My Mini Moog Voyager. Click to go to my web site...

Sunday, March 16, 2014

Synthasystem VCF

Ronny just finished a build and here are some photos and excellent modifications he made. Thanks for sharing Ronny.






Ronny wrote:
"- I added a second CV potentiometer.

"- I omitted the switch and added three separate attenuator potentiometers (25k)
  for the three inputs (LP, BP, HP). They sit before the 47k resistors. The 47k resistors
  connect directly to the former "switch outputs" now. This enables to get a kind
  of all-pass characteristic when mixing the same signal to multiple inputs or to get
  a kind of frequency-dependent interpolation with different input signals. I also like
  to add a bit of HP while primarily using the LP. I normailzed the "BP in" and "HP in"
  connectors to "LP in".

"- I used 330nF instead of 1.2uF for C10 at CV in to reduce drifting with steady CV
  and to enable faster modulation. Maybe I reduce it even further.

"- I drilled a hole into the Power PCB to easily adjust the "CV reject" trimmer without
  taking the filter apart. Luckily there was just a ground plane at this position on
  the power PCB that could be drilled without damaging something.

"- I had to omit the nice Steiner wave logo on the frontpanel, but added a little hint
  to you "DI" and me "RV" :-)

"Here are some other build notes that might be of interest for you:

"- feed it with +-12V in a Doepfer Eurorack system, but reduce -12V to -10V with
  your Power PCB, also use the filtering on the Power PCB (V+, V-)

"- used SSM2210 and 2N5172 as specified
 
"- used two 2N2907 with HFE of about 140 instead of the PN5138 (HFE measured
  with a  medium-class multi-meter)
 
"- had to use linear potentiometers for everything, because I did not get logarithmic
  ones of this size, but this still feels fine

"- used a trimmer having 200 Ohm instead of 250 Ohm, works fine

"==> self resonance starts at about 2 o'clock resonance potentiometer position, this is fine
" ==> have no problems with power noise, crosstalk or whatever"

Thanks again Ronny.

Monday, September 2, 2013

Moog 914 Fixed filter Bank progress

914 Clone and studio

914 clone, Eagle v. DipTrace...

I decided mid stream I wanted to migrate from Eagle to something new. A thread on the SDIY list got me thinking again about the offerings and some of the frustrations I have with Eagle. Eagle has been a great capture/layout system, but I've been more and more frustrated with some of its core operation and workings.

One package which came up was DipTrace. I gave it a look and like it. It's got a few oddities, but seems to be well supported, with reasonable pricing even for the full unlimited version, and full featured, more than I'll ever need for the 2 layer synthesizer circuits I do. And, very important, PCB-Pool, who I use for PCBs, accepts DipTrace format directly.

I've already found that editing/creating parts is as easy if not more so than in Eagle. Schematic capture is intuitive, PCB layout is also nice and the auto place is nice for a first go at least. A nice feature is you can hand place components which have to be in certain areas, the the auto place will put the other components around trying to minimize the signal length. Again, for the simple stuff I'm doing maybe not needed, but also works nicely and saves some time. There are some quirks I'm finding, like selecting which labels to display and placement, but I think I can make it work.

In the end, I bought a license and will be migrating my future work into DipTrace. The Steiner stuff is pretty fixed and I don't plan on any modifications. But if needed, I can export the Eagle schematic or PCB and bring it into DipTrace. Not the ideal, but a workable solution should the need arise. I'll also output all the Eagle designs into Gerber files for future proofing. This is something I tested quite a bit before I decided to buy.

That leaves the 914 clone I was doing a bit in limbo. I had already laid out one PCB and had two schematics completed. While I can import the schematic and even the PCB into DipTrace, I found that there is still some work to make the schematic useable. At this point, I think I will probably just start over in DipTrace. The schematics are really pretty simple for this clone and then I'll be able to make use of the enclosed and custom libraries I've got in DipTrace.

My time line for PCB prototypes is now a couple of months out at least. I need to learn DipTrace, double check the schematics, etc. but, I'm excited to get it done. I still intend to build two, one with inductors for everything and one with GIC simulated inductors.

Studio

My new studio is done. I just need to make time to actually re-connect all the instruments and a little organizing. I'll put up some photos after it's all hooked up and neat.

