Massdrop x Alex Cavalli Tube Hybrid Amp (CTH)

Folks in the headphone world are probably familiar with Cavalli Audio. Statement amps like the Liquid Gold and Liquid Glass are often considered end-game products. More recently, the well-received Liquid Carbon brought pricing down to triple digit territory, but $799 is still not what most consider "affordable".

Massdrop, on the other hand, is a company specializing in group buys for a wide range of enthusiast categories. Want a great deal on a fancy mechanical keyboard, fountain pen, pocket knife, wrist watch, or any number of other hobbyist items? Massdrop is your go-to source.

When the two join forces to create something special for headphone enthusiasts, the result is definitely worth getting excited about.

Massdrop traditionally offers deals on existing gear, but they've been dabbling in exclusive commissioned products more and more lately. Some examples of this include the Noble X, HiFiMAN HEXX, and the popular Sennheiser HD6XX. These all involve minor changes to existing products along with considerably discounted pricing.

Moving forward, I imagine we'll see more of those types of products, as they really are a big win for the community. Who wouldn't want the chance to own a well-regarded headphone for a lower-than-usual price? But Massdrop also has ambitious plans for being directly involved in the process by commissioning built-from-scratch designs that are not available anywhere else—nor will they ever be. The Massdrop x Alex Cavalli Tube Hybrid Amp, hereafter known as the CTH, is the first such product to launch.

Massdrop worked with Alex Cavalli to resuscitate a classic design from the Cavalli portfolio. For those new to the hobby, before Cavalli Audio made high-end amps Alex was known for his DIY designs. The CTH, which at the time stood for Compact Tube Hybrid, was a popular model known for making great sound from a tiny footprint. It was sort of a sleeper amp compared to some of Cavalli's other designs, and in my opinion one of his best works. Info about the CTH is still available at Cavalli's website. You'll notice the projected cost for DIY builders was around $200—keep that number in mind.

Commissioned by Massdrop, Alex Cavalli revisited his original CTH design and made numerous improvements. This is a capacitor-coupled hybrid design running a single 6922 tube and a discrete output stage. The original design allowed for swapping a wider variety of tubes, but this iteration is specifically built around the 6922 and its immediate variants. Tube swapping is easy thanks to the automatic biasing circuit. I'm told the production version will have a slightly larger cutout around the tube compared to this prototype unit, in order to facilitate tube removal.

Power output was beefed up to a full 1W into 50 ohm loads—significantly more than the original design. Output impedance is well under 1 ohm, and gain is set at 8x which is another improvement. Gain in the original model varied based on tube choice but was significantly higher no matter the tube...not generally a good thing in my book. The power supply is an external 28V power brick said to be quieter than the 24V PSU used in the old model.


The CTH chassis is well built and rather handsome in an understated way. It's very simplistic—just a single RCA input around back, and a pair of headphone outs on front in 1/4" and 4-pin XLR formats. To be clear, this is a single-ended design, with the XLR output being added as a convenience. I appreciate this because most of my headphones are balanced, and it's much easier to have a native jack than to use an adapter. I don't notice any sonic change whatsoever between the two outputs.

A quick word about volume control. I'm told Massdrop will be sorting volume pots for production units in order to ensure best quality. This process will involve a torture test using an extremely sensitive IEM (the Campfire Andromeda was floated as a possible option), to ensure channel matching stays tight enough at low volumes. The review prototype I have did not undergo this process and I do get just the slightest imbalance when playing at unrealistically low levels. More importantly, I also get a noticeable bit of noise which I'd describe as a sort of hiss, at very low or very high settings. It's more obvious with sensitive IEMs or headphones, and practically inaudible with a high impedance can like the HD650. While not terribly bothersome overall (I rarely listen that quiet, and never that loud) I'm still pleased to hear about Massdrop's quality assurance program, so every customer gets an ideal experience.

