The MXR M-113 Digital Delay has been one of the most popular first generation audio delays, as it had a good quality but was more affordable than the previous processors. Introduced in ’76 at around 1000 USD, it was still expensive, but a lot less than the other digital delays available in the market.
MXR was specialized in guitar pedals, this delay was instead offered in a 19″ rack unit and, same as the other effects of the professional rack series, (Flanger/Doubler, Graphic EQ, Pitch Transposer) became very popular and used by famous artists such as David Gilmour, Frank Zappa, Roger Waters, Brian May and Mike Rutherford.
Modular
MXR memory module
To contain costs, a modular architecture was chosen. Optional memory boards were inserted in slots, to increase the delay time, but these were pretty expensive, costing almost like a complete unit.
MXR Digital Delay Internal Cards
Digital noise..well not only that! :D
Unfortunately the M-113 Digital Delay, same as its collegues of the same period, is pretty noisy and not only referring to the actual standards. Apart digital noises always present, these processors have a marcated tendency to generate audio hum.
The Model 113, Digital Delay has a maximum bandwidth of 20KHz, but this decreases with longer delays, down to 2.5KHz. The longer the time between repetitions, the tighter the passing frequency band, being reduced through antialiasing filters (HPF and LPF) the more the delay time is increased.
MXR Digital Delay Test Drive
As there are several video examples already of this delay tested on guitar, I thought it could have been a good idea to try it, using some unusual but hopefully interesting sounds.
To record, I used a dbxDI box and the signal sent to a Universal Audio610 tube preamp, even taking all possible counter-measures, still a bit of hum is audible.
On the examples below, I feeded as sound source, a sweep from the filters in feedback of an old Korg MS-50 synthesizer, some piano chords I had recorded from a real piano and a couple of seconds of an oldschool reggae classic.
MXR Digital Delay, Test-01, (MS-50 Filter Sweep)
01) Dry sound, straight from the MS-50.
02) Delay Range 160ms, Delay Time x2, 50% mix and maximum regen (feedback)
03) Delay Range 160ms, Delay Time 0, 50% mix and maximum regen (feedback)
04) Delay Range 160ms, Delay Time 1/2, 50% mix and maximum regen (feedback)
05) Delay Range 160ms, Delay Time Sweep 01 (moving the Delay Time knob)
06) Delay Range 160ms, Delay Time Sweep 02 (moving the Delay Time knob)
MXR Digital Delay, Test-02 (Piano)
I chose these piano chords I recorded as, having long decays, are ideal to test the effect of short repetitions, when modulated. The effects space from phasing to complete madness. The last one is a strong modulation at the higher band of frequency of the sweep, reminding the effect of a ring modulation.
1) Dry Piano
2) Delay Range 1.3ms, 50% mix 3) Delay Range 10ms, 50% mix
4) Delay Range160ms, 50% + Mod
5) Max Frequency Mod
MXR Digital Delay, Test-03 (Rhythmic Loop)
On the following examples, let’s try something that really impressed me first time I played with a Powertran (An article on it, is coming soon). On the MXR the feedback has a faster decay and there’s not the “freeze” function, but the effect it is interesting, too. Once the delay is at tempo with a rhythmic pattern, having adjusted the decay time knob, all Delay Range buttons create a different version of the pattern, but on different speeds. Being the buttons based on a double time sequence, all these are compatible in tempo. Let’s experiment with a small classic reggae riddim loop:
1) Dry loop
2) Loop effected as sort of Beat Repeater
MXR Digital Delay, Test-04 (MS-50 patch)
Last example, this time using a more complex sound from the MS-50.
1) Dry MS-50 sound
2) MXR MS – 50%MIX, 75% Feedback
3) MXR MS – 50%MIX, 75% Feedback + Mod
4) MXR MS – 50%MIX, 75% Feedback + Fast Mod
**Updated February 27, 2026**
Refreshed the English for better flow and readability. Core ideas unchanged — still celebrating the "procrastinated" sound of vintage echoes and delays. Planning audio updates and continuations (RE-201 Perry dub, SDE-3000 Mad Professor style) soon. OSO certified as always! 🎶
Echo, unlucky nymph
Since ancient times, places destined for public speech or shows were chosen based on their acoustical characteristics. A powerful voice heard near a sharp rock wall could impress the audience and add a magical ingredient, as if the forces of nature were happy to help the venue by amplifying the desired message.
Nymph Echo on a Roman painting
The Echo was so important that it had a dedicated character in Greek/Roman mythology:
Echo, a mountain nymph, helped Jupiter distract his wife Hera with endless discussions while the god was cheating on her with other nymphs. Realizing the trick, Hera cursed Echo, removing her ability to speak. The only sounds she could make were the endings of the words she heard. As usual in ancient myths, the story ends in tragedy, with Echo dead but her beautiful repetitive voice forced to live on forever — only in the most remote and inaccessible places.
