[NelsonVandal]

It seems that everybody's reading that thread. I think we all agree that portable amps sound worse than home amps, maybe that's why we like to talk about them - they're not good enough, and we tend to hope that every new amp that comes around will be the saviour, and all they really are is same-same-but-different. But... we want portables to go with our DAPs. It should be possible to build a really good sounding portable amp.

With the introduction of LiPo's and LiIon's, it's now possible to have an acceptable playing time even with a "massive" current draw. There are good DC-DC step up converters with very little current loss. There are mulitlayered PCB's and a world of SMD parts. Why isn't there an all discrete fully class A iPod sized headphone amp that saves us from the evil "hifi-sound" as opposed to a more musical sound.

We have the money, we should have the power to demand this kind of amp.

 

[omendelovitz]

Quote:

Originally Posted by NelsonVandal /img/forum/go_quote.gif It seems that everybody's reading that thread. I think we all agree that portable amps sound worse than home amps, maybe that's why we like to talk about them - they're not good enough, and we tend to hope that every new amp that comes around will be the saviour, and all they really are is same-same-but-different. But... we want portables to go with our DAPs. It should be possible to build a really good sounding portable amp. With the introduction of LiPo's and LiIon's, it's now possible to have an acceptable playing time even with a "massive" current draw. There are good DC-DC step up converters with very little current loss. There are mulitlayered PCB's and a world of SMD parts. Why isn't there an all discrete fully class A iPod sized headphone amp that saves us from the evil "hifi-sound" as opposed to a more musical sound. We have the money, we should have the power to demand this kind of amp.

Don't have much time right now, and read my title as a quid pro quo, but my partner & I in Purity Audio (see my sig for our debut HP amp, hopefully ready to roll within a month) have developed a "transportable" desktop amp that is 100% class A. One problem we've had in translating this amp into a fully discrete transportable is voltage - 6-7V is the best we can design as power into an amp (we're thinking of Li-ion et. al options) currently, but our main problem is size; it looks like the smallest portable we can fit all the parts into is a case that's about the size of a PINT case (~2x the length of the standard iPod length). When the KICAS takes off and we have some time/money to plow into this idea, we will try everything to bring this to market. For the time being, Xin and his mosfet chip amps still rule (you just have to wait indefinitely for them)...

 

[Roam]

Quote:

Originally Posted by NelsonVandal /img/forum/go_quote.gif With the introduction of LiPo's and LiIon's, it's now possible to have an acceptable playing time even with a "massive" current draw. There are good DC-DC step up converters with very little current loss. There are mulitlayered PCB's and a world of SMD parts. Why isn't there an all discrete fully class A iPod sized headphone amp that saves us from the evil "hifi-sound" as opposed to a more musical sound.

Let's pick a nice non-portable amp design, in this case Kevin Gilmore's KGCA. The amp will consume around 10W on +/-16V voltage rails, giving a current draw of roughly 1/3 of an amp. If you want 3-4 hours of runtime, the battery pack alone will be at least the size of an iPod Classic, and the amp will be around the same size as well. On top of that the amp will get quite toasty, compromising its long-term reliability and if you're not careful you will get burned. Not exactly the most practical nor safe device around.

Bottom line. Even with miracle battery technology or even a fuel cell power source, portable amps face design constraints which home amps do not. By nature of their small size, portable amps are limited in heat dissipation & power consumption, which in turn places limits on their power output, maximum voltage swing, peak current capability, and output impedance. You can't break the laws of physics; size and power really do matter.

 

[greggf]

Roam X2

 

[Edwood]

This thread is.....

 

[NelsonVandal]

I can't see why a single channel in a headphone amp must consume 3 W to sound good. The current draw using 300 Ohm phones at 2 V is no more than 6 mA = 13 mW. Is this extreme biasing really necessary? Is there a world of difference between high bias and extreme bias? Do we really need +/- 30 V rails? Do you need 1000 W of pure class A i a in a speaker amp when only using 20 W maximum?

I was just saying, it should be possible to build a class A biased all discrete amp for battery use with a current draw of about 50 - 100 mA/channel, and there would still be plenty of headroom using 300 Ohm phones. I'm not interested in feeding a 30 Ohm phone with 20 V. I'm neithter interested in driving speakers with a portable headphone amp.

Should we just resign and be happy with crappy low biased class B opamps in fancy boxes. There must be something in between 2 mA/ch and 500 mA/ch.

 

[NelsonVandal]

Quote:

Originally Posted by Edwood /img/forum/go_quote.gif This thread is.....

Yes I agree, it's like 50 channels of s**t on the TV to chose from...

