[HiFlight]

I compared the Astrapi output to that of my LG G2 without the Astrapi. While my impressions are purely subjective based on what I heard using my Sony F1 overear phones and my Aurisonics One Plus IEM's, it appears as though the addition of the Astrapi results in the sound being about 3-4 times louder than without using the USB output. The difference is more noticeably when driving full-sized cans.

I am very pleased with the SQ of this tiny device. It delivers an effortless output that sounds very natural and lifelike. It sure beats strapping a DAC/Amp to my phone when using phones that challenge the headphone output of my phone. The battery drain is also much less than I expected.

 

[BruceBanner]

Sounds good, cheers for that. As someone who has a decent smartphone but a flakey HO socket, this then is very appealing. I also find standard HO volume too low.


Now this gets me thinking....
With Android devices, there is a 'mixer_path' file that controls the volume output of the device, it can be 'hacked' and values inside the text changed but only with a rooted device.
I wonder if the Astrapi completely bypasses this file entirely, if it does that is hopeful sign for someone like me who finds Android too low in volume.

 

[shigzeo]

   
From what we've tested, the Astrapi really cuts down the hiss on our IEMs. We've tested earphones such as the Altone200, T-PEOS H-300, Fidue A83, DN2000
and they all sound great with very little floor noise compared to the headphone out on my Macbook pro or Android smartphone!

Certainly it may be lower than a computer, but compared to an iPhone 4-6 (I have no experience before that), noise levels are higher. Max volume is subjectively higher than an iPhone 6 at max. But depending on the earphone/headphone, there will much much higher distortion through the Astrapi.
 
I LOVE the idea of this device, but I'm unconvinced of its efficacy as an amp. Its DAC portion appears to be good but it needs a better, higher current output stage. 

I've conducted some hardware RMAA tests (square wave no yet published) which I have published here. 

 

[shigzeo]

I compared the Astrapi output to that of my LG G2 without the Astrapi. While my impressions are purely subjective based on what I heard using my Sony F1 overear phones and my Aurisonics One Plus IEM's, it appears as though the addition of the Astrapi results in the sound being about 3-4 times louder than without using the USB output. The difference is more noticeably when driving full-sized cans.

I am very pleased with the SQ of this tiny device. It delivers an effortless output that sounds very natural and lifelike. It sure beats strapping a DAC/Amp to my phone when using phones that challenge the headphone output of my phone. The battery drain is also much less than I expected.

If only it worked as expected. The idea is so sexy, so appealing. But the actual performance of Astrapi leaves a lot of room for improvement. But you are right: strapping an amp and DAC to a smartphone is ridiculous. The thing is that a number of smartphones have very good DAC/amps already that are not bested by portable externals apart from total voltage output. But a number totally trump them. 

Astrapi would be THE one if its noise floor (amount of hiss through earphones) was lower and its ability to sustain current at any voltage level to any applicable earphone/headphone was perfect. The ergonomics of plugging into it rather than the bottom of a phone are in many ways better. 

 

[NLNH]

 
Certainly it may be lower than a computer, but compared to an iPhone 4-6 (I have no experience before that), noise levels are higher. Max volume is subjectively higher than an iPhone 6 at max. But depending on the earphone/headphone, there will much much higher distortion through the Astrapi.
 
I LOVE the idea of this device, but I'm unconvinced of its efficacy as an amp. Its DAC portion appears to be good but it needs a better, higher current output stage. 

I've conducted some hardware RMAA tests (square wave no yet published) which I have published here. 

 
You should measure the current
 
and the hiss is a relative thing, do look into correlation between gain and hiss and impedance

 
 
it really depends... and since every device output different voltage/current all devices are supposed to sound differently.

 

[shigzeo]

   
You should measure the current
 
and the hiss is a relative thing, do look into correlation between gain and hiss and impedance

 
 
it really depends... and since every device output different voltage/current all devices are supposed to sound differently.

Perhaps I will measure its output impedance. I didn't and should have. Hiss is relative, yes, but in direct comparison to an iPhone 6, it is greater with the same earphones. I imagine it won't bother a lot of people. It will bother some. As you said, it is relative. 
 
But voltage has nothing to do with sound until not enough voltage is supplied at a certain frequency, which is often caused by current problems. 

Anyway, lots of cool things going on with Astrapi, but it is a little too far from perfect for me. 

 

[edyeded]

Have you tried the Calyx PaT? Raving reviews. I wander how it compares?

 

[shigzeo]

  Have you tried the Calyx PaT? Raving reviews. I wander how it compares?

Astrapi is unique in that it works both from PC/Mac USB and from portable device-specific calls. I have not used PaT and likely will not, but it appears to be a different thing all together. Astrapi's strengths: size, machine quality, discrete and simple circuit that relies on device input for volume, put it in a niche which only it occupies. Handling it is wonderful. But the problems I mentioned are real. 
 
If they could be fixed: hiss, poor current supply to low-Ω loads, it would be pretty much perfect. 

 

[NLNH]

 
Astrapi is unique in that it works both from PC/Mac USB and from portable device-specific calls. I have not used PaT and likely will not, but it appears to be a different thing all together. Astrapi's strengths: size, machine quality, discrete and simple circuit that relies on device input for volume, put it in a niche which only it occupies. Handling it is wonderful. But the problems I mentioned are real. 
 
