Korg Forums

[Timo]

[Daz]

I don't think the Radias Filter(s) will self resonate as some real analog synths are able to when there has been and is NO input from the oscillators/noise gen etc. (i.e. totally unsolicited, spontaneous self resonance)

As I understand it that behaviour occurs because there is in reality ALWAYS a signal present at the input of the filters on some of ye olde analog synths; a little leakage from the oscillator circuits or some other electrical noise. That is enough to trigger the filter to resonate when the filter resonance is set to a very high value. Very high resonance means amplify a particular frequency range a lot ... so even a tiny inaudible amount of noise with the appropriate frequency contained in it will be amplified and become audible.

In a digital synth, when the oscillators and noise gen aren't singing, the input to the filter is just a whole bunch of zero's. Pure silence ... there are no noisy 0's So the filter really is getting no input to work with and hence won't just start resonating on it's own.

So the alternative is to send in an impulse, a brief moment of noise to trigger the filter to self resonate.

For example ... if you start from an Initialized Program and edit Timbre1 like so :

1) Turn the volume of all the OSC's to 0
2) Use EG3/VPatch1 to send a very short (attack=0 decay=0!! sustain =0) burst of noise into Filter1
3) Set the Resonance on Filter 1 to 127 and "tune" the filter by setting Filter Cutoff and Keytracking

Filter 1 will self-resonate (in the sense that it is making a sound with no continual audio input source). You can play the filter using the keyboard, as a pitched instrument and attract pets from around the neighbourhood with some very high frequency notes

Here's a screen grab from the Radias editor after making the above changes, showing the values I worked with :





Daz.

[meatballfulton]

[Daz]

[Khazul]

If your look for a VA that can sound more like a traditional analog, then I wouldnt recommend the radias - its filters just aint bitey enough, and TBH its oscs are just a little bit on the thin side.

Some others

Nord G2 - seems to do a reasonable job on both osc and filters, but not played with it much.
Nord Lead 3 - not played much, but seems to manage an analog sounds - cant really usefully comment on oscs and filters beyond - 'not bad'
Virus B/C/TI - oscs just a little bit thin, but filters have alot of character and so can be very passable depending on key range.
Alesis Fusion - very good oscs, filters not quite characterful enough - better than average, let down by only one filter.
Alesis Ion - as Fusion, though not sure basics osc sound is as good, more filter options - can be quite convincing at times.

Alesis Andromeda of course an excellent choice - if you want analog - get analog -can be hard to get hold of. Personally I've never been even slightly tempted by a moog little phatty, but could be good for you - just a mono tho.
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--- The Studio & Noises ----- Adam G @ MySpace ---

[chinard]

ok, one thing to pay attention to here if you are trying to get your filters to self-oscilate is the signal path.

In most synths including radias, the path is VCO => VCF => VCA
This means that even though your filters are oscillating you wont be hearing it because the envelope in the VCA is not letting sound through if there is no keys pressed.

what you need to do to hear it is to turn the other oscilator's mix down to 0, crank the resonance, set filter keyboard track to 100% and try playing the keyboard. if you get things set just right you should be producing a nice sine-tone from the filters.
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[meatballfulton]

OK a couple of things in reply to the last few posts:

-- I have owned quite a bit of analog, some vintage and some modern. I just sold off a big synthesizers.com modular system (patch cords and all) last summer when I was losing my job and had bills to pay. I don't expect a VA to sound just like analog, I would like one that behaves close though which is why I started poking around with the Radias filters. I'm a hobbyist and a Radias rack is far cheaper than real analog and has many goodies not available in analog (or at least not without $$$$$$$$)...the FX, sequencers, full MIDI control of all knobs, etc. plus it's in tune as soon as you turn it on

-- Daz, your understanding is more or less correct but in analog filters I'm not really sure whether it's residual noise or not that triggers the oscillation. When filters go in to self-oscillation they are in an unstable feedback loop. If there is no gain limiting in the circuit the filter output will just continue to rise until it hits the power supply rails and clips. I once owned a PAiA analog synth that did this, making really ugly squawks at high resonance because of clipping. I finally soldered in some zener diodes to make a crude limiter and the filters became controllable. You can hear an example of that here. On some analog filters, the design itself limits how high the resonance gets so it won't self oscillate. There are many vintage analogs (esp. those with 2-pole filters) that will not self oscillate.

-- Yes, I made sure the amp was wide open while I was messing with the filters.

Anyway, enough about the filters...beaten that one to death
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I sing the body electric

[nemmo]

I think it sounds pretty analogue.

[dulcimoo]

...add just a hair bit of noise if you need to make the filters self osc. My filters do so and very sweetly too.

[gdh]

I hate you guys, I hate you guys, I hate you guys!!!! ok so who is going to buy me a new monitor, I decided to get the Voyager, MiniD and radias to self osc. all at once. Geez my monitor sure didn't like it, glad I have a warranty.

[meatballfulton]

Just want to thank everyone here for all their input.

After a lot of investigation and playing around with a demo at GC a few times I picked up a Radias-R today.
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I sing the body electric

[Khazul]

Enjoy!
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--- The Studio & Noises ----- Adam G @ MySpace ---

[nemmo]

Nice.