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

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.