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rolandsh1000 uploaded a new video
(2 days ago)
Just a short video showing the wavetable oscillator waveforms of the Kaw...
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Just a short video showing the wavetable oscillator waveforms of the Kawai K3m. To me, this synth is a bit lifeless and cold (though still sounds generally nice) and I wondered why, since it has the terrific ssm2044 analog filters. So I decided to put the oscillators on the scope and this video demonstrates what they look like.
Many of them have a lot of extra high frequency content, and I can hear aliasing noise at low frequencies. Interesting to me is that they didn't include any basic SAW, SQU, PULSE waves, but there are a few very SINE looking waves.
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rolandsh1000 uploaded a new video
(1 month ago)
Just a short video showing the two "types" of sawtooth wavefor...
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Just a short video showing the two "types" of sawtooth waveform on the Korg Poly-61. The Poly-61 has two oscillators: DCO1, a digitally-reset analog sawtooth-core oscillator (much like that on the Juno-6, -60, -106) and DCO2, a coarse, divide-down-style oscillator, based upon a CD4520 counter and some summing resistors.
I think both are musically useful, but it's telling that Korg gave the user the ability to turn off _only_ DCO2; DCO1 is always on!
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rolandsh1000 uploaded a new video
(1 month ago)
Just a short video showing the oscillator of the Roland SH-1000, their f...
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Just a short video showing the oscillator of the Roland SH-1000, their first synthesizer. This synth is interesting because it uses a common organ Top Octave 6-stage Divider chip (LM3216) to create the oscillator waveforms. These chips are fed by a high frequency clock and they divide down the high frequency waveform for lower pitch generation. To create various waveforms, the various divided-down signals are mixed via resistor and capacitor networks to shape various oscillator waves.
In this video, I focus on the sawtooth wave, since that's a simple waveform that is usually generated in an analog synth by repetitively charging then resetting a capacitor with a constant current, to make a very smooth continuous ramp. In the SH-1000, not only does the sawtooth waveform have "bumps" due to the mixed pulses/squarewaves, but the shape of the ramp is different at different footage settings.
Roland had experience with these chips in other contemporary devices: I have a Roland EP-30 that has (I think) 8 of these LM3216 chips. It also tries to synthesize saw-like waves, but the resolution for the saw waveforms that keyboard is much worse. So, basically, if my SH-1000's TOD chip goes bad, I have quite a few replacements at the ready! ;)
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rolandsh1000 uploaded a new video
(2 months ago)
Demo of my modified Korg Poly-61. I got it for cheap off local Craigsli...
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Demo of my modified Korg Poly-61. I got it for cheap off local Craigslist because of some issues. The most problematic was the non-triggering keyboard. I swapped out the keyboard PCB from a dead Korg DW-6000 and now it works perfectly (I recommend if you can find a dead DW6k and you're trying to repair a Polysix or Poly-61, you'll be amazed how much better the DW6k keyboard works).
Anyway, the P-61 is a lot like a Juno-60 or -106, in that each voice has one real digitally-controlled sawtooth core oscillator (DCO), VCF, and VCA. So it's essentially an analog polysynth under digital control. What it has over the Junos: an extra true-digital oscillator (fairly lame, but useful for some things), real analog envelopes, two LFOs. What the Junos have over the P61: chorus, noise and, most importantly, analog controls to tweak all parameters.
The P61 designers apparently wanted to save money and followed the lead of the Rhodes Chroma and Moog Source in the user interface, so the P61 used a digital button interface to adjust parameters settings. IMO, this sucked because 1) it inhibited sound exploration 2) the resolution on the voice and modulation parameters was limited.
So, I decided to bring out a lot of these parameters of the P61 out to the panel and convert them to true analog control. This meant that these parameters could not be stored in patches (though other parameters still would be), but I was willing to forgo that since I basically just play for fun, not on stage. The parameters I brought out were the global ones (changes made by the microprocessor to all voices at once), which made it easy to have one knob or switch control all voices - all my mods are either switches or resistors/pots, no active electronics were added. I think you could make ALL of the parameters under analog control, but to go beyond what I did, you'd have to modify each voice circuit, which is a lot more work. :)
Controls added:
DCO1 waveform switch (saw, pulse)
DCO1 PW/PWM switch
DCO1 PWM amount
DCO2 on/off 'harmonic' switches: 2', 4', 8', 16'
VCF cutoff
VCF resonance
VCF keyboard tracking switch
VCA EG/gate switch
MG frequency
MG waveform (tri, squ)
MG DCO amount
MG VCF amount
Joystick:
- LFO2 waveform (tri, squ)
- LFO2/cutoff switch
- Joystick/Knob select switch (vertical joystick disabled in favor of rotary knobs)
- LFO2 DCO amount
- LFO2 VCF amount
In sum, these synths seem quite inexpensive for what's inside and with this added analog control (now it's somewhere between a Juno-6 and -60 as far as patch storage and user control), it's a lot more fun to play!
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rolandsh1000 uploaded a new video
(2 months ago)
Demo of my modified MXR-185 EPROM-based drum machine. A lot like the Li...
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Demo of my modified MXR-185 EPROM-based drum machine. A lot like the LinnDrum (I think it even weighs as much), but a bit kludgier: you can't change patterns on the fly, it seems to lock up when pattern data isn't defined as blank, et al. Still, I don't have the manual and I haven't dug too deep into the programming, so it might be much cooler (or much buggier?) than I'm aware.
The internal architecture is similar to the LInnDrum LM-2, in that it uses multiplexed clocks and also multiplexes the drum samples. The drum samples are mostly stored on 2732 eproms and seem to be linear (not companded though, like on the Linn). One lame thing is that the sounds are stored on the EPROMs in a scrambled fashion, such that the addressing is not linear. This is a problem because you have to know the scrambling order to make your own EPROMs (though I think the Oberheim PROMMER can burn them). The toms and the open hat have VCA enveloping (using CA3280s). The shuffle is really stiff, though - the microprocessor cyclically drives the control voltage of a master 555 clock and it doesn't sound great at all.
I modified this one with the same tuning circuits I used for the LinnDrum LM-2. The only one I couldn't get to work was the crash cymbal. I also added pots that modify the control currents that go to the OTA's that VCA the toms and open hat, so that allows you to change the decay of those samples.
Overall, the sounds are pretty punchy, though, and I think sonically it could compete with other similar EPROM based machines.
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I have the schematics for my Poly-61 mods. I'd be happy to trade them for pictures of your friend's mods!
you can email me for them: kerrybradley AT earthlink.net
on the CS01, the pitch is controlled by a clock on the main custom chip - you can easily octave drop the CS01 by putting a D-flipflop divider between the clock drive and that main chip. filter CV should be doable if you tap into the CV drive that the envelope is using to sweep the filter with an external resistor (I haven't tried that, though). to adjust pitch, I've considered writing a little microcontroller app that converted an input CV to a clock frequency that would adjust the CS01's clock, but other more fun projects are up first.
Um, no, I haven't blocked you...? It must be a Youtube thing? I'll go make a reply to one of your comments and hopefully that'll reopen your ability to continue the comments.
Sorry for this - I have no idea why that would happen!
Because I can no longer add comments and i was actually hoping to get some feedback on what I was doing here, but am unable to .
If so I will post my own vid and continue from there as I am having trouble with both the wave generator chips and the vca vcf chips ,John Wharton