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

Friday, December 24, 2010

Updates to Web Pages

Hi everyone. I've been working today between last minute shopping on the web site. I've completed the Sample & Hold, Peak Selector, and Phase Shifter pages. 

I've added some photos of the finished modules, too. 

The Trigger Converter panel went through some major revisions. 

I also updated all the schematics with appropriate version numbers and edited most pages for content and accuracy. I added explanations to the EG page in particular regarding a queer problem triggering the ENVDT with short triggers. The fix is simply changing a couple of resistor values. See the web page. 

I also re-did how the Power Regulation/Distribution PCB BOM is presented. I put it in its own separate file. I think that is more clear. 

I'll be adding some more modules to the pages before the end of the year. 

Merry Christmas to all who celebrate it, and Happy Holidays if you don't. 


Wednesday, December 22, 2010

VC Trigger, S&H, and Trigger Converter

The VC Trigger Generator, Sample & Hold, and Trigger Converter work great. There are some footnotes however:

VC Trigger Generator:
The first go around just wasn't working right, so I gave it to Nyle to look at. There were a couple of changes Nyle made. He moved where the Gate and Run switch connect and a de-bounce circuit. The push button switches I'm using bounce a lot. The good thing is it prompted Nyle to add some de-bounce circuitry to the modules so they should be more robust for everyone. He also added an LED for visual feedback of the rate and width.

Sample & Hold:
Worked first time. I was concerned that the high impedance nodes weren't guarded, but I spread out the legs of the FETs and kept the other traces as far away as practical to minimize leakage. It seems to hold for several seconds with no droop.

Trigger Converter:
Works fine first time, too. Although, the way I laid out the panel is opposite to how the PCB is laid out. I ended up rotating the PCB by 180 degrees so the jacks were close to the connectors.

I was playing around with the sequencer and EG and realized the sequencer clock was not triggering the ENVDT section; EG3. I took the EG and sequencer down to Nyle and we spent an afternoon trouble shooting. This resulted in changing two resistor values. The problem was related to my doubling the timing capacitor C3 because I had to use a 1 Meg pot instead of a 2 Meg pot. The clock output pulse of the sequencer is pretty short, about 0.0001 second. Using a doubled value for C3 prevented C3 from discharging while the trigger was active, and so the primary flip flop wouldn't stay "flipped". This is only a problem for short triggers and I could have just as easily used a smaller capacitor. But Nyle likes to have more robust designs. So, changing the two values ensures the EG will work with short triggers, too.

Last, UJTs:
The sequencer clock was saturating at about mid-span for the rate control. Nyle suggested tweaking a couple of resistors, but it didn't change anything. I was using a 2N2646 UJT, listed as a substitute for the 2N4891 originally used. I have several other UJTs, so I thought I'd try a different one, NTE6409 to start. That fixed the saturation. So, I tried a 2N4871 and it worked, too. The best thing is the 2N4871 is the cheapest, about $1 or $2 ea as opposed to $6 or $7.

With that new information, I swapped out the UJT in the VC Trigger Generator and that fixed some residual erratic behavior I was seeing. I also used the 2N4871s in the Sample & Hold in the random voltage sections.

OK, I've also made a couple of videos, but they really stunk. Nyle also suggested I do some videos for YouTube. I will make some, really.

Thursday, December 16, 2010

Still moving ahead

Hi everyone. I'm still moving ahead. Work kind of slammed me the past couple of weeks so PCB stuffing has slowed down. I've got more panels on the way and will have prototypes of the Ring Modulator and Headphone amp/A440 Reference ready for prototype PCB purchase soon.

I'm going to meet with Nyle tomorrow to go over calibration questions I have and the project in general.

Nyle made a recent appearance on a local morning show with keyboard player Richard Souther. They play a very nice version of the Holly and the Ivy and Nyle shows off his talent and his EVI breath controller. They also have a new Christmas CD available. Here are some links:

You can get the music here:

Very nicely done.

Merry Christmas and Happy Holidays everyone!


Sunday, December 12, 2010

More PCBs

OK, I've now got a stack of prototypes to build: Noise, Sample and Hold, Selective Inverter, Phase Shifter, and Voltage Processor/Mixer. Busy, busy, busy for the next little while. I also got a small order of Frequency Divider PCBs and VCO-B Triangle and Sine wave output.

I also ordered some panels, a couple of re-do's like on the VC Trigger Generator I added an LED, I added a jack for the Phase Reset for the VCO type Bs. I also re-did the whole Trigger Converter PCB, and some other minor changes. Check the website for the new files.

Still struggling about demo videos/audio. I'm also seriously considering selling pre-built modules. Probably start with the filter, maybe VCO, VCA, EG, don't know about the rest. Time will tell. Right now, I just want to get the rest of the modules tested and available.

There are some other minor updates to the web site, too. Keep in touch.

Stay tuned.

Saturday, November 27, 2010


I didn't get the audio/video up. Decorating for Christmas, family party, and just spending time with my wife and kids took priority.

That said, I did get the VC Trigger module together and working. I'm on the road next week and am going to stop by Nyle's to pick up the Frequency Divider and show him the Trigger Generator.

Next up will be the Sample & Hold.

I promise I'll get some video together right away.

Wednesday, November 24, 2010

It Works!

