TH VCO-1 finished

[a_guy_called_tom]

Hi all,

Today, thanks to the terrible weather, i was finally able to complete my new TH VCO-1 oscillator stack and i thought i'd share some pics here.
I choose the VCO-1 design because its a triangle core and apparently good for FM. The few tests i did so far are very promising, i like this VCO. I didn't use a tempco and did not match the transistors for the expo converter, i have yet to find out how good the tracking is..
Anyway, thanks to TH for making these designs available for the DIY community!

Greets,
tom

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[Tim Servo]

Hey Tom,

Nice work! I think you'll find that modern transistors are much better in quality and consistency than what people had to deal with twenty or thirty years ago. I've been able to get 4 to 5 octaves of tracking by just grabbing two transistors and throwing them in there. What I think is just as important as matching is good thermal coupling between the two transistors and the 2k resistor. I put the two transistors face to face, with the 2k next to them, with a small dab of heat sink compound between the two transistors and between the transistors and resistor. Then I put a piece of heat shrink tubing over all three components and carefully shrink it to hold everything together. I do this before I solder anything in place to avoid stressing the solder joints. As a finishing touch, I put a small dab of silicone sealant in the open ends of the heat shrink to seal the whole assembly off. By the way Magic Smoke Electronics (of which I'm a part of) sells 2k Tempcos for $3.50 each plus shipping (cheaper if you buy 2 or more).

Anyway, beautiful job there. Let us know how they sound!

Tim (having fun with heat shrink) Servo

[a_guy_called_tom]

Hi Tim,
Thanks for your comments! Seems like a great technique you have for putting the transistors and resistor together, i'll definately give that i try next time build something like this. However i'm quite surprised how good the tracking is even without tempco and termal cuppling of the transistors - certainly usuable for what i do with those vcos

Greets,
tom

ps. sound is lovely so far, can't decide yet if i should trim it for the pure sine or the more squarish sine which sounds great too... or maybe i should bring the trimmer to the frontpanel