My new 606 mod. I included some features that I think are new to the world.
Cymbal and open hihat got an attack/decay envelope which is fully sensitive to velocity. This gives you independent control over the attack and decay times and the volume of the instrument.
Also I added a ring mod variant to the existing six hihat/cymbal oscillators using XORs. Gives you a great range of metallic sounds.
Audio soon to come…
Features:
-Open Hihat attack, decay [velocity sensitive!!]
-Cymbal attack, decay [velocity sensitive!!]
-Control pitch of two oscillators for the cymbal and hihat metal sound
-Chose hihat sound to be, oscillators, two oscillators with ringmod, four oscillators with ringmod, mix
-Adjust hihat highpass
-Adjust cymbal highpass
-Adjust hihat+cymbal bandpass
-Adjust cymbal bandpass
-Low tom pitch
-Switch tom noise
-Snare noise amount
-Snare tune
-Snare decay
-Snare highpass filter
Have been working on a velocity sensitive AR-envelope for TR-606 and TR-808. Attack and Release times can be adjusted between 1ms and 5s and of course the open hihat can be cut by the closed hihat.
In the last post I talked about the portamento mod, today: voice spread!
Voice spread mod
This mod detunes each voice by an adjustable amount. The pitch of the voices is not detuned altered in the same amount or even with tej same polarity. Because of this I’d like to call this mod the “voice spread mod”.
let’s take a look at the Polysix schematics and look what happens when you press the unison mode button.
In unison mode the analog switch/multiplexer is activated and the pitch CV is connected to +5V and -5V over different resistors. Voices 0 and 5 are connected directly to GND therefore not altering the pitch, but for the other voices R119-R122 form a voltage divider with R116 and the resulting voltage leads to a slight detune. Let’s assume voice 1 is detuned by +2 cents, then voice 2 is detuned by -1 cent, voice 3 by +1cent and voice 4 by -2 cents because of different resistor values and different polarity of the connected voltages.
I wanted to change the amount of spread detune. One possibility is to change the voltages connected to resistors R119-R122. I also wanted a much larger amount of possible detune. To get this you have to replace resistor R116 with a larger value, 3k3 turned out to work fine.
Here you can see the full schematics. IC3A summs voltages from the envelope, LFO and some offst voltage. IC3B inverts the voltage to get positive and negative detune for the spread function. The switch labeled ‘spread on’ turnes on the spread mode even when not in unison mode.
Todays mod: Add pseudo portamento and voice detune/spread to your Korg Polysix
These are actually two different modifications of the Polysix I developed recently. I always missed the possibility of portamento in my Polysix, unfortunately it is quite difficult to add real portamento, because of the polyphonic nature of the Polysix. But it is possible to add some envelope-to-pitch functionality and this is basically what I did.
The second modification relates to the Polysix’s unison mode. In unison mode all the six voices are played simultaneously. But because this would not sound much different from playing one voice, the voices are slightly detuned in this mode. this is where my mod cuts in. It is now not only possible to adjust the amount of detune but it is also envelope and LFO controllable. The results range from fat phasing basslines to bell like sounds to weired huge strings. It is also possible to detune the voices when not in unison mode, the result is similar to a detuned polyphonic synthesizer which is also quite a nice effect.
Although the following description might sound a bit difficult to understand to beginners the ciruit itself is fairly easy to build. All you need is some soldering skill.
Portamento mod
The Polysix only uses one exponential converter for all six voices. The CV-voltages are multiplexed, fed into the expo-converter and ten demultiplexed and distributed to the six voiced. We want to alter the pitch exponential rather then linear, otherwise the lower notes would “glide” faster then the higher notes. This means we have to cut in before the exponential converter. We also would like to have only one potentiometer to control the amount and maybe one switch to control the polarity of the effect. This means we have to demultiplex the envelopes of the voices, control the amount and polarity and then feed it into the expo-converter. And this is basically what I have done here.
Picture 1 shows the portamento part of the circuit. IC1 is an analogue switch with 8 inputs and one output. Inputs x1-x6 of IC1 are fed by the outputs of the envelopes, A, B, C is the address buss of the Polysix multiplexing circuit. IC1 multiplexes the envelope voltages and they get into IC2A where some offset compensation and amplification is done. I wanted some kind of behavior that the note is detuned in the beginning and gets less detunded during the attack phase of the envelope until it reaches its normal pitch after the attack phase.
The picture above illustrates what is done to achive this. First the maximum amplitude of the envelope is substracted by R2 and TR2 to get 0V at the maximum amplitude. Then the Voltage is inverted be IC2A. TR1 adjusts the maximum envelope amplitude and therefore the maximum amount of detune. You don’t have to use a trimmer here, I used one to set ecxactly 1 Octave as maximum. If you dont care, just use a 100k resistor instead od TR1.
P1 is a potentiometer to adjust the amount of portamento, SW1 changes the polarity of the signal to get either positive or negative envelope amount. The output of IC2B is connected to the input of the Polisix’s expo-converter. (See later article for a connection diagram)
I just put insert jacks on my ‘things to check first’ – list. A couple of days ago I repaired a Soundcraft mixer, after disassembling it and figuring out the signal path (didn’t have schematics) it turned out that the contacts on the insert jacks were corroded disabling the signal flow.
The very same problem just occurred in an audio amplifier whose headphone jacket had the same problem leading to a defect left channel.
