mhelin

Economical tube mic/PSU connectors?
« on: September 20, 2018, 06:20:30 AM »
The 7-pin XLR or Binder connectors and sockets are expensive (for tube mic PSU's). Are the ham/CB radio microphone (don't know better name for them) connectors good enough to be used instead (in own projects, not as replacement generally)? There isn't much documentation on them, but they claim 500V DC insulation at  least.

Here some:
https://www.americanradiosupply.com/microphone-plugs/

Are there any alternatives? 5-pin XLR is a lot cheaper than 7-pin, and also the mini-XLR:s are pretty inexpensive. You could even go with a 4-pin connectors (gnd, audio out, B+, H+) unbalanced to a PSU with a built-in mic transformer. There are some inexpensive 4-pin mini-XLR connectors available on Aliexpress:
https://www.aliexpress.com/item/4-pin-Female-Mini-XLR-Male-plug-Audio-Microphone-Chassis-Panel-Mount-Connector-Adapter-10sets-Free/1921033375.html
« Last Edit: September 20, 2018, 06:39:13 AM by mhelin »
Mikko


L´Andratté

Re: Economical tube mic/PSU connectors?
« Reply #1 on: September 20, 2018, 06:36:15 AM »
Problem is you want seperate chassis and 0V connections, because it impacts audio quality, and you probably want P48, that makes 5 pins, 4 if you use a shield as chassis
And that is without pin for audio feedback to the power transformer ;D
Strictly amateur since 1973...

mhelin

Re: Economical tube mic/PSU connectors?
« Reply #2 on: September 20, 2018, 06:46:21 AM »
Problem is you want seperate chassis and 0V connections, because it impacts audio quality, and you probably want P48, that makes 5 pins, 4 if you use a shield as chassis
And that is without pin for audio feedback to the power transformer ;D
No need for the P48 as there will be a separate PSU (high voltage for tube and capsule + low heater voltage), but the two gnd's might be worth consideration. Well, the ham mic connectors have also 7-pin versions which cost the same as lesser pin ones, but there is no female socket available.
Mikko

Khron

Re: Economical tube mic/PSU connectors?
« Reply #3 on: September 20, 2018, 07:59:27 AM »
5-pin XLR's should suffice, then - audio +/-, overall ground, B+ and H+.

That is, for cardioid-only. Or also multipattern, if you include the pattern control inside the mic (as opposed to the power supply) :)

On most "modern" tube mic schematics i've seen, at least one of the 7 pins in the XLR isn't used, and/or is just commoned with the other ground pin (that is, for cardioid-only or PSU-pattern controlled ones).
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

mhelin

Re: Economical tube mic/PSU connectors?
« Reply #4 on: September 21, 2018, 09:06:33 AM »
Maybe the easiest way to go if you can mod your mic preamps is to  use regular 3-pin XLR connections but mod the preamps to use lesser current limiting resistors instead of the 6.81k ones, and increase the phantom voltage to at least 52V, or go straight to 60V which would be good voltage for most of the capsules and then for some of the tubes (put there a switch so that other mics can be used  safely as well). You could also build or mod an existing external phantom PSU supply box (like https://www.thomann.de/fi/millenium_pp2b.htm) for this purpose.

Then build or buy some nice DC/DC step-down converter modules with a good efficiency to supply the heater voltage and put these into your mics. If you accidentally plug this mic into regular phantom powered pre there will be no problems other than no sound - nothing will be destroyed.
Mikko

mhelin

Re: Economical tube mic/PSU connectors?
« Reply #5 on: September 21, 2018, 09:45:03 AM »
This guy converts phantom powered mics to use what he calls "active powering" which used +60V line in addition of balanced audio and ground:

http://www.rensheijnis.com/microphones.htm

He uses 4-pin XLR, and sells 2- and 6-channel PSU:s already. That's the next standard!

http://www.rensheijnis.com/ps402.htm


Mikko


 

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