I guess I'm one of those who prefer harmonic distortion and euphonic presentation to help me feel the music and not just hear it. In the end, it's about enjoyment. No apologies.
Feel free to listen to music the way you like best. I'm just explaining what's happening if you add an amp to the Mojo – which is a capable amp itself. You use it as a (highly unflexible) effect device, which it isn't designed for. There are better, more powerful methods for tayloring the sound to your own preferences, without the loss of transparency and purity, if you just dare to take notice of them.
I don't know that this is correct. Wouldn't that be equivalent to saying you won't get better sound using an amp (any amp) after your preamp? However, if your preamp is not capable of driving your speakers, then fine, but most are probably not. That means you will always be better served by getting enough power to drive your speakers by using an amplifier if your preamp cannot do it (and for which it was not intended).
Preamps can't drive speakers. That's the point. So you can't renounce a power amp – sad, but true. That means you add distortion and signal rounding. After all you could renounce the preamp – an artifact from the vinyl aera – and reduce distortion that way. There are many people who swear that preamps improve the sound compared to the direct connection or the use of a (resistor- or transformer-based) passive attenuator. That shows how harmonic distortion works: it often sounds pleasing to the ears.
I understand that Rob and John feel the Mojo can drive virtually any headphone adequately, which would be great. In practice, it will be up to the listener to determine whether the Mojo sounds best with their setup on its own or with an amp.
I will say that I totally respect the design philosophy that says "we have taken this approach and believe this is the best way" and the passion and engineering behind it. I will always go for this over the "designed by committee to be unoffending and the 80% solution" because it will give you the single malt rather than the blend. Your job to determine if it's right for you and your system. From a product perspective, I want the ultimate expression of the designers' views. But, that doesn't mean my implementation will be the same as the designers' in all cases.
Not even the designer forbids the use of an additional amp – he just explains the consequences for the music signal and the sound in technical terms. It's up to you if you can or want to live with the reduced transparency and added coloration. Just don't pretend for driving Headphone XY to its full potential the Mojo needs an external amp as an absolute truth! From a technical point of view it's the opposite.
I appreciate the principle of keeping the signal path as simple and clean as possible,.. but you are wrong. Most headphone and virtually all speakers need amplification. The design and quality of components determine how an amplifier will affect the sound.
Of course all sound transducers need an amplifier. The Mojo comes with one – it's just not a dedicated headphone amplifier like you're used to. In fact it's even better than most of them – from the technical data.
People often select amplifiers for a particular coloration... but it's also possible to build amplifiers which are pretty close to wire with gain.
So show me some neutral amplifiers! This pretension is just hot air, absolutely unsubstantiated. I'm sure many Head-Fiers have experienced themselves how different the different amps sound (despite the fact that they all sound the same according to the Sound Science Forum). And a few of them are considered neutral? I would accept the characterization «passably neutral», but that still wouldn't exclude very noticeable signal degradation. Rob Watts' experiences have revealed to him how every single electronics component (resistors, capacitors, wires, solder joints, connections, transistors...) degrades or colors the signal, so extrapolate that to a box full of electronics components like a headphone amp!
Yes, it would depend on the load. My HE6 sound like hot trash from the Mojo. Granted that's an extreme example, but given that many here are being quite absolute in their dogma it's still relevant to say. Even leaving that point to one side, you can take all of your own personal ideals about signal path and approach to audio reproduction and throw them out the window if someone else's ears prefer a different sound (for clarity, when I say 'you' that isn't a reference to verber, but to those dealing in absolutes here). Not much place for absolutism and dogma anywhere as far as I'm concerned, but so much less so in a subjective hobby.
Indeed, the HE6 is definitely an extreme example, and I think it can be classified under the headphones possibly overstraining the Mojo, like e.g. also the AKG K 1000. I don't have experience with it, but from the specs and the reports I take it that no portable amp can drive it properly. Now what does that prove for the rest of the much less critical headphones and IEMs?
With respect to absolutism and dogmatism: I haven't read anything from anybody in this thread pretending that you can't get a pleasing sound by adding an amp to the Mojo (or the Hugo). Where do you get that from? Personally I just fight against the dogma that the Hugo or Mojo doesn't drive this and that headphone to its full potential by means of the technical background – with the help of the developer.
If source direct is always best, why was there a popularisation of headphone amplifiers in the first place (when you could just as easily use the jack in the CDP, speaker amplifier, or MP3 player)?
