Hello, right now Im searching for a good operational amplifier that would be useable as a headphone amp.
It will serve just as unity gain buffer, but it will need to deliver some current to the headphones. They are 120 ohms, but if it will be able to drive lower impedances, it would be better.
60mA into 120 ohm load is nearly half a watt.
My plan is to make high quality tube preamp and feed the signal from the preamp to this gain = 1 buffer. Directly coupled to the headphones.
Btw sorry if you consider my question stupid, but I have really no experience with opamps and this would be my first project with them.
Thanks very much for recommendations. Best regards, Michal
It will serve just as unity gain buffer, but it will need to deliver some current to the headphones. They are 120 ohms, but if it will be able to drive lower impedances, it would be better.
60mA into 120 ohm load is nearly half a watt.
My plan is to make high quality tube preamp and feed the signal from the preamp to this gain = 1 buffer. Directly coupled to the headphones.
Btw sorry if you consider my question stupid, but I have really no experience with opamps and this would be my first project with them.
Thanks very much for recommendations. Best regards, Michal
Alex's suggestions are very popular.
The antique NE/SE 5532 is, after all this time, still a fine audio tool. Over 30mA per channel. Paralleled '5532 devices may be a cheaper way to get 60mA than any other common chip.
Tube amps are inevitably hungry. The booster may as well be greedy also, class A. Assuming you can still get functional power transistors in this global supply disruption a 200mA buffer is easy. Exact choice of opamp and input details is up to you. If you capacitor-couple in and out it can be single supply. The current source I2 can be the tubes' heaters.
The antique NE/SE 5532 is, after all this time, still a fine audio tool. Over 30mA per channel. Paralleled '5532 devices may be a cheaper way to get 60mA than any other common chip.
Tube amps are inevitably hungry. The booster may as well be greedy also, class A. Assuming you can still get functional power transistors in this global supply disruption a 200mA buffer is easy. Exact choice of opamp and input details is up to you. If you capacitor-couple in and out it can be single supply. The current source I2 can be the tubes' heaters.
Don’t forget the excellent @pmillett “Butte” headphone amp. It is exactly what the OP is asking for.
http://pmillett.com/butte.htm
http://pmillett.com/butte.htm
Same as @PRR, I'd suggest using four DIP-8 NE5532 dual opamp chips per channel. Seven of the eight opamps drive the headphone (each with a 1.0 ohm series resistor), the eighth buffers the input signal and provides whatever amount of voltage gain you feel is necessary. The seven opamp array gives 140mA max output current, more than enough for >99.5% of all headphone products.
Or if you find that concept too busy, consider just using one single LM675 power opamp per channel. Max output current is more than 3 amperes, plenty of grunt to drive headphones. Consider using Douglas Self's "XD technology" to bias the output stage in class-A for the first 20mA or so.
Or if you find that concept too busy, consider just using one single LM675 power opamp per channel. Max output current is more than 3 amperes, plenty of grunt to drive headphones. Consider using Douglas Self's "XD technology" to bias the output stage in class-A for the first 20mA or so.
No doubt; but isn't OPA552 low/no stock at the reputable distributors, at least for the next few months?
Yes, the present project may not be ready until April (Mouser's estimate), but it would be 😢 to be delayed too much more. A chip in the hand is worth ten on the wait-list.
Whereas:
 NJM5532D IC OPAMP GP 2 CIRCUIT 8DIP Nisshinbo Micro Devices Inc. | 49,054 In Stock |
("Nisshinbo Micro Devices Inc. is a global “Analog Solution Provider” focusing on Energy Management and Signal Processing founded on January 1st, 2022 by integrating New Japan Radio Co., Ltd. (NJR) and Ricoh Electronics Devices Co., Ltd.", so this IS the old audio-friendly New Japan Radio in new name-tag.)
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Well if you are willing to step past "a simple opamp" I am very fond of the TPA6120A which is a high performance dedicated headphone amp on a chip. Very clean, plenty of current. Alas not available in a through hole package, but it's easy and cheap to find these on a PCB ready to go. It's easy to try and you might like it.
I would recommend doing fig. 28 from LME49600 datasheet
https://www.ti.com/lit/ds/symlink/l...29740&ref_url=https%3A%2F%2Fwww.google.com%2F
It's not super simple, but it is simple enough, and will give stellar performance.
If something super simple, I think the best would be parallel NE5532, single OPA552, or maybe parallel OPA1688/1622.
Good luck!
https://www.ti.com/lit/ds/symlink/l...29740&ref_url=https%3A%2F%2Fwww.google.com%2F
It's not super simple, but it is simple enough, and will give stellar performance.
If something super simple, I think the best would be parallel NE5532, single OPA552, or maybe parallel OPA1688/1622.
Good luck!
For a simple buffer, look at the O2 schematic. Since there is no feedback from the output to the gain stage, the gain stage can be eliminated provided there is standard input levels from other gear.
Tpa6120 is unbeatable for 99.99% of the headphones found on this planet, but it needs one more op amp to drive it as it's unstable if driven from a high impedance source . 2x lm6171 looks like the next option to me.
If you wanna go cheap use 2x njm4556 ic's as here and you can't go wrong.
If you wanna go cheap use 2x njm4556 ic's as here and you can't go wrong.
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JRC4556AD, cheap and cheerful , see the chart by sijosae. Tip - use +/-5V supply with "real" ground
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I don't trust his assessement on 300ohms load or I find it irrelevant.I use opa2228 on 250 ohms bayerdynamic dt880pro with 6x gain and I get one of the best and loudest sound I can from an op amp.Bare njm4556 doesn't sound as good as opa2228 on 250 ohms in the same circuit.I think I recommended the class AA Technics hph amplifier with njm4556 for a 100 times and nobody showed any interest in building it ...but that's the circuit to make if you want your njm4556 to sound as good as tpa6120.Sijosae CMOY amp used opa2132 which is a very good op amp.Njm4556 can drive almost anything, but it needs help on the distortion side which the class AA circuit provides.
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Here is an old chu moy with opa134, you can use dual.
https://web.archive.org/web/2002122....org/projects/showproj.php?file=cmoy2_prj.htm
https://web.archive.org/web/2002122....org/projects/showproj.php?file=cmoy2_prj.htm
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How high do you think will lead to instability? I’ve not had trouble with it since I’ve always driven it with a source <600 ohms.
Same thought I have.
But I recommend using the single version: OPA1655. Better cooling with 2 devices.
OPA1655 can put out 100mA. It is stable at Gain 1 as far as I know.
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