[sdiy] Sine VCO - timing IS everything

[Peter Grenader]

Interesting this subject came up right now...

I've just built a Verbos version of the 258.  Got it plugged in for the
first time last night.  There are currently some part subs will be corrected
this evening, one of those was a Mouser sub of the required LF356 - they
supplied a NTE 937 instead.  Normally, I would have been a little bit
tweeked that they took it upon themselves to make this sub without
contacting me first, but in this instance it proved to give me much better
sine resolution than the LF356 did (found one of those in my rather large
'what was I thinking scrubbed projects to be used as spare parts' bin). I
then tried a 741 and a TL071, both of which didn't give anywhere near the
sine shape the NTE part did.

Now, I am not ruling out that this one 937 may be a bit of an odd ball onto
itself, but I just thought I'd pass this along.

I also cannot be wholly conclusive about these findings in that one of the
current subs is a resistor divider stuck in where the 1 meg trimmer should
that's there to adjust sine symmetry - and this all might change tonight
when the trimmer is received - I'll let you all know then.  I am hoping that
this pot will effect big changes because as it it, my wave shape currently
goes from sine to triangle, instead of sine to saw as it should.

BTW,  if any of you are thinking of making this board using Mark's' supplied
PCB art, be aware there are two errors you will need to fix that will cause
you  problems if you don't - namely the pin outs of the SSM2220 are wrong on
his layout and he's shorted out a 6.8k resistor.  I luckily caught these two
problems and fixed them before I imaged the traces. Subsequently I found a
listing of his about this on the archives, saying there were some problems
and would fix them and change the file, but I don't think he ever corrected
them, as I downloaded it just days before his site vaporized when he moved
back to the States.

best,

P