Natural echoes or reverbs from special rock formations or the reflective shapes of caverns were used to create dramatic effects on human speech, chants (and minds) for ritualistic or entertainment purposes.
The Art of Procrastination
Builders could, over time, recreate nature’s vast spaces through architecture. The possibility of impressing the public with special effects slowly moved from remote areas to cities. Acoustically shaped amphitheaters, and later closed spaces like theatres and religious buildings, were constructed for this purpose. Music began to be played in dedicated “chambers” or “halls”, with reflective walls and high ceilings, to achieve long reverberation times and decays.
At the beginning, recording studios captured the space where musicians played, with microphones pointed toward ceilings or walls to pick up the returning delayed sound, which was then mixed with the original.
Later, rooms were dedicated exclusively to reverberation. A sound from the control room was sent to an amplifier in an empty room or chamber, completely bare and lined with reflective materials. One or more microphones captured the effect, which was mixed back into the rest of the sounds on the mixer. To add color or create special effects, thin metal plates or springs were also made to resonate in the room and recorded.
Plates
By the end of the 1950s, technology had advanced to the point where the reverberation process could be standardized. Every major studio had a plate reverb like the EMT 140, or a simpler DIY version. The effect was achieved using a large reflecting surface — in this case, a metal foil held in tension by springs. A speaker inside the unit vibrated the plate, and a pickup captured the signal, which was then amplified through a tube preamp. A mechanical damper reduced the decay, and later versions used two pickups in different positions to create a stereo signal.
The effect is warm and beautiful, but unfortunately the technology required large spaces — the plates were often more than 1 meter long — and these reverbs were very heavy and expensive.
The effect was obtained through the use of a big reflecting surface, in this case a metal foil put in tension through springs. A speaker inside the unit, puts the plate in resonation and a pickup captures the signal then amplified, through a tube preamp. There was a mechanical damper, to reduce the decay and later two pickups, placed in different places of the box, to obtain a stereo signal.
Spring Reverb
Lee “Scratch” Perry and his Grampian spring reverb (Black Ark Studios)
A lower-quality delayed signal could be obtained using the same process but with springs in tension instead of plates. The idea, commercially developed by organ pioneer Laurens Hammond, was much less bulky than plates and even portable — to the point that it became standard on electric guitar amplifiers. Spring reverbs give a particular vintage flavour to guitars, drums, and percussive instruments — really great for old funk or reggae.
Tape Echoes
With advancing technology, magnetic surfaces in the form of tapes (Echoplex) or disks/drums (Binson/Meazzi) were used to record and reproduce delayed signals on dedicated processors.Roland RE501, RE-201, RE-150 Tape Echoes (maxproaudio)The tape loop was the first form of reproducing sound with delay. Two tape recorders were used before dedicated machines existed: one to record and the other for playback. The longer the distance between the record and repro heads, the longer the delay time.
Roland RE501, RE-201, RE-150 Tape Echoes (maxproaudio)
The tape loop has been the first form of reproducing a sound with a delay. Two tape recorders where used before dedicated machine were born, one to record and the other for the playback. Delay time increased, the furthest the second recorder was placed from the repro machine.
One of the most popular tape echo units has been the Roland RE-201 Space Echo, still highly sought after by dub producers today at pretty high prices. Its tape was left unrolled in a transparent compartment inside the unit. Raising the top and watching the tape move in an apparently chaotic way, listening to the smooth mechanical noise while smelling the characteristic chemical odour, remains a very unique experience.
Some special effects obtained with tape echoes were quite popular in the 60s and 70s, especially for sci-fi and dub. I recorded a few examples with my RE-201, with the “Intensity” (feedback) at maximum — conditions under which the Space Echo starts auto-oscillating, feeding its own noise.
The effects obtained are warm and immediately bring you back to the past. The first track, called RE-201 Slam, is obtained by slapping the unit forcefully; the shock is captured by the internal spring reverb. The third track starts dry and adds effects from the second part. Tracks 2 and 4 are sweeps, moving the “Repeat Rate” knob.
Many virtual tape delay plugins today are based on the RE-201 Space Echo, the most popular in the RE series.
According to Wikipedia, a bucket-brigade device (BBD) is a discrete-time analogue delay line, and an analogue delay line is a network of electrical components connected in cascade, where each element creates a time difference.
A series of capacitors created the delay. Summing a large number of them could produce the desired long echo.
Analog delays cannot reproduce the same sound for long — each repetition gets dirtier — and this, from the perspective of that era, was seen as something to improve. They are still very popular and produced for guitarists.
