Tuesday, 25 October 2016

NLC Doof Drum Module - Build notes

These are my build notes for the Nonlinearcircuits Doof drum module.
It's Eurorack format.
This is a very different circuit from the 808 & 909 clones doing the rounds today.
Can't believe I would ever tire of those sounds but its great to have something different.
This circuit uses a trimmed down NLC dual OTA VCO and the VCA from the NLC matrix mixer
(a future build).

 I built the OTA VCO over a year ago.
That VCO used a OTA or Operational transconductance amplifier.

The topology is common enough in many drum synths: Trigger circuit, envelope follower, VCO, VCA.

Get started with some tanning. It's the Aussie way.

Firstly the virgin PCBs & faceplate:

First get those !Cs in.
Now the rest of the SMDs
I'm using a 10K on the RL ... LED resistor
Stuff in the through hole stuff:
pOTS & jacks next.

Now the LED. Get the orientation right. The anode is the long lead.

initial tests:
Initially, with a headphone, I found the volume very low and the LED didn't light up.
The LED resistor I used was a 10K. This is for super bright LEDs.
I swapped it for a 1K and noticed a sudden increase in volume & that the LED lit up.
I decided to do another swap. This time for a 510 R.
Much much better !!!
Very loud and the LED lights up nicely thanks.
Andrew F suggested that in order to get a bigger output, I change the 220k next to the TL072
He has taken it to 4M7 ...which is way OTT, ....bounces off the power rails.
Maybe a more sensible range would be between 1M5 & 2M2.

For the moment I'm really happy with the standard Doof module.
Other mods include
1.  CV control of decay instead of freq... see build & BOM pdf
2. replacing the 10nF capacitor on the input with a link to
create 808 style extended drum hits with gates rather than triggers.

1. NLC Build Notes
2. Muffs : adjusting output level of the Doof
3. NLC blog spot 

Friday, 21 October 2016


How times have changed (thank goodness). 
I came across this pic the other day. Is this for real ? 
It's a drawing of a "cat organ".
Cruelty knew no bounds in the 17th century.

 Many credit Athanasius Kircher with the original design of this instrument. He was a German Jesuit scholar.

"The musician selected cats whose natural voices were at different pitches and arranged them in cages side by side, so that when a key on the piano was depressed, a mechanism drove a spike in the appropriate cat’s tail. The result was a melody of meows".

Synth lovers today respect all animals, especially cats.

This is what Spike has to say about all this:

Thursday, 20 October 2016

All about JFETS - matching for synthesizers

This is a very good introductory video on JFETs - junction field effect transistors.

JFETs can be either N or P channel.
The channel conducts current moving from the source to the drain.
A voltage at the gate increases the channel resistance and reduces the drain source current.
Therefore, the FET can be used as an amplifier or a switch.

This is an excellent device.....Peak Atlas DCA Pro.
The bits about JFETS are around 7mins & the PC applications are at 14:20.

We often want to use a JFET as a variable resistor, particularly in phasers.
The problem with JFETs is that it is much harder to make consistent JFETs than to make consistent bipolar devices. Therefore matching them is important.

 These are screen shots taken of the readouts from my Atlas Pro of one of the JFETS.

 Try to match the curves for each JFET along with as many other specs as possible.

I tested twelve J112s.
measuring VGSoff, Idss, VGSon in that order.
 These were the results:

1. Vsg (off) = -2.97V
    Idss = 0.51v
    Vsg (on) = -2.04V

2. Vsg (off) = -3.14V
    Idss = 0.50V
    Vsg (on) = -2.04V

3. Vsg (off) = -2.98V
    Idss = 0.51v
    Vsg (on) = -2.05V

4. Vsg (off) = -2.71V
    Idss = 0.54v
    Vsg (on) = -1.80V

5. Vsg (off) = -2.99V
    Idss = 0.51v
    Vsg (on) = -2.06V

6. Vsg (off) = -2.68V
    Idss = 0.55v
    Vsg (on) = -1.77

7. Vsg (off) = -3.60
    Idss = 0.46v
    Vsg (on) = -2.63

8. Vsg (off) = -2.90
    Idss = 0.53v
    Vsg (on) = -1.98

9. Vsg (off) = -2.66
    Idss = 0.55v
    Vsg (on) = -1.76

10. Vsg (off) = -2.89
     Idss = 0.53v
     Vsg (on) = -1.97V

11. Vsg (off) = -3.17
     Idss = 0.50v
     Vsg (on) = -2.24

12. Vsg (off) = -3.15
     Idss = 0.50v
     Vsg (on) = -2.22V

A huge variation in results from just twelve J112s
I'll go with 1 & 3

1. Vsg (off) = -2.97V
    Idss = 0.51v
    Vsg (on) = -2.04V

3. Vsg (off) = -2.98V
    Idss = 0.51v
    Vsg (on) = -2.05V

1. Stompville
2. Learning about electronics
3. Geofex
4. Edn.com

Sunday, 16 October 2016

Tokyo Akihabara Radio Center

This is where you can see some old school electronics.
.... the stuff that rebuilt Japan after WWII.
 Akihabara ‘electric town’ is famous for tiny retailers selling radios and electronic parts at cut-rate prices under the Sobu line tracks.
 It's a shade of what it used to be in the 50's & 60s but some of those "tiny hole in the wall" shops are still here, crammed together. It's worth a visit just for the historical aspect.
DIY old school with parts in open boxes and plastic containers.
Analog, digital, LEDS, knobs, jacks, resistors, capacitors, etc etc... the way it used to be before
the internet came along and killed off the little shops.
Most of thehe electronic shops that used to crowd both sides of this street have been displaced by game centres and animation shops. It’s also a great place to treasure hunt for old games.

