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Amp for AKG K702's & some technical questions...

post #1 of 15
Thread Starter 

I just purchased a pair of AKG K702s.  I'm now looking for an amp to power it.  After reading around (but no live testing) I think I've narrowed it down to the following (original budget under $500, but pushed a bit):

Woo Audio WA6:
http://www.wooaudio.com/products/wa6.html

Woo Audio WA3:
http://www.wooaudio.com/products/wa3.html

Burson Audio HA-160:
http://bursonaudio.com/burson_headamp_160.htm

Schitt Lyr:
http://schiit.com/cart/index.php?main_page=product_info&cPath=0&products_id=3

Heed CanAmp (which seem to get the highest praise with the K70X:
http://www.heedaudio.hu/en/products/modular-line/canamp

The amp will be connected to a Marantz SR6005.  The sources will vinyl (Rega RP1) or lossless 44.1/16 & 96/24 digital files going to my Marantz via an optical cable from my MacPro.

So, thoughts on these or alternatives in my price range?  Does anyone have direct experience and/or own any of these combos?

So some questions about some technical things that I've been reading and haven't quite understood even after reading (the tech side of me wants to know this stuff, but I know it's more about how I like the sound in the end and not the tech specs):

I've read someone say WRT the K70X's and the Lyr:
"I wouldn't use the Lyr with highly efficient/low impedance headphones like Grados or Ultrasones. The K701s aren't that efficient and a better match."

What does it mean that the K70X's aren't "efficient" and is that a bad thing?

I've read that you want a headphone impedance to output impedance to be around 10 or higher ("Damping Factor" ??).  I noticed that SS amps seem to rate their impedance as a single number.  For instance the HA-160 is listed as 5.6 Ohms (which would be 11).  However, tube amps seem to list their output impedance in ranges like the WA6's 8-600 Ohms.  Why is that and what does that mean for the ""Damping Factor"?

And finally, I've read comments like:
"I'm getting a little paranoid from reading a lot of reviews that almost all of the tube amps available will not be sufficient enough to amplify the 701/702"  I guess I'm not fully understanding why that is.

Thanks!

post #2 of 15

Why can't you just plug the AKG K702s into the headphone jack on the Marantz SR6005?

post #3 of 15
Thread Starter 

I don't have the specs for the Marantz headphone output, but I'm guessing a dedicated headphone amp would be better.  Especially considering how "difficult" the K702's are supposed to be to power.

 

I actually don't even use the Marantz to power my speakers.  I have a separate amp for that as well.  Essentially my Marantz is a pre-processor.

 

 

post #4 of 15
Quote:
Originally Posted by 1957GoldTop View Post
I don't have the specs for the Marantz headphone output, but I'm guessing a dedicated headphone amp would be better.  Especially considering how "difficult" the K702's are supposed to be to power.

I actually don't even use the Marantz to power my speakers.  I have a separate amp for that as well.  Essentially my Marantz is a pre-processor.

So how do the AKG K702s sound when you plug them into the Marantz?
 

 

 

post #5 of 15

You can try to get a used Violectric V100 on the FS forum. 

post #6 of 15

If you can grab a HA-160 used it would be great. 

post #7 of 15
Thread Starter 

I actually don't have the K702's yet... they get here today.  I was planning on testing them first, but thought they would need the amp since my Senheiser HD-595's sound pretty weak on the Marantz.

 

I actually have a local dealer that sells the HA-160 and another that sells the Heed so I might be able to test them out together (depending on return policies).  The HA-160 is more than I'd like to spend, but used could be an option.

 

Thanks!

post #8 of 15

I would recommend an Objective 2, considerably under budget and completely transparent. You're welcome to spend money on unknown quantities, but the O2 is just a verified wire with gain. Colour the sound to your taste with an equaliser and you've got audio nivana. Buy from Epiphany Acoustics or JDS Labs.

 

On your technical questions:

 

How an amplifier will cope with a headphone is almost entirely defined by the output impedance of the amplifier and the impedance and sensitivity of the headphone. The K701s are not really that hard to drive: not because I think so but because of maths. For example, you frequently see recommendations that an amp to drive the K701s must be able to output 400mw/600mw or some equally arbitrary number into their 60ohm impedance (power output varies with impedance).

