Tubbutec Polysex – dev blog

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Hi,

I thought I let you know what I’ve been doing since the last update. I worked a lot on my Polysix mod and will finally be able to sell it as a kit soon.

frontplatte4

Tubbutec Polysex

What does the Polysex mod do?

There are some sound demos at the end of this article which should give you an impression, of some (but definitely not all) the new sounds which are achievable with this mod.

There are two different mods which can both be used at the same time:

  • The pitch mod routes the envelope to the pitch. You can choose the polarity of the envelope and the reference point in the envelope where the pitch is not changed. This mod is very useful to create portamento like effects, brass instruments, percussive sounds and much more.
  • The second mod is the voice spread mod which is a very powerful tool. You can determine the amount of voice spread, route the envelope and one of two LFOs to it and switch voice spreading on and off in poly mode. This mod can be used to adjust and modulate the fatness of the sound in unison mode, in poly mode you can modulate how detuned the Polysix sounds. This can lead to more natural sounds, but can also be used to accomplish complex sound effects.

What will the kit include?

The kit will include a PCB, all necessary parts and a front panel which you can use to mount the controls onto your Polysix. The front panel is made of fully anodized and printed aluminum and done in Polysix style (see images above and below). Instead of original Polysix knobs the kit will only contain similar ones, but it is possible to use Polysix knobs (one can find used ones). There will be a version with the PCB fully assembled and tested,too.

panelproto

Prototype of the front panel made of plastic. I made this to check if everything fits as intended before having a large amount manufactured properly. The two switches on the right are not the final ones of course and as you can see I try a number of different knobs. The final version will be in Polysix style blue rather than grey.

Is it difficult to build?

No! The Polysex mod was designed as a kit, which means I tried to make it as easy as possible to assemble and install it. You will need basic soldering and metal work skills, but nothing you can’t learn by watching half an hour of a soldering tutorial on youtube. You will have to drill some holes into the metal casing of the Polysix, but precision is not needed because everything is covered by the front panel and will look very nice.

So why is it not already available? How long will it take? What are you doing the whole time?

At the moment I am working on collecting all the parts in larger quantities, getting the front panel and the PCBs produced, writing a manual and setting everything up nicely so you will get a good product and have a fun time 🙂

I have more questions!

Please don’t hesitate to ask them, I will answer and update this little FAQ.

Sound demos:

None of the sound examples make use of the effect section of the Polysix (or any external effects)

 

A simple arpeggio with mid attack and decay settings. The envelope to pitch amount is slowly increased to achieve a brass instrument like effect.

 

The whole Polysex mod is used in this example. A little bit of voice spread is set to achieve the sound of a slightly detuned synthesizer. Some more life is added by modulating the voice spread by the PWM LFO. Further more the envelope is routed to the pitch with the reference set to the sustain level and the polarity to negative, so that it pitches up as the sound decays.(The recording is a little bit distorted unfortunately)

 

Polysix in unison mode with the envelope routed to voice spread, long attack and release.
At first the reference is set to the sustain level, so the sound starts very dissonant, becomes more consonant and fat until it becomes a slowly phasing sound. As the key is released it reverses into dissonance.
The second time the reference is set to the zero level, the sound starts consonant, becomes dissonant and then consonant again.

 

An arpeggio in unsion mode. The voice spread amount is slowly increased – the sound becomes fatter and denser.

 

This sound demo uses voice spread modulated by the a fast PWM LFO.

 

Chords with long release and short attack, envelope routed to voice spread, with the sustain level as reference. As the chords decay, the sounds becomes more and more detuned. Sometimes the attack is set longer to achieve a sound that starts dissonant and increases in consonance.

 

The envelope is routed to the pitch to achieve a bass drum like percussive sound. The filter is modulated and different decay times and sustain levels are being set.

Midified CR78 and TR606 sound demos

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Here are two sound demos of a TR606 and a CR78 I midified.

Note the full velocity sensitivity capability of the 606 and the pseudo-velocity sensitivity of the CR78.

