Basic headphone amp

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openbookstudios

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Oct 5, 2020
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Hey y'all.

I'm looking for a very basic headphone amp circuit. This doesn't need to be able to provide hifi audio and power planars, just clear enough that the clientele can have clear monitoring during a recording session (I'm building these for a podcast studio) and have individual volume control. Only requirements are that i can power it via mains AC and not batteries since we dont want to worry about continuously replacing them, preferably balanced inputs and individual volume control. It won't need to power headphones more hearty than Sony MDR-7506s as its sole function is going to be for monitoring. Any of y'all have suggestions for something that might fit the bill?

If form factor matters I want to mount these underneath the table since the podcast has a video element to it and we'd want it to be out of frame.
 

grid_stopper

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Mar 2, 2016
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The DIYRE headphone amp, which i believe comes from douglas self's book, is both cheap, and excellent. It doesnt have balanced ins, but that is easy enough to tack on for minimal extra cost
 

Bo Deadly

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Headphone amps have been discussed here extensively. Every two years or so there's a big thread about the topic. I recommend that you search those out and review the posts because headphone amps are actually not completely trivial.

There are two major gotcha's. One is that you actually need to limit power. It's pretty easy to put too much power into phones suddenly and have someone rip the headphones off and become generally disagreeable or worse because their ears are ringing. The other is that you need to be careful about offset so that you don't burn out the coils such as on startup if one rail fails.

Just thinking out load I would parallel NJM4556 outputs with 100 ohm current limiting resistors on each output inside the feedback loop and 10 ohm mix resistors outside the feedback loop into a 470uF+16V electrolytic in series with the load. The resistors inside will adjust output swing depending on load but have the low output impedance for good fidelity while the electrolytic will protect the voice coil from DC.

If you're designing the power supply as well, a better way to limit power is to simply use a lower supply like +-5V and adjust part values accordingly. You really don't need or want +-15V for a headphone amp.
 

openbookstudios

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Joined
Oct 5, 2020
Messages
5
Headphone amps have been discussed here extensively. Every two years or so there's a big thread about the topic. I recommend that you search those out and review the posts because headphone amps are actually not completely trivial.

There are two major gotcha's. One is that you actually need to limit power. It's pretty easy to put too much power into phones suddenly and have someone rip the headphones off and become generally disagreeable or worse because their ears are ringing. The other is that you need to be careful about offset so that you don't burn out the coils such as on startup if one rail fails.

Just thinking out load I would parallel NJM4556 outputs with 100 ohm current limiting resistors on each output inside the feedback loop and 10 ohm mix resistors outside the feedback loop into a 470uF+16V electrolytic in series with the load. The resistors inside will adjust output swing depending on load but have the low output impedance for good fidelity while the electrolytic will protect the voice coil from DC.

If you're designing the power supply as well, a better way to limit power is to simply use a lower supply like +-5V and adjust part values accordingly. You really don't need or want +-15V for a headphone amp.
Not super looking to design one right now thats why I'm kind of looking for an off the shelf option or something that's already been proven to work that I could get a PCB made and source parts. I appreciate the information though!
 

openbookstudios

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Oct 5, 2020
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This one is almost as simple as it gets, works really well with many different types of headphones: https://www.gyraf.dk/gy_pd/hpamp/HP-Amp.pdf

/Jakob E.
Will definitely be looking into this too, thank you!
This one is almost as simple as it gets, works really well with many different types of headphones: https://www.gyraf.dk/gy_pd/hpamp/HP-Amp.pdf

/Jakob E.
Also, just spent some time browsing the rest of your site and it's very generous of you to have a good chunk of your projects available for us DIYers to tackle. I recognize your stuff as my Antelope interface came with an emulation of your gyratech ix preamp, not sure what you think of the emulation but I think it sounds fantastic and I may end up giving your G9 project a try at some point.
 

amplexus

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Jan 11, 2018
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Another vote here for the DIYRE unit. Built 10+ for a client’s distributed headphone system and they were super cost effective, easy to build, drove even my old Fostex RP planar cans really nicely.

Have zero doubt that Jakob’s unit is equal or better as well.
 

DKaye

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MidnightArrakis

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Sep 25, 2015
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Hey y'all.

I'm looking for a very basic headphone amp circuit. This doesn't need to be able to provide hifi audio and power planars, just clear enough that the clientele can have clear monitoring during a recording session (I'm building these for a podcast studio) and have individual volume control. Only requirements are that i can power it via mains AC and not batteries since we dont want to worry about continuously replacing them, preferably balanced inputs and individual volume control. It won't need to power headphones more hearty than Sony MDR-7506s as its sole function is going to be for monitoring. Any of y'all have suggestions for something that might fit the bill?

If form factor matters I want to mount these underneath the table since the podcast has a video element to it and we'd want it to be out of frame.
Here's a broadcast-quality off-the-shelf small headphone amplifier that is even designed to mount underneath your podcast table:


1636139627124.png

And.....this same company also offers a "Headphone Disconnector" device so either you or your talent can't go walking off and end up having your necked snapped by the headphones still being plugged in!!! -- Introducing the Headphone Disconnector. Insert it between your equipment and your headphone cable. The exclusive magnetic coupled connector is designed to release gracefully when force is applied to the cable. This prevents damage to your headphones, cables and equipment and it might even prevent injury.


1636139560304.png

Should you purchase either of these items from this company, PLEASE let me know, OK??? THANKS!!!

JBW

/
 

openbookstudios

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Oct 5, 2020
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Here's a broadcast-quality off-the-shelf small headphone amplifier that is even designed to mount underneath your podcast table:


View attachment 86019

And.....this same company also offers a "Headphone Disconnector" device so either you or your talent can't go walking off and end up having your necked snapped by the headphones still being plugged in!!! -- Introducing the Headphone Disconnector. Insert it between your equipment and your headphone cable. The exclusive magnetic coupled connector is designed to release gracefully when force is applied to the cable. This prevents damage to your headphones, cables and equipment and it might even prevent injury.


View attachment 86018

Should you purchase either of these items from this company, PLEASE let me know, OK??? THANKS!!!

JBW

/
I'm probably going to go the DIYRE route since they're so small I could put them in a really small chassis under the desk and get no complaints from the boss to save room, but those headphone disconnectors look incredible. I may have to get some just for my own studio use, great find!
 

gyraf

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..it can definitely drive the DT990 to their best, but whether those are usable for mix or mastering, I dunno really..

/Jakob E.
 

Whoops

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Last time I checked the O2 was the highly praised, now it seems the "Atom" is the real deal.
The Hi-Fi World changes very fast, but I would like to try any of these units anyway

 

ruffrecords

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Last time I checked the O2 was the highly praised, now it seems the "Atom" is the real deal.
The Hi-Fi World changes very fast, but I would like to try any of these units anyway

The O2 is supposed to be open source but I cannot find schamatics for it anywhere.

Cheers

Ian
 

Bo Deadly

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Here's a very simple one; run on single supply.
That circuit has problems. It has no current limiting resistors, no drain resistors, the feedback network resistors are unnecessarily large, that chip cannot drive heavy loads to a high level well (which ironically is exactly what the text claims the circuit provides) and it's a little fast for single supply with one film bypass cap.
 
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