[sdiy] AES Meeting - Evolver

[Tim Parkhurst]

Hello All,

Please forgive me for the rather long post, but last night's AES meeting
with Dave Smith was VERY entertaining and VERY informative. The Evolver is
nothing short of revolutionary (IMHO) and learning more about it's innards
was incredibly inspirational. 

Dave gave an informal, but very entertaining talk that covered several
subjects including his new company, synthesizers in general, the design
philosophy and genesis of the Evolver, and some guesses as to the future.
Although I'll try not to waste bandwidth with all of my notes, here are what
I thought were the highlights:

*****Dave Smith Instruments:
"I love being a one-man company. I work out of my house, I don't have a big
office to pay for, and I don't have to argue with someone or go to marketing
if I want to change something or add a feature."

"The drawback of being a one-man shop is that it's lonely (laughs). That's
why I call Roger (Linn) all the time to bounce ideas off him."

"I really like feedback and things that are a little out of control."

http://www.davesmithinstruments.com


*****The synth industry:
"25 years ago, one guy could do everything. Things were more 'hardware'
oriented. Along came the DX7 and that era, and all of the sudden you needed
very large investments in custom chips and lots of software. Now, things are
coming back to the point where a one-man operation can work. I do web
searches for parts and price quotes, download part spec sheets, I outsource
the manufacturing, and all the PCB layout and software writing is done with
relatively cheap tools that run on a fast, cheap PC." 

"I didn't want to do another retro analog synth. I wanted something with a
LOT of personality. I didn't want to do another software synthesizer either.
All the software synthesizers now seem to have a certain 'sameness' to them.
Software is definitely the wave of the future, but it's just not the same. I
wanted a neat little box to hold. I see a lot of room in the future to
explore the combination of analog and digital hardware."

"There are several problems with making a software synthesizer. For one, for
every soft synth you sell, you give away ten (referring to piracy). Also,
anyone who graduates from college can write a software synthesizer...and
half of them are! And the biggest problem is the OS. You spend half your
time porting to this OS and then that OS and this driver and that driver. A
lot of times, software has problems that are completely out of your control.
PCs crash, Macs crash, they all crash. (Holds up Evolver) This doesn't
crash. It runs all the time, and it'll still run five or ten or twenty years
from now." 

"There is NO way you could get everyone to agree on what should be included
in a MIDI 2.0 spec. I don't think it will ever happen."

*****Evolver:
Notes: Dave uses Eagle for PCB layout, 18 series PIC micros (programmed in
C), Analog Devices 2191 DSP programmed in fixed-point mode ("If I had it to
do over again, I'd do it in floating-point," said Dave).

"I was amazed by how easy it was to get into all this. So many manufacturers
help you with application notes and things. Like the switcher. I had to
design a switching power supply, all I did was copy stuff from ap notes.
They say 'do this, use this part, lay out the board like this, and it'll
work.' So I did that, and it worked!"

The 48kHz coming off the CODEC was the biggest emission problem when doing
FCC and CE testing. The Evolver had to go through twice, which ended up
costing about six thousand dollars.

The Evolver uses a wall wart for AC conversion. The benefits of this are 
1) It's very easy to use the unit overseas. The wall wart works from 100VAC
to 240VAC and includes three different plug adaptors. Dave has shipped to
over twenty countries. About 40% of Evolvers are shipped overseas.
2) You don't have to apply for UL certification if you use a pre-approved
wall wart. Apparently this is the main reason for their popularity.

Simple wave sequencing can be done with the two digital oscillators. Dave
used the waves from the VS. New waves can be downloaded through SysEx,
although there is currently no editor/converter program available.

There are four sixteen-step sequencers that can run simultaneously. Each one
can control the pitch of a different oscillator! Unfortunately, the
sequencers cannot control external equipment. Dave said he really didn't
think anyone would want to use such a simple sequencer to control other
stuff, but he's been surprised by how many people have asked for this
capability. This will probably be added in the near future, as the firmware
can be upgraded through SysEx.

The sound chain goes DSP -> D/A -> Analog (VCO, VCF, VCA) -> A/D 
There are two feedback loops (with a tunable delay) that go from the A/D
back to the D/A. These loops can also act as oscillators (great for
Karplus-Strong stuff). Check the signal path at

http://www.davesmithinstruments.com/downloads/signal_flow.pdf

There are two ICs labled "Marion" in the Evolver. Apparently, these were
designed by Doug Curtis for a Tom Oberheim project that never got off the
ground! Dave says he has a source to fab new chips when these units run out
(in about a year and a half). He also mentioned briefly that Doug may be
producing and reissuing some of the old Curtis chips again.

There are NO TRIMMERS on the Evolver PCB! All analog trimming and tuning is
done digitally. It is a VERY clean layout, and amazingly compact for what it
includes. There is a picture on the Dave Smith Instruments web site for
those who want to see.

********************************************
All in all, it was a very entertaining evening. The Evolver sounds AMAZING!
Dave did demos with a single Evolver sitting on a desk. No keyboard, no
outboard effects, nothing. It was hard to believe that all that sound was
coming out of a single monophonic synth! 

One quote from Roger Linn that I thought was interesting. "I try not to use
any components that I can't get out of the Digi-Key catalog. They have a lot
of stuff in stock, you can get it in a day or two if you need it, and a lot
of times they can beat the price of the big distributors." All in all, I
think we live in a GREAT time to be a Synth DIY geek!

Tim Servo
"Imagination is more important than knowledge." - Albert Einstein
 




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