Tag Archives: vintage

CRUMAR Spirit, vintage analog synth repair

It has been hard to find the time to write, this time!
I’m starting producing videos related to this blog and as my knowledge in video editing is absolutely basic, this means long preparation times. Lots of things to learn so most of the time usually dedicated to music had to be diverted in watching instructional videos.

Finally, after too long, I decided to turn the Crumar Spirit, a first 80s monophonic analog synthesizer, back on to check if it was still working, given that last time it had shown signs of “tiredness”.
While recording a video, I realized that something strange was going on. Sudden jumps in intonation, notes that didn’t want to play, or that sounded intermittent.. then suddenly the worst! The keyboard started emitting only the note pulses (Gate) and no longer the pitch. (CV)
..and so once again, abrupt split to the opposite cerebral hemisphere and here I am again to repair “in the field” my junk!
Inspecting the interior of the Crumar Spirit, the first suspect was certainly the Input/Output board, where the CV/Gate data enters and leaves the synth. And in fact, the culpable was found there! At the height of the connector, a track of the circuit was broken, perhaps due to the action of the connected plugs, over the years.
With a simple bridge, I was able to repair the circuit and bring back into the Spirit, its spirit!

Yamaha NS-10 reborn, Avantone Drop-in Replacement Tweeter

Yamaha NS-10 reborn, Avantone Drop-in Replacement Tweeter

It was long my Yamaha NS-10 monitors had both tweeters dead, I love these speakers so much that I was costantly thinking on fixing them, but didn’t want to spend a fortune. Unfortunately, the blown tweeter is a very common issue with these monitors and as the NS-10 remains an indispensable tool for lots of people, the original tweeters are still in high demand. As the NS-10 speakers are no more in production that is long already, finding parts was getting pretty hard and the originals, reached very high prices. This is the reason that forced me years ago, to buy a pair of Yamaha MSP-5, monitors that I love very much, but that are not “my” NS10s.

Last week, with great surprise I discovered that Avantone Pro, the company of those classic tiny monitors, are selling identical copies of the original NS-10 speakers and at a really attractive price. After reading all I could and watching a few videos, I decided this was the best way to go and wanted to give a try to these replacement tweeters. I bought mine through a big online shop at 122 euros each, really a fraction of what I could have spent for NOS Yamaha NS-10 tweeters.

As promised the replacement is a drop in, there’s no need of adapting anything, the shape of the replacement speaker is identical to the original. All is as simple as soldering the speaker cables to the new tweeters and screw the tweeter back into the monitor.

I’m surprised at looking how identical to the original these tweeters are, all details are exactly the same, only the ring around the tweeter dome, has a slightly lighter grey colour. Is it this the difference that allows Avantone to clone the Yamaha speakers, without copyright infringement repercussions? Sure you understand I’m just kidding, I’m sure if they can freely sell a so exact copy, these details have been cleared already.

Original Yamaha tweeter on the left

After the installation and the promising sound test, I’ve been mixing for several hours, completely forgetting I was doing so on the new tweeters, perfect prove that I was feeling absolutely confortable with their sound!

I’m very happy with this upgrade! :)

70s Electromechanical Hammond L-100PS, Maintenance / Repair

My initial intention was to include this post in my “The Dark Side of Vintage Machines” series, but reflecting more, there really wasn’t anything dark on such a simple action as adding lubricant to this super heavy, but solid as a rock instrument, to bring it back to life!

I must admit that I’ve been lazy and recur to virtual instruments when I needed an organ sound, for too long even having the real thing. The plugins level of fidelity in reproducing the classic tonewheel sound, has reached an impressive level since a long time already. It might look like a sterile excercise, going back to record from the original instruments, when this process has been done with extreme care from team of experts several times in the last decades, to bring us such great sounding virtual instruments, so easy to use. An organ keyboard not being sensitive, can be imagined like a series of ON/OFF switches, this way the interaction with the instrument interface can be easily reproduced today, using a simple MIDI keyboard, better not weighted.