 

Considering the driver reaches its limits at 200mw (IE you start damaging it) I find such recommendations spectacularly moronic, regardless of all the handwaving about "headroom."

 

As for the requirements of the individual headphone itself, it is designed to be driven from an amplifier with a low output impedance: this can be confirmed with an email to AKG. In the overwhelming majority of cases, you want an amplifier with an output impedance <1ohm for optimal damping. 

The ranges you talk about are not output impedance, but a range of headphone impedances that the manufacturer has decided to say the amp can drive. They are pretty meaningless. Output impedance is a single value.

As for the efficiency of the headphones themselves, they are more inefficient than, say, the HD650s, but are not really a difficult drive. Something like the Lyr would be a waste of money (on several levels if you ask me).

post #9 of 15


 

Quote:
Originally Posted by 1957GoldTop View Post


I've read someone say WRT the K70X's and the Lyr:
"I wouldn't use the Lyr with highly efficient/low impedance headphones like Grados or Ultrasones. The K701s aren't that efficient and a better match."

What does it mean that the K70X's aren't "efficient" and is that a bad thing?

 

 

All the amps you listed are good amps, though AFAIK all the Woo amps are OTL tube amps.  On paper, the 70x would work best with SS or hybrid amps with high current instead of high voltage tube amps.  I say on paper, because that isn't always true (Schiit Valhalla, on paper, shouldn't be a good match, but somehow, it is.)  If considering the Woo models, definitely check other threads to be sure owners of the combo are happy with them first.

 

"Efficiency" doesn't mean the same thing as for fuel consumption...bad efficiency isn't a bad thing, other than, for use with battery powered sources, the less efficient the faster it drains your battery (the higher volume you need to set.)  "inefficient" in this context means low-impedence high-current headphones.  The K70x and most orthos/planars tend to be "inefficient."  Meaning they don't take much voltage swing (which OTL tubes tend to provide) but need more current (amperage) to move the motor (magnets) in the driver.   "efficient" headphones on the other hand are usually (but not always) in high impedence packages (Beyerdynamic high-ohm headphones, Sennheiser HD600, HD650, HD800, etc.)   They don't take huge amounts of current to power, but need large voltage swings to get past the impedance.  They'll use less power, but they take a bigger thrust of it to move, to simplify it. 

 

So on paper, efficient, high-impedance headphones like Beyer 880/600 like OTL tube amps.  They don't drive a lot of current, but the tube section yields big voltage swings.  Inefficient headphones like K70x tend to like SS amps...they don't need the big tube voltages but they feed on the high current SS outputs.  300ohm Sennheisers (and 250ohm Beyers) can easily go either way, and sound different depending on how you drive them.

 

That, of course, is all on paper, and reality doesn't always match paper which is why subjective info from owners is important.   In the case of Lyr + K701 for example, Jason of Schiit commented that he likes the Lyr best with it (which makes sense, it was designed from the ground up for low impedence inefficient orthos) but for reasons even he can't explain, the low current Valhalla works well with them too.   Thus the all important "synergy" of gear.   Electrically, a pure OTL high-voltage, low-current amp shouldn't be a good match for K70x, but in some cases, other factors seem to make it a good match anyway.

 

Quote:
Originally Posted by PurpleAngel View Post

Why can't you just plug the AKG K702s into the headphone jack on the Marantz SR6005?


 

Quote:
Originally Posted by 1957GoldTop View Post

I don't have the specs for the Marantz headphone output, but I'm guessing a dedicated headphone amp would be better.  Especially considering how "difficult" the K702's are supposed to be to power.

 

I actually don't even use the Marantz to power my speakers.  I have a separate amp for that as well.  Essentially my Marantz is a pre-processor.

 

 


K70x can take a lot of current, though the definitioin of "difficult to drive" seems to vary on these forums.  AKG's selling the rebranded Q701's (same drivers) as mobile device friendly.  A silly notion, but they're trying to cash in on the i-market.  Sure, you can "drive" the 701's from an ipod.  They might even not sound putrid.  But without sufficient power, they certainly won't be able to reproduce their full range and precision to the level they're capable of.   That's what amping is all about.  Sure, you can get sound feeding strained power into any can, even orthos, but the amount of power needed to fire the drivers with precise control and start and stop the driver "on a dime" is different than the amount of power needed to move it at all. 

