DIY Neumann U47 valve microphone, ioaudio MK47

Equinox U47 enclosure

There’s no doubt that the Neumann U47 is one of the most respected valve microphones ever made, been used to record the best vocals in the history of music. For this reason, lots of copies or variants have been built in the last 50 years, up to been recreated recently, even from one of its original manufacturers.
The hardest aspect to reproduce has always been the behaviour of the valve used, the Telefunken VF14, a military radio tube discontinued in the 60s (this caused Neumann to stop the production of this model) and very hard to find, until Telefunken reissued it under the name VF14K, a few years ago.



ioaudio MK-47 kit 01

I’m not a microphone expert, I only had built a pair of AKG C12 “clones” in the past, based on the Apex460 and made a few repairs of old micros, but absolutely wanted “that” sound and a tube microphone sounding different than my pair of DIY C12.
I found this project a few years ago on GroupDIY, while it still was called and I liked the idea of using a pair of 6028 tubes to reproduce the VF14  and wanted to give it a try. Building a PSU and finding a microphone body hasn’t been really a problem, as in the same moment other builders had offers of kits for the ’47.

I remember opening the box, the kit’s more curious parts were the Soviet condenser with Cyrillic markings on it and the specially tailored transformer, reproducing the original Bv.08 trafo.


ioaudio MK-47 kit 02

I don’t remember the MK47 building to be difficult at all, all was explained very well in the MK47 Build Support thread of the groupDIY thread:

and on the instructions included.



ioaudio MK-47 kit 03
ioaudio MK-47 kit 04

Max Kircher’s ioaudio is still building kits for vintage microphones, their actual kit is an upgrade to transform a U87 into a tube U67, something I would like to build, one day for my 87.

Thiersch STW7 Red capsule, front

As capsule I chose the  Thiersch Elektroakustik, a perfect reproduction of the M7 capsule, with the membrane in two different flavors, PVC or PET (mine).







More tricky was building the power source, but I’ve been lucky to find a suitable pcb in Prodigy’s “White Market”.

As body, I used the Equinox Systems copy of the U47 enclosure, very nicely done.



This remains up to today my preferred microphone in the studio, I use it mainly on voice.

Jurassic DAW: 1st generation Mac Pro hosting Pro Tools HD TDM, upgraded

Days ago I arrived to the conclusion that to import files from my production PC to the Mac in the studio, I needed a faster solution. Every time having to make dozens of bounces, was getting really too stressful. What I needed, was the possibility to open my Reason 10 projects started at home, in a Reason rewired to Pro Tools HD in the studio, having this way complete compatibility.

The first thing I tried to do, has been checking for a Pro Tools upgrade offer in my Avid account, but not surprisingly, on their upgrade program my old system was not even mentioned , being too old.

2006 Pro Tools HD TDM Core and Accel cards
ATI HD5770 Silent found on eBay

Calling a friend and sharing my idea to update my old DAW to make run on it Reason 10, the answer of the guy, expert in computers and audio systems was something like “Max, you have a dinosaur there! What you want to upgrade? buy a new system, instead”
Even if his answer has its logic and didn’t surprised me, I couldn’t afford the cost for a new Avid audio card on a new Mac Pro and even more, I didn’t want, nor needed all that power. At the end, I was still satisfied with the zero latency and immediate reaction to commands of my old Pro Tools HD and the number of TDM plugins I can run there, are a lot more of what I ever needed, as I record real instruments and use external effects, most of the times. The problem was Reason not wanting to run in Rewire, being my Pro Tools architecture 32 bit, while this DAW from version 8.2, is 64 bit only and Reason is the platform where I like to compose more. I tried unsuccesfully a 64 bit to 32 simulator, but seems to work only in one direction,  32bit applications to run on 64bit hosts, not the opposite that is my case.

Mac Pro double processors without heatsink

Serching on internet, I found my Mac could, with a limited amount of money, partially being upgraded, at least to a certain point. What I needed were some more RAM, a new graphic card and a couple of faster Intel Xeon cores.