Digital Delay Lines
Digital delays can repeat the same sound while maintaining the quality of the original, just like a sampler, only when the sample rate and bit resolution are high enough.The first commercial machines had very low resolution, so the samples were noisy and had limited bandwidth. This is the characteristic that, in my opinion, makes them attractive and useful even today, when clean sound is no longer the priority.
At the beginning, these machines were only within reach of professional studios or wealthy producers. Then Electronics & Music Maker Magazine published a series of articles with schematics and instructions for a DIY delay, making this new technology affordable and accessible to a wider public.
Being a lover of dub and vintage equipment, I’ve been lucky to own a few of the classic delay devices, bought when prices were extremely low because nobody at that time needed a bulky, noisy delay-only machine.
Vintage delay lines have an other interesting aspect.
Powertran Time Delay switches
Their buttons always select multiples of the original tempo. If the delay is in sync with the track tempo, pushing different switches gives a very fashionable beat repeater effect today, where, for example, a loop speeds up or slows down but always stays in sync with the song. Some machines, like the Powertran, had a freeze button, so the sample repeated without decaying — just like a sampler.
Effects obtained apart the Echo
A delay line can create a series of effects not strictly limited to repetitions of samples. By modulating the processed signal and blending it with the original, a range of interesting effects can be obtained.
Phasing
When the same signal is combined with its delayed copy, it’s like passing it through a filter. The resulting comb filter, if modulated by changing the delay time via a low-frequency oscillator (LFO), becomes the pleasant effect called phasing.
Flanging
Same as phasing, but with a longer delay (around 10ms). Similar to chorus but more dramatic, with a marked sci-fi character.
Chorus
Even more delay and slow modulation, possibly with dry and wet signals on opposite sides of the stereo field, gives the classic chorus effect that doesn’t need much more explanation.
ADT
Automatic Double Tracking,
Automatic Double Tracking was very popular in the 80s. The time delay is kept just below the perception of individual repetitions and is used especially on vocals to create the illusion of doubling without recording two different voices.
On the next posts, we will test drive three of the old-school digital delays still in my hands: MXR Digital Delay, Powertran Digital Delay Line, and the Roland SDE-3000
For “The Dark Side”, I mean the real nightmare always lurking, while playing with vintage machines: Their tendency to break apart, often in the middle of an important session.
Always the best option, if possible, is to be able to do some small fixes in “DIY mode”, to save money and have the repair done promptly. The older the machine, the easier the repair is, usually. This is valid, if some rare parts availability, doesn’t interfere in the logic.
Doing some tests recently, I found that the auxiliary VCA section of my Korg MS-50, had one of its jacks broken inside. The plug was not kept in its place, like if there was nothing inside to retain it. I suspected the positive pole plate got broken.
Good occasion to open up the synth and look what’s inside ;)
As soon as I unscrewed and removed the later panels, I remained impressed by the fact that in the interior of its panels the Korg MS-50,..ehm…IT’S EMPTY! :D It’s pretty impressive how Japanese technology was advanced, considering that this synth was in production, since 1979.
In the interior of the Korg MS-50, there are just a couple of thin PCBs, plus the PSU board.
What occupy much place, are the plastic slots for the jacks metal connectors plates.
The only thing really modular to me, is the placement of the jacks in the front panel, simulating the modules of a real modular synth. Modules can be connected through external connections only , same as a modular and not as the rest of the MS series, where some internal patching is placed already.
This not complete modularity, can look a bit suspicious by the most purists, but the sounds that this machine is capable to create are fantastic, even with it’s limited single oscillator configuration.
The Korg MS-50 have been pictured in Aphex Twin studio and should have been used by The Chemical Brothers.
REPAIR
Inspecting the interior, (with major relieve) I discovered wasn’t necessary to disassemble the whole synth, as removing the main PCB from the front plate, must be a really tedious process, considering all the jack bolts, to unscrew.
The cause of the fail for the broken jack, resulted in being the connector plate of the + polarity, that I found off its slot.
MS-50_int connector fail
Just some glue solved the problem, a much easier solution than what I thought was necessary, at the beginning.
TEST DRIVE
To test the VCA repair, I decided to make a demo, squeezing from the Korg MS-50 single oscillator, all its waveforms. I triggered them from its two Envelope Generators and a Korg SQ-10 Analog Sequencer that plays the sequence.
re several video examples already of this delay tested on guitar, I thought it could have been a good idea to try it, using some unusual but hopefully interesting sounds.
On the following examples, let’s try something that really impressed me first time I played with a Powertran (An article on it, is coming soon). On the MXR the feedback has a faster decay and there’s not the “freeze” function, but the effect it is interesting, too. Once the delay is at tempo with a rhythmic pattern, having adjusted the decay time knob, all Delay Range buttons create a different version of the pattern, but on different speeds. Being the buttons based on a double time sequence, all these are compatible in tempo. Let’s experiment with a small classic reggae riddim loop:
