41

EQ573 Equaliser / Re: Signal going through the unit but it doesn’t effect the sound

« Last post by JPK on November 12, 2025, 03:01:35 PM »

You should get 0.68VAC on TP1.
Except if the EQ stays in bypassed mode.
Can you check the DC voltage across D1 which also is the coil of relay RLY1. It should be above 20V when the EQ is activated.

42

EQ573 Equaliser / Re: Signal going through the unit but it doesn’t effect the sound

« Last post by Colindsv on November 10, 2025, 11:11:47 PM »

Ok all of the voltages without running signal were good.  All points A-N tested very close to the target measurement.

The next step was to send a sine wave and test.  Here is where I’ve run into issues.  I don’t know if it’s the way I’m testing though

I have a battery powered behringer cable tester that is also a tone generator.  It has a 1000hz sine wave at +4dbu.  I measured AC voltage at the pins of the XLR and got 1.4v

Plugged this into the unit and measured tp1 and 0v and I get a reading of 0.0 AC voltage on the meter.  

Is this because my sine wave is 1000hz and measuring 1.4VAC from the source?  Or should I be getting a reading?

43

SK49 Multi-patern Tube Microphone / Re: How long is the 7-pin XLR cable that comes with the SK49 kit?

« Last post by JPK on November 10, 2025, 07:57:12 AM »

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

44

SK49 Multi-patern Tube Microphone / Re: How long is the 7-pin XLR cable that comes with the SK49 kit?

« Last post by Alex Harmer on November 09, 2025, 07:40:07 PM »

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

45

SK49 Multi-patern Tube Microphone / Re: How long is the 7-pin XLR cable that comes with the SK49 kit?

« Last post by JPK on November 09, 2025, 04:14:07 PM »

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).

46

SK49 Multi-patern Tube Microphone / Re: How long is the 7-pin XLR cable that comes with the SK49 kit?

« Last post by Alex Harmer on November 08, 2025, 10:08:53 PM »

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

47

SK49 Multi-patern Tube Microphone / Re: How long is the 7-pin XLR cable that comes with the SK49 kit?

« Last post by JPK on November 08, 2025, 10:45:50 AM »

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.

48

SK49 Multi-patern Tube Microphone / Re: How long is the 7-pin XLR cable that comes with the SK49 kit?

« Last post by Alex Harmer on November 08, 2025, 12:15:01 AM »

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?

49

SK49 Multi-patern Tube Microphone / Re: How long is the 7-pin XLR cable that comes with the SK49 kit?

« Last post by JPK on November 07, 2025, 09:30:39 AM »

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

50

First Aid / Re: lunchbox help noise and buzz.

« Last post by JPK on November 07, 2025, 09:04:08 AM »