Massdrop is selling this device for $250. Let that sink in a little. That's not all that much more than the predicted cost for a DIY builder to throw together an original CTH back in the day. Keep in mind this updated model features significant improvements across the board, and that it has a much nicer chassis than the Hammond enclosure specified by the original. Also don't forget that DIY projects have the benefit of "free" labor. I honestly don't know how Massdrop manages to turn a profit on this thing. Obviously their business model revolves around spreading small margins across a large number of units, but still...the value on display here is remarkably high.

Lastly, I have to say a brief word about how this device came into existence. Veteran HeadFier (and all around good guy) CEE TEE, became Product Manager at Massdrop not too long ago. His beat is "Audiophile Custom Products" and we have him to thank for spearheading these projects—yes, I said projects in the plural, as CEE TEE has some big plans in the works. He's been engaging trusted community members for product testing/feedback; interacting with industry folks for potential new collaborations; and just generally handling this stuff like a boss. I'm not at liberty to say a whole lot more right now but I can promise some exciting new stuff in the very near future. I'm thrilled to have such an excellent member of our little community turn his passion into something large, something that will most definitely impact the hobby in a positive way. Massdrop is lucky to have him.


ab_ba's picture

Wow, thanks John! I'm glad I surfed over to InnerFidelity tonight. I've been curious about Cavalli for a while. What a great way to get an introduction to their sound.

geniekid's picture

Thanks for the info about the quality of the stock tubes, although I am a little curious what other tubes you tried.

Impulse's picture

As of this morning (day after the review went up) Massdrop still had like 200 of 1,000 max units/spots available. Guess it didn't generate quite as much buzz as an HD6XX or whatnot, tho it looks like just as much of a solid value.

AllanMarcus's picture

More of a solid hybrid value


Impulse's picture

From the vacuum of space.

Caligulove's picture

Note to UK people the Arcam rHead mentioned is £200 in most places now.

John Grandberg's picture

That's a steal of a deal, thanks for posting. I don't think Arcam promotes the rHead enough in the USA... it is hard to find online. Perhaps it can easily be found in brick 'n mortar stores.

buckchester's picture

I'm curious, are you able to reliably tell a difference between this amp and another in a blind test? Better yet, if using fairly efficient headphones that can be adequately powered by, say, an iphone or a macbook pro, e.g. Hifiman HE-400i, in a level-matched blind test, could you pick out this amp from the iphone or macbook pro? This should be the minimum standard required.

John Grandberg's picture

I've done my fair share of blind testing in the past. It sucks the life right out of you, makes you question your own sanity, and generally makes this "hobby" a lot less enjoyable (at least for that moment). It's also something I think everyone should try if at all possible.

I recommend reading Tyll's Big Sound 2015 series to get a bunch of good examples of folks doing blind testing, and how stressful/difficult it is. Ultimately, it CAN be done (see Roy's results). But it's a humbling experience that, for me anyway, reminds me to take great care in describing "night and day differences" or anything of the sort.

As for the CTH amplifier. Yes, I'm confident I could pick it out from an iPhone, just as I can pick it out from the solid state Arcam I compared it to. As the other fellow replied in another post, the HE400i benefits greatly from the extra juice provided by a dedicated amp, and that comparison in particular isn't really fair.

I wouldn't disparage anyone who couldn't tell the difference though - and I do think it's an acquired skill. Just like the Philips Golden Ear Challenge (sadly, now defunct) which at first seemed absolutely impossible. Eventually, I learned what to listen for, and success was attainable after much difficult (and not really very pleasant) work. I certainly wan't the only person to pull that off either.

pete111's picture

The HE-400i is not a "Fairly efficient" headphone. At 93 dB sensitivity, It's only efficient when compared to other planars. In fact I don't have experience with this articular amp (I do own the 400is), but the benefit of pretty much any dedicated amp compare to an apple device will be quite obvious, blindfolded or not.... We are talking about 50 time the power that the 3.5 mm output an apple device can provide. Personally I have a more portable solution than this but my he-400is certainly sounds dull and lifeless in my Iphone. In fact it can't drive them, no need for a blindfold to hear that. No bass, hearable distortion, sounds like 50$ headphones and need to be at max volume to get a decent level. If you where talking about IEM's your comment would have been relevent because it's not that obvious but really if you are talking planar headphones 100% of people will hear a major difference, no need to have trained ears, it will be obvious, and yes, I'm talking at matched levels.

