Below are the rest of the instructions I received, I keep going around and around on what parts to buy for the not included missing resistor and cap mentioned.
Don't know if these instructions make better sense to anyone here that could make them more straight-forward, but I'm slowly trying to work through it (my questions at the end):
"The BC12 is an easy assemble kit that is perfect for budding electronic enthusiasts. Whilst assembly is simple, this does not mitigate the incredibly sensitive parts that are included.
These parts must be treated very carefully and preferably wearing latex or non latex surgical gloves to ensure no oils or pressure contamination.
Let’s start with the PSU. The PSU if purchased as part of the kit, comes pre assembled. This both helps with assembly time and safety."
XLR
1 - B+ (125v)
2- H (6v)
3 - P (0-125v)
4 - Ov
5 - Ov
6 - Sig - Orange
7 - Sig - Yellow
Pin 2 tube socket to
Pin 9 "" ""15om Resistor
From PCB
K Joins to
Pin 3 tube socket
a Joins to
Pin 1
Black wire a (-) goes to bridge pins on tube socket 5-9
XLR from the PSU is as such and should be followed in the microphone xlr as well.
Pin 1 = B+ (this is the high voltage of 125v that powers the anode of the tube).
Pin 2 = 6.5V (this is the positive for the heater filament)
Pin 3 = 0-125v (this is the pattern control pin)
Pin 4 = GND. 0V (this is the earth rail for the microphone)
Pin 5 = same as pin 4
Pin 6 = Orange wire from Transformer
Pin 7 = Yello wire from transformer.
For the Tube socket, we are only using a single triode bank and thus will earth the other bank to ensure low noise.
Tube socket Pin configuration;
Pin 1 = anode
Pin 2 = grid
Pin 3 = Cathode
Pin 4 = Heater filament Voltage (pin 2 from XLR)
Pin 5 to Pin 9 are joined to ground.
Connections from PCB
f = Capsule Front
p = Pin 3 XLR
+ = transformer red wire
- = blue wire from transformer
a = anode pin1 tube socket
k = cathode pin3 tube socket
B+ = pin1 XLR
GND = GND pin 4 XLR
On the bottom left of the PCB, you will see a resistor with only one leg connected to the PCB, you need to solder the supplied yellow cap (one leg to the loose leg of resistor and other leg to pin 2 on the tube socket (this is the grid)
You will also join the 2 x capsule centre wires to the loose leg of the resistor and capacitor (these are left off the pcb for noise reasons as fiberglass pcb has a low impedance than the grid circuit)
Hint, the transformer glues into the hole of the Blank PCB inside the microphone and the wires are then poked through.
there are various included Photo’s that will also help you assemble the microphone.
My starting questions:
- Which loose leg do both middle capsule wires both connect down to? One resistor leg one cap leg? Both to one where the cap/resistor join? Does it matter?
- Weird to me Ben told @johnsonic different values for the missing cap and resistor from what is written in the doc.
- Capacitor -The instructions seem to mention a second 392k cap, but he said 2-10n would be fine too?
- I've emailed Ben a few times for more clarity and no reply (I know he's super busy).
- Resistor - The instructions say 15om resistor across pins 2-9, not sure what wattage rating is appropriate if I go with that.
- Resistor - But Ben also recently told Johnsonic to use a 100M resistor?
- Resistor - I can't make out in Ben's picture what the color bands to confirm what he's actually using.
- The colors of cabling from the XLR to the pins on the back of the PCB are also confusing to me.
- Pin 5 and 4 are the same? Does that just mean use jumper wire?
- It says the orange and yellow wires from the transformer go to XLR pins 6, 7? It doesn't look like that's the case in picture 3?
- Also the pack of my PCB has 4 pins all connected, in picture 3 it looks like 2 are removed and cables threaded through?
I don't know if these directions and build are really that confusing or if I'm just over-complicating things.
I'll try to post my steps in a straightforward manner once I get it working for anyone else that builds this in the future.
