DD-20

Boss DD-20 GigaDelay. This is actually a rather complicated pedal, so this wiki page is going to be a good bit longer as well.

This double-pedal has been discontinued by Boss. While there are some complaints voiced on different forums about the lack of fidelity of the digital codec in the pedal, we haven't noticed an issue. That said, this pedal is very versatile and has many features that most players might not ever use in the course of the writing, rehearsal, or performance of their music. We are a bit surprised that production of the DD-20 was ended, but that the Boss RE-20 Space Echo continues to be produced. It would seem the DD-20 didn't sell as well as the RE-20. After going back and reviewing the Owner's Manual and writing the Wiki entry for this pedal, it's clear that as a pedal, the DD-20 is probably far more complicated than most casual musicians first expect. Compared to the RE-20, the configuration and functions are far more complicated. It's a fine pedal for a musician, but it takes a lot of working with and a lot of familiarity, so it's not hard to see why it was outsold by the more familiar and less complicated RE-20. Creating the familiarity necessary to be good with this pedal takes time.

Despite the fact that the DD-20 has been obsolesced by the Boss DD-500, it's interesting to note that for 40 years Boss has been successful with pedals employing broad "metal cap/flap"-style footswitches. With the emergent success of Dunlop/MXR, and along with legions of boutique and home builders that use the simple button switches, it seems Digitech/DOD has been coaxed away from their previous transition to the Boss-style "metal cap/flap" switch and back to the button switch. We believe that much of this seems to do with the fact that players have come to perceive that a button switch on a pedal signals that it's always true bypass. This seems in turn to have put Boss on the defensive and now Boss has returned to their mid 1970s-era button style footswitches for certain pedals, even if those switches don't actually make the pedals true bypass.

Controls

• Knob 1 - "E. Level": (Effect Level) Fully counter-clockwise results in an inaudible delay effect. Fully clockwise results in repeats that are just as loud as the original dry signal before tapering off.
• Knob 2 - "F. Back": (Feedback) Select the number and intensity of repeats starting at fully counter-clockwise with one repeat and fully clockwise resulting in enough repeats to begin self-oscillating.
• Knob 3 - "Tone": Turned fully counter-clockwise this knob emphasizes bass; turned fully clockwise emphasizes treble frequencies in the delayed signal. The knob at noon results in delay repeats without any frequency alteration.
• Knob 4 - "Mode": Use the Mode knob to select among several delay types:
  • Sound on Sound (SOS): Record loops with facility to record on top of the loop you've already recorded. On/Off light flashes in record/overdub mode, stays on in playback mode.
  • Twist: Causes an acceleration in the delay and shifts the delayed note pitch up when the left pedal is depressed. When the pedal is released, the delay slows down and the pitch drops back down. On/Off light flashes when left pedal is held down for this mode.
  • Warp: When the left pedal is depressed the all repeats are captured and then fed back to be repeated again. This results in ever increasing repeat feedback. When the pedal is released, the mass of built-up repeats slowly fade until pedal returns to original delay/repeat operation. On/Off light flashes when left pedal is held down for this mode.
  • Tape: Results in an effect similar to a tape delay where additional tape heads pick up signal and play it back. Holding down the On/Off pedal will allow you to use the Delay Time knob select between one or two tape heads in the delay effect.
  • Analog: Frequency-tuned to sound like an analog delay. Treble frequencies are rolled off for delay repeats.
  • Standard: Unmodified digital delay
  • Dual: Sort of a slapback effect, not unlike the "Tape" setting but you can set the time (50-300 milliseconds) between the "dual" delay repeats. Holding down the On/Off pedal will allow you to use the Delay Time knob select the spread in the "dual" delay effect.
  • Pan: Bounces the delay effect between the left and right stereo outputs
  • Smooth: A delay effect that "smooths" the repeats with the addition of some built-in reverb.
  • Modulate: Modulates the delay sound. As if you put your delay-wet output through a chorus pedal. Holding down the On/Off pedal will allow you to use the Delay Time knob to select the amount of rate and depth in the modulations of the delay effect.
  • Reverse : Delay repeats are played in reverse, creating a reverse-gated delay sound - almost like your instrument is a magnetic tape or vinyl record being played backwards.
• Knob 5 - "Delay Time": This is the largest knob and is used by other features in the pedal, but it's main purpose is to -
  • simple knob-turn: speeds up or slows down delay by milliseconds.
  • slight push-down with knob turn: speeds up or slows down delay by hundreds of milliseconds.
• Footswitch 1 (left) - "On/Off": This turns the pedal On and Off; helps set and control other features.
• Footswitch 2 (right) - "Select": Depending on the modes set for the pedal, this switch selects between the manual, and each of the 4 memory banks.
• Button 1 - "Tap": Tap this button to set the repeats to match your tempo. Holding down this button toggles the view of delay time from milliseconds to Beats-per-minute (BPM). Top of the unit has a "Control Pedal" jack which allows an additional pedal for use as tap tempo.
• Button 2 - "Tempo": Allows you to set the delay time in terms of note lengths, from quarter-note to triplets to dotted whole note. Please see Owner's Manual for a more in-depth description.
  • Buttons 1 & 2 together: "Light": This controls whether the backlight on the digital display is on or off.
• Button (red) 3 - "Write": This button is used to save a delay setting to a preset and how to use this is described below.
• Button 4 - "Select": Use this button to select from among the four banks of delay settings you may have previously saved.

