U67 de-emphasis network

[dmp]

Question can anyone confirm or enlighten ,my tertary winding measures 12 ohms on my multimeter does tha sound right ?

Well if it measures 12 ohms its not open - so that's good. I found both of my BV12 had at an open winding. The windings that were not open did have the right ratio (Actually ratio should be P/S 6.92:1, P/T 21.6:1.) Both bobbins can be measured separately.

Best way to test your bv12 is to connect a test tone at the primary, measure the voltage at the secondary & tertiary and calculate the ratios.
My opinion is there is definitely something off about the Bv12 but I am going to try to get it working, as it fits the PCB footprint. Even with correct coils that are not open (probably from poor winding), they have a lower thickness of laminations (less than 7.1mm) If I were starting a new build, I would go with Moby's for sure.

 

[dmp]

To start with, I never measured a microphone capsule that had a high frequency boost of 9 dB...

How do you measure microphone capsules? What high frequency boost have you measured in k67 capsules?

A measurement on a U67 microphone through the 'messeingang' shows -5 dB @ 15 KHz.

The messeingang is the calibration input, described in the '63 manual. Why do you think the measurement (always) shows -5dB @ 15 kHz?

 

[RuudNL]

How do you measure microphone capsules? What high frequency boost have you measured in k67 capsules?

The messeingang is the calibration input, described in the '63 manual. Why do you think the measurement (always) shows -5dB @ 15 kHz?

I have measured many K67/K87 capsules in a 'flat' circuit. Usually the HF boost was in the region of 5 dB.
The 'messeingang' measures the complete (de-emphasis) circuit, with the microphone capsule in place.