Author Topic: Headphone amp schematic  (Read 11696 times)

egasimus

Headphone amp schematic
« on: January 17, 2013, 08:53:35 AM »
Can anyone give me a schematic for a very simple stereo headphone amp? One which could drive low-impedance headphones (24 ohm, 32 ohm), and which I could build 4 times on a single piece of vero in an afternoon, with easily available parts?

davent

Re: Headphone amp schematic
« Reply #1 on: January 17, 2013, 10:20:42 AM »
Build yourself some CMOY's, simple, low parts count and work fine with a NE5532 if you don't have the more exotic/expensive opamp available. And they do sound great, work fine with my Grado headphones.

http://tangentsoft.net/audio/cmoy-tutorial/

dave
"If you always do what you always did- you always get what you always got." - Unknown
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Pyr0

Re: Headphone amp schematic
« Reply #2 on: January 17, 2013, 02:42:49 PM »
Or you could try the MXR Headphone Amp




pickdropper

Re: Headphone amp schematic
« Reply #3 on: January 17, 2013, 04:33:53 PM »
Build yourself some CMOY's, simple, low parts count and work fine with a NE5532 if you don't have the more exotic/expensive opamp available. And they do sound great, work fine with my Grado headphones.

http://tangentsoft.net/audio/cmoy-tutorial/

dave

I second the Tangentsoft site, although I would recommend building the Pimeta.  It's a nice sounding amp that does well with lower impedance loads (although 24 and 32 ohm loads aren't terribly low).

egasimus

Re: Headphone amp schematic
« Reply #4 on: January 20, 2013, 02:54:48 PM »
Woah, both have a quite big parts count for a single stereo pair! I'm not looking for hi-fi sound, just something to use for band rehearsals, so 5 minutes before I had to leave the cafe (because I haven't had Internet at home for a month :icon_evil:) I found this on Reddit, and decided to go with that. I've managed to fit my four stereo channels on a small piece of perf, and I'm waiting for tomorrow to get the remaining parts...

Johan

Re: Sv: Headphone amp schematic
« Reply #5 on: January 20, 2013, 03:06:31 PM »
This is what lm386 was designed for...j
DON'T PANIC

kodiakklub

Re: Headphone amp schematic
« Reply #6 on: January 20, 2013, 03:51:03 PM »
I found this on Reddit, and decided to go with that. I've managed to fit my four stereo channels on a small piece of perf, and I'm waiting for tomorrow to get the remaining parts...

i guess size isnt an issue  ;) those caps are gigantic.
+1 for the mxr amp. -1 for vero

http://www.minidisc.org/schem.gif
386 headphone amp....http://www.minidisc.org/headbanger.html

goulashnakov

Re: Headphone amp schematic
« Reply #7 on: January 20, 2013, 03:55:28 PM »
Woah, both have a quite big parts count for a single stereo pair! I'm not looking for hi-fi sound, just something to use for band rehearsals, so 5 minutes before I had to leave the cafe (because I haven't had Internet at home for a month :icon_evil:) I found this on Reddit, and decided to go with that. I've managed to fit my four stereo channels on a small piece of perf, and I'm waiting for tomorrow to get the remaining parts...

Eeyup.  The TDA2822 is about as simple as you can get for a stereo headphone circuit.  The datasheet for it is a classic example of a "good" datasheet, because they were thoughtful enough to include schems for typical applications, including portable audio.  Although the project you found on reddit sure does like it capacitors super-sized.

I know for a fact that you can run 8ohms off 3V with this chip.  An old portable radio I had ran off 2 AA's and used a 2822 in bridged configuration to drive a humiliatingly tiny 8-ohm speaker.  That said, you should have no issues with your impedance requirements.  Hmm... now I kinda want to go dig up the pcb I salvaged, lift the chip, and see how it sounds through a full size speaker at 3v.  Jus' fer laffs.

PS.  Four stereo channels?  You setting this up for more than one person to listen at once?  Or are you using an actual "four-channel stereo" headphone system that I only read about in fairy tales and pulp fanfictions?  That would be pretty effin' sweet.