Bringing back my old Hammond to life, could have meant spending tens of hours of care and possible frustration, in case of unsuccess. I switched it off last time many years ago, when almost all of it was working, but it was already in urgent need of oiling its internal mechanism with the once rare to find, but now easily available on internet, “Hammond Oil”. Its rotating speaker amplifier, an Italian transistors pseudo “Leslie”, was in a horrible state too, roaring as a jet at take off, when switched on.

Hammond L100PS

I could have avoided the stress of the repair once again, resisting to my conscience that was pushing me towards being more responsable and keep my instruments serviced, with the excuse that it is pointless to spend energy to have something only a little bit better sounding. This time I had a deep sense of nostalgy for my organ, who had been with me for almost all my life and I had loved so much and a sort of sense of responsability, towards this piece of technology of big mechanical complexity, possibly extremely difficult to manufacture again, today.

I don’t want to be too boring, just let me add a little story as it can be funny..or tragic? :D

My first organ was a transistors Farfisa, a way more technologically advanced machine, with respect to a classic tube organ like the Hammond, it could even emulate the gliding of a synth, with its “Synthslalom” function! :D I knew already the old electromechanical organs were particularly sweet sounding, but couldn’t imagine that even a humble spinet size keyboard like the L-100, was a real killer, able to recreate the sound of the progressive rock organs I was so crazy for, until I had to occasion to test an used one at a shop in my city. The price was extremely cheap, as nobody wanted to carry such a heavy “portable” instrument around, or buying for home an ugly looking keyboard with just organ sounds when, for the same money, they could have bought a huge wooden console full of colored lights, a drum machine and plenty of inspiring buttons like “Bassoon” or “Tuba”!
The occasion was great, but I was still a student and completely budgetless.

Making a formal promise to my parents that I would have been a very good student, I could convince them to finance the money the shop wanted. The thing worked and for a while I could enjoy playing day and night my real Hammond, through its amazingly sounding, wooden tube Leslie amplifier.

The day I knew I had failed school’s exams I was already in a horrible mood, this become a day of mourning, as soon as returning back home, I realized my Hammond had disappeared, brought back to the shop by my parents, as my promise to be a good student hadn’t been respected.

I’ve been lucky that prices remained pretty low for over a decade, until I could find one more “P” (this one is labelled L100PS), that having a job already, I could afford, the one I’m telling you about on this post.

Hammond L100PS without cover
Hammond L100PS insides

instead of being a painful process, I found my Hammond, once oiled and switched back on for the first time after a decade, in a pretty good shape.

What resulted more problematic, was fixing the rotating speaker amplifier, that once on, used to start screaming as crazy! Substituting a few capacitors and transistors, fixed the problem and helped reducing its always being present hum noise, very much.

Cosmosound rotating speaker amplifier

On my new track “Tonewheel” on Soundcloud:

I recorded it with a pair of MD-421 and simulated the Leslie tube saturation, missing on my transistors amplifier, passing its recorded signal through my recently built pair of Fairchild tube equalizers.

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 Sound Is In The Iron, DIY Neve 2254 Limiter Compressor

To upgrade my studio to the new production and mixing setup I’ve been dreaming for so long, I needed a few more hardware processors, like equalizers, reverbs and compressors. Several years ago, I built a IJ Research Neve 2254c (a DIY stereo or dual mono Neve 2254, with the sidechain circuit taken from the Neve 33609) and still being enthusiast for its sound, I wanted something similar, without having to spend a fortune on a “real” AMS Neve 33609 stereo compressor, or on a pair of 2254R
Choosing to build a couple of AML Neve-2254 seemed to be the more logical option, hoping to have a good performance and not going bankrupt in the process.

Diode Bridge Compression

On Youtube there’s an interesting interview with Rupert Neve, explaining the origin of this family of limiter compressors and the development of their technology.

Neve was contracted in 1969 to find a substitution for the limiter compressor modules installed on Pye (Philips) mixing consoles at ABC TV, who promised buying a big number of units.

