[miceblue]

I didn't realise you were using the ER4s. It may be a sweet spot for Astrapi. Anything below 32Ω, and perhaps up to 40Ω, proves to be problematic for Astrapi to properly supply with enough current. I've written about it here. 

Did you ever measure the output impedance? I would think that's more of a limiting factor than the current delivery, based on what you've measured. My OPPO PM-3 sounds just fine with the Astrapi, and planar magnetic headphones are immune to the amp's output impedance.

 

[H20Fidelity]

   

 
 
I didn't realise you were using the ER4s. It may be a sweet spot for Astrapi. Anything below 32Ω, and perhaps up to 40Ω, proves to be problematic for Astrapi to properly supply with enough current. I've written about it here. 

 
Thanks.
 
Why exactly has SM2 shown such a crooked curve in this test?  Its 32ohms, (like you said a problem area)
 
Also did you (or can you) measure the output impedance for us?

 

[Peter West]

All the numbers in the world can't compete with the subjective experience. The Cozoy Astrapi I'm using with my IPhone is cheap and cheerful and works better with some of my headphones and IEMs than others. Yesterday afternoon took a break from the air conditioning listening to the Fostex HPa8c and the main setup in the front room and went outside with the IPhone streaming TIDAL into the Astrapi and just for fun into an Aune B1 Class A amp driving my LCD-Xs (instead of my usual ultra-cheap and cheerful T-Peos D-202Ns). It's kinda like dating a perfect 10 and then you meet her younger sister...(flashback to The Lovin' Spoonfuls). I'm not talking about audio perfection but fun with portable audio. YMMV but for me the Astrapi has a place in my audio kit and I've spent more on a business lunch that wasn't anywhere near as satisfying.

 

[shigzeo]

Did you ever measure the output impedance? I would think that's more of a limiting factor than the current delivery, based on what you've measured. My OPPO PM-3 sounds just fine with the Astrapi, and planar magnetic headphones are immune to the amp's output impedance.

The headphones aren't immune to anything. But they present a much more even load across the entire frequency spectrum. Rather than dipping to 8Ω or less, or 100Ω or so, they stay relatively flat. That is a blessing, especially to poor amplification. 
 
Proper current allows voltage to remain stable. The Astrapi doesn't provide enough current to low-Ω earphones precisely because of a number of factors, one for sure being: a higher than optimal output impedance. I'm guessing here because no, I did not measure it. I used to measure output impedance, and probably still should, but it's easy to extrapolate: if you get such a crazy curve as seen by the SM2, or the flatter dynamic ES7 (minimal deviation), we are probably looking at an output impedance between 3 and 5 Ω. 

 

[strengthofmind]

I get a high pitched background noise when using this with AKG K451 or Soundmagic E30, but not Sennheiser HD 438 (possibly just because I cannot hear it).

Any thoughts or recommendations? Defective unit?
 
n.b. Just using the E30s to be thorough and because they were to hand, aware they are not ideal.

 

[wongzuohan]

I'm thinking of getting one of these but there are other mini dacs out there that got my attention like the HRT microstreamer & the Resonessence Labs Herus. Which one should I get? I currently have on my daily carry a Westone W50 with stock cables (not braided) paired with an iPhone 6.

 

[money4me247]

  I'm thinking of getting one of these but there are other mini dacs out there that got my attention like the HRT microstreamer & the Resonessence Labs Herus. Which one should I get? I currently have on my daily carry a Westone W50 with stock cables (not braided) paired with an iPhone 6.

Herus is not that good for portable usage due to battery drain and boxy shape. I would recommend something like the astrapi, aegis, or ha-2 for iOS devices so you do not need the extra camera adapter kit.

 

[wongzuohan]

Okay thanks for your suggestion, I have to ask though, what is the difference between the astrapi and the aegis?

 

[money4me247]

i havent heard the aegis but it is larger in size so more powerful amp maybe? there are a few reviews comparing them. if i was spending $300 though, i wld personally get the ha-2.

 

[wongzuohan]

i havent heard the aegis but it is larger in size so more powerful amp maybe? there are a few reviews comparing them. if i was spending $300 though, i wld personally get the ha-2.

The aegis looks sick though, I'm not too worried about the price but what I'm concerned about is the size, I don't fancy carrying big amps/dacs around, I would personally like small ones much like the astrapi and aegis as I always wear skinny jeans, and I don't want to look like I have butt implants when I'm out and about

 

[NLNH]

i havent heard the aegis but it is larger in size so more powerful amp maybe? there are a few reviews comparing them. if i was spending $300 though, i wld personally get the ha-2.

one is 16/44.1 and another one is 24/192 lol, different structure

 

[money4me247]

lol i actually don't believe higher bit depth and sampling rate beyond cd quality makes any difference due to nyquists sampling theorem. often its just that hi-rez files are different masters

 

[NLNH]

lol i actually don't believe higher bit depth and sampling rate beyond cd quality makes any difference due to nyquists sampling theorem. often its just that hi-rez files are different masters

but you should believe better power supp., parts and circuitry will help lower-bit files sound better

anyways integrity takes a big role because you can put a lot of resources into some old 16bit circuitry and just make a highend chip sounds with a supa low budget circuit.... chip is just integrated circuit and quite often the other part of the circuit r left not commented : p

how to operate the chips at favorable conditions also matters, dont forget we are always playing with chips that has much performance plugging into AC


all depends anyways....

 

[money4me247]

but you should believe better power supp., parts and circuitry will help lower-bit files sound better

anyways integrity takes a big role because you can put a lot of resources into some old 16bit circuitry and just make a highend chip sounds with a supa low budget circuit.... chip is just integrated circuit and quite often the other part of the circuit r left not commented : p

how to operate the chips at favorable conditions also matters, dont forget we are always playing with chips that has much performance plugging into AC

all depends anyways....

yup, no worries. I am sure the designers at cozoy worked hard to make the aegis sounds better than the astrapi. $300 price point though, market is a lot more crowded. a good deal of solid options, though I do believe the aegis has one of the smaller form factors available. should be a solid option if smaller size is a consideration.

 

[wongzuohan]

Well I just got mine 4 days ago and the lightning connector broke when I bent down to tug at my jeans it broke my heart as I really liked it