[Alex Harmer]

I am hoping to hang the SK49 microphones for orchestral recording from our local town hall. 

The ceiling is around 18 metres above the stage. 

Will the 7-pin XLR reach down from the power supply (in the ceiling), to rigging drop length, which is about 17 metres?

If not, do you recommend a good cable supplier?

Thanks  

[JPK]

I am sorry, the cable is 6 meters long so you will need a longer cable.
https://www.designacable.com/7-pin-xlr-tube-microphone-cable-neutik-sommer-sc-octave-mic-lead.html

[Alex Harmer]

Thank you, that’s fine.

My question now becomes… will I need to adjust the heater output voltage on a 25 metre cable run?

I think for 25 metres the voltage drop may be around 0.4v with 22AWG cable. Would it be safe for me to run it at 6.1v instead of the recommended 5.7v from your setup guide?

[JPK]

I think the best method would be to check the voltage across R13 in the PSU.
You want around 140mA in the tube heater so the voltage should be about 0.14 * 27 = 3.78V.
If the current falls under 133mA (3.6V accross R13) you can lower the value of R13 to increase the current.

[Alex Harmer]

Thank you. 

Last question:

The cable you linked above has a lot of different variants, depending on the microphone. If you look at the drop-down menu, you will see. 

Which microphone cable is the SK49 compatible with, in terms of its XLR pinout?

Thanks,
Alex

[JPK]

Probably Telefunken M16 Mk2 and t.bone.
But I would first check the compatibility with them:

• Pin1: B+
• Pin2: Heater+
• Pin3: Pattern voltage
• Pin4: HPF relay
• Pin5: audio
• Pin6: audio
• Pin7: Gnd

If the cable has some thicker wires they should go to pins 7 (ground) first then to pin 2 (heater).

[Alex Harmer]

Thank you! Very helpful.

Here is the Telefunken M16 Mark II pinout:

• Pin 1: B+ (tube HT) 
• Pin 2: Tube heater (filament)
• Pin 3: Pattern control (remote pattern voltage) 
• Pin 4: Ground / chassis 
• Pin 5: Audio 
• Pin 6: Audio 
• Pin 7: Ground / shield 
  
  Will that be okay? It looks like Pin 4 is a double-up and could easily be used for the HPF of your SK49. 
  
  Cheers
• Alex

[JPK]

Yes, this cable will work if the two ground wires are independent and not connected together in one of the XLR connectors.