Input/Output Jacks

• Input A (mono) - This is the primary input
• Input B
• Control Pedal Input - This jack allows one to plug in an additional control switch pedal for additional flexibility.
• Headphones Output - Headphones can be plugged in here for listening.
• Output A (mono - dry + wet)
• Output B (stereo or only Input B)
• AC Adapter Input - 9-volt power supply plugs in here.

There is a table below that gives better detail on the full range of possible uses of the input and output jacks.

General Information

As previously mentioned, this is a complicated pedal so the information and the instructions in this section aren't really offered for people renting our DD-20, but for people who own the pedal (and ourselves as a reference!).

If you're going to be using the DD-20 long-term in your signal chain, it'll help for you to configure the different modes on it so that it starts up the way you want when you power the pedal on.

Operation

We're starting with Operation, because every time anyone gets a new toy, they want to play with it right away. As described above, this won't make for success long-term, but we agree it's hard to read the manual first.

Left Footswitch

• Tapping the left footswitch toggles the delay on and off.

Right Footswitch

• holding down the right footswitch will toggle between selecting one of the memory presets, and the tap-tempo function, as shown by the LED indicator next to the footswitch.
  • In memory preset mode, quickly tapping the pedal iterates through the memory presets: Manual, and Presets 1,2,3, and 4.
  • In tap-tempo mode, quickly tapping the pedal to the tempo will set your repeats of the delay to the beat of the music.

Setting the Delay Presets

The DD-20 has 4 presets and a "Manual" delay setting. Here's the procedure for saving a delay setting to a preset:

Using the Looper

The SOS, or Sound-on-Sound mode has up to 23 seconds of sample time

1. Turn the MODE knob to “SOS.”
2. Press the ON/OFF pedal to start recording. Play what is to be used as the basic phrase. The remaining memory is indicated as a percentage in the display.
3. Press the ON/OFF pedal again to stop recording. Loop playback of the recorded phrase begins at the same time you press the pedal. The loop time is indicated in the display as shown below. The TEMPO indicator also flashes.
4. Overdub another phrase. Sounds are overdubbed during loop playback only while the pedal is held down. Continue to hold the pedal down as you play the phrase you want to record.

• If the ON/OFF pedal is held down only for a brief period, loop playback stops, and the recorded phrase is erased.
• By pressing the MEMORY/TAP pedal during loop playback, you can have the delay applied to the guitar sound as loop playback continues. However, you cannot overdub. To stop loop playback, press the MEMORY/TAP button again (we recommend Pedal Mode 2 or 3).

Setup

Here's the boring part of using the DD-20, but setting up the pedal will both set your expectations on how it will work, and will help build the familiarity that you need to work with the pedal with a minimum of difficulty.

LED Indicator

Changing the LED lighting of the 4 memory presets was one of the first things we wanted to do, but it took a long time to find. In order to change the memory preset indicator lights from the number of lights changing to the position of the lights changing, hold down the WRITE and SELECT buttons down while plugging in the AC adapter. All the LED position lights will flash. Using the SELECT, you can toggle between Led1 mode (position) and Led2 mode (number of lights). Once chosen, pressing the WRITE button saves this setting. From that point, until changed or reset, the pedal will startup the LEDs indicating in this mode.

External Pedal Control Modes

Setting the control modes on the DD-20 allow you to plug an additional momentary or latch pedal switch into the top and then to be able to use that plugged-in pedal for your preferred function:

1. (Ctl1) Mode 1 only works with a latch (on/off) style (example: Boss FS-5L) pedal. Turns the delay on and off.
2. (Ctl2) Mode 2 only works with a momentary (tap) style (example: Boss FS-5U) pedal. Sets the tempo of the delay by tapping in your tempo.
3. (Ctl3) Mode 3 only works with a momentary (tap) style (example: Boss FS-5U) pedal. Iterates through the memory presets.

To configure the Control mode, when powering up the DD-20 (plugging in the AC adapter), holding down the right footswitch allows one to choose between the three control modes. The factory preset is for control mode 1 (Ctl1), as shown in the digital display. To change the control mode, power up with the right footswitch held down. Use the select button for the desired control mode, and then press the WRITE button to save the control mode. From that point, until changed or reset, the pedal will startup in this control mode.

Output Modes

Output modes are not to be confused with the control modes, described above. The output mode selected determines both:

1. which output jacks get signal supplied to them, and
2. which signal level is sent to those output jacks.

This is part of the required "familiarity" described above that this pedal requires in order to make using it easier.

