I bought an instrument (Akai MPC) that I use headphones with. I want to let friends listen to projects as I work on them, so I need a second pair of headphones. I bought an identical pair of headphones and I bought a Y-splitter. I had both headphones plugged in and it worked as well as I hoped. Am I going to damage my MPC? Or if I do this with my laptop, could it be damaged?

Tell me I can do this.

Thanks!
Mark

 

It will not damage the MPC, or your computer/audio interface. Both sets of headphones are essentially a parasitic load/draw from the outputs of either one. If you will have a problem, it will be that both pairs of headphones will be underpowered when you have them both connected.

The splitter is passive, so it is not adding any amplification at that point, just like a passive headphones controller would. Like a passive Mackie Big Knob almost. A headphones amp with two r/l output pairs would be better where your splitter is. But maybe you do not need that anyway.

 

Just to note that when you have 2 pairs of high impedance headphones ~250-600 ohm, they could be rather hard to drive loud enough if the hf amplifier is not strong enough. Driving 2 low impedance headphones ~32-64 ohm should sound perfectly alright in both cases. Most of the people use low impedance headphones, but pedant idiots like me like high impedance headphones (600 ohm) because they generally sound better - flatter, but they are much harder to drive loud, so I can't use them with my Discman... they're too quiet.

The hf amplifier works harder with high impedance, just like a normal amp works harder with more speakers. Now look at the numbers and draw some conclusions, since every hf amplifier should work with my 600 ohm cans... it should be possible to drive even more than 2 32 ohm headphones with any good hf amp. cheers!

 

Also, if one of you has a 250 Ohm and the other a 30 Ohm, to raise the level of the signal of the 2fiddy to a usable level the 3rdy will be much louder. If you can swing it, a headphone amp would be a good option even if the two headphones were both low impedance so each of you could set your own usable level. They need not be expensive.



https://www.thomannmusic.ch/behring...obgKbcLxLa0-Ou7nFSWZyh4DMwc0q2KxoCux8QAvD_BwE

 

Last edited: May 1, 2024

Sorry, that's wrong in many ways. An amplifier doesn't "work harder" with higher load impedance, it just has to deliver more output voltage. In fact, it has to "work less", as it doesn't have to deliver so much output current. Some time ago I made this little calculation example as an overview for what an amplifier has to deliver to drive 100 mW of power (which is quite high) into different load impedances:

100 mW - load impedance - voltage - current

- 600 Ohm - +20.0 dBu - 7.75 Vrms - 21.9 Vpp - 12.9 mArms
- 250 Ohm - +16.2 dBu - 5.00 Vrms - 14.2 Vpp - 20.0 mArms
- 80 Ohm - +11.3 dBu - 2.85 Vrms - 8.1 Vpp - 35.6 mArms
- 70 Ohm - +10.7 dBu - 2.66 Vrms - 7.5 Vpp - 38.0 mArms
- 64 Ohm - +10.3 dBu - 2.54 Vrms - 7.2 Vpp - 39.7 mArms
- 32 Ohm - +7.3 dBu - 1.80 Vrms - 5.1 Vpp - 56.3 mArms
- 16 Ohm - +4.3 dBu - 1.27 Vrms - 3.6 Vpp - 79.4 mArms

So 16 Ohm headphones can be driven with just 3.6 volts peak to peak, just a small battery power supply is enough. But the amplifier output stage has to deliver nearly 80 mA output current.

To drive 600 Ohm headphones, the amp needs 21.9 volts peak to peak, so a small battery is not enough. For example, the 3.6 volts that drive 100 mW into 16 Ohms would only drive 2.7 mW into 600 Ohms. That's why high impedance headphones are very quiet with low voltage battery powered devices.

And now for the parallel connection of two headphones. If you put two 600 Ohm headphones in parallel, the resulting impedance is 300 Ohm. So the amplifier needs to drive 200 mW instead of 100 mW. The voltage is the same, but the output current is sqrt(2) higher with 18.2 mA rms.

If you put two 32 Ohm headphones in parallel, it's like connecting one 16 Ohm headphone, so you have to make sure that the amp can deliver enough current.

That's what I wrote about in the other thread when I mentioned that most manufacturers don't give enough information about their headphone amplifiers driving capability.

 

Last edited: May 1, 2024

That was enough to explain the whole concept.
Having two equal impedances in parallel is same as for resistances: will be half.
If you use a 32 and a 16 ohm you'll have 10.7 ohm.

 

Thank you very much guys!

I should have given headphone specs:
38 Ohm impedance each (identical headphones)

But I don't have specs on the MacBook Pro's internal headphone amp.

 

Should be ok as they sum up to 19 Ohms and there are IEMs with only 16 Ohms. For example I used Shure IEMs rated at 17 Ohms and they worked fine with my MacBook Air M1.

Which MacBook Pro do you use? Since about 2022 MacBooks feature a headphone amp that delivers a higher voltage to high impedance headphones, but in your case it would be the standard 1.25 Vrms. That delivers about 40 mW to your headphones each, should be plenty enough to get them real loud, depending on their sensitivity.

https://support.apple.com/en-mide/108351

 

It's a 2018 MacBook Pro 15". My hearing is sensitive thankfully, so I don't need a lot of power to the headphones. As long as I don't push the headphones much, I should be fine?

 

Yes, because the 19 Ohms of your headphones in parallel are nothing unusual, you can buy 16 Ohm headphones everywhere. If you push it too far and the output stage runs out of current, it usually distorts but does not damage the amp. I never heard of any MacBook headphone output damaged by using consumer headphones.

 

I think you're a bit overcautious about it, but the skin is yours, so try at 0 volume and increase gain gradually.
To me no risk of burning gear.

 

I own one of these, and it works well for purpose.

 

I was the one who asked you this about the Motu 828es AVB interface. Their tech specs show the correct impedance values, but the highest it shows is 55ohms. I connected a spdif coax cable from the Motu to a Sony Digital Audio Control Center I already have for other reasons. Two checkboxes to add it to the routing matrix and it works perfect with the 250 ohm Beyerdynamics. Now my little analog headphones amp can stay with a few drum machines and I don't have to power up console mixer, and can take them into another room too. Without buying another headphones amp.

 

I have a Donner 4 channels (I guess more or less the same thing under the hood), and yes it drives quite a lot of power.
The only thing is that after one year or so it begins to crackle a bit at low level, using only a fraction of the entire pot span.

 

If you are not very familiar with electronic basics it's not easy to understand the whole source/load impedance or voltage/current thing. It's the same for every amplifier and load, it doesn't matter if it's for a microphone, line, headphone or speaker. Main thing is Ohm's law:

https://en.wikipedia.org/wiki/Ohm's_law

But especially with headphones, there are sooo many wrong assumptions and statements as "high impedance headphones need more power" which are just not right, it's way more complicated.

 

use some pot cleaner on it.
no studio is complete without a can of Deoxit D5 (also a can of fader lube from Deoxit)

 

we were all really hoping you'd help with getting the economy going by blowing some more money on gear, but maybe next month okay???

 

I was hoping someone more knowledgeable about electronics would chime in. Gosh, it's just Ohm's law that we learned about in secondary school... Thanks! Very enlightening. Cheers!

 

Last edited: May 2, 2024

Right but I'm lazy.

 

Last edited: May 2, 2024

Do you mean Deoxit F5 for faders?