TR606:

CR78:

Some more infos about the CR78 mod:

Depending on the midi velocity sent to the device, the master volume is adjusted. That is of course not the same as full velocity sensitivity, but gives you a surprisingly great amount of flexibility. Think of the 808 for example which has one accent track – this is similar, but you can adjust the accent on the fly.

Repairing a Novation Supernova with an overvoltage damage

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This Novation Supernova just came in.

probably due to overvoltage on one of the outputs two of the outputs failed.

Which is actually really lucky, take a look at the damage!

This is the bottom side of the PCB, the trace coming from the connector vaporized and you can see how much heat must have been there: A large area of the solder resist is gone too. If you look closely you can see, that the trace actually fused with the surrounding ground plane. I believe this is what saved the Supernova, because it protected the rest of the circuitry from the high voltage.

Novation Supernova (2)

This is the other side. I already desoldered the connectors. As you can see there was a lot of heat here, too, the trace acted like a fuse and melted and the 47Ohms resistor exploded. Wow!

Novation Supernova (1)

These are scorch marks on the metal enclosure which was about 1cm away from the PCB.

Novation Supernova (3)

Apart from that only some more resistors and an op-amp failed. Amazing when you consider what must have happened here!

I replaced the broken SMD components, redid the broken traces and the two outputs are working again 🙂

Novation Supernova (8)

In the picture above you can see the replaced opamp and some replaced resistors. Unfortunately I didn’t notice a broken 740 ohms resistor before I ordered the parts. I used wired one instead, doesn’t look as nice, but works as well.

 

 

A new power supply for a Yamaha DX21

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Look at this horrible “repair” job someone did to the power supply of this Yamaha DX21 (which broke again of course)

The main electrolytic capacitor has been replaced with just some other one, definitely not a low-ESR type, connected with quite long and thin leads and then glued into place somewhere in the case. The switching transistor is glued into place too and the traces leading to it are almost, but just not quite broken.Yamaha DX21 (3)

An additional power LED had been added, but instead of connecting it to the 5V rail, it is connected directly to 230V via an capacitive “led power supply”.

Yamaha DX21 (2)

Last but not least there is some strange sticky stuff all over the place, might be electrolyte from the capacitor, or some kind of glue that was used for something. It is hard to tell, it is an awful mess in there. Yamaha DX21 (1)

In cases like this instead of trying to fix the existing power supply it is better and cheaper to replace it with a new one.

Yamaha DX21 (4)

 

 

Sequential Tom power supply

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This Sequential Tom needed a new power supply. It states to need 15V AC, but after a little bit of reverse engineering it turned out to actually need 2×7.5V AC. It is quite unlikely to find a wall adapter with 2×7.5V AC, so I had to build an own power supply. It is just a (fused) transformer in a case, and a plug attached to a cable that fits into the back of the Tom. Done 🙂

sequential tom (2)

4x Midi CV Interface rev.2

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While waiting for my Polysix mod PCB, I am working on rev. 2 of my midi to cv interface. Rev 1 was working well, but I realized I wanted some more features.

midi2cv4

The new one will have:

  • 4 x CV out, 12 bit precision each
  • 4x Gate
  • Glide / portamento control for CV outs
  • For each CV you can switch glide mode between (on/auto/off)
  • For CV 3/4 you can choose individually whether they output midi notes or midi velocity from CV 1/2
  • Each CV can be controlled by midi notes and midi controller
  • FM in
  • Midi learn
  • Leds for gate and CV out
  • Doesn’t use smd parts an can be built by everyone

This basically enables you to have 4x polyphony with a modular synthesizer !…..and much more 🙂

 

Polysix Mod PCB coming soon

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I am currently working on a PCB / kit for my Korg  Polysix mod. It will be available soon and feature both mods: portamento and spread detune.

This is a design for a front panel – Polysix style:

p6moddesign

It could look like this:

p6moddesign2

And here is a rendering of the PCB:

p6 spread detune pcb

Currently a prototype board is being produced, for some last checks before a larger order of boards.

If you are interested, have any suggestions or questions, let me know in the comments 🙂