I tried to get some audio and video, but I was way over driving the audio input on my camcorder, so here's a still. Top: VCO, VCF, Triple EG, VCA. Bottom: Peak Selector, Sequencer. Not shown: Frequency Divider (Nyle still has it). At the very bottom is a Frac Rack with some utility modules I put together;  Blacet Bar Graph, 2 mini O'sopes, A440 tuner, and a Yusynth Voltage Standards module (thanks Yves,

The good news is it all works! The Sequencer, Frequency Divider (THANK YOU Nyle), VCO, VCA, VCF, EG; it's a real system that now needs expanding!

And, expanding it is... I have prototypes for the Selective Inverter, Voltage Processor/Mixer, Phase Shifter, and Noise Source on order and have received prototypes for the Sample and Hold and VC Trigger.

The sequencer is amazing. Unlike any other analog sequencer I've seen or used.

I will have some video and/or audio this weekend. I'll figure out someway to get an audio and mic feed into the camera. If I have to use the built in mic, I will but I'd like higher quality audio. I want to do some tutorials to show how the different modules work and the effect of different connections.

Update on the Frequency Divider. I think I wrote that the divide by 11 was dividing by 7. There were two problems. First, I had installed a 2.2k where a 22k should go and there was a 3.9k resistor missing in both my schematic and Nyle's original schematic which should be in series with the reset diodes to the Flip Flops. It's kind of funny. Nyle said he probably would not have found the missing 3.9k if not for my stuffing mistake. He explained that sometimes the final schematics were drawn after the PCB layouts were done and the modules were in production. They often did the layout from the first "hand drawn" drawings (really, they were all hand drawn, but the final ones used drafting tools so were much easier to read). I am really spoiled being able to use a great layout tool like Eagle. Worth every penny.

Bottom line is Nyle did get it figured out. I added the 3.9k to the schematic and ordered a small production run.

So the next couple of months should see the culmination of the Synthasystem.

Stay tuned.

Saturday, November 20, 2010

New user build

Tony just finished his VCF PCB and wrote, "just finished my VCF, waiting on the panel but it tested out fine and is mean and nasty!

thought you might like to see a picture of my populated board as i used a lot of NOS parts. all carbon composite resistors, a couple vintage transistors (5138s) and .1uf caps, and original AD SSM chips.

thanks again, it was a lot of fun. i look forward to building more Steiner circuits."

Thanks Tony!

Wednesday, November 17, 2010

More modules

Sorry, no photos or audio...

I received some PCBs:


  • VC Trigger
Small production run:
  • Power/Regulation
  • Sequencer
  • VCA/Mixer
On order:
  • Sample & Hold
  • Phase Shifter
  • Voltage Processor/Mixer
  • Noise
Small Production Run:
  • VCO-B with Square and Sawtooth
  • VCO-B with Sine and Triangle
  • Peak Selector
By "small production run", I mean less than 10, sometimes just a handful.

I'll try to catch up the website for the new modules. 

The modules left to go:
  • Ring Modulator
  • Selective Inverter
  • Tuner Monitor
  • Voltage Follower (Slew)
  • Some keyboard. Either the two voice or the MKB. I think Nyle would like me to do the MKB, but for my own goal, I'm still leaning towards the Two Voice. I have a Fatar keyboard and just need to figure out how to make it behave like a bus type rather than a multiplexed. The MKB actually could use the multiplexed keyboard easier, so I don't know...
In testing:
  • Frequency Divider
So, really the end is in sight for the capture of all the Synthasystem modules. I still need to punch out some panel designs and then actually finish building the things. I'm hopeful by early next year I'll have at least one of every module working and racked.

I will probably offer the Microcon as a PCB, too. I don't think I'll do the Synthacon as the Synthasystem is much more interesting to me. The Microcon is interesting as a standalone desktop or rackable synthesizer. However, it does use Vactrols which I have heard are banned in Europe now. Nyle has suggested he might have a workaround, so stay tuned.

New modules? Well, Nyle and I have discussed this and have a couple of ideas. I'd like to see a formal trigger delay and Nyle has some other interesting ideas. So, if interest is really there, maybe.

Friday, November 12, 2010

Frequency Divider

The Frequency Divider is done, but I'm having a problem. The divide by 11 is dividing by 7, not 11. All else works just as it should. I've gone over my schematic capture many times comparing to Nyle's original and just following the logic. I can't find an error either in the logic or my capture. I've tested continuity, switch operation and wiring, no luck. Nyle has taken a look at my capture and didn't see anything either. I must have some kind of wiring error, but it escapes me.

More prototype and limited run production PCBs are on their way. Should be here next week.

Sunday, November 7, 2010

Frequency Divider and Peak Selector

What's new you ask?

I've been working on the layout for the VC Trigger Generator (ready for prototype) and the Sample & Hold. I've had some good help from the SDIY list again regarding "guard rings" as well as some one on one instruction from Nyle on the topic. The Sample & Hold is almost ready for prototype. I had it done and realized I needed to add the circuitry to accommodate Voltage Triggers. I added the components but now have to clean up the auto-route.

Next, the Peak Selector is done and seems to be working, although it still baffles me a bit. I need to get it hooked into an actual patch to see what it does.

Last, I have my Frequency Divider PCB stuffed and behind a panel. I now need to hook up the panel controls and see if it works. I am hopeful...