Cooling fan slot, the hardest part to remove





What was really an impossible task, at least to me, was having

Heatsink plate polished with Isopropyl Alcohol

a Reason more recent than version 8.1, working in Rewire with my hardware Pro Tools.

Intel Xeon core, once removed the heatsink

Unfortunately, a younger version of Reason Rewire in my system is impossible to make it run, it is not seen in the RTAS plugs list.

After a couple of weeks of trials and fails and lots of readings in specialized webs, I found a combi that works well for my machine:

Pro Tools HD 8.1, combined to Reason 8.1, perfect match even numerically! :D

Downgrading has been the only possibility to have complete compatibility. Using external gear, I can renounce to the last versions soft synths, the sacrifice is not that big using mostly real instruments.

Pro Tools and ATI 5770 PCIe cards installed

The total cost of the operation, including delivery of the parts, has been 326.80 euros

179 eu used ATI HD5770 (needed to run with the upgraded processors)
55.80 eu used 16Gb memory upgrade
92 eu 2x used 3.0GHz Quad core processors

There’s plenty of information regarding the upgrading of a Mac Pro 1.1, so it doesn’t make sense to go deeper.

Unfortunately I couldn’t find any information online, regarding Pro Tools HD TDM compatibility with recent versions of Reason. Through downgrading of Reason to version 8.1.1 and having Pro Tools software version 8.1, the combination is very stable and hadn’t any crash or problems.



Useful links:

The Art of Procrastination, Powertran Digital Delay Line

I’m very excited to start writing about this delay processor. A piece, I believe, that deserves some more words, as I couldn’t find too much written on it. The reason for not being popular, not to be found on its low digital resolution or for being very noisy, but for the reason that it has never been produced in series. The Powertran DDL came out in 1982 as a DIY project, published on the popular electronics magazine Electronics & Music Maker, so just a small number of units were built. The project was developed by the electronic designer Tim Orr, famous for the EMS synthesizers. The idea was giving access to the new digital technology, before extremely expensive and present only in big studios, to a wider public.

I’ve been lucky enough, to having fun with three different units of the Powertran Delay in the past, all a bit different from each other. Being the DDL a DIY project, all these processors had some modifications like the optional CV/Gate or additional knobs/switches.
The first unit I had was borrowed, a friend kindly left his Powertran in the studio and it remained in my hands for several years. Being his music more focused on acoustic instruments, he wasn’t using it anymore. Those were times when a dirty digital sound wasn’t appreciated too much and just a few bit-reduction plugins like the Digidesign Lo-Fi, existed. My friend’s Powertran had voltage control too, samples could be played from the keyboard, through a MIDI/CV interface and its dirty 8-bit sound reminded me a bit, the Emulator Paul Hardcastle had used in “19”, a song I’ve been loving so much. The Powertran delay became the crazy spice for almost anything experimental I’ve been doing, until before moving the studio to an other country, when I wanted to give it back. My actual Digital Delay was bought on eBay in a lucky bid, as very few units were still around, a few years ago. Unfortunately, my second unit, bought in the UK in 1999, had died after a few years of use and I couldn’t stay without a DDL!

The Powertran Digital Delay Line front panel is pretty simple and there’s nothing surprising, apart the time selector switches same as the MXR, we have already seen in a previous post.

Powertran DDL Time Delay buttons

The Time Delay buttons always select multiples of the original tempo. If the delay is in sync with the track tempo, pushing different switches, gives a today very fashionable Beat Repeater effect, where, for 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 could be repeated without decaying, same as a sampler.


“Digital encoding for studio quality results. Time delays from 0.625ms to 1.6 seconds. Produces all popular time delay effects: Phasing, Flanging, ADT and chorus, Echo (including “freeze” for infinite repeats), Time domain vibrato, etc.”

Powertran Digital Delay Line

The Powertran Delay has a delay time of 0.625ms to 0.64 at 10KHz Bandwidth, while it has 1.6ms up to 1.6 seconds at 4KHz, these times can be halved through the delay knob.
The modulation LFO has a range from 0.025Hz, up to 17Hz and a triangular shaped waveform.

