Korg SDD-3300 Triple Digital Delay

pic of Korg SDD-3300

pic of Korg SDD-3300

Last Update 08-20-2011

The Korg SDD-3300 is an effect tweaker's delight and is one of my favorite effect boxes.  Two things have to be declared right up front:
So what is a "triple digital delay"?  Well it's like having three sophisicated delays with an audio patchbay and a couple of mixers all in an itty bitty two space rackmount box. And it's programmable with MIDI.  Each delay goes from 0.5ms to 500ms, has highpass/lowpass filtering in the feedback loop (but alas, no filtering in the effect input), and has a pair of LFOs (triangle waveshape only) for sweeping the delay.  You can route the output or feedback of any one delay to the input of the other two, and you can invert the audio signal. An impressive block diagram is here.  Quite a lot of power in this underrated effect box, but you need to know the concepts of modulated delay processing (chorus, flanging, phasing, quadrature effects, ensemble effects, etc) to exploit it to the max.  Harmony Central used to have a good primer on effects based on delay processing but it is now 404.

Like I said, don't expect instant gratification.  This box demands that you do your homework.  It does have factory programs, but they don't show off the box.

So what is unique about this box?  When I saw one in a store years ago, my impression was "what am I going to do with a triple digital delay?!?"  At the time I wasn't aware of the internal features and even if I was I would have no clue how to apply them.  In those days when I thought of "delay" the words "echo" and "slap" still permeated my narrow thinking.  Many moons later I learned the architecture of sophisicated effects such as quadrature chorus, ensemble effects, and thru-zero flanging. 

I had also grown bored of the standard FX offerings in multiFX boxes - I wanted more.  The multiFX I had been using colored the original sound too much and it clipped too easily in its internal digital domain, so the S/N ratio suffered.  The SDD-3300 had neither of these problems - when you listen to the unprocessed and processed mp3s below, note how the timbre of the original signal is unaltered.

A chorus is a 20-30ms delay which delay time is modulated by an LFO.  Many pseudo-stereo chorus units "cheat" by using an inverting the chorus output to get a 180 degree out of phase signal for a second "stereo" output.  Well if you sum those signals to mono, they cancel out and your chorus effect disappears, along with your original signal if you're using a mix of wet/dry in both outputs.

A quadrature chorus has dual chorus units whose L-R LFO waveshapes are offset by 90 degrees.  Unlike pseudo-stereo chorus units, the quadrature chorus does not cancel out when summed to mono.  The SDD-3300 has a neat feature where you can phase lock the LFOs between each of its three delay units. Quadrature chorus is cakewalk on the 3300; just use a pair of delay units, pan them L-R, set the LFOs 90 degrees apart, and modulate to taste.  This is what it sounded like with my Memorymoog:

Quadrature Chorus mp3s
Unprocessed Signal
Quadrature Chorus effect

Big deal, right?  Let's get more sophisicated and dial up an ensemble effect.  Remember those 1970s pop/rock songs with that really sweet angelic high string sound?  That was an ARP Solina/String Ensemble, built by Eminent in Holland and licensed to ARP for sale in the USA.  The key to the Solina string sound was its ensemble chorus effect.  All you needed was a nasal static organ sound, feed it into this ensemble chorus, and you had instant strings.  Eminent had a patent on that effect, and other string machine makers tried their own variation of this effect to circumvent the patent but the Eminent architecture remains unique.  However the Solina string sound defies sampling - the ensemble chorus is mysteriously resistant to sampling and I have yet to hear a sample that does it justice.  As the vintage craze progressed, so did the interest in the Solina.  But there wasn't a sampler out there that could capture the Solina, and polyphonic analog synths tried in vain to nail the sound.  Probably the best Solina impersonator is the Alesis Andromeda - Brian Kehew dialed up "String Ensemble" for the factory bank, in preset bank 2 #065.  But the Andromeda has a vast set of sound shaping tools that go beyond any other polysynth, even softsynths or VAs.

So if you can't sample a Solina and you can't get that sound on a polyphonic synthesizer save the Andromeda, how do we emulate a Solina?  A popular remedy was to extricate the Solina ensemble chorus circuit board and shoehorn it into a dedicated box with I/O jacks.  That was a solution until the supply of used Solinas started depleting and our landfills became recipients of scavenged Solina carcasses.  The BBD delay ICs for the Solina have been out of production since the 1970s and the last maker of BBDs (Panasonic) ceased production in 2001 so cloning the ensemble chorus with original parts is out.  The only option is to recreate the Solina ensemble FX with digital delays, and that's where the SDD-3300 comes in.  What is the ensemble chorus?  It is not one, not two, but three modulated delays.  Hmm, SDD-3300 is a triple delay unit (a light bulb goes off in my head).  Each delay in an ensemble effect is modulated by a combination of two LFOs.  Hmm, each delay in the 3300 has a pair of LFOs (those bulbs are getting brighter).  The LFOs in an ensemble effect are offset by 90 and 270 degrees.  Hmm, the LFOs in the 3300 can be phase offset (those lights are blinding now).