 Akihabara is centered around Akihabara Station, located on the JR Yamanote, Keihin-Tohoku, and Chuo Local lines. Take the "Akihabara Electric Town" exit. (ラジオセンター), 1-14-2 Soto-Kanda.

 By subway : travel to Akihabara Station by the Hibiya line (H15), or Suehirocho Station by the Ginza line (G14).  


Friday, 14 October 2016

Bonsai - Narita, Japan

Some trees that just wowed me as I was waiting for that plane to take me home.
Mountain Maple ... 80+ years old.

 Chinese Juniper ... Over 100 years old.

The literal meaning of Bonsai is "potted plant".
But these are more than just potted plants.  It's an art form that is alive and constantly
changing..... an attempt to represent nature in miniature.

Bonsai, their growth, flowers, fruits and leaves are so beautiful.

Paintings of bonsai can be found in picture scrolls of the Kamakura period (1192-1333).

Tuesday, 11 October 2016

NLC Phase/Flange 329 - Build Notes

These are my build notes for the Nonlinearcircuits eurorack version of the Aries 329 Phase Flange.
"Circuit is based on the Aries 329 phase/Flange, which is not the same as but shares some similarities with the Arp Quadra phaser and the Tau pipe Phaser. This version is nearly all smd and uses BCM847 matched transistors."

The old Aries brochure:

Some pics of the NLC panel & virgin PCBs

 Andrew supplied this board with the matched 847s already soldered onto the PCB.

Some NLC words of wisdom.

Eat your Makeup is a short film by filmmaker John Waters starring Divine, Mary Vivian Pearce, David Lochary, and Maelcum Soul. (1968)

First solder the ICs.

This row is of the 22nf caps. Don't use cheap ones.

Install the rest of the SMDs
It's time for the JFETs
JFETs can be either N or P channel.
The BOM specifies either a J108 or J 112. Both are N-channel.
The module needs two of these matched FETs.
G= gate, S= source, D= drain.
A voltage at the gate controls the channel resistance (between the S & D).

 Andrew reckons that you do not need to match them to 1μV. Just buy a batch of at least 10 or so and find the 2 closest to each other.  Maybe with in a few mV is okay. ??

I purchased a batch of J112s from Mouser and tested them using my Atlas DCA Pro.
Its a wonderful device which will make your job so much easier.

It's important to match the FETs as closely as possible. In my batch of 12 the results varied greatly.
I tested for VGSoff, Idss, VGSon in that order.

If you can get VGSoff very close and Idss in the ballpark, you should be ok.

You can see my full test results here:

There was a huge variation in results from just twelve J112s.
Maybe I'll get a batch of 20 to 30 next time to get closer matches
Today I'll go with 1 & 3

1. Vsg (off) = -2.97V
    Idss = 0.51v
    Vsg (on) = -2.04V

3. Vsg (off) = -2.98V
    Idss = 0.51v
    Vsg (on) = -2.05V

Main components are in.
Now its time for the jacks, switches & pots.

This is what the final module looks like:

Calibration is very important.
When I first turned the phaser on I was confronted with a loud continuous screech.
Adjustment of the trimpots eliminated this problem.

The main one is the 50K pot near the phase jack.
It also controls the amt of clipping at the outputs. A lot depends on the FETs chosen
Check out Andrew's NLC build notes for further info regarding calibration.

1. Muffs
2. NLC Blog
3. NLC Build notes
4. NLC Blog 2
5. Retrosynth Ads blog
6. Original aries schematics for the phase-flanger
7. Muffs - NLC 2016 modules

Synthesizer shopping in Tokyo

Japan is a powerhouse in synthesizer manufacturing and I expected on a recent trip
to Tokyo to be swamped with shops selling all manner of keyboards.
However, they are not as common as one might expect.

Below are the ones I found. Please email me if you know of more.
The largest three are 5G in Shibuya-Ku and Echigoya & Ishibasi in central Shibuya.
Ochanomizu is the home of numerous guitar shops. I found two along the main street,
Kanda Surugadai that also sold synthesizers.



Ishibasi in central Shibuya:
Synth website.

BEAM building, 2nd floor.
31-2, Udagawacho, Shibuya.

Echigoya (Shibuya):
It's right across the road from Tower Records.
 Its on the 9th floor:

Five G in Shibuya-Ku:
Le Ponte Building, 4F, 1-14-2 Jingumae
Shibuya-Ku, Tokyo 150-0001

EMS Polysynth

Moog Memory Moogs
ARP Odyssey & Roland Jupiter 8.

EML 500

Korgs:MS50, MS20, SQ-10 sequencer & The Korg vocoder.
Wow ... three Roland 808s