Review - Drop Cavalli Tube Hybrid (CTH)

(si prefieres ver esta review en español, haz click aqui)

The (Mass)Drop Cavalli Tube Hybrid is an amplifier that was launched as a joint venture between Alex Cavalli and the company (Mass)Drop. For those of you who are not familiar with (Mass)Drop, I included a basic background of the company in my review of the Sennheiser HD6XX which you can find here: Review - Sennheiser HD6XX.

This amplifier is supposedly based on the original Compact Tube Hybrid, an amplifier that was introduced many years ago by Alex Cavalli as a DIY project. I have never had the possibility of trying out the original DIY version but my understanding is that the current Drop Cavalli Tube Hybrid (which I will now refer to as CTH) is very different.

I have owned the CTH now for about a year and it has become a stable part of my listening set up. Although I have tried a couple of other hybrid tube amplifiers, the only two that I have kept in my possession are the CTH and the Loxjie P20. While there are differences between these two amplifiers, I will make a few comparisons between the two. If you would like to see my full review of the Loxjie P20, you can find it here: Review - Loxjie P20.


As the CTH (and the P20) can be considered an entry level hybrid amplifier, therefore it does appeal to many starting out in the headphone world, I will give a brief explanation of what a hybrid tube amplifier is. If you are someone who is already involved in the headphone world, you should probably just skip this part and move on to the real part of the review.

A hybrid amplifier, or rather a hybrid tube amplifier, is an amplifier that uses both tubes and solid state circuits in order to create the final output. While it is not always the case, the majority of hybrid tube amplifiers use tubes in the preamplification stage and then use solid state amplification for the actual power.

The idea behind this is to have the benefits of solid state amplification while still being able to include a little of the “tube flavour” that is so famous in the HiFi world. This is not something that is limited to just the HiFi or headphone world however, it is also very common in guitar and bass amplifiers, attempting to recreate the same sound as a tube amplifier but without the issues that come with tubes (such as output load matching etc.). In the case of guitar and bass amplifiers, the “tube effect” is usually much more pronounced and is very noticeable (for better or for worse) whereas the HiFi world is much more subtle and will probably even go unnoticed by many people who aren’t aware of what to look for.

There are many reasons why someone would want to opt for a hybrid option rather than just a full blown tube amp, one of the most mentioned is due to the output impedance which can interact in undesired ways with low impedance headphones and especially planars. However, some people do actually like the results of that interaction.

But I digress, so let’s just get on with the review!


I’m afraid that the box that the CTH arrived in is in storage somewhere, behind far too many other boxes, but it was pretty simple anyway.

A plain cardboard box with the Drop logo inside which we find the amplifier, the tube and the power supply, which is a wall wart.

Build an aesthetics…

The amplifier case is similar to so many other Drop offerings, a plain black box with a small tube protruding from the top of the amplifier.

On the front there is a nice large volume knob, a power switch (push button), a power LED, a 6.35mm TRS output and a 4 pin XLR output. Note that this is not a balanced amplifier and the 4 pin XLR is solely for commodity when using headphones with a balanced wire ending in an XLR4, the output is still unbalanced and there is absolutely no difference between using the XLR or the TRS.

On the back of the unit we find the RCA input connectors and the power input, nothing more.

All in all the aesthetics are simple and functional. It is not going to become a piece that is the center of attention but at the same time it will blend in pretty well in any set up.

The build quality is decent, with no obvious issues, and the volume wheel is very smooth and responsive. There is a bit of channel imbalance at very low levels but way below the level I would ever listen at. The P20 uses a digital potentiometer for volume, with a display, which avoids channel imbalance and gives a better visual reference, however, I personally prefer the volume control on the CTH.


With one input, one output (ok 2, but they are the same) and a volume wheel, there really isn’t much to explain as far as functionality.

When you turn on the amplifier, you do have to wait for the unit to “warm up”, during which time the power LED stays red, switching to white once the unit is ready for operation. In reality, it is not actually warming up, it is just in a protection mode to prevent pops and other unwanted issues like rushes of current etc. Even if the amplifier is warm (i.e: in use), if you turn it off and back on again, you will need to wait for it to go through the same procedure.

There is a protection circuit in the amplifier to protect against shorts when connecting and disconnecting the TRS connector. If you plug in or remove the TRS while the amplifier is on and volume is turned up, it will go into protection mode (the LED goes red) and you will need to wait for it to go back to the “ready” status before getting any sound. To avoid this, make sure to turn the volume down before inserting/removing a TRS. You can also power off the amplifier to insert/remove but when you turn it back on, you will need to wait for the amplifier to go back to “ready” status again.

