrade

Made an 8channel mixer for the Volca mix. Initially passive, going to the AUX input. Then decided to go Active buffered with VOLUME control. Follow Video instructions. Keep DIY Spirit Alive!!! Re8et MODS!!

FIRST STEP IS THE PASSIVE MIXER, IN WHICH YOU NEED TO RREMOVE THE TWO SPEAKERS, AND THEN CONNECT THE TWO SPEAKERS OUTS TO TWO MONO JACKS, THAT WILL ALSO GO INTO THE LATER ACTIVE BUFFERED OPAMPS INPUTS, AND WITH THE VOLUME POT, THE VOLCA MIX UPGRADE IS READY TO ROCK WITH NOW 12 INPUTS!

Topolona restyling: work in progress

A complete restyling was necessary, from the first experimental unit, some stuff has gone, like the sequencer.

The modular power module has moved outside, and all connections are being polished, cable trimmed to minor possible lenght, reduce clutters of cables, and allow easier and safer internal modifications when the unit is open.

I’ll upload some pictures here and there on the making.

Volca Mix Filters mod v 1.0 by Re8et

This simple mod transforms the douible throws filters to either Hi cut or Low cut or normal behaviour without excessive modding like adding an extra circuit, which is on the way… so stay tuned!

This mod is based on the reverse engeneering of the filters structure. Which has a fully analog path. Here I made some incompletes drawing attempts schematics.

All ground com are shared, I used a 47 Ohms before Gnd, and it works ok.

Volca Modular Space lead patch

Super nice lead patch for the Volca Modular. Has a lot of grit on the bass, but with ratio, fold, and mod increasing, the sound change completely to a starky, space lead just add a little bit of reverb. The extra keyboard is a Korg Monotron keyboard, re-adapted for the Topolona project, to accept the skin tone cable on the virtual ground, the purple on the V in, and the out goes into where the purple goes in drawing. The second oscillator has a pass into an external solar modulation and diode-parallel axial cap distortion module before going into the second filter; but I did not include that in the drawing and simplified it a bit as it is very subtle modulation and sounds very good equally without it. Enjoy.

Sound of the Space Lead by Re8et

Patchblock midi and lfo patch share thread

Patchblock sharing patches thread with all default blocks or if added blocks must be saved internally… I use all default blocks for mindsake.

Assuming I’m not the only one who got a patchblock, due to it’s irrisory cost, and it’s GUI almost obsolete, but still working.
No manteinance, no documentation on block language, bugs everywhere etc etc, but one could still find one for 10 bucks, put on a midi
hack, or midi input and output; and yet still manage to make some nice patches with it and if willing to share them, I will start this
almost nonsensical thread to which I will be the only one partecipating. 

There was also a eurorack conversion at some point but the hardware it’s absolutely the same and it costs threefold a bela with audio shield.
But I hope that someone has one forgotten somewhere and perhaps could give it a refresh on new breath. 

Patch description:
Midi note subtraction with left knob -transposing up and down any incoming midi note and output on midi out.
Midi clock and Volca trig with trigdiv multiplier on button 1 with 8 different division-multi to lfo bpm sync and gate-trig out 0-0.5 volts on R audio channel
4 Lfo’s plus any mixed combination of these with button 2. Left knob set rate division and Right knob amplification. All Lfos’ goes audio rate.
Lfo out to Left channel only biased to 0-0.5 volts for easier post amplification without need to dc-bias for positive range only.
Amplification to 0-5 volt range must be done on separate circuit.
LFO MIDICLOCK NOTEALTER SIMPLEv4.zip(1.43 KiB)

Original thread kindly hosted at Reasontalk 🙂

https://forum.reasontalk.com/viewtopic.php?f=12&t=7519568&p=520381#p520381

Volca Nubass Vactrol upgrade Re8et mod update 2020

The Volca Nubass official Re8et vactrol mod guide.

Choose a vactrol, or make one. Take dimensions and cut out the plastic to allocate the unit over the three small caps as in picture. Make sure the unit will close with the vactrol in place before proceeding to next step.

Get a 1N4148 and put it in parallel with the cv input side, reversed, to block neg voltages.

Connect the leads to the Drive mid and out pin as illustrated. Use small cables and cut the leads as short as possible. Connect the VTL with the input minijack.

I put it under the tempo sync input with the same cut out technique and it fits perfectly.