Powertran DDL circuit board

The input signal, once amplified, is passed through two switchable HPF at 4KHz and 10KHz, working as anti-aliasing filters. The ADC analog to digital converter is an 8-bit one. The dynamic range of the Digital Delay is 72dB. The RAM memory is 16K bytes.

Powertran DDL PCB L
Powertran DDL PCB R

Included are some examples of the crazy effects obtainable with this processor:

Interesting links:

Free impulse responses from Floaudio:

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.


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:


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.


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

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.

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.


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.


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


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.


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:

2018 SGAE/Safecreative. All rights reserved.


maxpro comes from maxprofessor, a nickname that was given to me while I was a fan of the Dub master Madprofessor, trying Dub techniques in the studio and giving classes of music technology, in a music school.

As I grew up under my mother’s piano, I’ve been lucky to learn playing pretty early in age. My first teacher, is still an excellent classic piano performer.

I was still a boy, when my father arrived home with a stereo radio and a good pair of headphones, this fact can have helped me in developing my musical tastes, for sure.
As we are talking about the beginning of the 70s, the only local radio station transmitting stereo, was an American one, with lots of fresh Funk, Soul and Jazz on air all the time, music I’ve been loving (and played) for the rest of my life.

Playing a Farfisa VIP500 (end of the 70s)

At the age of 14, discovering progressive rock and in particular Emerson Lake and Palmer and the Yes, I started playing rock organ and later keyboards with local bands, turning slowly from Rock to Jazz Fusion and Acid Jazz.

In the years, I had the opportunity to study Jazz with three excellent teachers: Still in Italy, Jazz piano with Danilo Memoli, while in Spain, Jazz guitar with Marcelo Saenz and harmony with Leonardo La Peruta.

Hammond L100-PS, Farfisa VIP500 + TR70 and Leslie 145-P

Regarding the technical side,  I started composing and arranging as soon as MIDI was introduced.
My preferred machine for sequencing on those times, was a Yamaha QX-3, but was the arrival of a small Macintosh SE and  MOTU Performer, that consolidated a long marriage with digital music creation and production.

Max in Il Cantiere control room, mid 90s
Rhodes and Hammond at Il Cantiere studio in the 90s

In the 90s I built a production/recording studio in the north of Italy, based on Digidesign Pro Tools III on a Macintosh 9600 and ADAT.

I soon became specialized in Dance music and Reggae.

Il Cantiere studio control room, in the mid 90s

I’ve been lucky on those times, to be working with the best Dance DJs, producers and singers in my area, releasing a few records with majors such as EMI and WEA.

This image has an empty alt attribute; its file name is ESdigitalstudio.png
My studio, before 2006 upgrades
Soundgroom control room: Trident 80b, Otari MTR-90II 2″ 24 tracks and Ampex ATR-102 1/2″ tape recorders

At the end of the 90s, I moved to the south of Spain where I opened a production/recording studio, updated including analog tape, in 2007.

It was based on a 1980 Trident 80b mixing console, a 2″ tape 24 tracks Otari ATR90II and an 1/2″ Ampex ATR102 for the master. On the digital side, it had a Pro Tools HD rig, with Apogee X Series converters.

I’ve been lucky to have an excellent technician helping me, there. Brian had worked as engineer at Trident Audio in London and was very kind in sharing lots of his precious knowledge, to me.

I’m now producing mainly on Propellerhead Reason, but using external gear, as well.

I have a post that explains a bit how I do work, here:

You can listen to my music online in the following links:

Even if I’ve been more active on the technical side, these are some works I’ve done in the past, as composer/producer:

  • Two Mads, “Till The End Of Time”, single, with the singer Susy Dal Gesso and versions from DJs Danny Hussein and producer Roger Lyons, IDM/WEA
  • Ultracynic, “Got To Have It”, Remix with DJ Angelino , Planet 4 12″
  • Phasemod, “Noize Beam”, with DJ Klima, EP, Moonlite/Time Records
  • Cyberdread “No Definition”, LP, with Tony Bowers (Simply Red) and Ubidread (Radio Rebelde), Dance Factory/EMI
  • Let’s stay together, single with Nick Hussey and Jay Rolandi, Planet 4 Italia
  • I’m burnin’ single with Susy Dal Gesso and Nick Hussey, Planet 4 Italia
  • We Feel It, single with singer Susy Dal Gesso, Not Only Music (TODD)
  • Wildgroove, “Wild Inna Jungle”, Remix, Dance Factory/EMI

A DIY USB Theremin, Theremino Theremin


The Theremin can easily be consider the grandfather of the analog monophonic synthesizer. Looking very much as a vintage laboratory tool, its two antennas tend to make it look more as an experimental valve radio than a musical instrument,  with some obvious Cyberpunk flavor!