Monday, October 25, 2010

Yes, the project is still alive...

Been awhile... The EG production PCBs are in. I also received the Frequency Divider prototype PCBs, one for me, one for Nyle. I think I posted this, but I also have the prototype Peak Selector PCBs. At Nyle's request, I'm working on the layout for the VC Trigger Generator and the Sample & Hold. I have a two output version of the VCO done, too; Square and Sawtooth. I have a second combination, Sine and Triangle, in the works, too. Sort of an attempt at the VCO type "B" Nyle had. I think they may be good for modulation or LFO applications. They're based on the standard VCO design so they'll work for audio, too.

Wednesday, October 13, 2010

Rack and Roll

I got the first three modules racked and have ordered some "Gator" cases to put the racks in. I thought it would be fitting to make this synthesizer "portable"

As always, you can visit the website for details, schematics, build notes, order forms, etc.

Monday, October 11, 2010

Progress on my own system and general update

As I already posted, I received the production VCO and VCF PCBs. If you were waiting til they were in stock, they're here so order away!

I also finished my own first official VCO and Triple EG. I haven't taken time yet to actually rack them and hook them into my audio system, but will try to make time this week so I can record some audio. The VCO calibrated right up with no problems and I am getting decent tracking.

This EG isn't as packed with voltage control as some newer EGs, but the Damp and Quathin are fun and I really like being able to turn the attack knob essentially into a trigger/gate delay time knob. Combining the output of EG3 with EG1 or EG2 is also very unique and you can put together some very complex envelopes this way. I also ordered a batch of Production EG PCBs.

I'm working on my filter right now and should have it done tomorrow evening. Next up a VCA I think, then my sequencer. That will be the first 5 done and verified.

I received the prototype PCBs for the Peak Selector and will try to get one stuffed soon. Nyle will also get a PCB to play with and test. And, I ordered the prototype for the Frequency Divider. Useful module all around.

Saturday, October 2, 2010

VCO/VCF PCBs are in

I received the VCO and VCF PCB order this week and so will be sending out PayPal invoices to those who pre-ordered. Next up will be the EG PCBs, sequencer, and VCA.

Thanks everyone.

Monday, September 20, 2010

Triple EG on its way

Here are some photos of the Triple EG in progress. The panel is a tight fit, but all the controls and spacers for the PCBs fit, which is the important thing.

Note on the Power/Regulation PCB, I did not add any regulators since this module runs on  +12 volts only. I put a jumper for the +12 volt regulator and the two filter caps, ferrite bead, and diode.

Also note the production version of this PCB has the trigger conversion circuitry on the PCB itself. This prototype is missing the conversion.

Next, I will stuff the two ENVDL PCBs.

Saturday, September 18, 2010

Panels are in. VCO/Panel stuffed ready to connect

The first panel order arrived, so I stuffed a VCO panel to see if it all fit right.I'm waiting on some MTA connectors to do the flying wires.

This PCB was stuffed like I expect most to do it, that is with a THAT340 for the exponential converter and PNP trio, and monolithic matched pairs for the other pairs. I'm choosing to panel mount the V/Oct trimmer (see the above photos for a close-up of the trimmer adapter) and the VC3 Var Scale. I'm using a pot for the VC3 Var adjust and a panel mount trimmer for the V/Oct.

I'm still taking pre-orders for all the PCBs and should have stock for the VCO and VCF before the end of the month.

Monday, September 13, 2010

Production PCBs ordered

I ordered a batch of production VCOs and VCFs today. I'll order other modules in a couple of weeks.

Sunday, September 12, 2010

Power Regulation/Distribution PCB

As I build up the release PCBs, I'm going to add photos of the working PCBs to help with component placement, etc. Up first is the Power Regulation/Distribution PCB. See the web page for more info.

Wednesday, September 8, 2010

VCF is filtering

Nyle called me tonight and I heard the first new/old Steiner VCF in 30 some odd years! It had a wonderful sound and the resonance was, to my ear anyway, much smoother than the clones I've heard.

Very cool to have this actually coming together.

Sunday, September 5, 2010

Pre-Order Forms are up

A shot from the Salt Lake Area Modular meeting showing the prorotype PCB setup Nyle brought along. Sequencer at the top, VCO in the middle right, VCA bottom, and ENVDL middle left.

I uploaded Pre-Order/Order forms to the website and Eletcto-Music sites. Please have a look and if you want to buy something, I will be making a production PCB buy later this month for some of the PCBs at least.


Saturday, September 4, 2010

SLAM 2010 Aftermath

Fun time, long, but fun. Nyle came by and brought the prototype Sequencer, VCO, VCA, and an ENVDL EG.

Here is a photo of the prototypes and a photo of the two tall racks which hold my modular as it stands today.

Friday, September 3, 2010


Tomorrow is the Salt Lake Area Modular meeting. I'll post some photos when I get back.

I've also released a poll on the Electro-Music forum to get an idea of which modules to work on next. I'd like to do the ones people will want to buy and build. So, go to the forum and vote please.

Synthasystem Module Vote

Wednesday, September 1, 2010

Synthasystem Sub Forum at Electro-Music

Thank you everyone at Electro-Music. The Synthasystem now has its own Sub-forum. Not much there yet. I hope it will be an active and interesting place to discuss everything Steiner/Parker!