Rupert Neve used a diode bridge as control device, as he reports on this interview:
“The diode is a non linear device with a huge amount of distorsion but if configurated as a bridge, distorsion lowers considerably.  “So you can apply audio across one set of contacts and you apply your control voltage across the other side, it’s a classic bridge configuration. And by carefully choosing the limits of control and signal, it gave a quite good account of itself “

Neve developed the device implementing parts of their products already in production, as the line amplification section was the same as the famous Neve 1073 microphone preamplifier. The original 2252 developed in the successful 2254 and in the stereo 33609.

AML 2254 kit

As I recently wrote about an other one of their kits, I want to be clear that I have nothing to do with AML, apart from being a happy customer. Based on my previous experience with this company, I expected the kit not to be too hard to build and all the parts of the best quality. On this aspect, I had a confirmation once received the box from the postman. Holding it, it was so heavy, this could only meant there was a good quantity of IRON in that box! (more later)

Unboxing the AML Neve 2254 Compressor Limiter

As expected all parts were carefully sealed in separate labelled bags and the texts on the boards, were easy to read

DIY Neve 2254 PCB

The front panel is made of high quality switches from Greyhill,  The scary part for me has been programming them. This is done through inserting some tiny metal cylinders, in one or two of the programming small holes and when I say small, I mean almost impossible to me to see, without proper magnification lens.

Greyhill Switches

While building the Fairchild EQs, hasn’t been easy at the beginning to complete this task. Last time, to program the switches, I tried grabbing one of those tiny pins with the wrong tweezers and suddenly one of them took off, landing somewhere on the floor. It has been hard to explain to my dog, who came running for help, what there was so interesting to stay sniffing under the table for so long!

Switches programming slots

“The Sound Is In The Iron”

This phrase supposedly said by Rupert Neve, means that iron in the audio transformers has big importance to get the classic Neve “Sound”.

DIY Neve 2254 Carnhill Transformer

Same as the Fairchild equalizers of the previous article, AML included only electronic parts of the best quality.

DIY Neve 2254 Assembling

The Carnhill transformers included are handbuilt faithful recreations of the classic units they built for Neve, under the name Saint Ives Windings.

DIY Neve 2254 tranformers

The VU meters are the same Neve used to mount on the 2254 console modules. I like the original look, but I prefer the Sifam I mounted on my 2254/33609, as these are easier to read.

DIY AML Neve 2254 VU Meter

Included in the kit are the classic Marconi knobs, I really love them!
The part that I enjoyed less (as usual) has been building the frame. This one is solid, it works, but is more complicated to build than the one chosen for the equalizers. To be honest, I don’t like the vinyl adhesive front face neither, it looks good with a shiny white granular texture, but I’m not sure how long it can lasts and I find the classic RAF grey blue of the original, more attractive.

 

DIY Neve 2254 Completed

To calibrate the pair, I had to recur to the Pro Tools Signal Generator, as the new function generator I had assembled, couldn’t reach 20dBU or the 7.74v RMS required

DIY Neve 2254 Calibration

Here we are, the two DIY Neve 2254 completed, tested and now in good company in the rack!

AML DIY Neve 2254 and IJ Research DIY Neve 2254c

 

DIY AML Fairchild Tube Equalizer and its Magic Eye magic

Before finding this DIY kit on the AML online shop, I didn’t know anything about Fairchild equalizers. I knew this manufacturer was famous for the 670 limiters that I had used many times in different software reissues and that was the same Fairchild factory, building those fat Flying Boxcar planes that used to impress me very much, roaring low over my head while a kid.

Pultecs as rain

As I had no tube EQs in the studio, my initial idea was building a couple of classic Pultec equalizers clones. Sure there is no need to explain more, my typical readers can possibly know more than me about. Searching for the best way to go, I remained surprised to see how many clones or Pultec inspired equalizers exist today in the market, in the DIY or finished product form. Even big manufacturers like Behringer, recently introduced their Pultec, under their Klark Teknik brand, at an insanely cheap price.

