I received the final prototype boards on Monday, and assembled the first one using parts from the test BOM (Bill-Of-Materials) order. The purpose of doing this is to make sure the Bill-Of-Materials and the board are correctly specified, so that when I send the order to manufacturing, I can expect it to work.

It didn’t work at first, which was cause for concern, but it turned out that one of the PNP transistors was no good. Once I had replaced it, everything worked perfectly.

Once the Tempco resistors have arrived (mid-August), I will build the rest of the boards, and send them off to my test subjects.

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I found myself going down a rabbit-hole of 3D rendering products and techniques when I’d rather be building synthesizers, so I’ve opted to present each module in the simple Kicad render. The first System 300 will come with 12 modules shown below.

• 2x AT-317 VCO
• 1x AT-314 LP VCF
• 1x AT-327 Multimode Filter
• 1x AT-315 Balanced Modulator
• 1x AT-318 Sample & Hold/Clock/Noise Generator
• 1x AT-324 Dual LFO/Lag/Inverter
• 1x AT-323 Dual Mixer
• 1x AT-321 Hex Attenuator
• 1x AT-316 VCA
• 1x AT-312 Envelope Generator
• 1x AT-326 Output Module

I have not yet figured out how to get povray to produce the output I want, so here is a rough (non-raytraced) rendering of the whole set of modules I intend to make.

I will try to make a more viewable version early next week.

Sent off the penultimate prototype boards to manufacturing this morning.

Here are 3D renderings of each.

Feeling very pleased with the layout. Should prove easy to assemble, and have good noise rejection characteristics.

The final version of VCO board will be SMD, and organized for robotic assembly, but I wanted to begin with a through-hole version; both to verify the circuit design and basic layout, and to make available to interested builders who don’t enjoy SMD work.

Also created a Bill Of Materials (for mouser.com) this morning and put in an order so I can validate it before publishing.

Waiting on the good folks up at KrlBantry in Manchester, NH, to deliver a batch of custom spec 3k Tempco resistors. Should have the first batch in early August. At the moment, the prototype experiences frequency drift as the transistors in the Exponential Converter heat up. Going to thermally bond the 3 transistors in the Expo Converter to the Tempco, and pack it in some kind of foam or potting material, to minimize thermal gradients between them. This is the way Dennis Colin did it in the AR-317 and it works extremely well.

I got back from CA last night, and finally got the chance to troubleshoot the triangle-to-sine waveshaping circuit.

These are the results.