Questions about Balanced & Unbalanced

[TooMuchRain]

I understand that adapting a balanced output to an unbalanced cable has a risk of damaging the amplifier, but I only have a very vague understanding of why this is the case. I was wondering if anyone has a clear explanation for why this is the case?

Furthermore, I have seen places saying you can't adapt a balanced output to unbalanced input, but what about the other way around? Can you, for example, drive balanced headphones with an unbalanced output, if at the cost of a poorer SNR or whatever? Also, what about adapting 2.5 mm balanced to 4.4 mm balanced and vice versa? I know that 2.5 only has four poles, whereas 4.4 has five, and I've seen several adapters from 4.4 mm to 2.5 mm, but I have only found like one adapter going the other way. Is there a difference between the two types of balanced output, and how does that affect adapting them?

 

[Roseval]

One amp driving the left, one driving the right channel and they share a common ground.
This can be done with a 3 wire connection (TRS) or a 4 wire (like you connect speakers to an amp)
What is called balanced in the headphone world is having 2 amps per channel, one driving, one pulling.
If you insert a TRS you make a direct connection between the outputs of 2 amps.
This is how you build your own smoke generator.

4.4 might allow for a separate ground .
You can go from one to the other as long as it is TRRS
See: http://www.diyaudioblog.com/2016/02/headphone-connectors-pins-pinouts-for.html

 

[silent-circuit]

Driving balanced headphones with an unbalanced output - fine. 2.5 or 4.4 (female, headphones side) to 3.5 or 1/4 inch (male, amp side) adapters are fine. I have a couple of these since my "nice" IEM cables are almost all 2.5 or 4.4, but I can run most of them off my phone (3.5) without issue. Most aren't that power hungry.

Similarly, converting from one balanced standard to another is fine - I also have a couple 2.5 to 4 pin XLR adapters, and a 4.4 to XLR adapter as well.

What's not okay is something like a 2.5 or 4.4 (on the amp side, male) to 3.5 or 1/4 inch (on the headphones side, female). These adapters tie multiple grounds together. That has a very good chance of damaging the amp.

 

[TooMuchRain]

One amp driving the left, one driving the right channel and they share a common ground.
This can be done with a 3 wire connection (TRS) or a 4 wire (like you connect speakers to an amp)
What is called balanced in the headphone world is having 2 amps per channel, one driving, one pulling.
If you insert a TRS you make a direct connection between the outputs of 2 amps.
This is how you build your own smoke generator.

4.4 might allow for a separate ground .
You can go from one to the other as long as it is TRRS
See: http://www.diyaudioblog.com/2016/02/headphone-connectors-pins-pinouts-for.html

Oh lol, so the ground sleeve on the 4.4 isn't actually used for anything?

Driving balanced headphones with an unbalanced output - fine. 2.5 or 4.4 (female, headphones side) to 3.5 or 1/4 inch (male, amp side) adapters are fine. I have a couple of these since my "nice" IEM cables are almost all 2.5 or 4.4, but I can run most of them off my phone (3.5) without issue. Most aren't that power hungry.

Similarly, converting from one balanced standard to another is fine - I also have a couple 2.5 to 4 pin XLR adapters, and a 4.4 to XLR adapter as well.

What's not okay is something like a 2.5 or 4.4 (on the amp side, male) to 3.5 or 1/4 inch (on the headphones side, female). These adapters tie multiple grounds together. That has a very good chance of damaging the amp.

Ah, thanks! Why is it that 2.5mm male to 4.4mm female then is basically nonexistent? Like this is the only such adapter I could find: 2.5mm Male to 4.4mm Female. Lol I have a pair of iems for which I broke the 3.5 mm cable, but they also came with a 4.4 mm cable, so was kinda wondering about all this stuff. Although I decided to upgrade my iems anyways (since these have their 2 pin holes somewhat broken and all that). Was just kinda thinking of getting a dac with both balanced and unbalanced, but they usually come with 2.5 mm jacks.

 

[castleofargh]

A headphone's driver is just a coil, starting at one hand and coming out at the other. So you alway start at the headphone with 2+2 wires. You can join one from each side and have a TRS solution for a single ended amp. That junction can happen anytime, it doesn't matter too much. Some cables will join the 2 wires where you see the cable joining, some will, do it at the last moment inside the plug at the other end of the headphone. When you do it with an adapter at the amp, you do the same. So a ”balanced” headphone cable with a single ended adapter is simply a single ended cable.

On the other hand, using a TSR plug anywhere around a balanced amp will directly link 2 amps by one end when they were never designed to meet. That's not known to be a great idea for those amp sections.