Looking on the AML web for info on their Pultec kits, I totally fell in love for their Fairchild 627 reissue, instead. When I crave for new gear, I try to stay tight to my technical side and using logic, considering what is really needed. This brings me most of the time to fix, mod and recycle old gear still in my hands, instead of buying something brand new. OK, after decades soldering and fixing things, I can consider myself a bit a tech too, but I’m mainly a musician, then deeply attracted by fantasy and details that can look futile, but are extremely fascinating to the non-logic (illogic?) part of the mind! That green glowing “Magic Eye” on the front panel was too intriguing and it was calling for my eyes!
I had seen it already, so far in time but still, it was so intensely fixed in my memory! Like coming out from a Sci-Fi movie, the feeling was a mix of curiosity and fear, so green and scary to only possibly being an alien artifact and sure able to promptly take control of my mind! :D

The “Magic Eye”, the VU meter grandfather

Before the 1960s, needle VU meters were extremely expensive, high tech precision tools mainly for scientific equipment, telephone and military use. VUs started becoming a practicable form of measuring an audio signal, only after mass production started in Japan and LEDs made the application on consumer products, very cheap. Electron ray indicator tubes were the way to go, to have a reliable visual representation of the presence and amplitude of an audio signal. First implemented on radios to make it easier tuning to a station, they can be found on vintage tape recorders and televisions too. The magic eye is a miniature cathode ray vacuum tube, the same as the screen of old televisions, plus an amplification stage, like in usual tubes. While the rest of the “screen” (anode) is illuminated by the electrons strikes, a part (electrode) is kept dark until a signal is detected and the flow of electrons is allowed to run in that area too.

Building the AML Fairchild 627 EQ

Once the kit arrived the connection with aircrafts strangely was evident again, this time in the form of a deja vu: The PCBs were cleverly cut in the resin board, in a form it resembled me the plastic aircraft model kits so popular in my youth, where you snap off the part you need from the mainboard, through pre-cut junctions.

AML ez-627 PCBs

My previous DIY builds never started from complete kits, all I usually had were a couple of PCBs and a BOM (Bill Of Material) list. Often, finding the right components to buy and where can become a boring and long process. This time there was nothing to worry about, only buying the valves that weren’t included in the kit. These are pretty common tubes available easily, what I couldn’t find were matched pairs, as I would like to have installed, at the beginning.

AML ez-627 unboxing

The quality of the boards is excellent and all components locations are labeled carefully. Same with the electronics, included in the kit are quality parts from manufacturers like Wima and Vishay. The transformers are Carnhill, the same I installed years ago in my DIY Neve 2254/33609 hybrid compressor (hopefully a good theme for a future post).

Assembling the 627

Arrived at the end of the project, the two Russian 6E5C/6E5S (C is an S in Cyrillic) hadn’t arrived yet, they were lost somewhere in the north of Spain. Calling the post office they told me my “Magic Eyes” had been held by customs (?), I can imagine the officers looking at my alien-ware, guessing what the hell are those for…

Building the tower for the Magic Eye, like somewhere in Mordor…

How does the 627 sound?

Even if the choice of building this processor might having being influenced not only by technically related reasons, I’m very satisfied with the results. All I passed through my units, in a couple of days they are alive, sounds very full and warm. I only tested my new pair on bass and guitars while mixing a new song, yesterday. As frequency action, its higher band goes up to 10kHz, below the 16kHz a Pultec EQP-1A (my initial choice), can work. The 627 is not too useful for brightening the higher part of the spectrum or shimmering, but very nicely working on lower frequencies. Testing it on bass, the tone I obtained was super fat and the action way more dramatic than I expected, in seconds I had a huge synth bass ready. I had to bounce the track to free the unit for processing some guitars, but I forced myself to limit the test to them only, or I would have started passing the whole song track by track, through the 627s! :D

I hope to make a follow up to this post, with the help of my OSO http://www.originalsoundsonly.com squad, with some audio tests, soon.