Monday, August 30, 2010

Sub Forum at Electro-Music to come!

I've had the pleasure to find out the Synthasystem project will have its own sub-forum in the DIY section at!

Thanks Guys! Electro-Music is a great site. Support it and donate.

(OK, MuffWiggler, too :) )

Friday, August 27, 2010

PCBs came today

The latest prototype PCBs are in today. If all goes well with the test builds, I should be ready to start a serious PCB buy for all who are interested in about a month!

Top to bottom: Sequencer Logic and Output/Pot, Power Distribution/ENVDL/ENVDT, VCA/VCF, Trigger converters, VCO

It's getting very close.

I'm also still working on the capture/layout of the Frequency Divider and Peak Selector.

The most annoying thing about these boards is that PCB-Pool deletes any objects closer than 0.01mm to a pad. Normally, that's not a problem for me, but by using bigger pads on these PCBs, some of the orientation landmarks were deleted on the regulators, and some, not all, of the "leads" on the diodes were deleted. It's annoying since I bought 50 power distribution PCBs in this run. Oh well... I've changed the libraries so that won't happen again.

Monday, August 23, 2010

working, working, working

I've been spending a lot of time on the project pages. I've had some good feedback, and I think they are close to done. I've also been re-considering the way I'm handling the trigger conversion. For the Sequencer and any other module with a lot of trigger ins/outs, the piggy back board is the way I will go. For the EGs, and others where there is only one or two trigger jacks, I'm going to put the conversion circuitry on the PCB with the option to bypass the conversion and use the S-Trigger directly. I've already modified the EG PCBs to do that and I think it makes the most sense. I could even add the option to have a front panel switch, or a PCB dip switch to select the mode. That may be overkill. I think people will either want to use the S-Triggers or not.

Besides that, I've started work on the Peak Selector and the Frequency Divider. Nyle suggested these ones next, so why not?

Wednesday, August 18, 2010

VCO Project Page is up!

I decided to start adding the project pages. The VCO and Power/Regulation pages are up with more to follow. If there are errors or problems, let me know. Please understand these are not quite finalized and when the last batch of prototype PCBs come in, there may be changes. I'm pretty sure these are very close to finalized.

Thursday, August 12, 2010

PCBs ordered

After some last minute discussion with Nyle regarding physical location for the filter caps/resistors I froze the current layouts. It took all my willpower to hit "submit order" on this one. It was a lot of money. Here's hoping people will actually buy some of these modules to recoup some of the investment. :)

Nyle also played the mini system for me on the phone. He's using an old VCF he still had, but it still sounded great. It's satisfying to see this project moving along and getting so close.

The current order of PCBs won't be for sale, but for final prototyping and test building.

ENVDL #1/#2
Trigger converter 8-S to V and 8-V to S converters (general purpose stand alone or on top of another module)
Trigger converter 4-S to V and 12-V to S converters (mostly for the sequencer)
A bunch of "chiclet" PCBs to allow easier panel mounting of trimmers for the VCO.

Most are smaller quantities, like 5 or 10, but I did buy extra power/regulation boards, because you need one on each module, and a boat load of the chiclets since they are small and very cheap.

I decided to go with the PCB shop I've been using, They have always done a great job for me. I also purchased expedited shipping so I could get the PCBs received and going.

Next, while I'm waiting for PCBs, I need to look into shopping carts I guess for web ordering. I'm thinking PayPal is the way to go as they will take cash or credit cards.

Stay tuned.

Tuesday, August 10, 2010

VCA is working

Thank you Nyle! He stuffed a prototype VCA board and reported to me it was working. One more tested.

I have the Gerber files ready for all but the sequencer. In a final dimension check, I realized the pot/output PCB was too tall, and the pots/LEDs on the panel were too high. I had to re-do the PCB and panel layout. It's done, but I want to revisit it tomorrow.

I'm going to send off the email to Circuit Graphics tonight for the other PCBs.

I'm excited.

Thursday, August 5, 2010

Power supplies and VCO

Nyle and I had another good discussion about power supplies and he reported the VCO, "is standing tall." He is very happy with it and has the output voltages about the same level. I've made what I hope are the last modifications so I can get some PCBs in production.

Nyle strongly suggested, and I agree with it and have done it on my MOTM and JH VCOs, to put the V/Oct trimmer on the panel or at least front panel accessible. I've used a Vishay-Spectrol adapter which lets you mount a 3/4 inch multiturn trimmer on a panel and the adjust it with a fine screwdriver or a trimmer adjusting tool. the make tuning the V/Oct so much easier. Nyle also suggested losing the "VAR VC" and making the third VC input be some defined fraction (like 1/2) of a volt /per octave. Or, the user could just have 3 matched v/oct inputs. To that end, I've modified the panel and the schematic/PCB to reflect this.

We also discussed power supplied, but no firm decisions were made. We mostly discussed the advantages of making his circuits run on +/- 12 instead of the +12 / -10 they use now. When we figure out what we're doing on that front, I'll post here.