Check ground connections they are isolated from the audio circuit twice.

Optional you could add a small cap in series before the ground connection on the VTL, try it on a BB with the cv to get some dynamics or soften possible Jittery introduction.

Close the unit without gaps and power up!

Good Job! You now have Gate control over Drive output on your Nubass!!

The mysterious world of Roland D-05 / D50 menu… and the one and only real time controller… aka… the Joystick.

The D-05

 

 

The Roland D-05/D50, is a mysterious synthesizer… it comes from an era when electronic calculators were popular, in the 80’s. Every parameter of this complex -four  part synth is acccessible through the endless menu, and the tiny screen will only show two parameters at a time!

When in local mode, the Joystick will modify one of the two parameters, based on its axis movement. X direction affect L1. Y direction L2. Of course you could accidentally move X instead o Y and vice-versa….

 

Of course you can use the free editor and save yourself from doomsday editor digging apocalypse.

http://www.d50librarian.co.uk/

 

Anyway. Let’s dig into the manual to try to understand how this synth tries to communicate WITH US!

 

We can access the ARP page, to use the Joystick for altering the ARP settings

We can try imagine what this mean, but this is otherwordly uncomprehensible to me at this stage.

We can change LFO’s t TVA output, however, based on the patch structure, you might end up earing no wobbling effect at all

Some mysterious words of advice

The common mode of operation affects the overall sound of the Synth, but still you need to dig in either upper or lower part.

In Midi mode is possible to SepCh, thus use two different MIDI input at the same time. Play a Drum sequence in the lower section, and a Lead synth in the upper section.

In BASIC mode, it is possible to use the Joystick to affect Reverb type, that is at the OUTPUT stage, so it is something that you will certainly hear the effect if assigned to the Joystick (I’m joking, you can’t assign the Joystick…)

Joystick can change output mode, or Reverb type, but NOT AMOUNT>….

Here we see, that common, is INSIDE one of ONE of the TWO tones previously selected. Unless you are not in WHOLE UPPER MODE, if you would like to assign the Joystick to filter cutoff and Resonance, You’ll have to switch through tones and parts to get to the right one (Nevermind envelopes,…

This is the MASTERMIND , only the TRUE MASTER that can go through this path, will be able to move forward….

 

 

 

So, this is all, more or less. The path to quickly enter the desired mode of operation of the Joystick for EACH OF THE 512 PATCHES you can store on your unit, means you have MASTER the MENU and WRITE DOWN the STRUCTURE for each PATCH or…. you will have to debug each patch individually EVERY SINGLE TIME.

Otherwise ARP and OUTPUT are the only two settings one can safely assume will change your sound immediatley (once you have entered the RIGHT PATH, obviously). By which, I strongly reccomend to write down the button sequence for entering each section on the MIGHTY PAPER TAPE.

The desired path for entering Reverb mode, should go FUNCTION, PATCH EDIT, REVERB, LOCAL.

So good luck trying to edit a bass to a wobble dubstep style, with control over TVA amplitude. One suggestion, try WHOLE. and UPPER only.

Topomixmix mixer module Nutube 6p1 schematics and simulations.

 

Here are the Schematics for the Topomixmix mixer module with the Korg Nutube 6P1 Triode. I used EasyEda.

THE LM358 ARE JUST FOR THE SIMULATION, YOU CAN USE 072 OR 5532. I ALSO USED A UA776CD BECAUSE I SCRAPPED AND OLD SOUND CARD….

 

If you guesss why single triode… this is not a cyrclotron…. and I had a half Nutube available. Just half. Don’t ask.

I’m still learning about frequency response simulations, and I have to thanks Rezzonics and this project by Andifierman here if I was ever able to reproduce the Nutube triode in SPICE simulator.

So, this is just one part of a modular mixer that goes into Topolona.

EDIT / LAST VERSION 1.4 – SINGLE TRIODE INVERT THE PHASE – IN 1.0 AND 1.1 TRIODE PHASE IS MIXED INVERTED.

The Nutube can not accept much more than 1v p-p at input. Or it can but it will go into distortion mode. While the dry signal has plenty or input-throughput room to bear with.

VERSION 1.4

SIMULATION RESPONSE ON TWO SINEWAVES

8hz 1A and 16Hz 2A on inputs A1 and A2.