Links:

Most of the information on the Fairchild 627 Equalizer I could find online, comes from this link: http://www.preservationsound.com/?p=8602

The instructions on how to build the AML version of the 627, are online:
http://www.audiomaintenance.com/downloads/ez627_colourbook.pdf

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

 

Echo, Nymphs and the Art of Procrastination

Echo, unlucky nymph

Since ancient times, places destinated to public speech or shows, were chosen in base of their  acoustical characteristics. A powerful voice listened near a sharp rock wall, could impress the public and add a magic ingredient, like if forces of nature were happy to help the venue, amplifying the wanted message.

Nymph Echo on a Roman painting

The Echo was so important, to have a dedicated character in Greek/Roman mythology:

Echo, a mountain nymph, was helping Jupiter in distracting his wife Hera, with interminable discussions, while the god was cheating on her with the other nymphs. Realizing the trick, Hera cursed Echo, removing her ability to speak. The only sounds she could emit, were the endings of words she could hear. As usual in ancient myths, the story ends in a tragedy, with Echo dead but not her beautiful repetitive voice, forced to live forever, but only in the most remote and inaccessible places.

Natural echo or reverb of special rock formations, or the reflecting shape of caverns, were used to create a dramatic effect on human speech, chants (and minds) for ritualistic or entertainment purposes.

The Art of Procrastination

Builders with time could, through architecture, recreate nature’s big spaces and the possibility to impress public with special effects, could  slowly move from remote areas to the cities.  Acoustically shaped amphitheaters and later, closed spaces like theatres and religious buildings were built for this function. Music started being played in dedicated “chambers” or “halls“, with reflecting walls and high ceilings, to obtain long reverberation times and decays.

At the beginning, recording studios used to record the space where musicians were playing, with microphones pointed to ceilings or walls, to capture the returning delayed sound and the signal was mixed to 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 empty and with reflective materials. One or more microphones were used to capture the effect, that was mixed to the rest of the sounds in the mixer. To add colour or to obtain special effects, metallic thin plates or springs, were recorded while resonating in the room, too.

Plates

At the end of the 50s, technology arrived to a point where the process of reverberation could be standardized and every major studio had a plate reverb like the EMT 140, or a DIY simpler version of it. 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.

The effect is warm and beautiful, but unfortunately the technology needed big spaces as the plates were more than 1 meters long and these reverbs were very heavy and expensive.

 

Spring Reverb

Lee “Scratch” Perry and his Grampian spring reverb (Black Ark Studios)

A low quality delayed signal, could be obtained with the same process, implementing springs in tension, instead of plates. The idea, commercially developed by Laurens Hammond, the organ pioneer, was much less bulky then plates and even portable, to the point to become a 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 the advance of technology, magnetic surfaces in the form of tapes (Echoplex) or disks/drums (Binson/Meazzi), were used to record and reproduce the delayed signal, on dedicated processors.

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 searched by Dub producers has pretty high values, today.  Its tape was left unrolled in a transparent compartment inside the box. Rising the top and watch the tape moving in an apparently chaotic way, listening to the smooth noise of it, while smelling the characteristic chemicals odour, remains a very unique experience.

Some special effects, obtained using tape echoes, were pretty 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 where the Space Echo starts auto-oscillating feeding its own noise. The effects obtained are warm and immediately bring back to the past. The first track, called RE-201 Slam, is obtained instead slapping the unit with force. The shock is captured by the internal spring reverb. The third track is dry at the beginning, while has some additional effects from the second part. Track 2 and 4 are sweeps, moving the “Repeat Rate” knob.

 

Many virtual tape delay plugins of today, are based on the RE-201 Space Echo, the most popular of the RE series

http://daily.redbullmusicacademy.com/specials/2016-inside-a-space-echo/

Bucket-Brigade Device (BBD) or Analog Delays

In the wiki we can read that a bucket brigade or bucket-brigade device (BBD) is a discrete-time analogue delay line and that an analog delay line is a network of electrical components connected in cascade, where each individual element creates a time difference. A series of capacitors created the delay. Summing a big number of those, could create the desired long echo. Analog delays, cannot  reproduce the same sound for long, each repetition has a dirtier sound and this, with the eyes of those times, was seen as something to improve. They are very popular and still produced for guitarists.

