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The BOSOZ Preamplifier

Last Updated: January, 2006 to X-CCS-BOSOZ:

I have just finished ripping apart the preamp and installing a pair of new circuitboards that add the Pass Labs "X" differential circuitry, as well as adding a constant current source. As you can see from the original, space is limited, so I had to create an external power supply.

This variation on the BOSOZ is called the "X-CCS-BOSOZ."

I felt bad disassembling all my hand wiring, removing all that perfboard that took two years to put together. But, I used most of the original parts, resistors, MOSFETs, and capacitors in the rebuild. Performance is improved and it looks a lot better, although it takes up 2 boxes, rather than one. It also runs cooler than the original.


Picture
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Description
Power Supply - HighRes Front

A high resolution picture of the power supply with the lights dimmed.
Power Supply - HighRes Side

This is the external power supply, top view. There is so much capacitance in the four power supplies (greater than 35,000 uF) that I added my Soft Start circuit to reduce turn-on power surge. The case is from Par-Metal.

Power Supply, Bottom View
Don't know why I put this in, but here is the underneath of the power supply. Feet are not yet installed.
Preamp, Top View
Preamplifier, Top View-- A lot of wires running around. I see a lot of very neat components made by other people but somehow the method of doing that eludes me. The inside is different, you see the red circuitboards and the added INA134 board for an additional pair of single ended outputs. The exterior of the preamp is the same (except for the fuses being replaced by WBT RCA jacks). Looks like I actually used the 9 pin dsub connector installed years ago.
Front View-LEDs "ON"
Well I finally drilled ventilation holes in the preamplifier top cover. As you see, I don't have a special tool for this, its all done with a hand drill so it turns out quite poorly. I wanted to start using this right away so did not take the time to wait and have someone drill a nice grid into the cover.
Front View-LEDs "OFF"
I've got a lot of switches on the front panel, they swith off all the LEDs, as shown. Note that the the 2 LEDs used for backlighting the gears cannot be turned off.
Backlighting LEDs
Here is how I backlight the frosted glass of the microscope slide mounted behind the gears. Wire ties are fixed on the volume knobs with LEDs in them, using epoxy to fasten the LEDs. The LEDs have insulated leads. This arrangement allows the LEDs to be carefully aimed so that there are no hotspots on the frosted glass.
Rear View
Here is the rear view, note the pair of outputs where the fuses used to be. The Dsub-9 connectors are used to connect the power supply to the preamp.

Since I was going with an external power supply, I had to add a bunch of features to the preamp, as I had room for more circuitboards in there.