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:

VCO
VCA
VCF
EGs
Sequencer

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

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!

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.

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.

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.

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.

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.

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.

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.

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.

Parts, parts, and more parts.

I got the huge (about $1200.00) Mouser parts order. I also got word the power supply panels have shipped. I also setup a meeting with Nyle next week.

So the past couple of days, I've spent free time re-doing the sequencer PCB. I decided to split the schematic into two PCBs, one for the sequencer guts and one for the CV pots, output buffers and level pots, and LEDs. While doing it, I also decided I'd go ahead, break my rule, and design the "pots" PCB for vertical PCB mounted pots. I hate flying wires and when I actually added up how many there were going to be to the pots, I decided PCB pots were looking pretty good. This also means it should now fit in any cabinet. It also means the MOTM guys will be stuck with 1 inch spacing on the pots in the panel or will have to resort to flying wires, sorry guys. I suppose if there is huge interest from the MOTM/DOTCOM format for this module, I can layout and make a larger spacing pots board. We'll see what happens.

Next, I'm going to let the sequencer design sit for a day or two then revisit it. I want to build a couple of modules now and make them work. I've got everything to do it now, so here's hoping I'll have time this weekend. My day job has really backed up on me, though due to the recuperation from the total knee, so I don't have much of a life these days. I will try. If I get the sequencer sequencing, VCO humming, I'll post samples here first and will make sure it gets onto the SDIY list and MatrixSynth, and Synthtopia. It will be the first "new" Steiner module in 25 or 30 years.

Sequencer encore

Ok, I found an old ad. The sequencer is in the top left of the cabinet with the other modules. The sequencer on the Synthacon is a scaled down version of the Studio Sequencer. You can see the jacks are below the pots and the left side controls were re-arranged. There isn't enough resolution to see the exact arrangement of the left hand side stuff, but I'm ok with that. I think Nyle moved the 8/16 step switch over there, too. Looking at this and the schematic again, I also realized I had forgotten the output level pots. Adding those added another 7 HP to the width which didn't make me happy. I wanted to leave at least 28 HP so any other module could fit by the sequencer. Looking at this and the older version, I saw Nyle left off the tic marks on the step CV pots. By doing the same, I reclaimed the 7HP and brought the width back to 56 HP. I also re-arranged the left side controls to what I think they probably were. Here is the result.

Sequencer

Here is the current panel for the sequencer and a photo of an original sequencer. I can't find it now, but I saw a photo of a black finish sequencer, so later release, which had an updated layout. The biggest difference was putting the jacks on the bottom rather than on top. I can't find the photo now. But, I'm going to move the jacks to the bottom because it makes sense.

Goals for the next couple of weeks:

• Build and verify the circuit for the sequencer, VCO, and VCA. I will have more than enough parts to do it this week when my Mouser order comes.
• Finish schematics for the same and the ENVDL, adding the Doepfer connectors and voltage regulation circuits. I've got a good start on this already.
• Decide on how best to mount the PCBs. Most can be vertical, but the VCO and sequencer will need to be flat; parallel to the panel. I'll need to re-think the sequencer and split it into two boards. I don't want to mount the pots to the PCB. I want people to be able to choose their own components whenever possible.
• Get a prototype board ready to order for the ENVDT.

More panel fine tuning

First, I've had a couple of questions regarding availability. I want to make it clear I intend to release the schematics and PCB artwork. I don't think I'll release the Eagle files themselves. I fully intend to approach this with the intent to provide a reasonably wide audience the chance to have these modules. For the DIY people PCBs and maybe parts kits through the Bridechamber and maybe other sources. I will post schematics here as they are checked, tested, and verified. I will also give them a more permanent home on a web site so the hard core DIY'ers can have at them. For those who don't want to solder, I might offer fully assembled modules, maybe in limited numbers or limited modules, I'm not sure yet. So, the basic answer is yes, I will make this all available.

Here are the four panels I've finished so far and a shot of a standard Synthasystem. I've played around with spacing, font sizes, etc. and I think I've got some standards which will work. Nyle used multiples of 1.75 inch wide panels. I'm going a little narrower. Where his VCO and EG used a 7 inch wide panel, I've shrunk them down to 28 HP, or about 5.6 inches. It makes things a bit tighter, but now, 3 units can live in an 84 HP euro rack. The VCO could probably be smaller, but I also want to be able to mount the PCB behind it parallel to the panel due to its size. I want people with standard euro racks to be able to use these things, too. I'm going to scale the other modules from this size and use 14 HP and maybe 7 HP panels for Nyle's 3.5 and 1.75 inch modules. the filter and VCA fit nicely on a 14 HP module. I'll try the Phaser or some other single wide in a 7 HP space and see how it all works.

