The next section I've done is the VCA:
Next to the VCF section is the ADSR and AR section, which I've finished now, too:
Powering up again, connecting the according ADSR and AR outputs to my oscilloscope and pushing the button shows the following waveforms (after some fine-tuning of the sliders):
This looks pretty good, I think.
Now that I have all components available, I was able to build up the three VCOs, attaching the small boards with the according connectors to the main board:
Meanwhile I had also finished the VCF part. As you can see I'm not using the built-in power unit, but will be using my own external power supply:
More than one month has passed, but finally I have managed to get all the required components. I was still missing the 2N4125 transistors for the small VCO boards and 4 ceramic capacitors of 5pF. As replacement for latter I got some 5.1pF capacitors through some relatives in the Netherlands. The 2N4125 transistors I've found when looking for the reverb tank. Banzai Music in Berlin, Germany, who offers such reverb tanks, also sells electronic components and interestingly they also have the 2N4125 available.
Having the transistors and capacitors, I was able to finalize the three small VCO boards. Once done I've cut them apart:
And here's the reverb tank:
The other missing parts were the Peerless loudspeakers, which I've found at Straßacker Lautsprechershop in Karlsruhe, Germany:
Today my order from Thonk arrived. A lot of jacks, the tempco resistors (incl. a spare one) and the potentiometer for the pre-amplifier:
Earlier this week also the small order from Balzer CFS arrived. With that I now also have the CA3046 ICs and the 2N4870 and 2N5459 transistors. Unfortunately, in contrast to what was promised, they didn't have the 2N4125 transistors.
So, as of today I'm still missing:
- 3x 2N4125
- 4x Ceramic capacitor of 5pF
At Muff Wiggler I've found some hints and a circuit for transistor matching. I've built that circuit on stripboard and now can start with the transistor matching: The TTSH design uses various pairs of 2N3904 and 2N3906 transistors. These pairs should each have a very similar base-emitter voltage (within 2 mV difference).
And here we go for the matching. Measuring transistor after transistor:
All 2N3904 NPN transistors are pretty equal, with a base-emitter voltage of 615mV to 617mV. The 2N3906 PNP transistors spread a little more, from 603mV to 609mV, but many with 606mV or 607mV.
Many components are available now, a few remaining that are still missing should arrive soon. It's about time to start soldering. Before doing so, I have sorted all resistors and capacitors:
That will help in finding the correct ones. I'm starting with the three VCO boards. Earlier already I had mounted the sockets for the CA3046 ICs. Yesterday evening I have added the resistors:
Yes, I should make less pictures and start soldering…
A few components are still missing. Knowing more or less for sure that I wouldn't get these e.g. in town, I have now also ordered jacks, tempcos and potentiometer at Thonk. Let's see when those arrive.
For some unknown reasons Mouser had split my single order into two parts. The first, largest part arrived today. The rest should arrive soon, too. The box is just a box:
Well, there are a lot of components inside, packed in two larger bags:
Inside, in yet smaller bags, are all the components:
Meanwhile I have ordered a long list of components at Mouser. Together with the TTSH order confirmation, a link to a project at Mouser was provided. This project has 138 positions, of which unfortunately a few items were not in stock. The Mouser project, however, also is not complete: A number of (rare) components must be obtained elsewhere.
Interestingly, Mouser offers two of the required rare transistors: 2N3954 for over €20 and 2N3958 for over €12, both listed as end-of-life.
As source for a number of missing components I have found:
- Conrad in Munich, for a few regular components.
- Balzer CFS in Munich, who seem to be able to provide the CA3046 ICs and some of the rare transistors.
- Thonk in the UK, for the jacks, tempco resistors and potentiometer.
Since I will be using my own power supply, I removed a number of components from the Mouser project. The power supply I have available is from a long time ago, from my youth when working with some Formant parts:
The 9V transformer in blue (for the 5V part) is new, but not needed for the TTSH. I have mounted the power supply with its transformers on an aluminum frame. It weighs 2.5kg in total and may offer some stability to the case that I will be adding later.