• output modes 1 & 2: instrument level: use between your instrument and the amplifier
• output modes 3 & 4: line level: use in the effects loop of your amplifier
• output modes 1 & 3 (odds): Input A & Input B are combined
• output modes 2 & 4 (evens): Input A & Input B are separated

To configure the Output mode, when powering up the DD-20 (plugging in an AC adapter), holding down the left footswitch allows one to choose between the four output modes. The factory preset is for output mode 3 (Out3), as shown in the digital display. To change the output mode, power up with the left footswitch held down. Use the select button for the desired output mode, and then press the WRITE button to commit to the output mode. From that point, until changed or reset, the pedal will startup in this output mode.

Using the Output Modes

We tried listing out how to use the output modes with the output jacks individually, but when we attempted to combine this with the understanding of how to use a single input versus two inputs, it got pretty difficult to conceptualize how everything's supposed to work. We found that building a lookup table provided the cleanest presentation and understanding:

Output Mode	Operation	Input Jacks	Output Jacks	Sound Mix	Notes
1	-10dB (instrument)	Input A only	Output A only	dry + wet	"stereo" * signal
1	-10dB (instrument)	Input A only	Output A Output B	dry + wet dry + wet	"stereo" * "stereo" *
1	-10dB (instrument)	Input A Input B	Output A Output B	dry + wet dry + wet	Output A: Input A dry + wet Output B: Input B dry + wet
2	-10dB (instrument)	Input A only	Output A only	dry only	mono signal (dry only)
2	-10dB (instrument)	Input A only	Output A Output B	dry wet	Output A: dry Output B: wet
2	-10dB (instrument)	Input A Input B	Output A Output B	dry + wet dry + wet	"stereo" * "stereo" *
3	+4dB (line level)	Input A only	Output A only	dry + wet	"stereo" * signal
3	+4dB (line level)	Input A only	Output A Output B	dry + wet dry + wet	"stereo" * "stereo" *
3	+4dB (line level)	Input A Input B	Output A Output B	dry + wet dry + wet	Output A: Input A dry + wet Output B: Input B dry + wet
4	+4dB (line level)	Input A only	Output A only	dry only	mono signal (dry only)
4	+4dB (line level)	Input A only	Output A Output B	dry wet	Output A: dry Output B: wet
4	+4dB (line level)	Input A Input B	Output A Output B	dry + wet dry + wet	"stereo" * "stereo" *

Additional Notes:

• * We're using the Boss DD-20 Owner's Manual "stereo" terminology. What they mean by "stereo" seems to be a mono signal that is dry + wet. We believe this use of the term "stereo" is incorrect but we've chosen to use it in order to maintain consistency with the Owner's Manual. It's probably more meaningful to your use of the pedal if you read column 5, "Sound Mix", than column 6, "Notes".
• If in Output modes 2, and 4, if the pedal is "off" then no signal will go through Output B.

Pedal Manual

https://static.roland.com/assets/media/pdf/DD-20_OM.pdf

Phase Inversion

The fact that there is no schematic available means that we're unable to determine, without an oscilloscope, if the DD-20 inverts the signal phase. That said, the schematic is probably so complicated (and given that there's a digital component as well) that it would be almost impossible for the lay person to be able to trace and determine whether this pedal inverts. Once we get it up on our bench with an oscilloscope, we'll report here if the phase is inverted.

Modifications

It is possible to lower the hiss that some hear in their DD-20 Gigadelays. We will likely be making this modification ourselves to our own pedal as soon as is reasonably possible.

From:

• http://music-electronics-forum.com/t16606/

Recently I became interested in improving the sound of my DD-20 Giga Delay. To that end I replaced the original cheap/low performance M5218 and NJM2100 op amps with modern low noise/high performance OPA1612 and OPA2365 respectively. Additionally, I added film bypass capacitors across the electrolytics which couple the various analog stages. Bypass capacitors help retain transparency in AC coupled circuits.

...

(later in the thread...)

The initial change to OPA1612s raised the quiescent current draw of the DD-20 to over 200ma which was a slight cause for concern; although I tried to track down possible oscillation I was unable to find anything with an oscilloscope. However, after switching to OPA1642s the current draw is now closer to 180ma, with perhaps slightly less background hiss.

Sometime soon I'm planning on revisiting the high-cut capacitors in the delay path because I'm getting a little aliasing distortion when used with my homemade A/DA flanger. I don't mind to lose a little bit of treble on the delayed signal. My biggest reason for making modifications was to open up the frequency response in the dry/bypassed path. Without modification, the DD-20 is a bit of a "tone sucker" IMO.

So it appears that it's possible to exchange the M5218 opamps with OPA1642s and the NJM2100s with OPA2365s. This would require some delicate work with desoldering braid and very clean resoldering in of the replacement opamps. OPA (also known as Burr-Brown) opamps are known to be very low-noise.

Schematic

None available.

Artists

• Alex Skolnick

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Additional Sources

1. http://www.bossarea.com/boss-dd-20-digital-giga-delay/
2. https://www.youtube.com/watch?v=1gTiHUSg6G4
3. https://www.youtube.com/watch?v=0X-Mvo-Sy2M
4. http://equipboard.com/items/boss-dd-20-giga-delay-digital-delay-pedal