[Mrniceguy633]

Hey guys. I'm new to this world of headphone amps. Appreciate these kind of posts, so thank you for that and job well done. Noob question: under the O2s speed, transparency, and sound stage you said "reference". What does that mean as far as speed, transparency, and soundstage goes?

 

[ClieOS]

It means O2 is the reference for other to compare to. In simpler terms, O2 is the best in the categories.

 

[Mrniceguy633]

So for speed, the E17 is "tiny bit softer in kick but really good overall" in comparison to the O2. Ok, that makes sense. Thanks for taking the time to answer

 

[AstralStorm]

Another fun observation of yours truly:
 
FiiO  E17 is borderline unstable with harder loads like certain BA IEMs including Brainwavz B2 and SE-5, producing some distortion that's audible. (-60 dB?) We're talking sines > 16kHz at -6 dB, so it's definitely not clipping.
 
Funny thing, E7 doesn't have this issue and I haven't spotted it before connecting SE-5 and B2 to the E17 (after fixing the jack - same result also via L7 connector, so I didn't mess up). I wasn't sure what I was hearing, so I connected a spectrum analyzer. It's clearly subharmonic distortion suggesting instability.
 
Sorry I didn't catch it earlier - I didn't have headphones that are sensitive enough at the highest end. Seems DT1350 and GR07 just don't expose this flaw.

 

[Evshrug]

What is a "BA" IEM?
Drat all the tube-amp reviews, they almost unanimously are preferred in comparison to SS amps by those that own them, but I haven't seen any measurements or point-by-point ratings as ClieOS has done here. An O2 or the top amps from the sub-$100 amp thread seem to make the most sense to me, but I mainly (really only) need an amp for my AKG Q701, and most people seem to suggest exotic tube amps for it.
Which direction is earth?

 

[sygyzy]

BA stands for Balance Armature. This is in contrast to the other IEM design which uses dynamic drivers.

 

[AstralStorm]

It might be that balanced armatures present more inductive load which destabilizes E17. Anyway, that is a pretty bad mark against this amp. Pity.
GND is available as the "ring" in the minijack.

 

[Slickman]

 I'm getting the C421 because it has bass boost, if the O2 had bass boost I would get that but it doesn't,

 

[ClieOS]

What is a "BA" IEM?
Drat all the tube-amp reviews, they almost unanimously are preferred in comparison to SS amps by those that own them, but I haven't seen any measurements or point-by-point ratings as ClieOS has done here. An O2 or the top amps from the sub-$100 amp thread seem to make the most sense to me, but I mainly (really only) need an amp for my AKG Q701, and most people seem to suggest exotic tube amps for it.
Which direction is earth?

Tube amp just generally measure badly when compared to solid state stuff, so most just doesn't care to do it. Of course that is in the nature of tube amp as they are much more noisy due to how they operate, but that doesn't mean they'll sound bad. I actually have a portable tube amp (from a Chinese company) with me right now and will write a review on it, probably next week. I can imagine a warmish tube amp can go really well with Q701 myself.

It might be that balanced armatures present more inductive load which destabilizes E17. Anyway, that is a pretty bad mark against this amp. Pity.
GND is available as the "ring" in the minijack.

I measured my E17 and noticed some odd harmonic distortion with B2 as well (much less with CX300). But they are well under -70dB (most are under -80dB) and still presents less than 0.1% of total distortion. I don't see a big problem there myself.

 

[Evshrug]

ClieOS,
Yes, it is this nature of a tube amp that makes it unpredictable for someone with zero experience listening to tubes [sic]. Since the Q701 isn't a very sensitive headphone, the hiss is far less of a problem than with sensitive IEMs, but... I don't have a clue what the positive side is of that trade off.

I realize that an amp ill-suited for sensitive IEMs may be beyond the scope of your reviews, but if you have one (they make portable tube amps?!?), a review of the characteristics listed here in comparison to your reference O2 amp would clear so much mystery for me! Who makes your tube amp, Bravo?

Astral,
Thank you for clearing that up for me. I was only aware of dynamic, electrostatic, and orthodontic type drivers.

 

[ClieOS]

The portable tube amp I have with me now is made by a Chinese company called, well, 'Tube Amp'. BL-2 to be the exact model name.

There is always something magical about a growing vacuum tube.

 

[Evshrug]

Oooooh...

The tube amps I was looking at were the little dot I+:
http://www.flickr.com/photos/barbutti/3233988718/
And this one:
http://www.amazon.com/Bravo-12AU7-Tube-Headphone-Amplifier/dp/B007VF69GQ

If your tube amp sounds pleasant and is available for purchase in the USA, I might have to put it on my shortlist as well.

 

[putente]

Quote:

The portable tube amp I have with me now is made by a Chinese company called, well, 'Tube Amp'. BL-2 to be the exact model name.

There is always something magical about a growing vacuum tube.

 
 
That's true! And that amp looks good! How's the sound and price? I can't seem to find it on eBay, though...

 

[alphaphoenix]

Don't know the specs, but sure looks like an ALO Continental clone.

 

[ClieOS]

That's true! And that amp looks good! How's the sound and price? I can't seem to find it on eBay, though...

Surprisingly analytical and clean for tube amp, though more suitable for high impedance headphone rather than low impedance IEM.

Don't know the specs, but sure looks like an ALO Continental clone.

The company has been making portable tube amp years ahead of ALO, so this isn't a clone at all. The guy behind the company began to develop portable tube amp since 2005, and the first commercial model (BL-1) was released back in 2007.