 

[Bluetick]

Last weekend, the wife, kids, and I went up to the MD/PA border for a fall festival. There is little hope in me listening to something decent on the in-dash system, so I usually take my portable rig along...you know...to tune out the family noise.

Wifey drove.

It was a lovely Saturday, and the leaves had began to really show their beautiful fall colors. It was sunny, and so I slid open the sun roof, reclined in the passenger seat and listened to radiohead's videotape. It's already a nice song, but hearing it while watching the sun filter in-between the trees made the song all the more interesting. It is like watching a movie about the song. Everything you see becomes part of the music, and adds a special element that is continully changing as the landscape does.

The point of this is that, while I am out- I rarely consider the fidelity of my portable rig. Because it is portable, and that luxury can add special elements to the music I listen to, it's merits are based largely on that alone (for me). Yes, I'd love a higher quality portable, but I rarely complain. If my portable rig was also my main rig- then yeah, I'd complain.

 

[Roam]

Quote:

Originally Posted by NelsonVandal /img/forum/go_quote.gif I can't see why a single channel in a headphone amp must consume 3 W to sound good. The current draw using 300 Ohm phones at 2 V is no more than 6 mA = 13 mW. Is this extreme biasing really necessary? Is there a world of difference between high bias and extreme bias? Do we really need +/- 30 V rails? Do you need 1000 W of pure class A i a in a speaker amp when only using 20 W maximum?

First, we need to look at the requirements of a good amp. A good amp needs a reasonably high voltage swing, decent current delivery capabilities, a low output impedance, and low distortion. Since you're discussing high impedance headphones, let's move current delivery down the list for the purpose of this hypothetical.

Voltage swing is fairly easy to address as is low distortion, output impedance gets a little trickier. Broadly generalizing, there are two basic methods to achieve low output impedance, throw lots of power at the output stage or dial in a bunch of negative feedback. The former approach will drive power requirements through the roof while the latter will have all kinds of undesirable effects if not used judiciously; these can range from poor sound all the way to the amp self-destructing with certain headphones. Unlike resistors, headphones are a reactive load, in short, they can do all kinds of bad things to an amp's output stage if it's not up to the task.

Quote:

I was just saying, it should be possible to build a class A biased all discrete amp for battery use with a current draw of about 50 - 100 mA/channel, and there would still be plenty of headroom using 300 Ohm phones.

Sure, as long as you only use a 300 ohm headphone. Just don't expect miracles if you plug an inefficient 30 ohm headphone into it.

Quote:

Should we just resign and be happy with crappy low biased class B opamps in fancy boxes. There must be something in between 2 mA/ch and 500 mA/ch.

Of course there's something in between, it's going to be the size of an iPod Classic or larger and it's still not going to sound as good as a home amp which can afford to burn 20W per channel.

 

[Spareribs]

Quote:

Originally Posted by Bluetick /img/forum/go_quote.gif Last weekend, the wife, kids, and I went up to the MD/PA border for a fall festival. There is little hope in me listening to something decent on the in-dash system, so I usually take my portable rig along...you know...to tune out the family noise. Wifey drove. It was a lovely Saturday, and the leaves had began to really show their beautiful fall colors. It was sunny, and so I slid open the sun roof, reclined in the passenger seat and listened to radiohead's videotape. It's already a nice song, but hearing it while watching the sun filter in-between the trees made the song all the more interesting. It is like watching a movie about the song. Everything you see becomes part of the music, and adds a special element that is continully changing as the landscape does. The point of this is that, while I am out- I rarely consider the fidelity of my portable rig. Because it is portable, and that luxury can add special elements to the music I listen to, it's merits are based largely on that alone (for me). Yes, I'd love a higher quality portable, but I rarely complain. If my portable rig was also my main rig- then yeah, I'd complain.

I think that's an important point. Last year, someone posted a question why people use DAPs when there are more interesting gear out there like higher end tube amps and CD players. He couldn't fully understand why people use such portable devices and I thought it was somewhat sad that he couldn't fully understand.

Music is much more important than sound quality and it is so meaningful in life. As you have implied, music can have a different perspective when listening in unexpected enviroments. It becomes a sound track in your life. It's not about sound quality. I love hearing a song when I am outside and unexpectedly, it gives a different meaning. This is the beauty of music and I fully believe that enviroment can also change the perspective of music when it becomes internalized.

 

[holland]

Quote:

Originally Posted by NelsonVandal /img/forum/go_quote.gif There must be something in between 2 mA/ch and 500 mA/ch.

Of course there is. You don't need 20W/ch power consumption. Even in home amps, that's into world class amp territory, like the Dynahi as an example. Boomana's thread wasn't about using the best home amps only. Many people utilize amps considerably less in output with exclamations of greatness.

