[Degenerator9000]

The reason why you rarely see very powerful class a amps that are portable isn't that they require too much power, it's that they would run too hot at low volumes. How hot they run is inversely proportional to to the volume level on class A. They don't actually require much more power than A/B. Just that A/B doesn't run as hot at low and medium volumes.

Yehh that's why I said
"The tradeoff is that you're never going to find a portable class A amp with the overall power of the O2, as they're incredibly inefficient."

I guess I should have specified what I meant, but the inefficiency I'm referring to there is the heat dissipation for high power class A systems necessitating (at worst case usage scenarios) a heat sink that isn't exactly portable @ this point in time afaik.

Although I'd argue that the ~20+ percent more efficiency you can squeeze out of an A/B design would be a significant factor too re: battery size/life, as you're gonna need an even bigger heat sink for a compact high power class A battery powered amp than a large desktop one of the same output powered by AC assuming you want to keep both the same temp.

 

[Audman71]

ProtegeManiac,



 

What headphones did you take with you?

 
I took my Koss Pro (either DJ100 or DJ200) with me.
 

 

It's easier to hear differences in the bass and treble than the midrange, unless of course one amp is deliberately colored as in some tube implementations. One of my solid state amps has a nasty cymbals splash, while my other SS amp was smooth yet detailed on any headphone, and then I have a hybrid now that sounds closer to my reference SS amp (save for noise from the tube coming up at around 2:00 on the dial, which is too loud anyway). The reference SS amp leads in rendering solid bass thuds, followed closely by the hybrid, and then the other SS. If you're choosing between amplifiers, focus on the treble and bass to hear any issues more easily.

Hearing the differences bewteen product noise and distortion levels is one thing, but my ears might not be so great that I could tell the difference between amps in terms of sound. You're talking to a guy who can't tell much difference, if any, between 44,100 khz and 96,000 khz sample rates, or 16 and 24 bit for that matter (I'd listen closely, and any differences I may have heard would be so insignificant I wouldn't be sure if they were made up in my head, despite the fact that I understand why they should theoretically sound better) 

.
 
Anyway, I'll have to test the amplifiers to properly judge whether or not the sound is all that different, but it does sound plausible that the sound would be altered by the amp.
 

  That can depend on the headphones you plan on using, and for what purpose. If you'll use the amp and headphones with the Presonus interface, then accuracy is key, get something like the O2 or the Meier Jazz. Barring very high impedance (or very low sensitivity) these will drive pretty much any dynamic headphone and some planars as well. If you have high impedance headphones, OTL tube amps like the Valhalla2 are also an option as they are best for such headphones (they don't do well at lower impedance, or at least not as well as most SS amps).
 
If you want a generally neutral tone but want to make sure you get no harshness even on some rough recordings, look into getting a hybrid or tube amp (as long as it won't have impedance issues or output level deficiencies for your headphones) that has for the most part a very low THD rating. That means it will generally be neutral throughout the range, but there's enough tube distortion to soften up the rough edges; or you can look at that another way, in that there is a tendency for some solid state designs to distort in a way that makes the treble sharper (ie if THD was comparable, the tube/hybrid and SS amp can have a tendency to sound different once you get to that level of distortion that it's audible on both). 

Thanks for the recommendations. Next time I have a chance I will try to give those a listen.

 

[Shetzu]

The reason why you rarely see very powerful class a amps that are portable isn't that they require too much power, it's that they would run too hot at low volumes. How hot they run is inversely proportional to to the volume level on class A. They don't actually require much more power than A/B. Just that A/B doesn't run as hot at low and medium volumes.

Hi. I could not set my eyes off your post. It was very informative. I have just ordered the iFi iCan Micro  Class A amp for my regular use. I want to know will it be able to drive the Shure 535 IEMS  too . Normally I would use the amp with my Fidelio X2 and my other gear.

 

[ProtegeManiac]

Quote:

Originally Posted by Audman71 /img/forum/go_quote.gif

 

I took my Koss Pro (either DJ100 or DJ200) with me.

 

I found a rating of 99dB for it - whether that's sensitivity (@1mV) or efficiency (@1mW), at 38 ohms that's very easy to power with decent amps and most mainstream devices. The nominal load isn't too high, and as such barring OTL tube amps and the like, that's where most devices and amps make the best power-to-distortion ratio output. Basically, even if you used it on an iPad, you're not near enough where distortion will be easily audible. Granted, at that price point you're probably trading smooth response with sensitivity/efficiency, but really at that price if it doesn't immediately sound very "wrong" and unnatural those are good enough.

 

What other headphones did you try, with and without an amplifier?

 

Quote:

Originally Posted by Audman71 /img/forum/go_quote.gif

 

Hearing the differences bewteen product noise and distortion levels is one thing, but my ears might not be so great that I could tell the difference between amps in terms of sound. You're talking to a guy who can't tell much difference, if any, between 44,100 khz and 96,000 khz sample rates, or 16 and 24 bit for that matter (I'd listen closely, and any differences I may have heard would be so insignificant I wouldn't be sure if they were made up in my head, despite the fact that I understand why they should theoretically sound better) 

.

 

You're not really supposed to, the bit depth and sample rates aren't as important as mastering quality. Sometimes, as was the case when upsampling was a huge fad, they eventually realized the real reason why people can hear differences - the process of upsampling a 16/44.1khz file distrorts the signal, but people were interpreting the high freq non-linearity as "wow more detail! whoo hoo!"

 

Quote:

Originally Posted by Audman71 /img/forum/go_quote.gif

 

Anyway, I'll have to test the amplifiers to properly judge whether or not the sound is all that different, but it does sound plausible that the sound would be altered by the amp.

 

You'r going to need headphones that have low sensitivity/efficiency or high impedance to get some differences between amplifiers, unless one amp will just totally suck with one of the headphones - like if one of them was an OTL amp and one headphone was a 32ohm Grado.