Wednesday, August 4, 2010

More work and module tuning

OK, more progress. Nyle has been tweaking the VCO and has made one connection change with the triangle wave DC Bias. He also explained to me the Sync Bias trim is what is used to take out the nasty spike in the saw and triangle wave. So to those who were worried about it, Nyle reports the spike is gone. Adjusting this also boosted the output levels for the saw and triangle waves. I made the preliminary changes to the PCB layout and will talk to Nyle tomorrow or Friday. He's working on evening out the output levels so they are all about the same, so a few resistor value changes most likely.

I am so glad Nyle is helping with this. I didn't want to start messing with the design, but with Nyle helping, these modules should work better, but sound just like the original.

I also found a local PCB fabricator who has extremely good prices. Nyle said he has used them for his EVI so I think I may give them a shot at the next round of PCBs. It will save about 40%. I just want to confirm the quality and usability before I commit to buying too many PCBs from them.

Tuesday, August 3, 2010


Thank you Nyle!!! He got the sequencer debugged and working better than ever. Here are some photos from Nyle's workbench. You can see the added components at the upper left of the photo testing features added in the later black faced sequencers. The schematics were corrected, Nyle has given those a once over and so the sequencer is ready to order as soon as I re-do the PCB layout since some components were added and a couple were moved. I already briefly described the functionality, so won't do it again here. I've always been fascinated by sequencers and this one of Nyle's is pretty cool.

You can see the touch keyboard Nyle made years ago which he is using to "play" the sequencer, very, very cool. Nyle is one who has an uncanny intuition for circuit design. 

I've also put up what I hope will be the production PCB parts layout with component values. Two PCBs plus a Power Regulation board. An optional trigger conversion board can be piggy backed, too so you can have voltage triggers in and out rather than S-triggers. Also, an updated panel layout and a photo of the original Vlotage Sequencer. This early sequencer lacked the "gate", "stop" "VC clock", "rym" and "keyboard sum" features. The later sequencers with black panels had these features added.

This is going to be a big PCB order which makes me nervous.

I have recruited some help to test build these next PCBs (after Nyle and I have built one to make sure they really work right) as a sort of test run to see if the documentation and BOMs work well. I'm really excited again.

Finally, ready to order next PCBs

I'v spent several hours re-working the PCBs for the current modules. I think they are ready to go. I've run the ERC and DRC checks, visually inspected the silk screens, added notes, and comments to the silkscreen where there was room and a need, and I breadboarded the output buffers and found a mistake in the schematic and got it all fixed. The only thing I haven't done is stuff the prototype VCA. It's pretty simple, but I'm too anxious to order.

I'm waiting on Nyle to finish his testing on the sequencer. He's really making sure it all works and is improving the design. It's great working with him. As I already posted, he's verified the VC clock control and has done preliminary testing on the "gate" circuit and it's looking very good. Nyle's been putting in a lot of time on this, too and his efforts are making this better than I dared hope for.

I'll keep moving on the project pages, too. I'd like to get some preliminary parts lists up so people will be able to start finding sources for parts, too.

Monday, August 2, 2010

Power regulation project page

I have the power regulation PCB page up. Give it a look and let me know your thoughts to make it better.

Start here:

Sequencer panel

This is close to the final panel for the sequencer. There are a couple of neat features which will be part of the production. The "RYM" switch connects the CV out of row "C" to the VC Clock input. This allows you to vary the clock rate by the output of the sequencer. The Run switch turns the internal clock on and off. The Stop switch is a little different. Normally, the Steps switch will select how long the sequence is and will reset to step 1 as soon as the sequencer hits the selected step. When the Stop switch is on, the sequencer will go through one sequence only and then stop and hold the selected step. So, if you set the steps to 6, the sequencer will play the first six steps then stop and hold on the sixth step. Reset manually resets the sequencer. When the Run switch is down, the Advance pushbutton simply advances the sequencer by one step to allow setting the CV voltage for the step or for manually advancing the sequence. The A/B switch can link row A to row B and gives you up to 16 steps for a sequence. The Gate/Reset switch and jack are interesting, too. When set to Gate, and the Stop switch is down, you can feed a key down gate signal into the jack and the sequencer will cycle through the sequence while the key is down and then stop when the key is up. If the Stop switch is on, the sequencer will cycle through one sequence, then stop and hold the last note while the key is down. It will do it again on the next key down. The Keyboard Sum adds the keyboard CV to the output of the sequencer row A (or row A and B if the A/B switch is on 16), so the sequencer output will track the keyboard. This is nice for setting up an arpeggio that maintains the right scale relationship to the key pressed.

OK, I think this is all correct. When everything is all tested, I'll make corrections if I need to.

Sunday, August 1, 2010

VCO output, triggers, and sequencer

First, here are schematics for the VCO output buffers and the trigger convertors. I'd love comments if you think these could be done better. The output buffers are specifically setup to even out the gain of the VCO and will have onboard trimmers to do this. The triangle and sawtooth are about 2-3 vpp, the sine is about 12 vpp (if memory serves) and the pulse is about 14 vpp. The idea is to amplify the saw and triangle to 10 vpp, and attenuate/buffer the sine and pulse to 10 vpp. The pulse also has a DC offset at 50% duty cycle hence a DC offset on the first opamp for the pulse.

The trigger convertor has 8 S-Trig to V-Trig convertors and 8 V-Trig to S-Trig convertors. The idea is this can be its own module with jacks, or it can be piggybacked on the EG, Sequencer, or any other board which needs it. Instead of wiring right to the panel jacks, the user can put this board between and interface it seamlessly with current V-Trigger modules.