Realistically you only need about 100-300mA for a 32ohm headphone, 500mA is even too much and 100mA is more than adequate for most listening. Look at the sensitivity ratings of headphones relative to mW. If you can about about 1mW-2mW before clipping you will be able to make the HD650 and HD600 be at deafeningly loud levels. As for voltage swing, amps that have a good reputation put out considerably less than +/-30V. That's 60Vp-p. Amps that put out less are CK2III, M^3, and Dynalo, as examples. The M^3 in particular with a stock build only puts out about 13Vp-p (4.5Vrms). Utilizing 2 9V can easily give you the rail to rail voltage to output the swing that you would want, easy. You really don't even need that much, as shown with portable amps like the Mini3 which can output 3Vrms (as noted, line out is 2Vrms). The problem then is the current capacity for true and full Class A biasing and to feed your transistors with additional voltage and current.

You might be better off targeting a transportable than a teeny tiny portable, like LISA III size. Your JISBOS amp definitely sounds like it would be great, and as a buffer stage for a SOHA, it is reportedly very good as well. So what you should probably look into is a gain stage for the JISBOS, if you want to do an integration design of your own (not a ground up, more piecing together ideas from other designs).

If you use a mix of SMT and through-hole you can reduce the size considerably. If you can find the transistors you need in SMT, that would be even better and you can go pure SMT, though I'm not sure. I haven't researched it.

A very good sounding portable doesn't need to be competitive with or be in the same class as a reference amp for world class headphone amplification. I think many people miss that point and just look at world class specs and say that's what you need. World class, in many ways, is excessive. Nobody fully utilizes it. 500W/ch monoblocks, is in many ways, excess but for that small percentile.

 

[Bluetick]

Quote:

Originally Posted by Spareribs /img/forum/go_quote.gif I think that's an important point. Music is much more important than sound quality and it is so meaningful in life.

Well said, and I couldn't agree more. I often wonder what pieces of gear I would gravitate toward if I were never exposed to a forum, advertisement, or (another person's) opinion. I bet I'd be looking for more goosebumps. I wish I wasn't influenced by response, design, extension, specs, etc. As I grow older, I am continually developing a better "filter mechanism".

 

[MichaelPublic]

Hi folks, since this is high end vanity/hobbiest type equipment, what about fuel cells to power high quality portable amps, if we can get our hands on them. Anyone know anyone in Japan? Apparently fuel cell laptops may be available there already. I'm having trouble googling up a link to a for sale item though.
--------------------------------------------------------------------------
Samsung's Fuel Play
The docking station is designed for Samsung's Q35 ultraportable laptop. It contains a 1200-watt-hour fuel cell. Laptop users can power a computer for up to eight hours a day, five days a week for an entire month.

Samsung's dock uses a direct methanol fuel cell. The DMFC offers a maximum output of 20 watts, which is conducive to generating small amounts of power over long periods of time at low temperatures. That combination of qualities makes the DMFC ideal for laptops and mobile
--------------------------------------------------------------------------
from:
http://www.technewsworld.com/story/54905.html

 

[MaloS]

Quote:

Originally Posted by omendelovitz /img/forum/go_quote.gif it looks like the smallest portable we can fit all the parts into is a case that's about the size of a PINT case (~2x the length of the standard iPod length).

We already have a Lisa III available to us.

Answer to the OP: in all honesty - the main issue with delivering the amp we want as a portable is the power. Power will always be the main issue with portable amps - batteries get heavier if we try to shoot for big jumps in SQ. Right now we have available to us Lisa III and the Pico which I think have the most drive out of all the portables, and while great, both are still behind comparably priced home amps (which was the original argument of the Disturbing Trend thread). (Lisa III comes at $500+, we are getting into class A and SET amplification area, and Pico falls behind the Gilmore Lite brethren, although Pico is AWESOME as a travel/pocket component).

More so, even if we design the amp with the desired capabilities. If you want something to perform as well as a good desktop amp, it basically has to be as small as a good desktop amp.

Oh...and we have great cans that do not require lots of power to drive. For a portable rig options we can get pretty high end, we just need to look elsewhere, not at k701 or hd650, as once again was another part of the points of the original thread. =]

 

[Hellenback]

I'd like to ask anyone who has posted in this thread, who owns both a good portable amp and a desktop of equal value, what percentage of performance is missing in the portable amp. To put it another way; will anyone go out on a limb and tell me HOW MUCH improvement I am going to hear between say an Arietta and a Move or a Hornet and a Heed? How much difference are we talking here? 10 %, 20 %? These things are quantifiable, (because sound can be measured) anyone?