They can handle the full voltage a synth PSU delivers and have reasonable gain, though a bit less than the BC55x. To be honest though in 95% of places the 2N3904/3906 pair are usually okay if the collector current is around 5-10mA. Lots of them at many places such as Farnell. Sorry if this is a bit obvious, but searching back through these forums I found a fair bit of info on substitutions, but not much explaining what the logic/reasoning is behind them.įirstly BC558 isn't obsolete.
Op-amps feels a bit tricker, as beyond the obvious it's not actually clear to me what the functional difference is between say an lm358 and a tl072? Is it mainly that the latter has jfet inputs so a higher input impedance? Beyond that I guess that vbe values, noise and power rating maybe? but what else might differ?įor a concrete question/example, the CGS VCA specifies bc558b transistors which are apparently obsolete, and I'm wondering if I could just use 2n3906 instead or if there's something I've missed? Transistors I get that it's primarily going to be about hfe, and in my current situation building a CGS panel with elby pcbs, pinout is going to be a consideration as well. I'm trying to understand how I can go about picking suitable transistors and opamps when I'm subbing in and out parts in a circuit, specifically what would I be checking for? Currently in the process of getting back into DIY electronics after a bit of a hiatus and attempting to get back up to speed.
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