Hi all - looking for some reference schematics for solid, decent headphone drivers that aren't overly complicated. Would prefer op amps vs discrete design for simplicity.
I'll be building myself a small mixer/headphone amp, and would like to see what some of the better headphone solutions are these days.
I've used the Behringer P2 on lots of gigs and it sounds fine to me, but I'm not finding a schematic easily. Any ideas on this or similar headphone drivers? (this would be for IEMs in particular; I imagine driving cans is maybe harder, because the larger speakers might require more oomph?)
Thanks!
Geoff
I'll be building myself a small mixer/headphone amp, and would like to see what some of the better headphone solutions are these days.
I've used the Behringer P2 on lots of gigs and it sounds fine to me, but I'm not finding a schematic easily. Any ideas on this or similar headphone drivers? (this would be for IEMs in particular; I imagine driving cans is maybe harder, because the larger speakers might require more oomph?)
Thanks!
Geoff
That looks like a really nice driver circuit! I'll keep it in the back of my mind.
It's probably more complicated than I'd like to use though, especially given all of the stuff I'm going to try and cram in this little box. Looking at mainly single IC solutions (whether that's a dual opamp, or maybe a headphone driver-specific IC)
It's probably more complicated than I'd like to use though, especially given all of the stuff I'm going to try and cram in this little box. Looking at mainly single IC solutions (whether that's a dual opamp, or maybe a headphone driver-specific IC)
This will be primarily for IEMs, which I understand can be low impedance, like 32Ohms-300Ohms. However, I don't think they need a lot of power behind therm because of the placement of the drivers so close to the ears, and the isolating nature of the physical design.
DIYA has a lot of "Terrible crap" HP amps using 3 transistors SE class-A simple with 1% THD and 10+ Watts of heat. But I'll go with sound-au.com or something very similar, which will give you less than 0.001% THD, and all the gain you want and ~5Vrms. And it could be half of a quad op-amp.Terrible crap. Sorry.
But it doesn't get much simpler than the circuit at sound-au.com. The only thing simpler would be a HP amp chip like those TI sells. Check their selector guides. You could use a couple LM386's but that will not be 0.001%THD.
The schematic from Rod Elliott works, but it certainly is not "what some of the better headphone solutions are these days". It seems to have been around forever and published many times, including by Douglas Self in his Small Signal Design Handbook. Mr. Self actually measured the distortion of it:
The 20dB/decade rise of distortion is a manifestation of the loop gain falling with frequency, and of not-so-linear output stage in that loop. With an NE5532 instead of the TL072, it would a few dB better. This kind of distortion has a sonic signature: unnaturally tight and punchy bass. glassy mids and highs, and amplified sibilants.
In his book, Mr. Self also demonstrated how to make it a bit better. But, if you want something really simple, just use an OPA1688 - with a 70mA output current limit, it may be a little challenged with low impedance IEMs, but 32ohm and above should be ok. Otherwise, it probably will work the same as Elliott's, without the complexity and with a much wider power supply range.
For best sound quality, consider Omicron.
The 20dB/decade rise of distortion is a manifestation of the loop gain falling with frequency, and of not-so-linear output stage in that loop. With an NE5532 instead of the TL072, it would a few dB better. This kind of distortion has a sonic signature: unnaturally tight and punchy bass. glassy mids and highs, and amplified sibilants.
In his book, Mr. Self also demonstrated how to make it a bit better. But, if you want something really simple, just use an OPA1688 - with a 70mA output current limit, it may be a little challenged with low impedance IEMs, but 32ohm and above should be ok. Otherwise, it probably will work the same as Elliott's, without the complexity and with a much wider power supply range.
For best sound quality, consider Omicron.
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The ESP circuits were some of the first I tried in audio more 15 years ago...At the time my best audio equipment was a crappy radio cassette player...but anything I tried at the time from ESP was at the same quality level as the proffessional equipment some of my recording engineer friends had in their rigs as I could get to check it on their studio quality headphones and speakers.Today's proffessional soundcards still have simillar if not worse headphones amplifiers than this simple circuit.Yes adding some current sources to bias the output trz may improve the circuit a little bit, having faster transistors or op amps, using much more complex topologies can technically do it, but hearing that improvement is a different topic entirely.
