For anyone who wants a smaller or easier to use version of my dynamic mic preamp, I've done a tiny PCB version, optionally available with an XLR housing.
Audio tests video on Youtube: https://youtu.be/T1MQ-IX4Mbo?t=295
Assembly video on Youtube: https://www.youtube.com/watch?v=_-fgi9NKWuo
PCB connection info, PDF file: PCB Preamp module.pdf
The PCBs, transistors and casings are available via this ebay listing:
These PCBs are just 1.2" x 0.4" (30 x 10mm approximately):
The passive components are already installed, using Uniohm resistors and AVX Kyocera tantalum capacitors at the input.
You can either use the ZTX851 transistors I'm offering as an option with the PCBs in the ebay listing, or use any type you prefer.
Connection-wise, the single pad at the top of the photo at each end, separated by the white line, is ground or 0V, the Pin 1 connection on an XLR.
The other two pads are for the balanced signal, XLR pins 2 & 3.
Straight-through wiring (eg. centre pad being pin 3 at each end) will give a phase reversal, or crossover connections (eg. centre pad in being pin 2 and centre pad out being pin 3) will maintain the same phasing.
One of the reasons for making these surface mount boards was to allow the preamps to be housed simply and cheaply. While searching for possible XLR enclosures, I discovered a range of XLR attenuators, sold under various brand names, which use an ideal inline plug-socket casing and are readily available at low cost.
The overall length of these is around 100mm; once the original attenuator resistors have ben removed, the PCB can be rigidly mounted to the output end plug using short pieces of component lead, with flexible wire at the input pads which can be soldered to the socket once the PCB & plug are inserted in the housing.
This photo shows an assembled unit with the plug pulled out so the PCB visible, and an unmodified attenuator:
The PCBs, transistors and casings are available via this ebay listing: ebay item 134609863647
Audio tests video on Youtube: https://youtu.be/T1MQ-IX4Mbo?t=295
Assembly video on Youtube: https://www.youtube.com/watch?v=_-fgi9NKWuo
The original prototype build: https://www.youtube.com/watch?v=nKuYq5OVaIE
And, building one on stripboard - functionally the same, but rather too big for the inline casing!
https://www.youtube.com/watch?v=yKFKRDoUV5E
PCB connection details: