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Review and Measurements of Apogee Groove DAC and Amp

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#61
Thanks, I'm from Italy. I was aiming at 300 ohms as the 20 ohms impedance of the Groove may ask for medium to high impedance Headphones. But I am no expert at all, just report what I've read...only I wonder if higher impedance means also has to drive. Anyway it seems that the Groove could handle this. Bought the Groove in super-mint conditions for 50 euros...
 
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PuX

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#62
Somebody suggested me Sennheiser HD660 or Beyerdynamic 880pro, being both models at 300ohm.
neither are 300Ohm.

HD660 are 150Ohm.

Beyerdynamic DT880 has multiple editions, including 250Ohm and 600Ohm. I have both and prefer the PRO version in terms of comfort vs one of the premium editions. 600Ohm is supposed to sound a little bit better but on most amps 250Ohm is an easier load.
 
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#63
@Veri @PuX. Thanks for your advice.
Anyway in relation to the 20 ohm impedance of my Apogee dac I’ll need to opt for a headphone not lower than 250 ohms, right? Even 600 would be fine or probably too much to drive? I’ not talking about sound quality but just with regards to matching. Just to know if there is a limit below which I must not go.
 

Veri

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#64
@Veri @PuX. Thanks for your advice.
Anyway in relation to the 20 ohm impedance of my Apogee dac I’ll need to opt for a headphone not lower than 250 ohms, right? Even 600 would be fine or probably too much to drive?
The 'ideal' ratio is 1:8 or better. So 20 ohm output matches best with 160ohm headphones or higher. ~1ohm output would match best with ~8ohm headphones or higher (so basically anything).

So yes the 20 ohm limits your choices a little but anything >160ohm should do well. Something at 300 like the HD650 would be a great match.
More info here: http://nwavguy.blogspot.com/2011/02/headphone-amp-impedance.html
 
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#65
I recently visited the Drop ( formerly Massdrop) site and I've noticed that some of the products are shipping to Italy ( where I live), some are not.
Sennheiser HD6xx are not, while I've seen a good deal on Hifiman 4xx which can be shipped to Italy. Costs are not so much, though I have to figure out taxes for import.
Anyway my question is about impedance which is 35 ohms, so absolutely not a good mach with my Apogee Groove dac/amp, but have read somewhere that damping factor does not have any influence in planar headphones (like this 4xx). Ask you experts if this is true. Beside this I also wonder if the behavior of Apogee, which has been very well tested here, would be power-like adequate due to sensitivity 93db and Groove's power out at low impedance which - if I understand- is not that great. Too many doubts maybe about this Headphones and probably better get a Senny from Europe, but the price is inviting and it seems 4xx are a good product. Thank you so much for your advice.
 

Veri

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#66
I recently visited the Drop ( formerly Massdrop) site and I've noticed that some of the products are shipping to Italy ( where I live), some are not.
Sennheiser HD6xx are not, while I've seen a good deal on Hifiman 4xx which can be shipped to Italy. Costs are not so much, though I have to figure out taxes for import.
Anyway my question is about impedance which is 35 ohms, so absolutely not a good mach with my Apogee Groove dac/amp, but have read somewhere that damping factor does not have any influence in planar headphones (like this 4xx). Ask you experts if this is true.
The part about planars is true. Most of them don't respond to output impedance, or if they do, at least not in a significant way.
 
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#67
Thanks @Veri, you confirm what I've read is true. Now the point is wether the Groove's power output is ok for this HE4xx or not, which at 93 db seem quite power hungry. From @amirm measurement I have assumed - as far as I can understand, but maybe easily wrong- that Grooves has poor power output at low impedances: despite 225mW claimed on the specs it delivered only 78 at 33 ohms before shutting down.
 
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Veri

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#68
Thanks @Veri, you confirm what I've read is true. Now the point is wether the Groove's power output is ok for this HE4xx or not, which at 93 db seem quite power hungry. From @amirm measurement I have assumed - as far as I can understand, but maybe easily wrong- that Grooves has poor power output at low impedances: despite 225mW claimed on the specs it delivered only 78 at 33 ohms before shutting down.
Yeah that might not be ideal. An E1DA over 2.5mm balanced cable to your HE4xx can push a multitude of that. Not sure the Groove will be plenty.
 

Head_Unit

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#69
How does a current drive differ from a voltage drive amp?
Yeah that is such a good question for this product, Apogee don't explain really what they mean by "Constant Current Drive™" so we have to guess a bit.
- A voltage amp ideally provides the same output voltage regardless of variations in load impedance.
- A current amp would ideally provide the same output voltage regardless of variations in load impedance. This is periodically proposed to remove a number of distortion mechanisms, the problem being the frequency response will tend to follow the impedance curve.
So although the high output of the Groove looks a good match to my 600 ohm AKGs, the current drive tends to scare me off.
 
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#70
Yeah that is such a good question for this product, Apogee don't explain really what they mean by "Constant Current Drive™" so we have to guess a bit.
- A voltage amp ideally provides the same output voltage regardless of variations in load impedance.
- A current amp would ideally provide the same output voltage regardless of variations in load impedance. This is periodically proposed to remove a number of distortion mechanisms, the problem being the frequency response will tend to follow the impedance curve.
So although the high output of the Groove looks a good match to my 600 ohm AKGs, the current drive tends to scare me off.
I've had it for a while and I can confirm that it does indeed have something special. Every headphone I plug in sounds very similar. Though I don't see the fr being affected, I can hear differences in staging (they image right at the driver). I can confirm that it does have a lot of brute with high impedance cans, and can drive even my hd425 vintage to fairly decent levels.
 
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