buckchester's picture

The Hifiman HE-400i is an efficient headphone. Every review I've ever read agrees. I can play them quite loud with my iphone 6S. Likewise with my Macobook Pro. I also have a Schiit Asgard 2 and a Schiit Modi.

The reason why I purchased the Schiit products was because of reviews that said things like you are saying. But try as I may, I cannot notice any sound difference with them whatsoever. I would consider myself to be quite a keen listener and I would say that I really wanted to hear a difference.

My experience makes me believe that people who make comments like yours might think they hear a difference, but if they didn’t know which product they were listening to, they would have a much more difficult time telling them apart.

Science has proven how much our biases can influence our judgment. Blind testing is how all these reviews should be done. I’m disappointed that the author hasn’t answered my question on this.

pete111's picture

OK, well your 6s must be miles better than my Iphone 6 cause mine don't have enough power to drive my 400i. We will have to agree to disagree. With all respect "people that make comments like yours" is quite a generalization. I don't buy on snake oil statement myself, i, like you, believe than in a lot of cases our brain can trick ourself, and yes, I agree, this has been proven. Now where our expectations can cause a bias, which is absolutely correct, blind testing is not "The only" way to evaluate audio product. As an engineer myself, designing audio products, I rely on measurments more than anything. The distortion figure when you ask the tiny chip of an Iphone to supply current to drive the 400i is real whether you hear it or not. I can't speak of the the macbook pro, it's probably better. No offence right?

buckchester's picture

Thanks, Innerfidelity for deleting some of my comments. I see certain topics are taboo around here. That's unfortunate for everyone. Well, maybe not your advertisers.

John Grandberg's picture

I thought our exchange was perfectly civil, and certainly didn't delete anything. Tyll very rarely has anything to do with moderating unless things get way out of hand. And I don't see any deleted posts as I normally would for "unpublished" comments.... it's as if they were just never there in the first place.

Maybe a technical glitch? I don't know, but all comments after a certain date seem to have been erased. See the early comment from "scientist1" which is obviously negative but was not deleted - we don't usually moderate that way.

Junki's picture

Maybe I'm too new to know what's going on, but the trend I've seen on Innerfidelity is the reviewer mentioning something going on the Wall of Fame doesn't necessarily mean it goes onto the Wall of Fame. The CTH and the HIFIMAN Sundara are old and new examples of this.

John Grandberg's picture

...Tyll made the call that only regular-production models can make it to the WoF. Which makes sense considering we don't know when Massdrop will have the CTH in stock, or for how long. It might end up being a fairly limited run, or you might only be able to order it during small window. Not fair if people see it on the Wall and want to buy it, but can't actually do so.

I haven't checked on the Sundara situation though. Might just be that Tyll needs to find time to update the Wall.

flummox's picture

I realize this is an older review but I am trying to make the exact same comparison made in the review with one added wrinkle. I don't have access to both units and my current integrated amp is an Arcam A39. I'm wondering if the rHead will give me much more than the built in headphone circuit for the A39. Arcam UK's response: "The headphone stage in the A39 is very good but the rHead is better. I can't tell you if you will hear a difference because peoples hearing and ability to discern sounds varies but the rHead is a dedicated class A amplifier so on paper at least it is another sizable step up." Hmmm... on paper. Does the reviewer or anyone else have any thoughts about this? From the InnerFidelity review it seems possible that the CTR will give me a slightly different audio flavor (staging, bass) than either the A39 or the rHead. If soothes would give me an Arcam option and a CTR option. Would be interested in the reviewer's or anyone else's opinion.