Korg DW8000 built in Chorus effect?

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Korg DW8000 built in Chorus effect?

Postby NCChao1268 » Tue Jul 25, 2017 7:16 pm

Have owned a Korg DW8000 for a few months and loving it, was wondering if this synth has a built in chorus effect in it? The manual claims that it has one as well as the Digital Delay. Anyone know how to create the chorus effect?

-Nathan
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Re: Korg DW8000 built in Chorus effect?

Postby commodorejohn » Tue Jul 25, 2017 7:23 pm

There isn't, strictly speaking, a dedicated chorus effect. But the delay time can be very short and also LFO-modulated, giving something like a basic chorus sound.
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Re: Korg DW8000 built in Chorus effect?

Postby madtheory » Wed Jul 26, 2017 10:33 am

I'd disagree about it being "a basic chorus sound".

Some of the classic chorus effects like the Juno 6/60/106 had only one delay line. So obvioulsy it does not detract from the sound, even though it does seem "basic". Of course there are other classic units like the Solina which used three delay lines. Those classic Rolands are analogue delays, so the effect has limited bandwidth and some distortion, which makes it nice. The DW era Korg digital delay lines are highly regarded- they also have limited bandwidth and some distortion, which is nice in a different way :)

To get a Juno type chorus, the delay should not be more than 12.8ms (that's the max the BBD chip inside can do) and the LFO should be a sin (although in the service manual it looks more like a soft sawtooth!). I don't know what the actual delay time is in the Juno, nor the LFO rate. You'd have to play around with it.
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Re: Korg DW8000 built in Chorus effect?

Postby Mooger5 » Wed Jul 26, 2017 4:46 pm

Number of BBDs per synth:

Junos: 2

DW6K: 1

Poly6: 3
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Re: Korg DW8000 built in Chorus effect?

Postby madtheory » Wed Jul 26, 2017 5:39 pm

Ah, OK that makes sense as the Juno is stereo. But aren't DW series DDL not BBD?

Boss CE-2 is AFAIK a single BBD (mono), and that one sounds very very nice :)

And compared to the Junos and the Polysix, the DW has the advantage of dual detunable (admittedly digital wave) oscillators.
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Re: Korg DW8000 built in Chorus effect?

Postby Mooger5 » Wed Jul 26, 2017 7:01 pm

While the Korg DW-8000 uses a DDL with variable parameters, the DW-6000 uses an old style BBD for its Chorus effect. They sound different.

The DW-6000 despite using a single delay line, is still stereo. The panning is made by in-phase and out-of-phase opamps in series with the BBD.
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Re: Korg DW8000 built in Chorus effect?

Postby Jabberwalky » Wed Jul 26, 2017 9:45 pm

The Korg DDL is creamy, and amazing. I'd almost go as far to say it's half of the Dw8k sound. The same delay was also in the much maligned Korg Ds8. As far as I know, the same delay is a rack unit, the Korg SDD2000
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Re: Korg DW8000 built in Chorus effect?

Postby Mooger5 » Wed Jul 26, 2017 11:31 pm

And the arp can be programmed like a step sequencer! Tricky but doable.
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Re: Korg DW8000 built in Chorus effect?

Postby madtheory » Thu Jul 27, 2017 6:41 am

Ah cool! I thought the DW8000 DDL might be related to the SDD2000 alright. It's the U2 delay :) Apparently the SDD3000 has a pre amp that guitarists love.

Interesting the DW6000 has a BBD. Does the Poly 800 mark 1 have a BBD as well? Pretty sure the mark 2 is a DDL.

Phase reversal is IMO probably the nastiest way to get a stereo effect. Sum those to mono and the effect disappears. Useful at times if you want something to be very far out to the sides in a mix, but only to be used sparingly! The Juno chorus gets the effect in a much better way, it's basically two slightly different modulated delays, right? Sum that to mono and it's still there :)

I've been trying to find what the delay time (s) and LFO rates are for the Juno, no luck yet.
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Re: Korg DW8000 built in Chorus effect?

Postby Mooger5 » Thu Jul 27, 2017 2:36 pm

madtheory wrote:
Interesting the DW6000 has a BBD. Does the Poly 800 mark 1 have a BBD as well? Pretty sure the mark 2 is a DDL.
Most probably mk1=bbd and mk2=ddl yep.

Phase reversal is IMO probably the nastiest way to get a stereo effect. Sum those to mono and the effect disappears. Useful at times if you want something to be very far out to the sides in a mix, but only to be used sparingly!

