Affordable headphone amp that doesn't suck?

I've said it many times, but the Behringer Powerplay I've got is awesome (HA4700). Tons of clean gain. Quiet. Low/hi shelving EQ per headphone out. Aux ins per channel. Thing has been great, for years. If I needed more channels or it broke, I'd buy another without hesitation.

The performance of any head phone amp especially one used to power multiple pairs at once has as much to do with the impendance of the headphones used and the output impendance of the amp. That said on the cheap always head good luck with used Symetrix 1/2 rack units.

I've been running my Rane HC-6 forever. I just send one mix out to the players, but there are inputs on the back that I might be able to make multiple mixes with...
It's got plenty of power for loud dates.

A good headphone amp doesn’t really need to “match” the headphones from an impedance standpoint, it needs to be able to have enough headroom (high enough supply voltage and available output swing) for high impedance headphones and enough drive strength (current drive capability) for lower impedance headphones while retaining high linearity and low noise floor throughout.

Something truly professional can do either and equally well enough but this will typically be a higher cost design. My favorite headphone amp is probably the one in the Dangerous Monitor ST, it’s basically so overpowered it “breathes” (and you have to be careful, it’s capable of extremely large output levels). I also have the RND unit; it’s similarly overpowered but I think it’s a bit more colored.

This actually requires a desired “mismatch”, ideally the headphone amp’s output impedance would be exceedingly low compared to even “low impedance” headphones (making it act essentially like “an ideal voltage source”, at least to the highest degree possible).

0.1 Ohms of Zout (output impedance) of G103 mentioned above is quite low, almost certainly “low enough” for any practical range of headphone load impedances. But a simple and budget friendly opamp chip might also have that level of output impedance but completely crap out (slew rate limitations, current limit, low output swing with clipping, other sources of distortion) for even moderate headphone levels. My point: it’s completely possible to have a terrible design or a really nice design having a low small-signal Zout.  

It’s tough to have really great headphone amps with the lower supply voltages typical of budget interfaces but they’re usually fine for headphones of moderate impedance.

Hello!

I am an engineer of several fields; nuclear, electronic, audio, music, etc…
That field is all about setting parameters to solve a problem.

You have set two criteria: affordable - doesn’t suck.

You give a definitive, material value for price: <$500. But “doesn’t suck” is in the wind.

If I may have leeway to fill in the blank; “doesn’t suck” to me means “leads to success”.

Every music engineering decision we make is lead by what our monitoring systems inform us with. IT IS THE VITAL GUIDING LIGHT.

I would not have had my career (nor any of my outrageously successful associates) with under $200 anything dealing with monitoring (or other gear adjacent to transducers)

Appreciate the value, and invest in, tools that gather return

A great affordable headphone amp, just don’t try to drive 6 pairs of MDR7506’s that sucker will shut down.

Don’t get me wrong the Rane line wort is a pretty good little PSU for line level, we even used them in the little Intelix VCA mixers, but when it comes to driving low impendance loads even with just 6 little 2w amps it craps out.

Another thing to look for is the little belt pack amps used by broadcast guys for fold back. Gain control on each performers belt.

Well, I picked up a used Behringer HA4000.  It fulfills the need for some extra channels (now I can serve up 4 different headphone cues) and it doesn't suck because I only paid $30 for it.  And maybe someday down the road I'll pickup a better quality "producer" hp amp... (or not since I don't really have any complaints with the current one but also have never compared to a really good one...)

I read their marketing material about class A vs. class AB, and I’m not convinced they fully understand the circuits they’re describing. Just about any basic opamp chip potentially used to drive headphones (or most practical loads) will operate in a push-pull fashion using essentially the same class AB approach, including the well known (not necessarily loved) JRC4580 mentioned above (using bipolar transistors, BJTs, internally). So it’s not clear what novelty their circuit is actually offering.

They might be using discrete BJTs in the feedback path in a class-AB arrangement, but this is a known (and decent) way to make a headphone amp. They are basically describing the 990 discrete opamp that was developed in the late 70s or early 80s.

Beyond that, if heat and battery life is of no concern it is basically a known fact that class A biasing (super inefficient) avoids any form of cross over distortion and is generally agreed to be capable of cleanest signal reproduction. But the vast majority of amplifiers use class AB biasing, resulting in suitable results : so what’s novel? Other than inefficiency (battery lifetime, etc.), what is wrong with class A?

About the 100 ohm output impedance: it’s either a mistake and it’s in milli-Ohms or they’re attempting some sort load matching with the goal of “maximum power transfer “: but this scheme requires something called “conjugate” matching of impedances which is essentially impossible in this case because headphones loads are not simply resistive (keep one value over frequency), they have inductive and capacitive components that are different for each headphone model out there (and probably bad matching between different units of the same model).

I’m a firm believer in “if it sounds right, it is right” mindset, and maybe that’s the case here somehow, but from an electronics perspective I fail to see what revolutionary technique is being offered. Would love to hear from anybody with first hand experience using the hpm-2 (and/or a schematic!).

Edit: I should clarify that it’ll obviously be functional or they’d have no product to offer, it’s just not clear that it’s a better design than options most of us have readily available, included in other gear for the headphone amp itself. The other features it offers seem quite interesting (mid-side variations, etc.)

Took a quick look into the CAPI, even though I couldn’t find a schematic for it, the PCB and parts list certainly seem to imply it’s a class AB design with discrete BJTs and some Texas Instruments opamps for feedback. A solid design for sure and also essentially what was described in the HPM-2. I think I’d go CAPI, in part because I like DIY.

Happy with my Little Labs Monotor, it was $300 used. I also have a M900 which is a great portable solution, but definitely needs the power supply to drive most headphones