headphone amp with lm4562 opamp

[umut1001]

hi everyone..i wanna build a portable headphone amp using lm4562 chip only.i will use +-9volts batteries for power supply.but i dont know what to do..is that enough to make a simple gain by adding two resistors to opamp? should i put something else to output of lm4562 for empedance matching ..or something like that? can anyone give me a suitable schematic?thanks a lot

 

[theAnonymous1]

You can start here......

http://headwize.com/projects/showfile.php?file=cmoy2_prj.htm

I'm sure others will chime in with more suggestions.

 

[SpittinLLama]

Search National for AN-1768 for one solution that uses two 9V batteries. Looks like it might be what you want.

-SL

 

[Minion]

I have Made a Headphone amp useing the LM4562 and it sounds really good but the problem is that it doesn"t have enough output current to properly drive a set of Headphones to ear splitting Volumes ,It does get loud enough when cranked but it still isn"t ear splitting , even with a really high Gain setting....

I am thinking that I might add a discrete output stage that will be better able to drive headphones ......

You could also Paralell a set of LM4562 chips to increase the output current.....

Here is the PCB design for the Headphone amp i built....

It has it"s own Onboard regulated supply so a seperate PSU board isn"t needed....

This is a 2 channel headphone amp and to controll the Volume I just put a dual 10K pot at the Input of each channel to controll the Volume.....

PS: the 0R resistor close to the LM7915 regulator is Just a Jumper...


Cheers

 

[SpittinLLama]

Maybe you should check the app note from National also. It uses a buffer to increase output current to 250mA.

-SL

 

[Zigis]

Cmoy amp from theAnonymous1 link is the best solution for simple headamp.
Use TLE2426 rail splitter better, instead 2 resistors virtual ground.
I made few amps with LM4562 with gain 2. Only problem - large DC offset, compared to OPA2134 - 40-60mV. I tested LM chip in my standart amp with gain 6, and get even larger DC offset.
Zigis.

 

[BWRX]

The LM4562 has a lower offset voltage (+/-0.7mV max) than the OPA2134 (+/-2mV max), but the LM4562 also has a higher input bias current (72nA) than the OPS2134 (+/-100pA). Both of these figures are to be expected because the LM4562 is a bipolar input op amp while the OPA2134 is a FET input op amp.

The high output offset voltage you're seeing could be due to poor matching of the input bias currents and/or DC offset present from your source.

 

[jackinnj]

see if you can get some samples from National of the LME49600 -- this will output 250mA with THD of 0.0003% or better.

 

[umut1001]

only opamp

hi..i will built it for my friend..he loves headphone amps but never listened yet i will use one lm4562 or opa2134 but i dont know which sounds better :S i use opamp only because i believe less parts sound best..thanks

 

[dfdye]

Well, "fewer parts" is not really a valid concept when dealing with opamps. Each "part" is really quite a few parts on one piece of silicon.

Either way, I am surprised that nobody has suggested a TPA6120 yet. I rather like them, but they are SMP's which may complicate things a bit, plus you would have to use more than one 9V battery, but they are designed as headphone amps and have quite a good reputation!

If you are looking for DIP-8 parts, I am rather partial to the OPA2134's, but I would be rather shocked if you could tell the difference between that and the LM4562.

If in doubt about the opamp, get a dip-8 socket and try a few!

 

[umut1001]

i am not an opamp expert and i dont know what are the differences when using as a headphone amp..i use opa2134 as a preamp and listened to lm4562 too..i liked lm4562 because i think it is more detailed..but opa2134 has more output current than lm4562..

 

[peranders]

I have Made a Headphone amp useing the LM4562 and it sounds really good but the problem is that it doesn"t have enough output current to properly drive a set of Headphones to ear splitting Volumes ,It does get loud enough when cranked but it still isn"t ear splitting , even with a really high Gain setting....

I am thinking that I might add a discrete output stage that will be better able to drive headphones ......

You could also Paralell a set of LM4562 chips to increase the output current.....

Here is the PCB design for the Headphone amp i built....

It has it"s own Onboard regulated supply so a seperate PSU board isn"t needed....

This is a 2 channel headphone amp and to controll the Volume I just put a dual 10K pot at the Input of each channel to controll the Volume.....

