Tag Archives: Korg MS-50

The Dark Side of Vintage Machines, Trident Series 80b fail and repair

I believe today analog consoles are seen by many as bulky, unbelievably thirsty of energy and continuously in need of maintenance items, in practical terms, obsolete tools.

The tendency, in the last decade, has been to abandon the traditional mixing desk in favor of virtual mixers or “control surfaces“: Focusing on  quality converters with as many as possible inputs and hardware gear, like equalizers and dynamics processors connected to a patchbay, to combine at wish.

This choice has great advantages in terms of variety of sound and physical space, considering that you buy only the modules you really need or like for your usual session, possibly with different audio “colors“, to have a wide sound palette, instead of lots of identical channels as in the classic console.

Of course I agree with this approach, but limited to the phase of recording. I find the classic surface controlling and placement of knobs, ergonomically ideal, being the result of decades of “evolution” in mixing down techniques in analog. For this reason digital control surfaces mimic the shape and workflow of the analog desks. When you start working out of the box, is way more comfortable to have easy access and visuals of the parameters you are adjusting.

Having an analog mixing desk, forces you to a sort of marriage to your equipment, your mixer is the heart of the studio, it will imprint its own sound and needs all your care and attentions and the older, the more care it will need.

It is annoying to find your preamplifer is broken, but having a failure in the mixing buss of the mixer, for example, forces you to do an immediate repair, or you will have no music at all!
Big mixers are modular for this reason, studios always had modules in stock, to swap them with already repaired ones, in case one of them was failing.

Trident Series 80b, Remix slider

 

 

 

 

 

 

 

On my Trident Series 80b, its oscillator needed to detect the failures, was broken, it couldn’t generate a sine wave anymore. Instead judging from the scope, it was generating a strange saturated square waveform. I will do what is possible in the future to fix it, in substitution the old Korg MS-50 oscillator has been useful as lab tool once again. This time I used its oscillator, rounding a triangular waveform through the LPF, to obtain the sine wave I wanted for the tests.

Korg MS-50 Synthesizer, used as test lab tool

One of the problems the console was having, was a false contact somewhere in the remix buss, making at low gain, from time to time, disappear the right side of the stereo mix. The Trident Series 80 has plenty of TL-071 opamps, spread everywhere on its circuits. Usually if there’s something wrong in the signal, those are the first components I learned must be checked.

Trident Series 80b, Remix Buss card connections

This time, the culpable for the Remix buss fail, was a wrong peeling of the wires that connected the mix buss card with its motherboard  (Echo Aux module) made sometime in the past. Because the copper core was cut too much, part of its filaments must have been lost with the shaking, during the various repairs in the last 35 years and the connection on both the positive audio rail and ground, was extremely fragile and intermittent.

While illuminating the mixer’s board with a strong spotlight, I realized for the first time that the resin the PCB is made of, is transparent. We are used to the squared,  mostly made of straight lines, tracks of the circuits of today, sure ideal for the mechanization process in their production. Looking at old circuits instead, I’m always fascinated by the “organic” shapes and in a certain way artistic, tracks “style”!

In all these years mixing ITB, I’ve been continuosly dreaming to return to mix in analog and to do so, try to remain as close as possible to the classic 70s and 80s studio setup.  Thanks to the energy put in the last several months, I could restore my old Trident console, fix its patchbay and slowly move from a recording only setup, to a complete production and mixing studio.

The Art of Procrastination, MXR M-113 Digital Delay

 

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 dbx DI box and the signal sent to a Universal Audio 610 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 Range 160ms, 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

Service Manual: https://app.box.com/s/4t78o8xtzd