Nyle has checked out the voltage controlled clock circuit for the sequencer and will next check the gate/hold circuits. He also has an idea to eliminate the three Germanium (Thanks Ian :) ) diodes and replace them with a standard silicon switching diode. One less archaic part to source.

I'm working on project pages. When all done, I will have general instructions and some specific details for each board. I also want construction photos where appropriate and calibration instructions. If there are more specific things you think will help, let me know.

Last, I've been re-working the PCBs all week. I'm very happy with all of it. The sequencer is awaiting Nyle's last testing, but the others, VCO, VCF, VCA, EG are ready to go.

Friday, July 30, 2010

System design

As the PCB and panel layouts progress, it's becoming more clear I need to standardize some things for ease of assembly and my sanity. To that end, I've taken all the power regulation/conditioning off of the main module boards and will use a common power PCB which can be built to work with any of the modules. The sequencer is the exception. It will have everything on its two PCBs. This will allow for more compact boards.

In what little spare time I had today at the office, I was working on the PCBs in progress which are:


I'm busy trying to get these PCBs done so I can get the next batch of prototypes ordered.

Thursday, July 29, 2010

Nyle got the Sequencer working.

This was great. I'm traveling and when I got off the plane, I saw I had some voice mail. I call in and I got this weird synthesizer sequence playing for about 30 seconds. I thought this is a weird prank call, and then it hit me. It was probably Nyle and he got the sequencer working. I hit "call caller" and sure enough, Nyle got the sequencer going already. There was one more schematic error, very embarrassing. I had the run stop switch pole to the wiper of the frequency pot. This then directly connected the wiper to the emitter of the UJT when the switch was supposed to connect to the charging capacitor. That was messing with the oscillator as well as shorting the pot wiper to ground through the UJT when it switched. That torched the pot and UJT, go figure... The image on top is how I had it. The image on bottom is how it should be.

Anyway, Nyle figured that out and fixed it, connected it to a VCO and played me a tune. It was probably the most fun voice message I ever got. So, he is going to verify the other circuitry then off to the prototype PCB shop.

One suggestion Nyle made was to rearrange the pad order on the switches. He thought it made more sense to put the "wiper" or "pole" of the switch in the middle. I agree. It's a simple fix for the rearrangement, but it means having to re-do some layout that use switches, like the sequencer, and EGs. The pots already have the wiper to the center pad.

I think I'm finally happy with the VCO layout. I want to add a couple of helps to the silk screen, then I  think I'll send it in.

Anyway, the resurrection is moving along!

Tuesday, July 27, 2010

Some progress.

Work and life have been taking some priority the last few days as well as two hard drive failures.

Nyle came by today and brought my O'scope back and took the prototype sequencer, VCO, and an EG. He's been great with this project. I think he's as excited as I am and in some ways, probably more. He's going to go over the sequencer and bread board the upgrades to make sure they work. So, I'm going to hold off on ordering the next generation sequencer til he's had a good look.

I've been tweaking the VCO layout for no really good reason. I've got an output buffer board designed and gave the schematic to Nyle for his approval. I used the same 741 OpAmps in keeping with the vintage feel. Since it is a daughter board and an optional addition, I don't think it detracts from the VCO itself. I've also adjusted the panel layout just a bit to make sure the mounting holes don't interfere.

I've got the layout for the VCF pretty much done. I just need to make sure the mounting holes work on the panel.

I've been working on the final layouts for the EGs, too. I'm still conflicted regarding how to handle the triggers and gates for the EGs, sequencer, and the other couple of modules which use/generate S-Triggers. Right now, I'm leaning for the daughter board option. The circuitry is very simple and I can put the convertors on the daughter boards and then give the builder the option. The other way is to have a separate module. For my system, I want the separate module. It keeps the other modules authentic and true to Nyle's original idea, but will let me interface with my other system when I want to.

I think I can get the VCOs and VCFs ordered this week. the EGs should be soon after. I'm going to wait on the panels until I get these next PCB versions finalized, then I'll order some VCO, VCF, and EG panels.

I'm still hoping to have PCBs, etc. up for sale before the end of the year, and if all goes well, maybe a couple of months for the first VCOs, VCFs, and EGs.

Sunday, July 25, 2010

More prototypes ready to order

I got the sequencer board stuffed and found an error in my schematic. It was in the logic section and was messing with the sequencing. I was able to confirm the flip flop logic is fine. I was not able to fully confirm the internal clock, however, since the production version uses an upgraded voltage controlled clock, I'm not going to worry about it. I did manage to burn up two pots however. Whenever I turned the pot to full CW, the pot smoked. This is weird because when I had a trimmer soldered in, the trimmer didn't smoke. I think in all my unsoldering/soldering around the clock circuit, I must have shorted something which was causing the magic smoke to be released.

So, I've made the corrections to the next version sequencer, I've updated the VCO to be two boards now (see below for details), and the VCF to be two boards. This lets me mount the VCF board parallel to the 14 Hp wide panel which I think will be satisfactory for most euro rack and frac rack users.