Master volume (yellow) at 50%, the 2A sine get distortion in the Tube. Output is phase correct.

Lowering the input to 1A each, and adjusting master gain and mix with wet prevalence, the distortion remain subtle in presence. Tube bias on A1 is at 50% of 22k and 5v.

Adding at 10k resistor after the 22k trimpot, the response of the tube is clearly visible.

In spite of the additional 10k resistor, an alpha pot could be used. Or. A cv input IC for to control the bias and a pot. Or just a couple patchbay patchpoints because I run out of space long time ago in the Topolona…

 

 

////// following with previous sch. /////things have changed since v1.0…

The wet and dry signal get mixed at a B10K pot. I have added a 1k resistor after the pot, and a couple 10R resistor before it. the response gets much better.

Also in sch 1_1 the voltage bias is 4.5, trimmed / divided at 50% by the 22K trimpot, while the filament is stepped down to 0.6 input to allow max threshold.

SPICE simulation 1_1 Sine wave 8Hz 3A input. Blue is mix signal pre final gain. Orange is final out at 1.5 Gain pot value (R9 is a B10K in reality). MIx pot dry prevalence.

MIx pot Nutube prevalence (wet signal) same 3A source sinewave

Upgraded 1_1 Schematic.

 

Here 1st simulation and sch. v 1.0

SPICE schematics 1.0 and a 60Hz sinewave 1A simulation with three probes points.
1st probe point is at Nutube A1 input to monitor the bias. (orange waveform at 2v)
2nd probe plot is the G1 output of the Nutube. At 1Vp-p input, a 5x gain is obtained without distortion. (Blue)
3rd Probe point is at output, where output gain goes all the way up to 16v p-k, and can go into distortion also if cranked to max. (The bottom orange)

 

VCA Mixer with limiter

Building a VCA mixer in conjunction with the Rakit mixer (Topolona).

Inspiration credit for schematics goes to https://kerimwilhelm.wordpress.com/2015/05/08/vca-based-analog-audio-limiter/

 

The circuit I built is exactly as its schematics; what is not very well explained in its schematics is that one single opamp can drive both circuits with +9/-9 volt. (SUBTRACTOR and ENV FOLLOWER).

Every channel thus in final circuit must have one opamp each. I simplified* the circuit taking every buffer opamp away. KERIMWILHELM schematics has AUDIO BUFFER and DC_BUFFER op-amps, please refer to its schematics. A maximum voltage of 3 volts has been recorded on the ENF output (Envelope Follower) and 0 Volt minimum.

The final build should  have a jumper connector on the Topolona patchbay section from the ENF OUT to the VCA CV IN (-0.7 /+ 3.3v) and a THRESHOLD** connection for biasing the V_REF voltage. (Jumping would enable the limiter, but otherwise the ENF can be routed elsewhere…) This design enables the scaling of the ENF through a series or resistors or single resistor on the patchbay, resulting in more or less compression level (not ENF treshold, that is the 5K resistor which brings the V_REF in to the SUBTRACTOR).

**this may vary in final build

 

Day 2: Testing multiple balanced and unbalanced signals, some of which with DC_OFFSET resulted in the VCA bad distortion. So, *buffered AUDIO_IN had been added back to DC_FILTER out bad offsets ( some Korg Volca MOD_OUT has some very bad DC offsets…).

The new circuit prototype behaves very well now, most importantly, with the ENF_SWITCH off (i.e. no ENF goes to the VCA) , the Audio signal do not degrades, or distorts, and has a small GAIN, because of the small 220R OHM Pulldown on the VCA control input (~20db GAIN).

The next test will be hook it up with the main Topolona Mixer +9/-9 voltage, with all 8 channels connected, all 12 op-amps powered, and both VCA’s. This test is critical for the VOLTAGE_REF. Depending on the fluctuations of the V_REF under load I could add one more BUFFER Op-amp for the V_REF voltage, which controls the DC_BIAS for the SUBTRACTOR and is thus fundamental to the whole circuit.

I am waiting for delivery of main resistors values, and caps, but have started the main PCB design, which has to go inside Topolona and has to be the smaller as possible.

Power consumption should vary between 150-300 mA and should not be a problem for the main Topolona +9v/-9v power rail (both Topolona max power output = 1amp, but there’s already some load, of about 500 mA…) . All IC’s are powered from the same +9/-9v.