I've been able to keep almost all the relative positions of the controls and jacks. The VCA is one exception. I just didn't have the room across the bottom for the jacks, so I ran then input vertically on the left side. They fit fine and I think they look fine. I'm going to start the sequencer next I think.

I've been thinking about the PCB on the sequencer and I might split the schematic into two separate PCBs and connect them with some ribbon cable. I don't think I can reasonably make the PCB much smaller than it is and it is deep. If i split it up, I can stack the boards and maybe even mount them parallel to the panel.

Here is a VCO panel. Again, I've used a couple of gray discs to show the knob sizes. I've kept true to how Nyle did the original with symbols instead of words for the wave shapes and his VC VAR input and control. This is an input which can be set to an arbitrary scale whereas the VC INPUTS are fixed in the original, but I added a 1 volt/octave trimmer on the PCB. The tuning was accomplished on the keyboard in the original design, and I'll still leave those controls there, but I thought for usability the VCO inputs have to be tunable and set to 1 volt/octave.

The FINE FREQ knob will be a slightly smaller Alco knob without a skirt, like the original.

A little more on the depth issue. I think for the deeper boards, like the VCO, I should be able to mount them parallel to the panel front. I'm pretty sure I can also do this to other boards, too. All except the most narrow ones, like the phase shifter, VC Trigger, etc. But, I think I can keep these boards sufficiently shallow to work fine. I found the deepest Doepfer module is about 4 inches deep. I will do what I can to keep to this maximum depth to allow the most users to build these things.

On board regulation

Thanks to some good input from the SDIY list, I've decided to just go ahead and add on board regulators. That way, I will guarantee +12 and -10 volts regardless what the power supply is.

My dilemma now is how long or deep I can make the PCBs. In my euro rack system, I can go as deep as 6.5 inches on the cards and not interfere with the power supply. Does anyone have any suggestions about card/module depth? I'd hate to get these things done and find out the ones people want won't fit physically in the racks. The longest ones so far are the sequencer, 5.9 inches, and surprisingly the VCO at 5.6 inches. Even though it may waste some board space, I am going to make them all 3.9 inches tall. This fits in a Blacet Frac Rack, and a standard Euro Rack. this way, I should be able to standardize some of the mounting dimensions to make it easier for those doing their own panels.

I made it into the office yesterday and picked up a bunch of packages which had come while I was home rehabilitating. The Pratt Read keyboard came (although I think I will use a new Fatar keyboard after giving this one a good look). the sequencer, VCA, and VCO prototype PCBs are in, including a bunch of wasted ENVDL boards (I knew it was too soon to order 10 of those, oh well). They work, but they are the wrong form factor now and they don't have the on board regulation. I guess it's part of the development. I also put in a big order to Mouser for parts to populate the prototype PCBs. I also ordered some extra of some parts and I started to order some of the finished panel parts, like knobs, pots, switches, and jacks. It really added up fast.

Nyle sent me scans of the original artwork for the Frequency Divider panel which will help me get a better match with the panels I'm doing. For my stuff, I've always used Bulgarian for the module name and then a casual script like font for the pots, jacks, etc. Nyle likes a blockish, sans-serif font like he did originally, and I think he's right. I re-did the Triple Envelope Generator panel with pot tic marks, a Helvetica font slightly angled and used all caps for the letters, like Nyle did. I think it looks good. For the panels I order, I don't think I'll use the tic marks since they add a lot to the panel price (about $1.50 for each pot), or maybe simpler ones. I put 19 mm circles on the first column of knobs to represent the knob size to make sure you can see the tics and that there is room for fingers to actually turn the knob. I think these will work well.

I think that's all for today. My knee is much better, so much so, I might feel up to soldering some resistors on the sequencer PCB tomorrow. I'd love to get it going and give it a try. If it works, I'll wait to see what the consensus is on depth and if I have to, try to make it smaller, add the regulators, and maybe call the sequencer good to go. I can also do a more careful build on the VCO. I was so anxious on the last one. I saw today I actually left off some components which may be a big reason why it wasn't working after the core :)

I'll have my Mouser order next week, about Wednesday, and I'm sure I'll be feeling up to building some stuff then.