The VCO will now be two PCBs with an option to add a third daughter board with output buffers and output "levelers". I'm doing this because I figure there will be those who want the VCO outputs to be +/- 5 volts. As it stands, the pulse is about +/- 7 volts, the sine +/- 6.5 volts, and the saw and triangle about +/- 2.5 volts. This way, I preserve the heart and true Steiner VCO on the two main boards and then can add a third which will allow it to interface better with modern stuff.

The VCO is one of the more complicated PCBs in the system and has a lot of components. I wanted to reduce the size of the PCB in case anyone wanted to mount it perpendicular to the panel or design a slightly narrower panel. I was struggling with this until I thought I could just make the power regulation on a separate board and cut an inch or two off the main board. Right now, the panel is 28 HP but the main VCO board is now 4.5 inches wide and 3.9 inches tall and would fit behind a 23 HP panel, saving about an inch.

I'm going to follow this approach for as many of the PCBs as it makes sense. I'm also going to use the daughter board idea for some of the trigger conversion circuits, too. I think that preserves the ressurection idea for the Steiner system, but also allows a user to integrate it into an existing system with less headache.

I wonder how many people will actually buy/build these modules... I guess even if it's only one, it's worth it to do it right.

Monday, July 19, 2010

VCO progress

With some great help and suggestions from Nyle, I think the VCO is good to go. I had to change a couple of resistors and, sorry, added two more trimmers. One will set the oscillator frequency range. You input 0.0 volts to the CV in and then adjust this to get the lowest frequency you want to have. Then, input 5 volts and make sure the high end is high enough. When I used about 0.1 Hz for the low end, the high end was inaudible to me.

 There is no high frequency trim and Nyle and I discussed this, and in the end, I don't think we will add one. those with perfect pitch might be annoyed, but then, no analog oscillator can be perfect. I have two or three VCOs with high frequency trimming and I found that if you trim the high end for good tracking, it can tweak the tracking in other parts. On a really quick tune job today, I got it tracking almost perfectly at about 440 to 880 Hz. At two or three octaves higher, I was off by about 1%. I was pretty pleased with that as from note to note, I really couldn't tell.

Nyle also wanted to add an additional possible trimmer to the triangle shaper. The 2N5163s they used were varying wildly and there were some which would not allow you to properly shape the triangle wave with the default trimmer. He found if you take the trimmer on the collector and put it on the emitter, you could trim the triangle wave. He wanted to make sure the end user could do that if the FET was problematic. So, I have trimmers on the collector and emitter. In normal building, the trimmer on the emitter will be jumpered to ground. See the partial schematic above. So if the FET doesn't let you properly shape the triangle, take out R63, jumper it to +12, take out the jumper to ground at R72, and install the trimmer. Or, you can just install both trimmers and start with R72 full CCW (shorted to ground). That said, the 2N5246s Nyle used in the later VCO cores haven't given me any grief and I've tried several random ones.

I tested the sync, and it works perfectly. I didn't try trimming the Sync Bias though. The only thing left really is the mismatch in output gains. I'm honestly tempted to just leave them. I've got enough trimmers already!

I've got the sequencer about half stuffed. Nyle found a couple of errors in my schematic capture, and thankfully I can easily take care of them when building the prototype. It may also explain why my simulation didn't work right, too...

Next up, I'll give the VCO a final check and blessing from Nyle and order some more boards. I want to build the VCA next and then get it's next revision and the classic Steiner filter boards off for prototype. I also need to get the type III EG and the next revision of the type I/II off.

I've checked the VCO panel and the VCO PCB will fit fine parallel to the panel, so shallow euro rack guys be happy if you want a Steiner VCO. Sorry, but it will be 28 HP wide. I could make it more narrow, but then you  will need about 6 inches clear behind it. The panel would also seriously depart from the original layout and I want it to be a close as possible.

Enough for now.

Expensive, but exciting.

Sunday, July 18, 2010

More on the trimmers

I thought I'd better clarify a bit on the trim pots. The VCO proper has 10 trim pots. Here is the Prototype PCB layout:

Min pulse width
Max pulse width
Phase sync trim
DC offset for the sine output
Sine shape
Sine shape bias
Triangle shape
Volt/octave trim
DC offset for the saw output
DC offset for the triangle output

More than other VCOs I've ever seen or built, but reasonably straight forward to set. The single turn trimmers visible in the photo on the edge of the PCB are simply surrogates for the panel pots. I used these because I thought it would simply be easier to deal with than a bunch of big pots with flying wires.

The next step for the VCO is to verify I can actually set the V/Oct trimmer and get it to track. I would like to verify the sync input, too.

Before I post the schematics, I need to add a provision for an onboard LED to provide a minimum load for the regulators if needed. Then as soon as I verify and triple check the component values, I'll order what I hope to be the last prototype and then this one should be ready to go.

There are only two more modules which are more complicated. The other ones, even the filter, are really pretty straight forward and I think they will turn around fast. The sequencer and the frequency divider will take more time. The sequencer just because of quantity, the divider because of complexity.

I think there is real reason to get the sequencer done soon if not next on the list. Nyle is very interested in having the sequencer well documented and he is excited to get it done, more than enough reason for me to put some effort into it. After that, I think the EGs, VCA, and VCF definitely need to be done as they are the core of any modular. The others are pretty simple and will come later.

It's Alive!

