About untergeek

Early digital immigrant. Father. Maker. Tinkerer. Serendipist. Journalist. Synth nerd.

Bitte nicht nach einer Kalibrierung für das Pitchbend-Rad beim Blofeld suchen. (Macht er selber.)

Waldorf Blofeld Keyboard white, view on the pitchbend wheel

One day, my trusty Blofeld started drifting out of tune – pretty unusual behaviour for a digital synth. Even if it was in tune first, the drifting started as soon as I touched the pitchbend wheel, so I suspected that this was the culprit.

Blofeld wheelbox

Opening the Blofeld (all 18 screws on the bottom – remember?), removing the wheelbox, and measuring the pitchbend pot confirmed that the potentiometer was indeed damaged – while an end-to-end-measurement showed 9k, the end-to-mid-resistance could be virtually anywhere, screaming “Mechanical Damage!” to me.

The potentiometer is 10k lin with a knurled 6.3mm shaft and an M10x0.75 mount. Waldorf seems to have used a Piher T-21Y type (datasheet). As I did not find something fitting in my parts boxes, I took it apart, cleaned it, adjusted the pickup spring, applied a bit of contact grease, refitted the pot and closed the Blofeld

And now for the good part…

Although I measured that the wheel now zeroed around the pot’s 5kOhm mark, it had most definitely shifted slightly, so I started looking for the calibration routine. There has to be a calibration routine, right?

But the good Blofeld seems to calibrate on power-up and on the first usage of the wheel – no calibration routine for the wheels needed. Phew!

Waldorf Blofeld Keyboard white, view on the pitchbend wheel

Important note: Be careful to ensure that the Molex connector for the wheelbox sits correctly – when I pulled the plug, the plastic holder for the pins got pulled towards the edge of the PCB so when I reattached the plug, it did not sit correctly. Rule of thumb: If the plastic of the connector is visible from the top, you might want to push it back under the PCB.

I am still testing the new shop, and I have just discovered a working plugin for showing shop and blog in English and German.

crash test dummies giving each other a thumbs-up

My, this is SO exciting.

I figured out that I have reached the point where the unpleasantness of having to buy, install and maintain a proper web shop has dropped below the unpleasantness of having to do everything by hand. (I am sure there is an XKCD cartoon for this.)

And there is also the fact that the many buyers of Bob’s firmware deserve professional handling of their inquiry. A machine is much, much better at this than me.

So this little blog is running WPShopGermany now – although I am not at all happy with their multiple documentation, things look reasonably well so far.

A German shop – for English speakers?

The WPShopGermany is fantastically well adapted to German laws and regulations, but not quite as well to speakers of other languages. To offer foreign language support, the makers recommend using the commercial WPML plugin – for which a license comes in at impressive 79 dollars, much more than I paid for the shop plugin. Which is all the more infuriating as the language files for US-English are all there (wp-content/plugins/wpshopgermany-free/lang/). And no, I am not using the free version.

Ve vill finally get se hang of your humour, was!

Luckily, I discovered that there is a newly developed free alternative to WPML, WP Multilang. Installing and activating the plugin made the shop run fine, with German and English texts – but I have not come round to translating every important title and page into two languages, so you might still have to employ GTranslate at some point or another.

To err is human. To blunder spectacularly is untergeeky.

I tell myself that this is the downside (backside?) of serendipity, but I tend to overlook things and produce errors. If you should serendipously stumble upon one of those – a missing translation, a missing order form, something running wild – drop me a line, will you? Cheers!


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Midifying Jenny, Step 1: Replacing the old keyboard chip with a Teensy

This is the first post in a series of small projects for retrofitting my JEN SX-1000 monosynth with a simple and cheap MIDI interface controller. Read about the basic idea here. Today, I am designing and building the micro-controller brain of the Jenny retrofit – if you are capable of basic soldering, it should not take you more than two hours and a couple of very common electronic parts.

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Jenny and friends in action

Vanity post: This is what a session with the JEN sounds and looks like, mainly playing it as a bass synth. Look out for the freshly integrated phaser from 20:05 onwards. Other electronic sounds are from my Blofeld, a Ferrofish organ and Synthstrom Audio Deluge beatbox, a Meris Enzo guitar synth, an occasional Octatrack sample, and Eberhard’s guitar.

The glorious monkey art was conceived and painted by my friend Gerald, who – apart from playing organs and the Deluge – edited the video as well.

The chip shop is down…

…as I am installing proper shop software after all. Safer and faster for you, easier for me.

Might take a couple of days though until the webshop plugin is running and properly translated.

If you are about to lose patience, or would like to contact me about any issue or question, please use the contact form. (Yes, I DO know that it stubbornly mistakes some people for spammers but please stick with me; there is also a mail address on that site.)

Jenny getting her very own phaser…

…and my sweet Lord, does it make her shine!

Nothing fancy here. After inserting the booster/overdrive in between VCO and filter section, I took another of those lovely Musikding.de kits for a phaser, built it, drilled some holes into Jenny’s housing and fitted it.

