Headphone amp?

[andrewretard]

hey
i was wondering if it was at all possible to drive a headphone with npn transistors and if so, how.
thanks

[Peter Snowberg]

The impedance is the big issue for a simple transistor amp. You can either use multiple stages of current amplification, or use a little output transformer to trade some voltage amplification for some more current.

Look at the 5th from the last picture here:
http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html

[andrewretard]

is there any with multiple transistors then?

[cd]

is there any with multiple transistors then?

WAY easier to use a regular non-inverting opamp stage with a gain of 10.  Use an opamp with a high current capability, like a 5532, or even a 741.

If you must use transistors, try a current booster like this one:

http://www.inform.umd.edu/EdRes/Topic/Chemistry/ChemConference/Software/ElectroSim/Booster.html

Of course, it's more efficient to use a push/pull output using an NPN and PNP transistor.

[andrewretard]

ok then how bout an easy 741 or 368 one?

[cd]

ok then how bout an easy 741 or 368 one?

Use a non-inverting stage with a gain of around 10.  Google that last sentence, or apply the input to the + of the opamp, use a 1k resistor from the - input to ground, and put a 10k resistor between the - input and the output.  Add the usual biasing resistors, input/output caps, etc.

[Gilles C]

This could help you.

http://www.redcircuits.com/Page31.htm

http://www.redcircuits.com/Page30.htm

http://www.tubecad.com/2004/blog0016.htm

http://www.techlib.com/electronics/audioamps.html

http://www.tricountyi.net/~randerse/amp.htm

http://ourworld.compuserve.com/homepages/Bill_Bowden/page8.htm#amp.gif

You need a minimum of components to drive a speaker or headphones. But it doesn't mean it has to use opamps, or be complicated.

Gilles

[erix]

I've built dozens of hi-fi headphone amps.

My favorite circuit is this one from the headwize.com site known as "Apheard's 47":


I've built a few versions of it and it's never failed to impress.

I have a site with a bunch of my junk on it -->  http://www.hbci.com/~erix/
Check out the "47 2.0" for a really simple build using a pair of dual opamps (OPA2132's) and the "Forehead" which uses a single quad opamp (OPA4228). Both of these designs use a BUF634 in the power supply portion of the circuit. You can leave it out but I think its critical for the hard-rockin' sound this amp is capable of producing.

ok,
erix

[andrewretard]

i really like http://www.redcircuits.com/Page31.htm

can it use a 9v supply though? how can i add a volume control? do u really need 1 for each channel or can u just connect the 2 sides of the jack?

sorry for so many questions, but thanks for the patience and help!

[TheBigMan]

I'm using a Ruby from www.runoffgroove.com as a headphone amp.  I use headphones with a built in volume control to keep the sound at a comfortable level.

[toneman]

]i like the Paia Headphone/buffer amp--

here--
http://www.paia.com/headbuff.htm

i put one in my StackInABox(SIAB)..
makes SIAB sound great in phones!!
plenty loud...4 me.

Still building the MXR-HP amp(from Tonepad or GGG?)
Looked like more drive than the Paia...
No results yet...other projects in the way....

T

[soggybag]

Erix: I like your web site. You have inspired me to try and make a head phone amp. Where do you get the parts? A lot of these I have not heard of before. In particular where did you get the fancy caps. These could be good for stompbox uses?

[guitarmonky55]

hey man, i know you!

i use the cmoy pocket headphone amplifiers to great effect for guitars.  i think i told you abot em, i make em in altoids tins.  just modify it for use with a single opamp or connect both channels of the output jack. (unless using mono headphones).

http://tangentsoft.net/audio/cmoy-tutorial/misc/cmoy-tangent-sch.pdf

[Gilles C]

i really like http://www.redcircuits.com/Page31.htm

can it use a 9v supply though? how can i add a volume control? do u really need 1 for each channel or can u just connect the 2 sides of the jack?

sorry for so many questions, but thanks for the patience and help!

The best thing to do would be to enter the circuit into a circuit simulator, and check what can be changed to keep the signals correct.

I once did that for another circuit, and it worked great.

Too bad I don't have time to do it, but if somebody else can, it would be great.

IMHO It is possible to use only 1 amp for both sides or 2 amps if desired.

From the text: "Tested with several headphone models of different impedance: 32, 100, 245, 300, 600 & 2000 Ohms.
Schematic shows left channel only."

If I were you, I would try it with 2 x 1.5V batteries first.

Gilles

[ethrbunny]

Toneman - can that PAIA build be run from a +9V source? I see the opamp wanting a negative lead... wait.. Ive seen this question before... there is a way to bias the opamp to run with a ground on the negative pole... *scratches head*.. Ill find it.. can you tell me if it will work with this opamp?

[ethrbunny]

tada! "virtual ground" is the term. Found a great reference that even talks about a headphone amp...

Now Im all aflutter with the notion of a BSIAB with a headphone amp.

The trick will be making the output jack different enough so that I won't inadvertanly plug it into my amp..

Im guessing that that would be bad.