Tuesday, June 25, 2013

New studio and Moog 914 clone

I am moving to a newly finished attic space for my studio. I'm pretty excited about it. This photo shows it with sheetrock and baseboards. The painters finished today and I should be able to move in this weekend. I get the far end, about 12 feet wide, and 15 feet long out of about 30 feet. The rest will be for storage. the two round "lights" are actually skylights. They install a mirrored tube to a clear dome cover and it collects and reflects the light like crazy. I will put some diffusers over the openings to help soften the very bright highlights.


Next, I have a new project. I decided to roll my own Moog 914 fixed filter bank. I have two of Yves Usson's version, and PCBs for Jurgen Haible's version, so why my own? A couple of reasons. First, I want it to easily fit behind a euro rack panel. Second, I want to have PCB mounted pots to minimize flying wires. Third, I found a source for inductors and I want to make it easy to use either inductors or a GIC simulated inductor like Jurgen offered. The result will be 4 PCBs which will fit behind a 28 HP euro panel.

Carsten Toensmann at www.analog-monster.de has his own 914 clone for which he made his own inductors. He has decided to offer a service of winding custom inductor values, in particular those found in the 914. I think he is also offering PCBs. Carsten is very helpful and I encourage you to look at his work. Really amazing.

I purchased two sets of coils from him and will build at least one of these clones with real inductors. The layout I'm making will allow for the size inductor Carsten is making as well as a simulated inductor for the high pass and band pass cells. The low pass will have to use real inductors or an active low pass filter like Yves Usson designed or Jurgen Haible designed.

I decided that I will have the option of using all the original Moog circuitry. Most of the parts are still readily available and the one transistor which is out of production, 2N2926, is still to be had at Nikko Electronics http://www.dalbani.co.uk/index.php. I have always had great service from them and highly recommend them.

Besides using the original Moog circuits, by flipping a couple of DIP switches and moving a jumper or two I'm going add the options of having a more useable output stage as well as an input stage that can handle higher input levels than the Moog original. In my simulations, the circuits I borrowed (from Jurgen Haible's fixed filter bank clone) match the frequency response of the original very closely with the advantage of a higher level output and higher level inputs. I am also adding even and odd cell outputs following Yves Usson's great idea.

I'm almost read to actually start the layout process. I've got the input and output stages designed and simulated. I have the basic bandpass filter cell designed as well as the high pass and low pass sections. I just have to copy and paste all the filter cells and adjust the values. Then, layout the PCBs. I think I might realistically have PCBs in hand by the end of July to middle of August. I'll post some samples when I have it built.

Friday, April 5, 2013

Project update



Project update:

First, some rather poor photos of my current setup.







Left Cabinet, left to right, top to bottom:

  1. Voltage Processor/Mixer, Dual Sample & Hold, Peak Selector, Sequencer
  2. 3 VCO Type A, 4 waveform outputs each
  3. 3 sets of: VCO Type B - Saw/Square, VCF
  4. Oscilloscope (www.Gabotronics.com XMega Xminilab)*, Ribbon Controller
  5. MIDI controlled DuoPhonic keyboard, Trigger Converter, Resistor Ladder controlled DuoPhonic keyboard connected to ribbon controller.

Right Cabinet, left to right, top to bottom:

  1.   Sequencer, Frequency Divider
  2. Dual Voltage Follower (Slew), VCO Type B - Triangle/Sine, Selective Inverter, VCO Type B - Triangle/Sine, ENV VD**, VCA/Mixer, Input Amplifier
  3. Voltage Processor/Mixer, VCA/Mizer, Triple EG, VC Trigger Generator, VCA/Mixer
  4. Multiple, Dual Voltage Follower (Slew), VCA/Mixer, Triple EG, VC Trigger Generator, Panel Power Output
  5. Noise, Phase Shifter, Ring Modulator, SynthTech Moog 904A Clone***, Dual Voltage Follower (Slew), YUSynth Moog 914 Fixed Filter Bank Clone****, Tuner/Monitor, Stereo Monitor*****
 The controller is an Arturia "Analog Experience THE LABORATORY 61" keyboard, I liked the wooden end caps and it's a great controller for my Arturia modeled analog synthesizers. As a side note, the Arturia Mini Brute Page, Mini Brute Details, about half way down has a photo of Nyle in front of a modular system you might recognize :)



Notes:

* Gabriel at Gabotronics.com has some really fun oscilloscopes and the Xminilab just begged to be put behind a panel.