They´re not hard panned left and right.There´s some phase inverting and reverting with gain adjustments going on both sides for eveness.
For instance the dry signal gets through both outputs, so when the effect is disengaged the output is dual mono.
With Chorus ON the left channel outputs the inverted sum of the dry signal and the effect. The right channel outputs the inverted sum of the dry signal with the reverted sum output of the wet left channel.
Besides, a chorus effect is not static. It´s mainly a modulated delay so there will be pitch wobbling.
By changing delay times you´re altering phase. Phase change is only perceived when compared to the original signal. The motion between channels is hence due to the artifacts created by the complex phasing and dephasing and the modulated delay times.
Merge both channels to mono and the atifacts will cancel out leaving just the wobbling, which confers the Chorus its primary role, that is creating the illusion of double.tracking.

The Juno chorus gets the effect in a much better way, it's basically two slightly different modulated delays, right? Sum that to mono and it's still there :)

I've been trying to find what the delay time (s) and LFO rates are for the Juno, no luck yet.


More on this later, sorry.
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Re: Korg DW8000 built in Chorus effect?

Postby madtheory » Thu Jul 27, 2017 3:40 pm

Mooger5 wrote:They´re not hard panned left and right.

On the Korg? They are though. Outputs are direct from op amp + and - , IIRC. Very simple and cheap way to make "stereo".
Mooger5 wrote:For instance the dry signal gets through both outputs, so when the effect is disengaged the output is dual mono. With Chorus ON the left channel outputs the inverted sum of the dry signal and the effect. The right channel outputs the inverted sum of the dry signal with the reverted sum output of the wet left channel.

Except for the first sentence, that doesn't make sense. Why? Because there's only one delay line! So the chorus effect is identical on both channels, except that one channel is inverted WRT the other. As I already said, when output is summed to mono (for example if you pan the two channels centre on a mixer, or an FM broadcast reverting to mono on the receiver) the effect disappears and dry sound remains.
Mooger5 wrote:Besides, a chorus effect is not static. It´s mainly a modulated delay so there will be pitch wobbling.By changing delay times you´re altering phase.

That is true when there are 2 delay lines with independent LFO. So it does not apply to the Korg. Roland did not need to do the polarity trick, because the two delay lines are "phasing" WRT each other all the time, as you say :)
Mooger5 wrote:Merge both channels to mono and the atifacts will cancel out leaving just the wobbling

Not sure what you mean by "artifact"s but on the Juno you will hear chorusing when L+R are merged, on the Korg you will not.
Mooger5 wrote:More on this later, sorry.

Looking forward to what you find out. Why apologise? :)
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Re: Korg DW8000 built in Chorus effect?

Postby Mooger5 » Thu Jul 27, 2017 7:19 pm

Well, download the service manual here: http://www.synfo.nl/servicemanuals/Korg ... MANUAL.pdf
and see for yourself.

You´re talking like both channels output the effect at identical levels when they don´t. On the left channel the effect is at unity gain and on the right channel it´s at just a quarter. As both have the effects at opposite phase, subtract the difference when merged together and you still get 75% of unity gain on that radio station.
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Re: Korg DW8000 built in Chorus effect?

Postby madtheory » Thu Jul 27, 2017 11:58 pm

Ok. I'll take a look at that tomorrow. So there seems to be a level difference- not the phase difference you claimed though. Nor is there phase modulation, which you also claimed.

A level difference is strange though. It would mean the sound is akwsys lop- sided!
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Re: Korg DW8000 built in Chorus effect?

Postby madtheory » Fri Jul 28, 2017 10:00 am

Checked it out. KLM-711 chorus board. Quite different design to the SDD2000, that one is more economical with ICs. It is a single delay with one output polarity reversed. But DW6000 seems to be using the M2516 to get a buffered polarity reversal on one channel. I don't see a level difference between channels, unless you mean the switched 100 ohm for "Low" output? Both channels are identical in that regard though. Or are you thinking of the NE570? That has two channels. But this circuit only uses one of them.
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Re: Korg DW8000 built in Chorus effect?

Postby Mooger5 » Fri Jul 28, 2017 6:15 pm

If the ohmic values were correctly printed, the (dry) left channel will be louder by one fifth in all circumstances. It´s also the channel indicated by Korg to be used for Mono. I could explain it in detail later.

I goofed where I said the chorus was only at 25% (in a static situation), on the right channel. I forgot to reverse the polarity after the second opamp stage in my calcs, which means it´s actually at 75%.

25% of the total chorus is what you+d get in case both channels merged to mono BUT it´s not so linear. Why? Because the chorus is continually changing its polarity once engaged. It´s only either ON or OFF, so there´s no messing around with its parameters. Thus, when the chorus changes polarity it goes back to those 75% level on the right channel and, at the same time, around 25% on the left channel. This makes for a sort of auto-panning effect when listening in stereo.

The 6000 was my first pro keyboard and I have very fond memories of it. I don´t recall it ever having one channel louder than the other.
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