(This file has been updated several times, this is the Jan 3, 1994 version)

My experiences with the DSD kit: Format Converter Revision Beta-2
or SCuMS Skimmer as I've been calling it.

I got my first of 2 DSD kits running smoothly today.  Board assembly went
smoothly, this is not a Grief Kit by any means but all of the necessary
information is included,  The board worked the first time I conected
everything up.  Nice job B&R.

Testing: This area fairly sparse since I have been using the board for a
marathon taping session and haven't done much playing around with the settings.
My setup involves my Sony 75ES and a friend's Panasonic SV3700 DAD decks.
I recorded a CD to a DAT and tried to copy the DAT to the 75ES which yielded
the usual PROH(ibit) message.  I put the DSD inline and the 75ES decided it
liked the data better.  My lawyer told me to erase the second copy, which I
did.  (As your attourney, I advise you to tell me where you hid the
SCMS bits ;-)

Wiring details:
- I mounted the board on an L shaped aluminum chassis that slides into an
extruded aluminum box.  I built my own 10 Volt DC power supply using a 16
volt center-tapped transformer (Triad F-90X) driving two 1N4001 diodes and
filtered by a 2200uF 25V capacitor.  I mounted the power supply components on
a terminal strip.

-The following items were mounted on the front panel of the chassis:
power switch, fuse, power LED, input select switch, 4 DSD LEDs, optical
input and output, and 8 position RCA jack bank.  I will probably put a bypass
switch and the other DIP switch functions onto the front panel as well.

- All exposed AC wiring was covered.

- Not really a mod, just a wiring detail: I have set up 3 inputs, two coaxial
and one optical.  A 3 position center off SPDT toggle switch can be connected
across the desired input select pins on the DIP switch, the center off position
selects input 0 (default) and the other pins select inputs 1 and 2.

- I used metal pin headers for all of the selectable jumpers and put small
shorting blocks on the pins.

- I put metal pins into all of the holes for the external wires so that the
board may be easily disconneced from the chassis.

|- I added a 74HC04 IC to drive all four LEDs.  This allows the LEDs to be run
|at higher current for more brightness without loading down logic pins.
|The basic circuit is: IC pin --> inverter --> 220 ohms --> - LED + --> +5V Bus
|except for D4 which needed 2 inverters in series for the inverted state of the
|ERF signal.  I decided to use the inverters on D4 instead of Q1 so that all of
|the LEDs are driven by the 74HC04.  The input to the unused inverter section
|was grounded.  I put the 74HC04 into a wire-wrap socket and bent
|the socket pins to fit into two holes (- on C7 and + on D4) near the top of
|the 8412 IC.  The 220 ohm resistors were soldered onto the wire wrap pins.
|Kind of ugly, but functional.
*** This mod works and is easy to implement but has been superceded by the
*** 7 segment LED mod which displays the sample rate as 2 digits.

- I drilled four 1/8" mounting holes in the circuit board, 2 on the corners
next to the output transformers and the other 2 next to U6 and R7.

- I tested the voltage regulator circuit before installing any of the
(expensive) chips.  I used sockets for all ICs, so I just soldered everything
on the board but put only the 8 pin voltage regulator IC in for the test.
Simply apply power to the board and look for 5 volts on the power pins of any
IC socket, on the 74HC74 ground is pin 7 and +5V is pin 14.  If you get 5
volts, finish the kit, if you don't, you can track the problem down without
damaging the expensive ICs.  Later, I measured the power supply voltage again
after inserting the ICs to confirm that it was still at 5V.  In my case, I had
less than 5 Volts and had to switch primary taps on the transformer to bring the
unregulated side up to around 9 Volts DC to achieve good regulation with some
head room.
 
- I was having dropout problems with one of my decks while using the DSD.  I
won't put any blame on the DSD, I'm still testing, but I decided to put bypass
caps on ALL of the ICs, AT the ICs as is often advised.  I soldered small
tubular 0.1 uF caps to the underside of U3, U4, U5, and the fiber transmitter.
The caps go from the IC ground pin to the IC VCC pin.

Suggestions for the second rev:
- Move the wire trace in the corner by the optical inputs so that there is
  room for a mounting hole in the corner.

- Mounting holes would be nice but may add to the cost of the board.

- Put the above mentioned LED driver IC into the circuit.

- Put bypass caps on ALL of the ICs and the optical I/O circuits.