Other than that, just adjust volume level to taste.

Main differences between CTH and P20 (on paper)...

Before continuing, I want to point out that I am using the CTH in it’s stock form, with the original Electro-Harmonix 6922 tube and the included power supply. I do have a couple of tubes I want to try out with this amplifier and I have also heard that a linear power supply does improve the CTH but I have not yet tried either. The P20, currently has triple mica Reflector OTK 6N3P-E tubes, which are ones that I am currently liking after trying a few others. 

Another thing to factor in is that the Loxjie P20 retails for around 100€ and the current tubes cost around 30€. The Drop CTH is currently out of stock but cost me (including shipping) around $190 plus import fees, so probably around 200€, meaning that the Loxjie (with the tube swap) is at least 70€ cheaper. We also need to consider that the P20 is a fully balanced amplifier that has both balanced and unbalanced inputs and outputs, however, the unbalanced outputs leave a lot to be desired, so I only really use the amplifier in balanced mode.

The CTH is quite a powerful amplifier, with 1 watt per channel (actually measured to have more), which is more than sufficient for most headphones owned by people considering this amplifier. In comparison, the P20 specs 665mW at maximum output but that is still sufficient for the majority of headphones.

I think that covers most of the differences in specs.


Now comes the part that I hate about reviewing amplifiers, trying to explain the sound. I end up using a bunch of words that aren’t even relative to sound but that is the nature of these reviews.

First let me say that if you are expecting the warm, gooey, smooth sound signature that you read about in tube amp reviews, neither of these amps is going to give you that. The sound is different to a strictly solid state amplifier, or at least a clean solid state amplifier, but the differences are marginal.

In comparison to say my JDS Labs Atom, which I use as a reference point for most of my reviews, the CTH smooths out the edges slightly, making things a little less direct, not quite as sharp. 

The bass of the CTH is smooth but well defined, giving the bass slightly more presence but without it seeming boosted or bloated, it remains tight. The P20 does put a little more emphasis on the bass but that is also related to the much higher output impedance of the P20 (47 Ohms against 0.5 Ohms of the CTH). 

When using the Sennheiser HD6XX with both amplifiers, the P20 seems to put the focus more on the low end, with more warmth in the higher bass and lower mid regions, whereas the CTH makes the focus shift more towards the upper mids, giving them a slightly more euphonic touch.

The treble is decent on both amplifiers, both present it in a way that doesn’t seem to be lacking and is clean, although I would probably give the edge to the P20 for cleanliness in the treble.

The two main differences between these amplifiers are that the P20 is a much cleaner amplifier, whereas the CTH has a much better output impedance. The P20 has zero background noise no matter what headphones are used, even sensitive IEMs have no background noise, whereas the CTH does make audible noise on some IEMs. On the other hand, due to the high impedance output of the P20, this affects the lower end of many IEMs and low impedance headphones, resulting in a bass that is not always preferable.

One other negative issue is that the unbalanced output of the P20 is much inferior to the balanced output, meaning that balanced cabling is needed for headphones and IEMs. 


The CTH is a decent low cost hybrid tube amp that delivers plenty of power and gives things a slight hint of tubes. I enjoy having the CTH available for when I want to sit back and relax but it is not an amplifier that I would really miss if I didn’t have it. 

The bass response is probably one of the parts that I most enjoy about the CTH and it also works well with the Ananda, smoothing things a little, but to be honest, the cleanliness and detail of the Ananda is what I love about it, so if I feel like a smoother sound, I would just opt to use a different headphone.

The P20 is a different beast and while the “tubeyness” is still only slight, I think that the high impedance adds to the flavour, making me feel like it does more than it actually does. I enjoy using the HD6XX on both amplifiers and I also modified the DT1990 to balance to use with the P20.

I currently keep both as one lives on my desk at work while the other stays at home. If I had to choose one of the 2, I would probably opt for the CTH and then replace the P20 with a full blown tube amp, because if I need to deal with output impedance issues, then I might as well go OTL.

My next step is to try a few new tubes in the CTH and also a linear power supply, I am interested in what the results might be.

So, at the end of the day, if you are looking for a first hybrid amp, then I would say go with the CTH unless you are sure that you will be using high impedance headphones and that you can run them balanced.