Monoprice Monolith Liquid Platinum Headphone Amplifier by Alex Cavalli

I don't know if I've ever sat down and written a proper impression of these things. I've been running it from my OG Modibit for years now, and I think it's an amazing combo for planars that like big current output.

A few years back now, I was in the market for a high-powered amp with balanced output. I wanted something that could throw ample current, something that could drive the planars I wanted to delve into with aplomb. I basically wanted a fairly neutral, even-handed, good-sounding amp with lots of power reach, to power my whole trip down the rabbit hole of collecting a wide range of different headphones.

Thing is, I didn't want to spend a ton. I'm not buying top-end headphones, I look at the range of headphones available and pick tiers with quantity of headphones in mind. Take some of the toppestest bells/whistles at a compromise or catch a deal in order to have a dozen plus headphones over the next 10 years if I want. Competent and good-sounding with most things is fine. Jotunheim had recently come out and I had signed up for the loaner. I expected I would like it enough for the price to settle my every-amp then and there.

And then, I spotted a like-new Liquid Platinum for the same price. I knew about the amp, but had considered it more extravagant than I needed (I wanted to invest in a better amp after getting more headphones, to have a better gauge for needs in a bigger investment.) I had a feeling I would like it, and it was an easy decision.

I think I briefly regretted it after trying the Jot, but I like this amp way more than the Jot now, and would probably spend $$$$ on a pure class-A JFET output section instead of that. Keep this because I think it has great character and represents the strengths of hybrid designs extremely well. It's an extremely powerful and capable amp that doesn't over-invade the sound of anything and mostly just provides full, even juice, but sprinkles a satisfying amount of opalescent tube dust that combats any dryness.


It has served me so well, it feels like a staple fixture on my shelf now. This amp is never going away, I think. It's been my planar powerhouse. I don't even think the SE out is remotely bad. It has a more relaxed temperament, but it's not like it's veiled. It's a nicely delicate and layered presentation. Detail isn't the main event, but it keeps a nice backdrop of microdetail fizzing about to keep things from sounding dead or muffled. I think it does the HD6xx's and HE5xx's fair justice.

The XLR is where the magic is for me, though. Such a natural, clean, full-bodied sound. It gets more of a class-a vibe with that crisp-but-never-sibilant dynamism and macrodynamic control. It's like from the upper mids down, it's a proper high-power non-nfb amp and then as we cross closer to the treble we get more of that tubey layered holography, that smooth and sweet "wetness." It really brings the music to life in all of the best ways to me. Especially with things like the LCD2C and Arya Stealth, which like power oomph and like many planars have some artificial notes about them. This, mixing with the Modibit's easy warmth makes for a fun and musically-engaging ride that retains very high technical performance.

It really isn't weak in any particular area there. The bass is deep, slammin and lively. The midrange is natural, textural, and detailed. The treble is brilliant yet easy. Everything I plug into it sounds at its best. I think they're still worth snagging now, if you can find one used for 3-400 bucks.


PS: I think this amp looks great and I will testify such in a court of law. I appreciate that it's not just another plain box with pretty paint on it. It looks like it means business with its sleekly dark but utilitarian vibe. And it delivers the business with style points on top. The Liquid Platinum wears sunglasses to business meetings, and always puts everything on the table.

 

Separate post, weighing in on the volume knob.

I'm thinking mine is probably a later revision, being that I bought it on the used market a good while after all of the retail units had sold through. I'd appreciate if anybody knows a definitive way to identify so my input on the volume thing can mean something.

I can only say that my unit doesn't seem to have any of the weird behavior with these gross imbalances or stepping issues.

If we keep it to stuff I own, I've run PortaPro, HD6xx, HE5xx, LCD2C, Arya Stealth, DT990 Pro, and my beater KZ x HBB PR2 planar IEMs (quite low sensitivity at 94dB/mW paired with 15 ohm impedance,) and maybe none of this stuff is in the right range for the issues, but I've never heard imbalances or had odd behavior moving into different ranges on the knob. The most I get it up to is 12 o'clock if that helps, usually significantly lower. Not so much as dust scratchies, yet.

One thing I do notice is that if I CRANK the knob, just dime it with nothing playing, I can hear the noise floor creeping up towards the top of the knob's range. I'm doing this live with my Aryas, right as I type this. The absolute threshold for me to detect it is around 1 o'clock, though it's *barely* there. Between 2 and 3 it becomes much more audible. Part of this is me having some grounding/hum issues with my SE chain and cheap Pyle power rack, and for the Aryas, that's probably becoming dangerous wattage to the Aryas themselves, and well past acutely-painfully dangerous for the ears. Turned all the way up, I hear the line hum very clearly, along with some hiss. And yet I remain convinced that the SPL levels this would produce with signal would instantly render you unable to hear much of anything for a time, let alone that noise under the primary signal. I've made the mistake of running the Aryas at 12 o'clock levels only once and my freaken ears did rebound spasms when the song stopped, like my eardrums had to do an emergency lockout or something.

It's a similar deal with the 2C's. Both balanced. The HD6xx's, I only have an SE cable for and I can't hear it at all through them. It's MOST apparent on the KZ PR2 iems and the XLR, becoming prominent at noon. Can't find an SE cable to test those with. But those are also dummy loud by 9 o'clock, well below where the noise floor shows up.


For me, not an issue. But I can see it maybe being a problem for lower sensitivity IEMs with the wrong power characteristics. I just can't think of TOO many things you'd be far enough on that knob with for it to be a factor at all, not with this particular unit. Not even HE-6's are gonna be a problem there, I don't own them but I've tried it. It would have to be very low sensitivity IEMs, I'd think. I actually wish I could find an affordable portable DAC/amp that could make those PR2s sound as good as they do from the LP.