Sources / Amplification
For this section I have used the standard, normal lamb pads as these are the preferred pads for my listening/tuning preference. Except for with the Mojo 2, the Caldera was always connected to the balanced output. With the Caldera’s 60Ω impedance and 95dB sensitivity it on paper isn’t the hardest to drive headphone though ZMF usually recommends using a dedicated headphone amplifier. They actually sell multiple headphone amplifiers brands in their shop and they work with brands to build the best amplifiers for their headphones. The Caldera is a transparent headphone and as such you will hear the impact of the amplification.
DAP
The Astell&Kern SP3000 without amplification usually isn’t a setup I usually recommend for full-sized headphones but the synergy with the Caldera is rather good. You lose a bit of the weight and body in bass and mids, but you in return get excellent PRaT, precision, clarity and extension. Because of the lighter weight, the focus is more on the upper mids and vocals so it might not be for everyone. If you like a more neutral tuning and excellent technical level, you have this right here.
Switching to the more powerful Cayin N8ii, with tube mode, solid state mode , Class A/AB and P+ power mode, we get a different story. In normal power mode you get a more relaxed sounding Caldera, if you switch to the P+ mode you immediately get more energy and a lively tuning. You here have more weight than with the SP3000, but the neutrality here is not as spot on. The N8ii is more musical and has the better mid timbre with the Caldera. I prefer the tube mode here most as you get that typical lovely emotional Caldera sound. The difference between Class A and AB is very small here. This combo is very different from the previous combo, and it will please a different type of listener. The N8ii does a perfect job however, no extra amp is needed.
Portable
To be honest, I did not expect the Chord Electronics Mojo 2 to have such a nice synergy with the Caldera. Of course you get the more digital, fast, precise and clean presentation from the Mojo 2, but there’s also good energy and musicality. Admittedly this combo is lighter in bass and mid-weight but it’s speedy and energetic. It’s more like the SP3000 with an excellent technical level, though I find the synergy and musicality of the Mojo 2 better in this case. A more neutral tuning with a lovely tight bass, energetic treble and lively vocals. Neutral, perfectly controlled and musical.
I have really been enjoying Woo Audio’s tube Tube-Mini with the Diana MR when I was traveling in the US the past few weeks. With the ZMF Caldera and Tube-Mini combo you get a slower, fuller sound with clearly some tube warmth. IT’s not the faster or most tight, concentrated presentation, but it’s soft and easy to listen to. Weight-wise it is fuller then the Mojo 2, but it isn’t as controlled. IF you prefer musicality and smoothness over peed and the ultimate detail, the Tube-Mini could be the portable amp for your Caldera, I certainly like it though I would still use a full sized desktop amplifier if I had the choice or option.
Desktop
The amplifier I have been using most lately is the SAEQ PDA-1b and lucky for me the synergy with the Caldera is excellent. Both units have a more neutral tuning and a very musical delivery. You get the tightness, precision and control from the SAEQ, mixed with the musicality and smooth delivery of the Caldera. You get a good amount of bass weight with a nice kick and the mid presence is neutrally pleasant. I really like this combo as both units complement each other. Note that I use the -10dB attenuation setting on the front.
The best amplifier discovery at the latest CanJam SoCal show for me was the Austrian Audio Full Score One, especially with the TTT engaged. With the Caldera you without the TTT function get the typical headphone sound while the TTT tech immerses you more into the music. You get a more airy presentation where timbre and decay improves. It is a nice combo but I liked the Empyrean 2 more with the Full Score One. I find the precision and control less present here, resulting in a more messy presentation. This combo isn’t for me personally.
Switching to tube amps, the first one we’re looking at is the Feliks Audio Envy. At shows it’s one of the amplifiers you often see to demo ZMF headphones with, so it couldn’t be missing in this overview. The Envy with its heavier presentation makes the Caldera a full sounding and musical headphone with a softer presentation, but for me the magic is lacking a little here. I am thinking about energy, sparkle and engagement. Usually I like most headphones with the Envy, but in this case I think there is better. It’s not a bad setup at all, but the Caldera to me simply sounds better with other sources. The Auris Audio Headonia with the 2A3 tube set is not available at this point as Auris is working on a new version of it but it is my favorite tube amp for many high end headphones.
The Headonia shows less body and weight as the Envy, but it makes up for that with extension, decay and overall precision. The Caldera here sounds more than full enough, but you get great energy, musicality and a very high technical level. This combo is fully recommended if you want some of the tube flavour added to the Caldera.
If you have seen ZMF at shows you might have noticed that Zach has a rather weird looking homemade tube amplifier to audition his headphones with. This actually is a Glenn2359 amplifier, that was custom built for him and I just happen to have one as well. My Glenn2359 uses 300b power tubes, C3G input tubes and a RK60 rectifier, there is no balanced output. I know these amplifiers have become hard to get so I am sorry to say that the Caldera sounds at its absolute best with this amplifier. And no, mine isn’t for sale. You get a nicely bodies presentation, excellent dynamics, great PRaT, perfect control, a tube flavour and a high technical level with a musical delivery. It’s awesome, so if you do get a chance to try this amplifier with your ZMF headphone, definitely do that.
If you are looking for a full sounding solid state amplifier, you absolutely need to look at Violectric and Niimbus. With the Niimbus US4+, the Caldera sounds good and full as you’d expect but like with the Full Score one I find it to sound messy during complex passages. If you like weight, bass presence and a warmer delivery, this do is a nice combo but for me it’s missing some energy, sparkle and liveliness.
I am sure there are dozens of amplifiers the ZMF Caldera sounds great on, so do make sure to demo first. As the Caldera is nicely transparent, your amplifier’s tuning will reflect in the Caldera.
On the last page of the article you will find the comparisons, the conclusion and the summary. Click here.
Page 1: ZMF, Caldera, Box & Accessories & Price
Page 2: Design & Build quality & Comfort, Specifications, Sound Pt. 1
Page 3: Sound Pt. 2
Page 4: Sound Pt. 4, Conclusion, Summary