PPS.  I shudder at the memories of times without my own int-turn-netz.  You have my utmost condolences.
"[It] ain't about 'Booty.'  It's about Tranzzistahs... ya dig?"

egasimus

Re: Headphone amp schematic
« Reply #8 on: January 22, 2013, 12:51:23 PM »
Just four headphone pairs, nothing esoteric; but I'd appreciate some more info on that system you're talking about - sounds interesting ;)

egasimus

Re: Headphone amp schematic
« Reply #9 on: January 23, 2013, 07:37:03 AM »
I finished that mother@#$%er - of course, way too late to be of any use to what I intended it for, but hey, it's my first finished project in ages, if not ever. I'm entertaining the thought of building some portable speakers, perhaps a 1W practice amp with this IC. Sure, the LM386 might have some interesting gimmicks, such as the variable gain, but the 2822 is pure gold! Just gotta find enough of them for all chanels (the KA2209 is a pin-compatible substitute, by the way, but I'm not sure whether both are equally good).

At 10V, the amp is LOUD - so loud that I have to turn my PC's volume control down to 1-5% just to be able to listen to this through my Sennheiser HD407s (which are really nice for their price, by the way!). I get a lot of white noise, some 60Hz hum, and I can even pick up some radio if the other end of the cable is unplugged. All that noise is really fun, but it has to go, so I have some questions about what I can do.

My actual setup is: input jack -> 4x 20kB stereo pots -> 4x TDA2822 stereo amps -> 4x output jacks. I intend to plug this thing not to already preamplified headphone outputs such as my laptop's headphones jack, or my USB soundcard's headphones output.

1. I'm gonna put a voltage divider, or perhaps a trim pot at the input jack. Do the actual values matter? I.e. is there a difference between using 10k:100k vs. 100k:1M?
2. How do I taper 20k linear pots to become 10k logarithmic again? And would that be detrimental in some way, to something?

PRR

Re: Headphone amp schematic
« Reply #10 on: January 23, 2013, 06:20:46 PM »
> I have to turn my PC's volume control down to 1-5%

Your PC is already loud enough to drive headphones.

The chip has gain of 100.

No wonder you have to turn it down to 1% = 1/100 to get modest level.

20K may be a low pot impedance, especially if you want to fake-taper and/or pad-down the level.

100K+10K to ground as pad. (The 20K pot sees the 10K which will firm-up the fake-taper.) Hang 1,000pFd here to ground to divert the radio signals (30KHz low-pass). Hang 2K wiper to ground so the level at "5" is much less than half, closer to 1/10th.

Put at least 27 ohms between a powerful "speaker" source and a headphone. I can't find specs on the 407, but with 12V supply you can easily burn 32 ohm phones. This will also reduce the chip-hiss in the phones. (And it gives additional protection to the chip against steped-on shorted cords.) Values as high as 100 ohms may be valid.
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goulashnakov

Re: Headphone amp schematic
« Reply #11 on: January 24, 2013, 02:45:21 AM »
Just four headphone pairs, nothing esoteric; but I'd appreciate some more info on that system you're talking about - sounds interesting ;)

I remember seeing "4-channel stereo" as a selling point in IMAX theatres.  I think the dimeadozen x-point-one surrounds have all but killed the market for it in home systems anymore.  There was a diy guide to making surround-ish headphones by macgyvering a couple extra drivers into an existing headset, but I can't recall where I saw it.  I'm thinking Headwize maybe... since they're into some pretty kinky audiophilia it wouldn't surprise me.

Put at least 27 ohms between a powerful "speaker" source and a headphone. I can't find specs on the 407, but with 12V supply you can easily burn 32 ohm phones. This will also reduce the chip-hiss in the phones. (And it gives additional protection to the chip against steped-on shorted cords.) Values as high as 100 ohms may be valid.

PRR, I might try that ~27-or-so ohms resistance addon for some of my earbuds I use with my laptop on the go.  Even with "open air" type drivers, the earbuds that get good sound isolation tend to have too much output even when the volume is at the lowest tick (and I think my favorite pair is also 32 ohms).  It would be nice not having to hover the mouse cursor over the volume control on the youtube GUI in anticipation of those instances where want of established standards for web-based video volume output is justified.  (we youtube junkies call it "ear-rape."  There's no confusing that one with "aural pleasure")
"[It] ain't about 'Booty.'  It's about Tranzzistahs... ya dig?"