PS: the 0R resistor close to the LM7915 regulator is Just a Jumper...


Cheers

Power ground <-> Signal ground => where do they meet?

 

[Minion]

Power ground <-> Signal ground => where do they meet?

Actually I wired the signal and Power grounds together under the Board useing a Large Gauge wire ... I haven"t noticed any ground noise problems and since my chassis was all Plastic I didn"t use a Power ground from the wall socket.....


Cheers

 

[jackinnj]

National has a current feedback opamp optimized for audio -- part of their performance series -- the LME49713 -- will do 90mA -- it is only available in surface mount (SO-8) but you can use an adapter. THD is down around 0.0003%

 

[ChuckT]

Well, "fewer parts" is not really a valid concept when dealing with opamps. Each "part" is really quite a few parts on one piece of silicon.

Either way, I am surprised that nobody has suggested a TPA6120 yet. I rather like them, but they are SMP's which may complicate things a bit, plus you would have to use more than one 9V battery, but they are designed as headphone amps and have quite a good reputation!

If you are looking for DIP-8 parts, I am rather partial to the OPA2134's, but I would be rather shocked if you could tell the difference between that and the LM4562.

If in doubt about the opamp, get a dip-8 socket and try a few!

Don't be shock, there is a big difference between 2134 and 4562.
LM4562 is so much better, so much more detail.

 

[umut1001]

i think so..i listened to both of them and i think lm4562 has much detailed sound

 

[dfdye]

Chuck, I am well aware of the two parts. I happen to have a good stash of both lying around and use both and like both. I do NOT, however, notice "so much more detail" from either part. In a ONE PIECE low powered headphone amplifier, the potential benefits of one over the other are negligible. Have you done a double blind test with the two parts? Can you HONESTLY tell me that you can HEAR the difference between the two in the same application changing ONLY ONE PART??? If so, I would love to know the application! Please send me a schematic so that I too can share in that "so much better" application! I would be happy to whip it up on some protoboard and see the error of my ways!

If, however, you are telling me that you like the LM4562's in a signal processing board, or a multi-part system in which the signal passes through dozens of opamps, then maybe we would have an interesting discussion. I don't buy it that you can hear the difference in ONE PART.

The irony in my earlier suggestion to put a socket in and try different parts is that once you hit a certain threshold for decent opamps, they sound pretty much the same! The point of the socket isn't to find the best opamp, rather it is to prove to yourself that they don't make an appreciable difference!!!

But hey, there is ZERO harm in using a LM4562, so why the heck not if you think it will help. I think most of us can swing the extra $2.

PS Just to clarify, if somebody just WANTS to use a LM4562, there is no reason that they shouldn't! I have no problem with the part and think it is excellent, just for the record.

 

[umut1001]

National has a current feedback opamp optimized for audio -- part of their performance series -- the LME49713 -- will do 90mA -- it is only available in surface mount (SO-8) but you can use an adapter. THD is down around 0.0003%

lme49713 is much faster than lm4562 and opa2134..so what is the advantages and disadvantages of this ? maybe better treble performance ?

 

[dfdye]

The bandwidth of all of those devices is sufficient to accurately reproduce much more than the range of human hearing! If you get a "faster" opamp, you won't necessarily get any difference over the audible frequency range.

While we are at it, the LM6172 is another high slew rate part that is perfectly capable of fine audio performance, but the speed of this part makes it prone to oscillation in poorly designed/laid out circuits. In this case, speed sometimes makes this part WORSE for a particular application than a slower opamp!

 

[umut1001]

The bandwidth of all of those devices is sufficient to accurately reproduce much more than the range of human hearing! If you get a "faster" opamp, you won't necessarily get any difference over the audible frequency range.

While we are at it, the LM6172 is another high slew rate part that is perfectly capable of fine audio performance, but the speed of this part makes it prone to oscillation in poorly designed/laid out circuits. In this case, speed sometimes makes this part WORSE for a particular application than a slower opamp!

i will make an headphone amp for my friend..i wanted samples of lme49713..because of high output..i want to make a simple space connectioned amp..i wont draw pcb..do you think it starts to oscillate because of high speed?.so is it a bad choice ?