If they could be fixed: hiss, poor current supply to low-Ω loads, it would be pretty much perfect. 

 
but that is not designed for low ohm loads at all... because you shouldn't need an amp but a good dac for low ohm loads.....

 

[shigzeo]

So what target device should be plugged into this tiny, really portable thing? A massive, high-ohm headphone? This is a portable DAC/amp for a portable device. It should target first the sort of earphone/headphone a serious music lover would have with them. If it can't drive low-Ω loads (it even has trouble with the ES7, but of course not as much as the SM2), then it should be desktop-size and have a label: "do not use with low-Ω loads" or "not for earphones". 

Its marketing page says 'ultimate portability'. 

What sort of headphones are ultimately portable, or does a person that purchases an ultimately portable DAC use? 

Again: I LOVE the idea. But the execution isn't great. And other than immediate power output, performance-wise it doesn't have anything on the iPhone. 

 

[NLNH]

  So what target device should be plugged into this tiny, really portable thing? A massive, high-ohm headphone? This is a portable DAC/amp for a portable device. It should target first the sort of earphone/headphone a serious music lover would have with them. If it can't drive low-Ω loads (it even has trouble with the ES7, but of course not as much as the SM2), then it should be desktop-size and have a label: "do not use with low-Ω loads" or "not for earphones". 

Its marketing page says 'ultimate portability'. 

What sort of headphones are ultimately portable, or does a person that purchases an ultimately portable DAC use? 

Again: I LOVE the idea. But the execution isn't great. And other than immediate power output, performance-wise it doesn't have anything on the iPhone. 

 
How about a 16ohm-32ohm earphone? And make sure we are talking about high ohms and non sensitive, but small drivers or ba  LOL
you are way too sensitive than many anyways... (those using se846 is another case because it is not a good match and is too loud because of the sensitivity from the beginning)
 
If it doesn't work for you then it doesn't work for you anyways 

 but for rmaa, try compare other products, may give you some interesting insights

 

[HiFlight]

I use my Astrapi with K3003, K10U and AS 1Plus from both my cellphone and from my Linux computer USB. It has been working entirely to my satisfaction with all of these combinations.

 

[shigzeo]

I use my Astrapi with K3003, K10U and AS 1Plus from both my cellphone and from my Linux computer USB. It has been working entirely to my satisfaction with all of these combinations.

It is great that you are happy with your setup, but according to Palois Audio, you should not use the K3003 or the AS 1Plus as they are too low-impedance. Imagine how much better they'd sound if Astrapi kept signal quality high even under load of popular earphones. I can wish.

 

[shigzeo]

   
How about a 16ohm-32ohm earphone? And make sure we are talking about high ohms and non sensitive, but small drivers or ba  LOL
you are way too sensitive than many anyways... (those using se846 is another case because it is not a good match and is too loud because of the sensitivity from the beginning)
 
If it doesn't work for you then it doesn't work for you anyways 

 but for rmaa, try compare other products, may give you some interesting insights

I have been running RMAA and square wave and other tests since 2009. I've tested hundreds of amps, DAPs, DACs, etc. I'm not suddenly testing Astrapi an saying it could do better. I'm talking from a boring experience and from what my ears tell me. And not only me. I've met now three people that use pretty normal (for these forums) earphones with the Astrapi that said: too high volume from step one (with iPhone 6) and too much hiss. 

Everyone's hearing sensitivity is different. I'm 35 now and not as hiss sensitive as I once was. But I used to be called hiss king. I've met several younger guys that easily take that from me. The point is that Astrapi doesn't allow enough control over volume. 
 
And in terms of audio quality, Alien (which appears to be made by the same brains) smacks it up/down/right/left in all metrics including hiss. So they know what sounds good. Why it wasn't implemented into Astrapi is a shame as the idea behind it is phenomenal. Honestly, if I could get Alien SQ from Astrapi: game over. 

 

[NLNH]

 
I have been running RMAA and square wave and other tests since 2009. I've tested hundreds of amps, DAPs, DACs, etc. I'm not suddenly testing Astrapi an saying it could do better. I'm talking from a boring experience and from what my ears tell me. And not only me. I've met now three people that use pretty normal (for these forums) earphones with the Astrapi that said: too high volume from step one (with iPhone 6) and too much hiss. 

Everyone's hearing sensitivity is different. I'm 35 now and not as hiss sensitive as I once was. But I used to be called hiss king. I've met several younger guys that easily take that from me. The point is that Astrapi doesn't allow enough control over volume. 
 
And in terms of audio quality, Alien (which appears to be made by the same brains) smacks it up/down/right/left in all metrics including hiss. So they know what sounds good. Why it wasn't implemented into Astrapi is a shame as the idea behind it is phenomenal. Honestly, if I could get Alien SQ from Astrapi: game over. 

 
In fact there are many ways to add extra steps and control to iphone (iwatch's knob, apps with gain knob like kaiser tone/ neplayer)....  using with android will give you a lower output that you probably won't complain, and noise level differs. It is not a product for you to sit in a silent room and blame the hiss anyways, this is portable gear, hiss is barely portable on the street unless you must use a very sensitive ciem with it (which is not recommended lol)
 
And should the sound quality of Alien be put into a cheaper product that has no battery inside and 1/5 the size? Probably no and shouldn't? It is another chipset and power constraints, space. programming all differs... not even practical to compare 

 Try compare to products of the exact same function.... anyways I kinda know what sound will make you happy now lol