More to come…
More to come…
When starting with the TTSH build last year I prepared the Formant power supply, that I still had from the past, as kind of standalone unit. Meanwhile I realized that this would be a little too big to easily fit into the TTSH case I've built. I decided now to redo this part. I've bought two new transformers (one delivering 2 x 18V and one delivering 9V) that nicely fit into the bottom corner of my TTSH case. I've added an aluminum rail to hold the three 2N3055 power transistors and the power inlet on the backside of the case:
The Formant power supply PCB now is mounted vertically on the side of the case, above the transformers:
A longer time ago I had bought an Edirol PC-50 MIDI keyboard, to be able to connect to some synthesizer programs on my computer:
Now it would be interesting to be able to also connect it to my TTSH. For that I would need some MIDI-to-CV interface. At http://midisizer.com/midi2cv-mk2/ I found a nice little PCB design, called Midi2CV. It seemed to fit to the TTSH. I have ordered the PCB, and the needed components at Mouser. The Mouser components arrived first. As usual a lot of little plastic bags:
The delivery of the Midi2CV PCB and pre-programmed ATMega328p microcontroller took a little longer. It left the US quite fast, but customs in Germany took about two weeks.
After a longer break, summer and autumn have passed, I picked up the work on my TTSH again. The TTSH is working, but not ready yet. Of course I still need to build a case for it. I never got to that last year. My idea was to have some space for additional modules below to the TTSH. I came up with following design:
I had some pieces of (beech) wood cut in the right sizes. Thickness is 18mm, depth of the case is 25cm. This allowed me to build up the case base:
Adding aluminum rails to mount the TTSH panel and four 15cm x 5cm (L-shape) aluminum panels at the bottom:
Now that the complete board is done, I could perform a first test. This covers VCO 1, 2 and 3, VCF, ADSR, AR, VCA, noise and sample&hold. At first all seemed to be working, but then I noticed two defects:
- One of the VCOs generated a way too high frequency compared to the others.
- The fine tuning of VCO 3 didn't have any effect.
It turned out that I had two bad soldering points: The 680pF capacitor on one of the VCO boards was loose on one end. And, the same was true for the 3.3MΩ resistor connected to the fine tuning slider of VCO 3. Correctly soldering both points luckily fixed this.
Here are two pictures of the main board functioning:
Mounting the front panel already gives a good feeling of how the TTSH will be:
Finally the main board is ready. I have now installed all switches, sliders and jacks:
Before soldering everything I had mounted the front panel, to assure that everything was correctly aligned.
Following are a few detail pictures:
Today I've mounted the last electronic parts, the LED drivers. Also the 7 jumpers for these and some headers to later connect the peripherals to. The next step will be the switches, sliders and jacks.
Earlier this week I've finished the Sample&Hold, Internal Clock and Analog Switch part:
The 1.5µF electrolytic capacitor (bright blue) at the bottom wasn't available with Mouser, but luckily I had a few of these from the past. Then I had made a little mistake: Soldered in a 10Ω resistor instead of a 100Ω one (near the 1.5µF capacitor, in vertical position). I only noticed when a 10Ω resistor was missing for the next section, the amplifiers part. Removing the vertically positioned resistor and putting back in the correct one was not that easy.
[Update] Then only later I detected that the analog switch was not working correctly. Channel A was always on. I had overlooked to solder one side of a 3.3MΩ resistor that controls one of the 2N5172 transistors, which actually can be clearly seen in the top-left corner of the above image. The fix was thus easy, luckily.
And thus also the amplifiers part was finished:
Earlier already I finished the mixer and reverb section:
And today I also finished the noise and voltage processors sections:
Note that i have not inserted the "noise transistor" yet. I want to insert a socket here to allow some experimenting and finding the best fitting transistor here. I'll also get a TL071 instead of a LM301 for the voltage processor, as indicated on the board.