Monday, December 12, 2011

Component Notes

You can read extensive info on David's site about component notes... rare parts, substituted parts, etc.  I'll cover just the basics when I discuss those modules.  In the meantime, I thought I'd mention a few things I'm doing, plus some general observations.

I decided to use 1% metal film resistors everywhere, except where 0.1% tolerance ones are called for. I tend to do this for all of my projects... it makes ordering easier, and I can generally read them better.  Though I'm starting out with just a few modules (2x VCO, VCF, VCA, S&H, Trigger Generator, and Voltage Follower), I made up a bill of materials for my 10-row "dream" Synthasystem (ahem!).  I ordered all of the resistors, diodes, rare parts, etc. for that.  The caps and most of the ICs I'll then order as I need them (same for the panel parts).

One thing that really caught my attention while putting together the BOM was how few different active components were involved!  In fact, only 13 of them, and three of them are used exclusively in the power regulation.  There's also only a handful of opamps in the system (all LM741, except for a CA3140 in the Selective Inverter).  Most everything is handled by transistors and diodes - it'll be a bit of a learning experience for me, as I'm unfamiliar with the non-opamp versions of many of these circuits. (Obviously you don't need to understand them to build them, but I'm trying to do both.)

There's quite a few SSM2210s in the system, but I'll likely be replacing these with pairs BC550B transistors.  They aren't in critical places; a THAT340 is used for the expo converter in the VCO.

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