Even though a lot has changed over the last 15 years, plenty of people are still arguing that there would be no audible benefit to lower distortion. To verify that claim, you just need to try it yourself. It is an interesting experience, and you may be surprised. Just make sure that the distortion actually measures low across the whole audio spectrum, not just at 1kHz.
Everything's debatable, but I just wanna drop one more here... ESP didn't necessarilly based his design on Douglas Self books, Studer A810 had that topology explored enough in the Service manual Part 3 at page 80, 90 and 92 as line output amplifiers and 131 as monitor speaker amplifiers at least a decade before D.Self wrote anything on audio.I find their approch very proffessional and robust and I didn't hear many Studer A810 owners complaining about not being able to improve those section by a simple recap, but if you want different op amps in it, be my guest! Still...talk to a Studer A810, 820, 827 owner before making any claim of improving Studer designs...
https://elektrotanya.com/studer_a810_sm_part3.pdf/download.html
https://elektrotanya.com/studer_a810_sm_part3.pdf/download.html
I have had very good results with the Burson V6 Classic single OPA. It directly drives 32 ohm headphones without a problem. I wouldn't recommend the Dual V6C because of the heating. The simplest scheme for a non-inverting OPA, the power supply should be done with say LT1963/LT3015 (+-12V), sounds much better than LM317/337 or 7812/7912. Voltage gain is 3x.
There's no "much better" regulator sound unless the power supply can't handle the currents.I hate to see on so many forums so many audio " guru" promoting the most expensive and complex solutions to problems solved 40...50 years ago in integrated form...As long as modern op amps have PSRR and CMRR factors over 90db at 100hz , 60db at 10khz and 40db at 100khz, a simple first order RC filter is enough to filter anything measurable out. Use the simplest and cheapest regulator to keep the supply within safe limits, smth like 78/79xx is enough for any post 1990's op amp supplying litterally anything and don't care about anyone's opinion until you can actually hear and measure something wrong and if it's the 78xx that makes noise, change the op amp with a better one or just rework the ground traces
With all due respect, it's not fantasy, it's been tried many times. I'm not forcing anyone to use anything, I'm just making a recommendation. If there are "better" OPAs, which subjectively sound better, be sure that this applies to voltage regulators, transistors, diodes and passive elements in PS.
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Studer A810 is a COMMERCIAL proffessional recording equipment that needs to insure that the supply is rock steady and won't damage the electronical components inside it or those attached to it.Besides there were tons of analogue regulators used to filter out the noise of the switching mode power supplies as Studer built big machines and needed a lot of power for the motors and the digital section.Studer A810 uses voltage regulators - Service manual Part 2 at page 131. Swiss engineers can't be wrong.
Diy headphones amplifiers can be supplied from any available power source and in 2023 they can benefit from improved operational amplifiers that you can be supplied as low as +-2.5v and even +-1v in some cases for regular 32 ohms cans. On the other hand I know at least one commercial well built and reveered audio equipment that has no regulators on the analog lines which solves all the fuss with exactly using njm4560 and njm4556 op amps supplied from rectified +-10v through 220 ohms and 220uF capacitors, nothing else.When I first saw that thing I was shocked thinking it was just a gross design fault, then reconsidered my opinion after a listening session.
Their best high end player at the time had just 78M12/ 79M12 followed by 27 ohms and 100uF to supply njm2114, njm4556 and HDAM circuits...and those were the peaks of 90's cd players at Marantz. One can't really improve anything in those players just by using regulators in one case or better regulators in the other, at least not if we're using modern op amps, although njm2114, 4560 and 4556 are still sonically hard to beat op amps .
The discussion was about using modern op amps in diy headphones amplifier and I simply see no reason of using any regulator with them.
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Years ago, when I was in the pro sound business, we threw together electronic crossovers etc and I used no regulators, no RC filters, nothing except proper ground wiring. There was no hum because the op-amps had good PSRR and a few mA from a 1000uF bulk cap is very little ripple. After I left, a friend bought one that a tech had wired wrong, which made it hum. I moved the ground connection, and it was fixed. I suspect those who use an elaborate DC supply simply don't understand ground currents. "Professional engineers" may or may not understand the finer points, but they tend to CYA design.