keskiviikko 26. huhtikuuta 2017

Eurocircuits Naked Proto

I am testing a new PCB-service Eurocircuits. They have a Naked proto service which is a fast proof-of-concept board with no soldermask and no silkscreen. The price is 50% lower than fully finished PCBs. With no soldermask it should be easy to cut tracks or add wire links if necessary. This is a proto of my interface to WAV trigger.

sunnuntai 26. maaliskuuta 2017

Sigma and Lovi-club instruments

We are preparing 50min of new music to our gig in Lovi Ambient-club (Kansallisteatterin Lavaklubi) 29.3. 19:00. Here are some pictures of our setup. Hopefully we can fit all this stuff to Lavaklubi's stage with Esa Kotilainen and Unfound.

Tower of synths! Korg MS10, SEKU and TTSH ARP2600.

Roland SH101, Eurorack Moog Prodigy and Nord MicroModular.

Another SH101 and Crumar Performer.

sunnuntai 5. maaliskuuta 2017

Sigma Live in Lovi Ambientklub

Sigma will play in next Lovi-klub in Helsinki Lavaklubi 29.3. with Unfound and Esa Kotilainen. Here is the link to Facebook event
We are going to play for about 50min floating soundscape with mostly analogue synths.

EWI and Mutable Yarns

I wanted to put my Moog Prodigy clone to one portable case where is everything necessary to produce sound with my EWI-controller. So I ordered from Thomann a custom case with their 3D configurator application It holds one 6U-frame from Clicks & Clocks.
I ordered Mutables Yarns MIDI2CV module so that I can have that also in this portable case. Until this I have used my trusted Kenton Pro Solo MIDI2CV-box for this application.

Yarns have one assignable CV-out from where I can control Prodigys filter with how hard I blow from EWI. Yarns can convert this MIDI-controller information to voltage between 0-5V. That's not enough for Prodigy where I need double of that. So I built a CV Processor module where you can offset the CV and/or amplify it with maximum gain of 2.

sunnuntai 19. helmikuuta 2017


This is a reference to my previous article about 24dboct-high-pass-filter. I built this two-layer proto of that circuit and it works great. Front panel layout is different because here I have a dedicated layer for pots, switch and connectors where I have more freedom on placement of components.

maanantai 6. helmikuuta 2017

Crumar Performer

I have been repairing my Crumar Performer string/brass synthesizer. One zener-diode was dying and made the master-oscillator to change the pitch randomly. Now this is fixed and it's time to make some modifications. I replaced the MK50240 top-octave generator with FlatKeys replacement box FK50240. This box has 12 synthesizers that create the desired notes from the master clock with a worst case error of 0.00005 Hz. There are also some extra features switches (scale,transpose,octave) that you can activate if you want.

Other modification comes from SoundDoctorin in this "Crumar Performer easy modification for release envelope" video. In the original Performer when you switch the brass-section on it kills the sustain on both brass and strings. With two switches you can choose from three options:

1. original setup where brass-section kills sustain on both brass and strings
2. Sustain works for brass-section but kills the strings sound
3. Sustain works equally for brass- and strings-section

I think the third option is most useful. Brass section adds nice fatness to the string sound.

P621-board where is the brass-switch. The white/black/red cables goes to the both separate switches.

Explanation of what to cut and where to connect the switches.

maanantai 16. tammikuuta 2017

LM723 heater circuit

I have been breadboarding several different heater-circuits for temperature stabilisation of LM3046 transistor array. They all use the same principle of comparator circuit that compares the measured temperature against the desired temperature set by a trimpot. Comparator then works as an on/off switch for heater-transistor that keeps the 3046 chip in steady temperature. I must say that I haven't found an bulletproof circuit that could accomplish this basically simple task. Until now that I found this LM723 based heater circuit.

LM723 is a voltage regulator designed primarily for different power supply applications. But it can also be used as a temperature controller. I have these great McGraw-Hill Publications books "Circuits for Electronic Engineers" where from I found this "Using transistor arrays for temperature compensation" article by Mahendra J. Shah. With 15V power supply it worked right from the box very good indeed. With only one heater-transistor it could rise the temperature from 30°C to 50°C in 5 minutes and reach the final 50.5°C temperature in 10 minutes.

LM723 has also some kind of comparator inside it called Error Amplifier. It seems to work more smoothly than just an on/off switch. There is also a reference voltage generator inside this IC that generates a constant voltage of 7.15V from where the desired temperature CV is adjusted with trimpot R1. I modified this circuit a little to be used from 12V power supply. The pin numbers of LM723 in my schematic refers to PDIP version of this IC. The original article claims that with this heater circuit the LM3046 array exhibits a temperature coefficient of -3.1 ppm/°C from 33°C to 50°C. Peak current that this circuit draws from 12V is about 80mA where from it comes down to 52mA when the circuit stabilizes. In Moog Prodigy you need two of these with total current need for 104mA.  I haven't compared this current consumption to Prodigys original heater circuit. But that's sure that it is a better circuit than the original. Next I must try this inside my Prodigy clone.