Analog tuner idea (try #2..no show)

[Synthfool at aol.com]

(forgive me if this gets posted twice, I didn't see a copy from DIY after 12
hours)

Hello all,

A while back I felt it necessary to build myself a box to help tune
synthesizers.

The unit I built is very simple- a six position switch that selects taps on a
voltage divider of resistors to give 0,1,2,3,4,5 volts out thru a 1/4" jack.
This parallels to two mini banana plugs for my voltmeter, so I can monitor
the actual output voltage. There is also an octave trim and a ten turn
"offset" pot that adjusts the output voltage up or down about 100mv. 
There is a voltage regulator, but no output buffering and as such the offset
control is needed to compensate for varying vco input impedances and loads.

While my unit is very usable, it obviously still suffers some drawbacks.
Having just ordered some .1% Holco resistors (from mouser) with plans to
build "Tuner #2", I thought I'd bounce some ideas back and forth with you
guys before I embark on my new version. Possibly we can come up with a nice
design and do a PCB layout and all.
It is a lot easier and more accurate to use something like this than a
standard 1v/oct keyboard, IMHO.

Here are some of my thoughts so far-

1. A dual rotary 8 pos switch (mechanical or electrical) that selects a xtal
divided audio tone along with the  output voltage. I would probably just base
my unit in the key of C, but I can see the possibility of doing a "key"
selector too. While the voltage would be easy to offset, I haven't explored
how difficult the frequency divider part is.

2. A thought based on the Digisound Cal-tuner that uses a ring modulator to
beat an internally divided tone against the vco under tune in order to
exaggerate the beating effect. This in conjunction with LED's possibly as a
tuning indictor using comparators.

3. Multiple 1/4", 1/8" and banana output jacks.

4. A momentary "ground" switch to facilitate back and forth tuning when doing
vco scale adjustments.

5. Sine wave converter for higher reference frequencys and square waves for
low freqs.
I find tuning vcos to sinewaves is easier, but at very low freqs the sines
tend to get lost.
Possibly an inverted vcf that will increase the harmonic content of the
tuner's ref freq as the ref voltage goes down.

6. A jumper with an alligator clip as a ground. This just seems to be a good
idea.

7. A built-in 4.5 or 5 digit DMM and amp/speaker would be nice too.

Any ideas?

-Kevin

http://synthfool.com

"Always put outputs to inputs and inputs to outputs. Putting outputs to
outputs and inputs to inputs just won't get you anywhere you want to go."

                        -From the Moog Modular Owner's manual