LM4562 Headphone amp with aux input

[hillio]

I stole bits and pieces from everywhere to cobble this drawing together. It's very basic, and I'm looking for ideas on how to make it "right" for what it will be used for.  Any and all comments/criticism/name calling welcome!

[miqbal]

The output is not stereo...

[Mark Hammer]

Does it need a reference voltage to serve as floating ground? (i.e., something halfway between 0 and 9v)
Does it need some sort of DC blocking on the output?

[jasonsmusicgear]

Here's one PerroGrande put together for me. It works great, but it's not a stereo input.


Jason

[Minion]

I have built a Headphone amp useing the LM4562, It sounds Really good accept that the LM4562 doesn"t really have the Output current capibilities to properly drive headphones to a ear splitting volume...The headphones get loud but still isn"t quite loud enough to listen in a noisy envoroment like when Jamming ......

The one I have uses a dual 15v supply with with the regulators rectifier and headphone amps on the same Board, If you are interested in the PCB design I can post it for you but I would suggest useing a OPA2134 as opposed to the LM4562 as it has a better output current capibility, My PCB is 2.5in x 3.7 in for 2 stereo Outputs with on board regulated power supply....

Cheers

[hillio]

The output is not stereo...

Yes, I didn't intend for it to be.

Does it need a reference voltage to serve as floating ground? (i.e., something halfway between 0 and 9v)
Does it need some sort of DC blocking on the output?

Yes and I don't know.  I was using the CMOY schematic as sort of a reference, and it just has a resistor in series with the output. (Which I forgot to put in my schematic) Does it need a cap or some sort of filter on the output?

Here's one PerroGrande put together for me. It works great, but it's not a stereo input

Man I wish I'd seen that earlier.  That's pretty much the same thing I was trying to accomplish without the summing amp.  Do the resistors alone work just as well?  The stereo input would be easy to add to that circuit.  Thanks for posting it.

@Minion: The PCB would be much appreciated, thanks.  I wasn't sure how well the 4562's would work for driving headphones.  Everyone has been raving about them for use in preamps and such, and I happen to have a few on hand.  The OPA2134 has the same pin out, so I'll give both a shot.  I also have some LME49720's and LM833 I might try just for the heck of it.   Thanks for the info.

[hillio]

Here is a another version with ideas from the other schematic and posts.

[miqbal]

Aha... it's stereo finally. It would feel so weird whether you had your ears covered by the 2 speakers of the headphone, but can only hear the sound from left OR right speaker, not both.

Hillio, what is exactly the "particular feature" that you need from an headphone amp? Is it simplicity, or versatility, or what?

[hillio]

Hillio, what is exactly the "particular feature" that you need from an headphone amp? Is it simplicity, or versatility, or what?

Honestly,  I just wanted something that sounds decent for practicing guitar without all the noise associated with the LM386 (Ruby) that I am presently using with my headphones now.  One volume knob for the guitar is all it really needs, as I am content to use the Mp3 or CD player's volume control for the aux input when I use it. Something simple and small is mostly what I'm after.  I guess it would be nice for it to be stereo.

[Minion]

Well here is the LM4562 headphone amp PCB design i did...I don"t know if it will suit your needs though, It is a true stereo headphone amp with individual left and right channels so if you wanted to run a Mono guitar signal through and get sound out of both ears you should build a simple Voltage divider and then split the output from your guitar to the Right and left inputs...this headphone amp has a 100k input impedance, if you wanted to use it for guitar you should change the 100k resistor in the input of each channel to a 1m resistor and use a fet input op amp like the OPA2134... This amp has 2 stereo outputs for 2 sets of headphones....




The PCB measures 3.7in x 2.5 in and uses LM78/7915 regulators and a basic Bridge rectifier the regulators don"t need heatsinks as the opamps don"t consume a lot of current, It has 2 seperate audio grounds that you have to connect to the main power ground useing a wire underneath the board or you can drill a couple extra holes into the Power ground and run the wires on top of the board, there are also 2 small jumpers that are marked 0R... It uses a standard 15v,0v,15 volt center tapped transformer, a really small one is enough (5VA)..


Cheers

[hillio]

Wow, thanks!   That thing looks awesome.  What PCB design software did you use to make this?

[Minion]

thanx...It isn"t my best work and the PCB design has a few flaws Like the Input and output connections aren"t close enough to the edge and there are a couple Jumpers but I go more for function than Fashion..lol

What I do is i design the PCB in Express PCB, then I take a screen shot of the Design and import the screenshot into Paint shop pro and Negitive the image (which then gives a White backround and Pink traces) add a Vector layer and trace over all the connections in Black and then remove the bottom layer and what I have left is the PCB design in black that i can print out and etch to PCB...I know there are probably better ways to do it but it is how I do it....

good luck

[miqbal]

..... Something simple and small is mostly what I'm after.  I guess it would be nice for it to be stereo.

No problem, here you go. It's from GGG: noise is minimal, simple, stereo, and very small current consumption.

Perhaps a 30mm X 30 mm PCB/perf/vero bord size should be able to accommodate the layout, including the LED indicator

[hillio]

Thanks!