Is connecting a headphone amp to headphone output of an audio interface ok?

[crx]

Or must they always be connected to audio outs?

 

[staticV3]

Is connecting a headphone amp to headphone output of an audio interface ok?

Yes. Every headphone output can also be used as Line output to connect external Amps/Mixers/etc.

You may have to double-check pinouts and signal voltages to ensure a proper connection, but fundamentally Headphone output->Line input is AOK.

 

[Mr. Swordfish]

The only real difference between a line out and a headphone out is that the headphone out has a volume control in the signal path and they (usually) can produce more current. Consumer level line output is nominally -10dbv or .316 volts. The headphone out is in that general neighborhood, depending on where you set the volume control.

You can usually use a headphone out just like a line out, although if you turn up the volume all the way you may overdrive the input. And as noted above, getting the connector-ology right is important. A stereo mini-plug to 2x RCA cable works for most situations.

 

[twsecrest]

Technically a line-output jack, can feed a better signal to the line-input on your headphone amplifier.
Connecting the audio interface's headphone jack to the line-input on the headphone amplifier is fine, if it's the only option.

 

[Mr. Swordfish]

Technically a line-output jack, can feed a better signal to the line-input on your headphone amplifier.

Why might that be? Some non-linearity due to the presence of a potentiometer in the signal chain?

 

[JeremyFife]

Sounds fine.
I suppose the question is, why do you want a headphone amp when you already have one? What are you looking for?

 

[Cbdb2]

Should be fine. But. I did that once. It was the HP out of a 6 channel Behringer mixer into a power amp. It worked fine if you didnt mind listening to a couple of local radio stations at low level under everything else. Very interesting phenomena and I have no idea where or why this demodulation occurred. Thats the only time Ive seen that so I doubt you will have the same problem, but just wanted to put out a general caution. Sometimes weird stuff happens when you work out of the box.

 

[DanielT]

But is using the headphone output of an amp that does not have a dedicated headphone amplifier to feed that signal into another amp with a RCA to 1/4 inch adapter optimal? It seems that it can possibly burn resistors, can possibly distort the signal, can create poor channel separation.It is covered in the video below.

Something I've never even thought about doing, by the way. But I just happened to see that video yesterday so I thought I might as well bring it up in this thread.

You more technically savvy people can comment if you think that what the technician in the video says and measuring with the oscilloscope is correct, see between:0:18-4:50
According to the video: RCA to 1/4 inch adapter and TRS to 1/4 inch summing adapter not ok.
TRS to 1/4 inch ok.

 

[SHB]

Two things to consider:

• Feeding a headphone output to a headphone amp could cause problems with gain staging and impedance matching. So long as you’re not over driving anything and causing distortion, the only downside would be some extra noise or less than linear frequency response.

• Some integrated amps power the headphone output from a highly attenuated output of the main amp section rather than a discrete head amp section. Running that into an external head amp is not likely to give great results or be necessary since the amp section will have more than enough output power.

Obviously, the ideal solution is to use just one headphone amp and not daisy chain them.

 

[twsecrest]

Why might that be? Some non-linearity due to the presence of a potentiometer in the signal chain?

I'm not the expert, but for best damping control of the headphone diagram, you want the source (headphone amplifier) to have a low output impedance, and I believe line-outputs function better with high output impedance, but I'm not the expert.

 

[popej]

IMO it should be OK. But why would you do it?

(Actually, my first reaction was: why stop at one?)

 

[Mr. Swordfish]

IMO it should be OK. But why would you do it?

A common application of using a headphone out as a line level source is a laptop computer - most don't have line outputs, so the headphone out is the only analog output. Using a stereo mini-plug to dual RCA cable works fine and won't blow anything up. (the video above is about plugging a mono 1/4" plug into a headphone out, which shorts one of the channels to ground, which older equipment might not like very much.)

So, if you want to connect your laptop, phone, ipod, ipad, tablet, etc to your stereo, that's the simple way to do it.

If you're just connecting a pair of headphones it's probably unnecessary, but a more powerful external headphone amp or one that handles low impedance headphones might be better than whatever is inside the unit.

 

[Cbdb2]

I'm not the expert, but for best damping control of the headphone diagram, you want the source (headphone amplifier) to have a low output impedance, and I believe line-outputs function better with high output impedance, but I'm not the expert.

