2021 16" MBP 3.5mm jack line level

[zephonic]

From Apple's support page I have learned that

The 3.5 mm headphone jack on compatible Mac computers features DC load detection and adaptive voltage output. Your Mac can detect the impedance of the connected device and will adapt its output for low- and high-impedance headphones, as well as for line-level audio devices.
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. This may remove the need for an external headphone amplifier.
With impedance detection, adaptive voltage output, and a built-in digital-to-analog converter that supports sample rates of up to 96 kHz, you can enjoy high-fidelity, full-resolution audio directly from the headphone jack on your Mac.

My question is, does anybody know what Apple considers line level? -10dbU? Impedance? Voltage?

Thanks!

 

[Chancha]

Line level is typically 300mV RMS, with professional gear going to I think 1200mV. I am unsure what's done on the new Macs' jack, but I vaguely recall even back during unibody MacBook Pro era, the 13" already had a single 3.5mm that double duty for both in and outputs, including line level, so Apple was already implementing some means of detection long time ago.

What exactly are you trying to do anyway?

 

[zephonic]

Thanks for your reply.

I am a keyboardist/pianist, and one of the ways I use my MBP is as a sound source for flyaway gigs. I have to rely on instruments sourced by local backline companies, and what I need or request isn't always what I get. So I have virtualized a lot of my keyboard rig into the MBP and just use whatever keyboards they give me to play the sounds from the laptop.

I have been running off the 3.5mm jack with an adapter cable (3.5mm> dual 1/4" plugs), and that works fine, for the most part. However, pro audio line level is +4dBU, so I'm trying to find out if Apple means -10dB line level, which is standard on most consumer gear I think.
There are any number of solutions to bridge this, a DI box being the obvious one, but a good DI box can be more expensive than an entry-level USB audio interface. So I'm just trying to gather information before I buy something that is not really necessary.

I know the old MBP's use to have digital output capacity on their 3.5mm jacks, which made it kind of perfect as you only needed a DAC, but that was removed with the 2016 MBP's and later.

 

[Chancha]

I *think* it is +4, but not totally sure. I used to work in a recording studio but nowadays have shifted back to music publishing, so my info may be off. But back when I was active, in my past experience with various Macs 3.5mm jack, the only instance where its a "gotcha" is with mic input not giving enough gain even for extremely small passive wearable mics if they are mono, but the TRRS input works instead since that's what was shipped in the earlier iPhones earbuds.

That said, it may be a good idea for you to invest in a certain interface anyway, as it gives you ways to meter and pre-amp or even mix the signal before entering whatever systems they are running.