** ENV VD

 The ENV VD is a Steiner design which I don't think was ever released. At least Nyle can't remember ever selling one. He explained it was a more "traditional" design to compete with the other guys. When the "DAMP" switch is in the up position, the DAMP knob controls the final decay, otherwise the DECAY knob controls the first decay to the DURATION LEVEL, and the final decay. The DEL/ATT switch changes the function of the ATTACK control to a delay to the start of the envelope and then has an immediate attack, like the ENVDT design.

*** and **** MOOG Module Clones:

The next two modules with asterisks are not Steiner designs of modifications of a Steiner design and technically, they are modern clones of the original MOOG designs.I'm including them because I know that back in the mid 70's when I started this project, I would probably have tried hard to get a MOOG filter, and maybe some other modules. My goal was to have the equivalent of a MOOG 55 system. Even though Nyle had his voltage controlled filter, I probably would have eventually tried to get my hands on a MOOG filter and the FFB because the 55 came with a FFB. It also came with a Dual Trigger Delay (see below). So, I added these two wonderfully designed modules to the system. At some point, I may actually try to do my own clone of the 904A, B, and C as well as the 914 using the original parts, but that is down the road. I may just buy them from COTK or MOS Labs and try to jam them into the Euro format I've chosen. Not too sure about that however...

I also have another Jurgen Haible Frequency Shifter which is based on the MOOG/Bode frequency shifter design if I understand it right. I might want to add that as well. We'll see.

*** MOOG 904A Clone:

I thought it appropriate to add a MOOG filter clone and Paul Schreiber's designs are wonderful. Give SynthTech a look, www.synthtech.com.

**** MOOG 914 Fixed Filter Bank (FFB) Clone:

OK, so I also wanted a fixed filter. Yves Usson's Fixed Filter clone is really excellent. I love that he split the cells. It gives a very cool left/right effect. yusynth.net/Modular/index_en.html

***** Stereo Monitor:

This last module with an asterisk is based on a Steiner design. I took the Tuner/Monitor Nyle designed, got rid of the "Tuner" and doubled the "Monitor". It makes for a great output interface to my DAW and keeps true to the Steiner designs.

OTHER PROJECTS:

Trigger Delay:

There were a couple of modules Nyle never did design and were ones I would probably have purchased or cloned back in the mid 70's when I started this whole deal. My first project one is a MOOG 911 Dual Trigger Delay which was included in the MOOG 55 system. Not too exciting, and Nyle has a delay built into the ENV DT and ENV VD, but it's a pretty straight forward design and fits nicely into a 1 unit wide module.


Pratt-Read Keybed Clone:

I'm still wanting to make a "real" Steiner keyboard. I found Gino at www.en.gino-midi.nl/index.htm. He is a DIY electronic organ builder and came up with a kit involving a silver plated rod, flexible phosphor bronze contacts, custom PCBs and (unfortunately) a custom built keybed. But, I have hope. I purchased a "contact kit" and when it comes, I'll have a good look at whether or not I can modify a modern, easy to find keybed with his parts, or something similar. Then, I can build the DuoPhonic electronics into a custom keyboard controller and fore go the MIDI conversion. I'll still keep the MIDI to Steiner module because it is just useful to interface to the modern world.


Microcon:

Chris at www.synthcube.com is going to be selling Microcon kits. He really does a nice job with them and I highly recommend you look at his site. You'll see he is also carrying the SynthTech MOTM modules and DIY parts.

I'm still selling the bare PCBs, but Chris makes it very easy with a complete kit.


Music?:

There you go. I've actually had a break from building and have been tweaking knobs, great fun. I can't call it music, but it is the icing on the cake for me. 40 years after  I first heard a squawk out of a breadboarded VCO and keyboard, I've pretty much finished it.

Stay tuned. I will post some updates from time to time and hopefully audio/video of what I'm doing. I also an trying to learn Adobe Dream Weaver so I can get the website updated and cleaned up.

