Has anyone built a Penfold?

[Josh Brandt]

> I'm interested in the Penfold design for a number of reasons.  Mostly the
> cost, ease of construction for a beginner, and availability of parts.  
[...]
> I'd be very interested in hearing from anyone who has built a Penfold. 

Well, lemme see... First thing is, don't use cruddy single-turn trimpots.
Ditch that idea, and use nicer multi-turn trimmers. I've got single-turn
pots on my double-VCO module, and it's not really stable at all, and pretty
much impossible to tune... 

Second, the oscillators aren't the most stable. They're kind of shaky. That
might be a result of my crappy trimmers, but it's something to keep in
mind... They definitely have to warm up to be playable. 

Third, the 12dB/8va filter isn't really too impressive... I'm planning a
couple of replacement VCF's (including the CA3080-based one kicking around
my website somewhere, as a 18dB/8va LPF... I think I can turn that into a
24dB/8va LPF by simply adding another stage to it. Nice simple little
circuit... 

Fourth, if you give me a bit, I'll put my cleaned-up and workable PCB
layouts on the web site as well. They're ones I've used to make working VCF
and VCO modules. 

If you haven't seen what's on http://www.ultranet.com/~mute, you might check
it out... That's where most people get the Penfold book lately, but who
knows? You might have a real copy of the book!

> Ideally, this project should ease me into building more complex modules as
> my experience and confidence level increases.  So the issue of compatibility
> with other systems (ASM 1, Digisound, Modulus) is an important consideration.

Hm... Yeah, that shouldn't be a problem. In fact, I've been using the VCAs
and EG from my half-finished ASM-1 module, instead of building them from the
Penfold plans. I still want to make some more Penfold modules, but that was
a good way to test things out. Its 1V/8va, and I've even driven my Penfold
VCOs from an MC202... Nice little weird fun. 8)

Josh