Thank you Nyle Steiner! (The top blurry cell phone photo is Nyle in front of his workbench.) I stuffed the newest VCO prototype and it basically worked first time. I was using a wrong value for a trim pot which prevented the triangle wave output buffer opamp from working, but I got that figured out and it works great! Here are some more crappy cellphone photos of the screen of a DSO Nano O'scope (long story but I loaned my bench scope to Nyle for a couple of weeks). The photos don't do justice to the screen of the Nano. Very cool little scope. I think this is the first new Steiner Synthesizer Company VCO in 30 years give or take. The pulse and sine outputs are higher than the triangle and saw outputs, so I'm going to triple check all the component values to make sure I'm doing this right. I'm also a little lost regarding the adjustment of the min/max width trim pots for the pulse wave. It's another question to ask Nyle.

Now, on to the sequencer prototype. I'm way excited again about this whole thing.

I've also got the rack/power distribution system figured out. I got the new power plugs and they fit perfectly in the existing cutout. I drilled the holes for the mounting screws and they look and work great. I don't know if anyone but Nyle and I will use the rack system, but it sure looks nice and I think will work as good as they look.

Another odd note. I decided to use adjustable regulators for the power section so I could get an accurate voltage on each board. I discovered through some kind help on the SDIY list I have to have a minimum current draw to effect regulation. I'm going to have to add some small load on each regulator because some of the circuits may not meet the worst case current draw to establish regulation, particularly on the -10 volt side. So another task before the next round of PCBs is ordered. Hopefully though, the next batch will be the first production boards.

Tuesday, July 13, 2010

Meeting went great!

I had a great meeting with Nyle today. We sat down for a couple of hours and in the end, I think I know what was going on in the later version of the sequencer. I've got the schematics modified and a first PCB layout done. I need to tweak the layout a bit, but I don't think it will be a problem. I'll still stuff the PCB I've got to verify the Flip-Flops and general circuit is right.

In the end, I also got to look through a lot of the files he kept from when he was building his systems. I got to look at other schematics, PCB artwork (some of it falling apart as it was hand laid out with tape on vellum and the glue is all dried out), wiring diagrams, photos, all sorts of good stuff. I found a couple of schematics I had never heard of before, too. An envelope generator with a variable damping and an "Up-Down" 3 row sequencer. They both look interesting and I think I'll incorporate them in the module list and build them as time goes on.

But, right now work has let up a bit and I'm going to be able to find time to solder some stuff. I am way to anxious to get the sequencer and VCO going.

I also started the project page on my web site. There is really not much there, but to see it, click on the Moog Voyager at the top of the blog and it will take you to my home page. Click ont eh Steiner Synthasystem link and you will get there.

Monday, July 12, 2010

Unexpected guest!

I got a call Sunday afternoon from Nyle. He was in Salt Lake for the Jazz Festival and wanted to stop by to see what I was doing and to show me a "box-o-stuff" he had from the days of Steiner Synthesizers. What a treat. We spent a couple of hours looking at the work so far, panels, schematics, etc. Listening to stories. I now know where the word "Quathin" comes from. Apparently,Stu Goldberg had a Rhodes electric piano. Nyle noticed that when you pushed the damp pedal, there was a sound, and it sounded like, "quathin". That sound was the source of the name for Nyles' Quathin function on the envelope generator.

Other notes, Nyle liked the look and quality of the Schaffer panels, which is a good thing.

The box also had some other information regarding his modules, in particular the sequencer. There were some additional schematics, older and newer, which cleared up a bunch of questions but raised some more. It appears for the last version, Nyle added a voltage control rate which was fed by row "C" of the sequencer. I do want to add this, so I'll have to ponder how he implemented it and ask him on Tuesday. He also pointed out I had the step switch wired wrong. Not a big deal and the way the board is laid out, I should still be able to test it all.

I was also able to clear up the update to the filter resonance circuit. Life is good. I'm moving along and hope I'll have the first module(s?) ready to go in a month or two.

All in all, it was a great visit and helped a lot. Right now, I'm re-scanning a lot of the paper at a higher resolution and tweaking the gamma, etc. to make sure I can see all the lines.

Sunday, July 11, 2010

First frustration is in...

I started to put some power panels together and I realized the snap in plug units I bought don't work in a panel thicker than 1.8 mm. I had the panels made with 2.5 mm stock. I found I could modify the snap in units, but I don't like the modification. I found some other screw in plug/switch combination units that are 0.5 mm bigger (about 0.020 inches). I bought some hoping they will fit with little if any filing needed for the existing openings. I can drill the mounting holes with little difficulty if they fit the openings.

I still haven't been able to make time to stuff a PCB. Oh well. Maybe Sunday or Monday evening.

Friday, July 9, 2010

First panels are in

I got the first batch of panels for the power supplies. They look great. The Steiner logo is smooth and just the way I want it. I'll be able to assemble one of these, too and make sure it all fits right in the Schroff racks I have.

I've also made some good progress on the VCO board with MOTM/Doepfer power options. I re laid out the whole power supply/regulation section, added outlines for the MTA connectors for the jacks, pots, etc. and so can consolidate some space and I know exactly how close and where I can put the connectors. I also rearranged some of the other components to shorten and untangle the ratsnest and also the actual traces. Things are getting exciting again.