Thanks for the interest.
David

Friday, October 12, 2012

Micron PCBs

OK, so I finally figured out how to get back to my blog so I can post...

I received what I hope will be the production PCBs for the Microcon. I stuffed one and gave it to Nyle to test. He should be through with it within a week or so. Then, I'll be ready to sell the PCBs, so please stay tuned. the initial tests on the last prototype were great. Nyle found some layout errors and made some suggestions which are reflected in the latest layout.

Sorry to be absent, but good things come to those who wait :)

Tuesday, April 17, 2012

Duophonic Module Assembled

Module before racking
Module in the rack and working
Doepfer MTC 64 MIDI to TTL voltage converter
The High Octaves reed relay PCB which sits under the Dopfer MTC 64 board



Top view of module. Top to bottom: MTC 64, HIgh Octaves relay PCB, Low Octaves PCB, Duophonic PCB
Side view of module. From left to right: MTC 64, High Octaves relay PCB, Low Octaves relay PCB, Duophonic PCB.
Side View of the module. From left to right: Duophonic PCB, Low Octaves relay PCB, High Octaves relay PCB, MTC 64

The Duophonic Keyboard PCB is fully working and it is sweet. This was the first "module" I built when I originally started this project in the mid 1970s, so it is fitting it is effectively the last module in this resurrection project. It is big and deep. Using reed relays instead of solid state relays meant I had to split the Pratt-Read keybed emulator into two PCBs instead of one. But the very low resistance and zero leakage of the reed relays made it worth the trade off.

If you have an old Pratt-Read keybed, or another switch-per-key on a common buss device, you don't need the relays or MTC 64. You can make a resistor chain on the switches, like in the original and hook it up. You can also make/configure your own custom controller to drive the keyboard electronics.

Essentially, here is what is going on. The MTC 64 takes a MIDI note on/off and turns on an individual TTL level (or turns it off, you can configure it) for each note number from 0 to 63. I take 0 through 60 (for a standard 5 octave controller with 61 keys) and connect each one to its own reed relay. This acts like the buss/key system on the old keybeds. On the other side of the relays is a resistor chain so that when a key is pressed, it taps into this chain and sends this signal to the "buss" input into the electronics. So, the Duophonic electronics sees exactly what it expects, a voltage divider resistor chain, just like the old Pratt-Read keybeds.

This particular module acts like a MIDI to Duophonic Keyboard converter, but there is no reason you can't just build the Duophonic electronics into a dedicated keyboard, or even an external module.

The Duophonic Keyboard was pushing the technology at the time when most others were still using monophonic keyboards. The Duophonic was  both a low note priority monophonic keyboard and a two note keyboard.

There are some interesting "features" of this particular keyboard. The upper voice tracks the lower voice when an upper key is not pressed; there is no sample/hold for the upper voice due to the way it's generated.

Next, you can either have a new trigger/gate on each low key press event, or only a new trigger/gate when the previous key is released before the next key is pressed. Nyle calls this legato or lift playing respectively. The upper voice does not generate a gate/trigger.

There is a pitch bend knob. I chose to make this a big knob with a finger spinner to make it easier to turn. Also, because the pot is not spring loaded, I chose one with a center detente to make is easier to feel when I was back to center. Nyle added an electrical dead spot in the Pitch Bend, too so if you miss the detente, you will still be OK.

There is a Portamento knob, and I added a jack for a normally closed foot switch so I could dial in a Portamento and then hit a foot switch to activate it.

There is also an Auxiliary Scale which can be tuned for other scales and it can be switched in and out.

There is a reverse switch reverses the keyboard, and a Range switch lets you shift the keyboard output up or down by octaves.

Now I have all the pieces to my Synthasystem, I'll try to get some additional video/audio up of all the pieces working together.

Next, since the keyboard is done, I'll start ramping up on the Microcon!

Wednesday, March 21, 2012

Duophonic Electronics Work!

Here's a shot of Nyle after he and I had checked out the duophonic keyboard electronics. Hmmm, looks like the scope is off. No wonder we couldn't pick up a signal...

You can see some of his original Synthasystem modules in the left corner.

The Duophonic electronics all work and I've ordered some production PCBs. Next step is to figure out packaging and finish the panel.