Invented by Lev Termen almost 100 years ago, its name Theremin is the Americanized version of the inventor’s name. The ghosty like and very natural sounding voice it has, could have become much more popular if it wasn’t for the Theremin’s ridiculously difficult interface, that make playing it in tune a really hard task without a proper preparation. The two antennas capture the movement of any object around. Arms and hands are used for the two possible variables that can be changed: Pitch and volume. What sounds pretty easy is in reality very tricky, the movements must be very precise, millimetrical. I suppose this is the main reason Theremin has been popular to violinists. Violins are notoriously difficult to play in pitch with precision, to do it you have to dedicate a hard work of learning.


Just a few manufacturers build theremins today, the most popular one, being Moog Music still producing one of the classic designs:

Obviously they’re the perfect choice if you’re looking for a reliable service, but possibly limited to professional performers only, due to their expensive price.

To save some money, several DIY kit exist, a couple offered by the same Moog company, a classic is a kit from Paia:

One extremely cheap and valid alternative is the Theremino Theremin.


To be honest a Theremin with a USB port only, can look extremely suspicious to the more traditionalists of us.
Especially considering that from a Theremin, we  should expect one of the purest analog sounds possible,
having to do with a soft synth sound generator, can look not too interesting.
What we will consider here, is the opportunity to have a valid and easy to setup interface, to be used to drive our trusted analog synths. The scope of this experiment will be to play through the Theremino Theremin interface a 1977 Minimoog. Using one oscillator only and its triangular waveform, we should arrive to a pretty good Theremin sound!

As the cards can be bought already assembled, mounting a Theremino Theremin is an easy and fast operation.

What we need for a complete Theremin is a Master and two CapSensor cards. All is connected through simple multi connectors ribbons and the USB is connected to the PC.

Theremino Master

What happens is that the two antenna capture the movement of the body and generate SLOT values, that are converted from the Theremino Theremin software in notes. Usually the left hand is used for volume and the right for pitch information.

Originally the Theremino Theremin was able only to play its soft synth, but recent developments permit do a lot more. Installing the LoopMIDI shareware application, Theremino Theremin slot data can be converter in MIDI values through the Theremino SlotsToMidi, avoiding the use of the Theremin soft synth, but using the MIDI to play a real synth instead. To be closer in sound to the original, we will use a vintage Minimoog, converting MIDI to Voltage control, through a Kenton Interface.

The Theremino engineers designed a special card to be used as PWM to MIDI converter, but only the DIY design project and schematics exist.

Theremino PWM to CV


more information here:





I hope to write soon a follow up, experimenting with practical examples. The idea is to drive my minimoog through the Theremino Synth antennas.

Elektron Analog Keys broken keyboard and repair


OK, a failure can happen even to the most modern synths,  most commonly caused by a failing component, but finding a tiny polystyrene pellet right inside the contacts of my Elektron Analog Keys keyboard, has been really surprising. The small fluffy ball, found the way through, still in the production phase I guess, as when I opened the keyboard assembling all looked clean and the rubber tops were well sealed. As the warranty had expired already, I had the perfect excuse to check what was inside the only of my “unexplored” synths.

There are plenty of tiny screws to have access to the “insides”, better using a powered screwdriver.







Keyboard assembly







Keyboard PCB







Contact pads






Under the contact pads is where I found the small pellet


Simply removing it and assemble all parts back, the synth’s keyboard returned to working smoothly.


     Elektron Analog Keys PCB







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.



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.










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.




Interesting articles on the MS series:

A post regarding MS-50 adjustments: