Since it's home made PCB time, let me present my little build:
In 2003, I've been gifted two(2) Brüel & Kjær(yes, I can pronounce it) mikes, 4188 capsules with 2671 preamp:
Those familiar with the system knows, that those preamps need current supply between 2 and 20 mA, and the output will stabilise around 12V DC.
Back then, I was still living in a former communist country, but working for an international electronics building company, I've had access to some scraps and leftovers(the B&K's were leftovers from a production line).
So, let's build an adapter!
And now, let's see what crimes I've commited 17 years ago...
The wire harness:
The PCB, in the front is the rewinded transformer: originally 12V, now 2X15V+30V; SMPS duties done by TOP224Y;
From the left: that's how it looks when you make a mistake late in the carving process(first OP07 from the left); center: TL431 reference for the current generators, 7824 supply for the current generators;
Top left: current generators; Bottom left: output amplifiers(10X, IIRC);
Overview of the whole teardown; the Lifelex LC-301 knife was used to carve out the PCB;
I've took out this adapter from his storage to change the interiors to something more modern and lower noise, like LT3080 current generators with OPA1602 amplifiers,
since this unit has a S/N ratio around 40dB(maybe?
I really should take some measurements befor I retire it..).
When I retire this board, it will get his own, nice ESD-safe bag, within a nice LDPE bag - I can't imagine better retirement for a board, but I'm open to suggestions.
Tools used:
50VA East Germany soldering gun, 100VA Soviet soldering gun, fret saw(for the front and back panels), Fluke 75 Mark II(yes, I already had it) and much more that I don't remember and got lost, but certainly was no scope involved, since I din't own/rented one around that time.
Materials:
The only parts what I've bought for this project are:
- The case
- The blue LED
- Copper clad for the PCB
Everything else is leftover or recovered from scrap; some parts(like the TOP224Y) were brand new, but dropped on the production floor, so deemed "unreliable".