The SDD-3300 has a factory string ensemble patch, but they didn't quite get the emulation right.  I did some research in the Analogue Heaven search archives and found the architecture of an ensemble chorus.  Turns out that the dual LFOs run at 6hz and 1hz with three derived signals of each at 0, 90, and 270 degrees.  Each delay unit is modulated by a mix of the phase offset signals.  It is also possible to route the three chorus units for a stereo signal.  Well I dialed up everything on the SDD-3300 (with the exception that the maximum phase offset of 240 degrees), dialed up a simple nasal ramp voice on the Memorymoog, and this is what it sounded like:

String Ensemble mp3s
Unprocessed Signal
String Ensemble effect

So non-keyboardists are now retorting "what am I going to do with a string ensemble effect?!?"  Well boys and girls, if we tweak the string ensemble chorus it isn't hard to get a choir ensemble patch.  Choir ensemble effects can make simple vocal harmonies sound like a big group:

Vocals through Choir Ensemble mp3s
Unprocessed Signal
Vocals thru Choir Ensemble effect

A simple Memorymoog analog synthesizer voice through a choir ensemble effect, and you have an abbey of monks:

Analog Synth through Choir Ensemble mp3s
Unprocessed Signal
Choir Ensemble effect #1
Choir Ensemble effect #2

Guitars don't sound half bad either:

Guitar through Choir Ensemble mp3s
Unprocessed Signal
Guitar thru Choir Ensemble effect

To my knowledge, not one multiFX box offers an ensemble chorus patch.  THAT is why the SDD-3300 is a unique box.

The phase-offset LFOs are a feature I exploit a lot on the SDD-3300.  Check out these effects:

Assorted Chorus mp3s
Unprocessed Signal
Stereo Sweep
Dual Chorus
Quad Chorus

Triple Delay Flanger+Chorus
Stereo Imaging

Hear how the SDD-3300 can produce a massive pipe organ sound (reverb is an Eventide 2016):

Pipe Organ mp3s
Unprocessed Signal
Pipe Organ effect

The ability to cross signals between delays gets some unique effects.  Here is a Memorymoog thunder patch through a neat "Valley Echo":

Thunder mp3s
Unprocessed Signal
through "Valley Echo" effect

If you're willing to tackle the learning curve, you will reap sonic rewards out of this box that no multiFX can do.


The SDD-3300 has 64 memory slots, MIDI In, Thru, and Out, a 2x40 LCD screen, menu page buttons, and six sliders for editing the sounds. This is five better than one or none at all on most FX boxes and is much better than increment/decrement buttons, but sometimes I confuse the sliders as I move between menu items. You can name each patch.  It has a MIDI program mapper and you can load/save a single program or the whole kit-n-kaboodle.

The delays can go from 0.5 to 500 milliseconds at 16Khz bandwidth 88Khz sampling rate and you can apply 12dB lowpass and/or highpass filtering to the feedback path. If you chain the three in series you can get 1500ms (1.5 seconds) of delay. I have read reports of 3300s with each delay out to 1500ms, but that sounds more  like someone confused total system delay of 1500ms.  The delay resolution varies depending on the range you're in; the longer the delay, the more coarse the resolution. Each delay has two LFOs, and you can control the phase of each LFO relative to the LFO in the first delay or you can run them asynchronously.  You can get up to 110% feedback for runaway loops. Each delay can be used as sampling units for playing over looped audio, and you can assign a MIDI note to trigger each unit.

Three input sliders adjust the levels at the rear panel jacks.  The input sliders have enough control to accept anywhere from -10dBv to +4dBu signals so it will work with pro audio gear or with guitar rigs.

There's an input mixer and an output mixer for each delay unit, with levels for any of the three input busses, feedback busses, output busses, and effect busses. Not only that, you can invert *any* of the inputs off the busses. This allows you to configure the delay units in parallel, in series, or any combination, and you can cross feedback lines to your taste. The nicest plus is that you can tap any combination of effect lines to the outputs for the ultimate stereo processing. It's like having a programmable patchbay for three delay boxes. This is one *seriously* configurable box.

There's a peak level LED above the three master input sliders and a four segment input level LED for *each* input and output mixer. The LEDs are also critical to make sure you're not clipping anywhere in the system, which is easy to do. Once you've "normalized" the levels and made them as even as possible, you'll get the best S/N ratio. I have seen signals go into +6dB without any audible clipping.  Let me tell you it's a *gas* watching these things dance in a complex stereo effect.

On the rear panel we have input, direct output, mix output, hold/trig, and level control for each independent delay unit.

Changing the delay time interrupts the audio signal which is common for a digital delay, but it's about a one second wait before the audio comes back in. Likewise with the bypass function - when you enable it the effect does not come on immediately. This is not a box you'd use for live realtime tweaking.

The manual is well written and tells you how to operate the unit, but it doesn't give you any basics of delay processing, IE parameters for chorus, flanging, doubling, etc. The block diagram on the top of the unit is reproduced in the manual. It even provides the MIDI Sysex codes for remote editing!

Cons: On the SDD-3300, the LFO intensity is *not* attenuated with a VCA, it's software attenuation. In other words, a smooth waveform at full intensity (31) becomes very discrete at low intensity values (especially below 10). The firmware just feeds lower dv/dt to the DAC, resulting in a very coarse stepped sine wave with the peaks flat for almost 1/4 of the cycle, which means that the sweep isn't continuous. It was very obvious on the scope, watching the delayed signal being modulated in discrete rather than continuous motion. I found that it's safe using intensity values equal to or greater than 20.

Hard to call this a "flaw", 'cause in my attempts to duplicate a couple of gorgeous sounding SDD-3300 stereo patches on the SDD-1200, the "flawed" 3300 still sounded superior.

All mp3s encoded with RazorLame.

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