I think he wants to drive an amp from a HP out. So its a low impedance out driving a high impedance in. All good. The only drawback might be an extra stage of noise and distortion, but Its probably no audible.

 

[Cbdb2]

but a more powerful external headphone amp or one that handles low impedance headphones might be better than whatever is inside the unit.

Than why not drive it with a line out? Dont know what gear he is using or what he wants to achieve, might not have a free line out?

 

[Mr. Swordfish]

I believe line-outputs function better with high output impedance, but I'm not the expert.

No. A brief intro to impedance:

When the phone company started stringing phones together a hundred years ago, the employed Thevenin's theorem which says you get maximum power transfer when the input impedance matches the output impedance, and set 600 ohms as the standard output and input impedance for everything.

But there's no good reason to maximize power transfer when interfacing line level gear*, and the flattest frequency response comes from using a low output impedance and a high input impedance. The 7-to-1 or 10-to-1 rule is commonly cited.

So, almost everything today uses low output impedance and high input impedance.

* speakers are different and do need to transfer power; power amps typically have output impedance of a fraction of an ohm.

 

[Cbdb2]

The impedance matching was also used because the lengths of the transmission lines were long enough to become.. transmission lines. Where impedance matching is important.

 

[popej]

If you're just connecting a pair of headphones it's probably unnecessary, but a more powerful external headphone amp or one that handles low impedance headphones might be better than whatever is inside the unit.

Or maybe headphone amp is something like this:

 

[twsecrest]

Or must they always be connected to audio outs?

What is the make and model of your Audio Interface and headphone amplifier, if you own them?

 

[crx]

I want to buy the Slate Immersion One headphones that are planar unicorns and the internet says they are extremely difficult to drive and require some insane power from a very special amp that are like only 3 in the world that can do right now, and all those are Toppings. Something like that.

I don’t understand a darn thing about impedances and ohms. Tried to learn… it’s worse than nuclear physics.

I have a little Volt 176 interface at home which only has one pair of outputs going to my studio monitors.

A lot of people say you absolutely must get the best amp for those headphones otherwise they sound like crap and will be a waste of money. But I don’t want to waste money upgrading the interface just to get two extra outs and on top of that buy the preamp if headphones output of my existing interface is ok to use and won’t degrade the audio.

I read so many threads on this whole issue at gearspace and watched YouTube videos and the more I read and watch the more confused I get.

Lots of subjective opinions but I wonder if there’s actual some hard measurement data that is indisputable that says “yes measurements show clear degradation” or “no, the signal with proper gain stating remains unaffected”

 

[DVDdoug]

I don’t understand a darn thing about impedances and ohms. Tried to learn… it’s worse than nuclear physics.

Resistance and impedance (both Ohms) are "the resistance to current flow". (The voltage is mostly independent of the load.) With nothing connected you have infinite resistance and no current flows. The lower the impedance, the more current you get. If the impedance is too low "bad things" can happen. For example, if you connect 4-Ohm speakers to an amplifier rated for 8-Ohms, you might burn out the amp. But in the real world with headphone amps, it's highly unlikely that anything bad will happen.


I you live in the U.S, you have 120VAC at your wall outlets at all times. With nothing plugged in (or nothing turned-on) no current flows and you aren't consuming any power (no wattage). A 1000W hair dryer "draws" more current than a 100W lamp.

A lot of people say you absolutely must get the best amp for those headphones otherwise they sound like crap and will be a waste of money.

Probably not true. Most amplifiers (most electronics actually) are better than human hearing. A more powerful amplifier will go louder and some amplifiers have "features" like equalization/tone controls. If your headphones are loud enough without a separate amp, don't sweat it. And if you want to improve or change the sound, try equalization or tone controls. (Sometimes if you boost the bass you end-up needing more power.) ...And to some extent, louder often sounds "better".

If you really don't like the sound of your headphones, you probably bought the wrong ones. But to a large extent you CAN change/correct the sound with EQ.

People say lots of things and MOST audio/audiophile websites are dominated by nonsense. This is one of the few rational-scientific audio resources. You can't trust AI either, since AI is "learning" from all of the nonsense.