 

Digital Delay Lines

Digital delays, can repeat the same sound, maintaining intact the quality of the original same as a sampler, only when sample rate and bit resolution are high enough.

The first commercial machines had a very low resolution, so samples were noisy and with a limited bandwidth. This is the characteristic that, in my point of view make them attractive and useful still today, when clean sound is no more a priority.

At the beginning, these machines, were only at the range of professional studios or rich producers. Until Electronic & Music Maker Magazine published a series of articles with schematic and instructions for a DIY delay, making affordable and available to a wider public this new technology.

http://www.muzines.co.uk/articles/digital-delay-effects-unit/3714

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 affordable, as nobody on those times needed a bulky and noisy delay only, machine.

Vintage delay lines have an other interesting aspect.

Powertran Time Delay switches

Their buttons select always multiples of the original tempo. If the delay is in sync with track tempo, pushing different switches, gives a today, very fashionable Beat Repeater effect, where for a example a loop is faster or slower, but always remaining in sync with the song. Some machines like the Powertran, had a freeze button, so that the sample was repeated without decaying, same as a sampler.

Effects obtained apart  the Echo

A Delay Line, is able to create a series of effects, not stricktly limited to repetitions of samples. Through the modulation of the processed signal and blend it to the original, a series of interesting effects are obtained, too.

Phasing

When the same signal is combined with its delayed copy, it’s like having passed it through a filter. The Comb Filter resulting from counter phasing if modulated, changing the delay time through a Low frequency oscillator (LFO), becomes the pleasant effect called Phasing.

Flanging

Same as Phasing, but with longer delay (10ms). Similar to chorus, but a more dramatic effect and with a marked SciFi like, character.

Chorus

Even more delay and slow modulation, possibly with dry and wet signals on the opposite sides of the stereo field, gives the classic chorus effect that doesn’t need too many words more.

ADT

Automatic Double Tracking, was pretty popular in the 80s. Time delay is kept just below the perception of the single repetitions and is used especially on vocals, to give the illusion of doubling, without the need of recording two different voices.

 

On the next posts, we will test drive, three of the oldschool digital delays still in my hands:
MXR Digital Delay, Powertran Digital Delay Line and the Roland SDE-3000

 

 

 

References and interesting articles:

http://www.loopers-delight.com/tools/powertran/powertran.html

https://www.researchgate.net/publication/312026934_Echo_problems_in_ancient_theatres_and_a_comment_to_the_%27sounding_vessels%27_described_by_Vitruvius

https://soundgas.com/blogs/news/grampian-type-636-history-technical-spec

https://www.soundonsound.com/people/lee-scratch-perry-daniel-boyle-recording-back-controls

2018 SGAE/Safecreative. All rights reserved.

The Dark Side of Vintage Machines: Part 1 – Korg MS-50, failing jack connector repair and test drive

KORG MS-50 1979 Modular Analog Synth

 

Korg MS-50
Korg MS-50

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.

Korg MS-50 Inside 01

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

 

Korg MS-50 Inside 02

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
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.

Korg MS-50 and SQ-10
Korg MS-50 Patched, SQ-10 connected

Sawtooth – VCF – VCA – Valve audio preamp
PWM – Divider – VCA2 – Adding Amp
Triangle – (no ADSR) – Adding Amp
Adding Amp – Audio Amplifier – Transformer audio preamp

 

The signal split is sent to two different preamps, to spread it into the stereo field. No effects apart some dynamics control, have been used.

 

LINKS

 

Interesting articles on the MS series:

https://www.sequencer.de/korg/korg_ms20_ms50_ms10_sq10.html

https://www.sequencer.de/syns/korg/MS50.html

A post regarding MS-50 adjustments:

https://www.muffwiggler.com/forum/viewtopic.php?t=63534&sid=75a570d9988dbe7bd5d1122cb6973b44