You can absolutely use those headphone jacks, some of them probably aren't even bad, but they are certainly not designed for audiophile demands (with exceptions). Therefore the use of dedicated headphone amps among demanding music lovers. If you attach them to those devices via line out, you bypass their own headphone amps.
Mojo and Hugo on the other hand use the amplification stage of the DAC to drive headphones, so there's no possibility to bypass it, hence you'd use the same signal for driving an external amp that you'd use for driving headphones. So there's nothing to gain in terms of signal accuracy. Fortunately this built-in amplification stage is of very high quality, has extremely low distortion (much lower than typical headphone amps) and an exemplarily low output impedance.
Is anyone naysaying this absolutely sure that the load characteristics for any amplifier are the same as any other? Multi crossover IEMs handle substantially differently to a single dynamic driver, and I can say as an EASY to observe fact that the Pure II+ can drive the Layla's more cleanly (treble opens up, always an easy tell)...
It's in the nature of audio electronics that the pure, unaltered signal is more critical for system synergy than a degraded signal warmed up with euphonic harmonic distortion. With the «right» distortion spectrum you get a wonderful smoothness to the sound, easily mixed up with cleanness.
That is the key here, what the load does to the amplification, and we know that is not perfect on the Hugo (hiss on IEMs and reported inability to drive harder cans like the HD800 to their upmost ability), so why can the same not be true here?
That the HD 800 be hard to drive is an urban legend just like the topic at hand. From my long-term experience with it I can tell that I haven't heard it better than driven by the Hugo directly. The myth has its origin in the fact that the HD 800 benefits a lot from smooth and dark sounding amps (to most people's ears), at least when unmodded, whereas its high efficiency in fact makes it a very easy load for every desktop amp. Its 450 ohms are a harder task for some portable devices, though.
Indeed Mojo and Hugo are not perfect, no electronics component is. Other people may prefer other gear or feel the need to alter the sound by adding external amps. I absolutely understand that. I for one am never satisfied with the factory sound from buyable Hi-fi components. It's just that amplifying a signal that's already strong (and stable!) enough for the intended purpose just for the sound effect that comes with it is an absurd strategy – if you look at it this way.
Just a short abstract of my own audio history. I was a fanatic (hobbyist) speaker builder until a tinnitus hit me. During this time I also experimented a lot with different electronics. One day I replaced my Conrad Johnson PV-6 preamp with a stepped attenuator made of hand-selected resistors. Shock! The carefully tuned speaker sound was out of balance, there was a roughness and unorganicalness that wasn't there before. It took me several days of work on my crossover network (with 4th-order slopes!) to find a satisfying balance and much more for the optimal sound. Which finally was a revelation in terms of purity and transparency. This was my first conscious encounter with the world of forgiving euphonic distortion.
Since I'm into headphones (which are much more tinnitus-compatible in my case) I have experimented with the direct connection of headphones to DACs – the Theta Pro basic II with 5 ohms and the Bel Canto DAC2 with 15 ohms output impedance were suitable candidates. The latter was my standard DAC before the Hugo. And against my audio philosophy I decided to use a Meier Corda amp to drive my pair of HD 650 at that time instead of the passive attenuator built for that purpose. Because I liked the sound better with the headphone amp – and I'm no masochist!
This changed with the arrival of the Hugo and the use of a FiiO DAP as digital drive. The Hugo itself provided such an organic and rich sound the Bel Canto wasn't capable of. And most importantly: I had an octave equalizer at my disposal which made me more or less independent of component synergy.
Well, that's my message for the amp defenders: It's true that amplifiers can make the sound more forgiving and pleasing, but it comes at a price: they put you further away from the original sound waves captured by the recording microphones by stamping their own characteristic on the signal. Don't trust amps! They are highly overrated. None of them is as neutral as a piece of wire. But sometimes you can't avoid them. If you can, however... don't miss the opportunity! But yes, this path requires a bit of work (let's say instead of financial means!) from the user. Because for maximizing the sound equalizing is mandatory. To fix the notorious nonlinearities of headphones which require the notorious synergetic effects in the first place. The more so as the omnipresent forgiving smoothness and warmth (added by most amps) serving for masking those deficits isn't there anymore. So you may encounter hard edges instead. But once you have found the right configuration and settings, you will be all the more rewarded with a sound closer to reality. – Your mileage or sonic ideals may vary.
