TTSH - The Human Comparator - ARP 2600 Replica - VCO 2

This is part 5 of my TTSH (Two thousand six hundred) build.
You can see my full build thread HERE
There are two awesome TTSH threads in Muffs.
2600 clone - Two Thousand Six Hundred (TTSH)
and
Two Thousand Six Hundred (TTSH) Project General Build Thread
The DSL-Man site has a very good TTSH thread
And of course the official build thread is here
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VCO 2
The 2nd VCO has four waveforms: sine, pulse, saw, ramp.
It's my favoutite VCO

 Rear panel view

 

Front panel view for VCO 2

First install resistors, IC sockets, MTAs if you like.

Install trim-pots, caps, etc.

 2N3954 TRANSISTOR
This is a ultrarare transistor.

3.5mm jacks The one on the left is from Thonk.

The PJ301BM jack from Thonk on the left is ideal for the TTSH project.

The one on the right is a standard (modified my me) 3.5mm jack.

It's simpler just to get the ones from Thonk.

The jack needs to be installed on the sine VCO. Then test with your scope for the relevant waveforms.

You will need a 2N3906 & 2N5172. 

The 2N3906 a common PNP bipolar junction transistor.

The 2N5172 is a NPN. 

Note that on an authentic ARP 2600, the sine wave is shaped from a sawtooth core. The ARP 2600 oscillators are designed as "sawtooth core" oscillators, and the sine wave is created by sending this sawtooth wave through a waveshaper (a circuit that converts the shape).

Wave Shaping Method: VCO2 (and VCO3) generates a raw sawtooth wave first. A "sine shaper" circuit then converts that sawtooth into a triangle wave, and subsequently, a sine wave.

The sine wave on the 2600 is not perfectly pure; it often has triangular overtones, particularly at the peak of the wave.

If you are seeing a square wave instead of a sine, it is likely that the "gain" or "purity" trimmers inside the unit (on a clone) need calibration.