Cadet VCO Matched Transistors

cadet

#1

I’m going to be building a few cadet VCOs in the not-so-distant future and will be ordering sufficient quantities of Q2, Q4, and Q5 to match and bin (a lot) more than I need for my own builds. Vbe will be within 2mV or better per pair. Putting out a feeler to gauge interest. Let me know!


#2

2mv its pretty good match, check Ian Fritz method its very easy I get good results with it.


#3

Thanks for the link! There’s some good stuff in there!

I usually match transistors with a semiconductor curve tracer; rock-solid test sources, 2 channels, and an A/B switch makes quick work of the “swap, match, repeat” process! The 2mv Vbe spec was chosen because the BOM’s recommended vendor (Thonk) matches to within 2mV. That match differential should give a pretty good yield, but I’ll be shocked if I can’t come up with a few “supermatched” pairs :wink:


#4

Do you mean you’re planning on selling the matched transistors? I might be interested if the price/shipping is right.


#5

is the effect of not matching transistors that the frequency ranges (of 2 VCO’s) won’t match exactly?
thus making it more difficult to create certain shapes?


#6

Yes! Price and shipping will be a nominal charge. Most likely a few dollars to cover materials and postage.


#7

The usual effect of transistor pairs in a VCO having gain or Vbe too far off from each other is drift and tracking issues.


#8

mmh. I have not seen those effects yet, so I think I’m good.