I have been using Jenny as a bass synth recently, and I am quite impressed by the quantities of life and fun this old machine is adding to the mix. She doesn’t do that much in terms of tonal range, but what she does, she does well.

Drilling holes in Jenny’s front

I rediscovered an old trick when drilling metal: use a bit of alcohol, not on the person drilling, but on the surface you want to drill. And don’t go too fast.

A Pre-Filter Booster Stage for Jenny

Giving my JEN SX-1000 a bit of additional low growl by adding a pre-filter overdrive.

A nice little addition: Insert a booster circuit kit where the coupling capacitor between oscillator and the filter used to be. Come on, you’ll have to take out that damn capacitor anyway. And it sounds really nice, punching through the mix (samples below) – especially in combination with the sub-oscillator mod.

I do admit that you might think that this is a superfluous mod. After all, when you drive this circuit – any circuit – into overdrive and into clipping, the resulting wave form will, gradually, start to resemble a square wave.

But I could do it, so I did it. And I like it. So let’s get started.

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Using an Arturia Beatstep (or something like it) to control the Matrix-1000

MIDI controllers

Hi, I just bought and upgrade a matrix 1000 to 1.20 , I saw your video on youtube where you control yours with a Beatstep Arturia.. I’d like to control mine with my key lab but I don’t know how to do that ! can you help me ?

I tried to build a template for the key lab with Arturia software (midi control center) but all button and fader on the keylab are midi cc , and if I assigne midi cc 21 for the cutoff it doesn’t work.. I don’t know how to make rnpn with Arturia controller..

If you did with the Beatstep I’m pretty sure it can work with key lab..


Hi Clement, I hope you don’t mind answering your mail in public. Using simple MIDI CCs won’t do the trick; you’ll have to use NRPN. (To be honest, I don’t know whether the Keylab can be programmed to send NRPN but like you, I am pretty confident.)

What is this NRPN thing after all?

You do know about MIDI CCs. This is one type of MIDI command where you send a controller number – 0 to 127 – followed by the value for that parameter. Quite a lot of synths assign a CC number to each and every parameter, for example the Roland JX8P synths, or my wonderful Creamware Pro-12 VA synth. The big advantage being that those synths do not only receive MIDI CC values, they also send them – when you change a parameter or switch to a different patch. A fader box attached to the synth can be made to show the settings for each individual parameters, like my Pro-12 panel for the iPad. Spoiler: The Matrix-1000 won’t do this.

The problem with MIDI CC: sometimes, 128 controllers won’t be enough, especially as quite a lot of them have pre-defined meanings. It is pretty crowded in CC-Land.

To overcome this, NPRN was defined – same idea as CC, different way to do it. The main difference being that there are not 128 possible controller numbers but 16,384 of them – and, by the way, they can send a much higher range of values; instead of 0-127, values from 0-16,383 are possible. But, another spoiler, not with the Matrix, and not with Arturia controllers, either.

You see, NRPN is not really a different MIDI command. It is a way to use the MIDI CC command to transmit a larger range of values. A full NRPN sequence is not one MIDI CC command, but four: using four designated CC controller numbers to send a more complex message.

  • CC 99 is the higher part of the NRPN controller number (the MSB).
  • CC 98 is the lower part of the NRPN controller number (the LSB).
  • CC 6 indicates the MSB part of the value: the coarse setting of the parameter.
  • CC 38 indicates the LSB part of the value: the fine setting of the parameter.

As MIDI can only transmit values from 0-127, the wider ranges for parameter numbers and values are transmitted in two parts.

How do I use this with the Matrix and Arturia?

The Matrix with V1.20 interprets NRPN as follows:

  • The NRPN controller number is the number of the parameter you wish to change. As Matrix parameter numbers are in the range of 0-98, this means that the first part of the message – CC 99, the higher part of the controller number – is always 0.
  • The NRPN value is transmitted as a coarse value – via the MSB of the value message.

So to transmit the value for the DCO MIX parameter (#20), you’ll have to set the controls in Arturia’s MIDI Control Centre to:

(fixed a mixup here 07-Mar-18, thanks Jörg!)

  • BANK MSB -> 0
  • BANK LSB -> 20 (the number of the parameter)
  • DATA ENTRY -> COARSE (transmit the value in the MSB)

Arturia MIDI Control Center screenshot

If you managed to get a grip on NPRN, you may have noticed that Arturia is actually cheating: The NPRN transmission from the Beatstep does not make use of the full range possible. But at least the Matrix won’t make use of the higher resolution anyway.

More on the Matrix-1000 with V1.20 and NRPN here.

Extended iPad control panel for Creamware Pro-12 ASB synth

Certainly the last post in this blog this year – a happy 2018 to all of you, with loads of creative endeavour and technical discoveries!

Version 1.2 of my iPad control panel for my brilliant virtual Prophet, the Creamware/Soniccore Pro-12 ASB. Read here about it. The new version does not only allow access to all the hidden parameters you cannot reach by turning the synth’s knobs, it shows the actual settings for the sound as well – a true addition if you want to look at what the sound actually does. Once again, you need the TB Midi Stuff app for it to work, which is about 4 Euros.

You can get it from my dropbox or from the TBMS forum thread.