TTSH (ARP 2600 clone) build notes - Ring Modulator (DIY)

The Ring Modulator build of the TTSH synthesizer. 

This is part 10 of my TTSH (Two thousand six hundred) build which is an ARP 2600 clone synth.
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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 There are actually 3 circuits here: the Ring Mod, a envelope follower & a pre-amp.

The TTSH ring modulator uses the ARP 4014 submodule circuitry.
The 4014 was used in both the ARP 2500 & 2600.
The schematics from ARPtech are here

The large white square corresponds to the 4014.

 4014 closeup consisting of two LM301 op-amps and four matched transistor pairs.

The original ARP 2500 & 2600 used matched TZ-581 & TZ-81 trannies.

The TTSH uses their modern counterparts, the 2N3904 & 2N3906

(see the link to the schematic above)

It's sometimes tricky to match transistors. Oakley sound has a Euro clone of the 4014 that use THAT 320P PNP arrays & THAT 300P NPN arrays. It's a neat way to avoid the problem of getting those perfectly matched transistors.

The lower section of the ring modulator. This is the section outside the 4014 sub-module.

There is a mistake in the Cap orientation. The schematic indicates that the top left 10uf capacitor

needs to be rotated so its negative terminal is connected to the cathode of its 10uf pair.

R32 (18K resistor) connects to the anode of c21 (10uF cap)
C20 & C21 should connect via their cathodes
if the original schematics are correct

The inputs of the ARP 2600 & TTSH ring modulator are normalised to VCO 1 & VCO2.

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Front plate of the TTSH synth

                                                                                 

       This is the corresponding PCB front side.

                                                                                                                                                                                                  

 Resistors,Diodes, Capacitors.

These 2 resistors on the extreme right connect directly to the 4014 module. They are your audio input points when you come to test the ring mod.

Install the trim-pots. (This is a pre-soldering pic. I use blutack to hold the pots in place).

Transistors & ICs are in. Ready to test.

An original 2600.