How to enable high-impedance headphone mode on recent Macs (volume volume/thin sound) for headphones below 150 ohms

[plant550]

Hi, I'm trying to find a way to manually enable or 'trick' the amp within newer Macs into high-impedance mode.
Planar magnetics sound thin/low volume sound to me. They are below 150 ohms and so don't trigger the higher voltage output.

"When you connect headphones with an impedance of less than 150 ohms, the headphone jack provides up to 1.25 volts RMS. For headphones with an impedance of 150 to 1K ohms, the headphone jack delivers 3 volts RMS"

So far I have tried first connecting an adapter into Mac, then plugging the headphones into that but nothing has worked.


Has anyone found a way to manually enable high impedance mode?

 

[JIW]

Hi, I'm trying to find a way to manually enable or 'trick' the amp within newer Macs into high-impedance mode.
Planar magnetics sound thin/low volume sound to me. They are below 150 ohms and so don't trigger the higher voltage output.

"When you connect headphones with an impedance of less than 150 ohms, the headphone jack provides up to 1.25 volts RMS. For headphones with an impedance of 150 to 1K ohms, the headphone jack delivers 3 volts RMS"

So far I have tried first connecting an adapter into Mac, then plugging the headphones into that but nothing has worked.


Has anyone found a way to manually enable high impedance mode?

Assuming 150 Ohm is the lowest impedance it does not clip at 3 V RMS, the maximum available current is 3/150 = 0.02 A RMS. At X Ohm, clipping is thus at 0.02*X V RMS already.

The adapter you need is going to be a voltage divider. To get X Ohm to 150 Ohm at the headphone output, you need to add 150-X Ohm in series with the headphones, which reduces maximum output to the headphone to X/150*3 = 0.02*X V RMS. There is thus nothing to be gained by adding an adapter.

If you want higher output, you need an amplifier.

 

[staticV3]

The CS43131 can be tricked into "high gain" using such an adapter cable, but IIRC another ASR member tried the same on their MacBook, also without luck.

So it looks like Apple are using another mechanism for impedance sense.

Edit:
Here's the thread

M2 Macbook Pro’s Low Impedance Power Output Problem

Macbook provided 1.25 volts rms under 150 ohms and 3 volts rms over 150 ohms. However, planar headphones generally have low impedance and sense, regarding that they are hard to drive. The question is how can I get 3 rms with planar headphones like he400se on M2 MacBook pro?

www.audiosciencereview.com

 

[plant550]

Thanks for the responses. I've also tried one of these Sennheiser adapters so far, following the instructions you mention.
But wasn't able to change the impedance mode.

From what you describe in the other thread it might not even be possible to add the toggle via a software update