 

So back to AVR headphone outs.  I haven't tried a Marantz 600x series.  I almost bought one but there were some known issues with the series so I bought a Denon instead.  I can't say if the Marantz falls into the same trap as most AVRs or not.  It's possible they don't and they have a real headphone out tied to the main amplifier section.  If so, your AVR may be a good option as-is.  If it's like most AVRs though, as good an amp as the main unit may be, the headphone out is usually not coupled to the main amplifier and is, on its own, a very cheap op-amp with horrible output-impedence.  Think, at best, something like a Fiio E9...but that may be wishful thinkng.  

 

PurpleAngel has a point though, since you have it in front of you, it's always worth a try!  You may like it.  Or not.  But at least you'll know.

 

My vote goes for Lyr...I'm running my HD650's and my K702's on it and am thrilled.  I bought my K702's specifically for use with Lyr so I haven't tried them on anything else yet.   My HD650s were "transformed" by it compared to my SS Headroom Micro Amp and all AVRs I've used it with.  But I haven't heard the other amps with them, and know only by reputation they are excellent amps.

 

Though I'm awaiting a response from Woo about a defective headphone stand, unfortunately. 

 

 

post #10 of 15
Quote:
Originally Posted by Willakan View Post


As for the efficiency of the headphones themselves, they are more inefficient than, say, the HD650s, but are not really a difficult drive. Something like the Lyr would be a waste of money (on several levels if you ask me).



 

They are very inefficient for a headphone of 62 Ohm impedance and 105 db sensitivity. I have Q701 and HD650, and no matter which source or amp is used, Q701 need about 1/3 higher volume settings to reach the same loudness level.


Edited by derbigpr - 3/5/12 at 10:44am
post #11 of 15
Thread Starter 
Thanks for all the detailed info.

I decided to go with the Lyr because they have a return policy. So, I can take it and my K702's to the local dealers that sell the CanAmp and HA-160. I know it won't be exactly the same as my system, but I can judge them relative to the systems the dealer has.

But, I'm liking e sound of the Lyr... On paper (and I've always wanted tube gear which doesn't hurt)
post #12 of 15
Quote:
Originally Posted by IEMCrazy View Post
All the amps you listed are good amps, though AFAIK all the Woo amps are OTL tube amps.  On paper, the 70x would work best with SS or hybrid amps with high current instead of high voltage tube amps.  I say on paper, because that isn't always true (Schiit Valhalla, on paper, shouldn't be a good match, but somehow, it is.)  If considering the Woo models, definitely check other threads to be sure owners of the combo are happy with them first.

"Efficiency" doesn't mean the same thing as for fuel consumption...bad efficiency isn't a bad thing, other than, for use with battery powered sources, the less efficient the faster it drains your battery (the higher volume you need to set.)  "inefficient" in this context means low-impedence high-current headphones.  The K70x and most orthos/planars tend to be "inefficient."  Meaning they don't take much voltage swing (which OTL tubes tend to provide) but need more current (amperage) to move the motor (magnets) in the driver.   "efficient" headphones on the other hand are usually (but not always) in high impedence packages (Beyerdynamic high-ohm headphones, Sennheiser HD600, HD650, HD800, etc.)   They don't take huge amounts of current to power, but need large voltage swings to get past the impedance.  They'll use less power, but they take a bigger thrust of it to move, to simplify it. 

So on paper, efficient, high-impedance headphones like Beyer 880/600 like OTL tube amps.  They don't drive a lot of current, but the tube section yields big voltage swings.  Inefficient headphones like K70x tend to like SS amps...they don't need the big tube voltages but they feed on the high current SS outputs.  300ohm Sennheisers (and 250ohm Beyers) can easily go either way, and sound different depending on how you drive them.

That, of course, is all on paper, and reality doesn't always match paper which is why subjective info from owners is important.   In the case of Lyr + K701 for example, Jason of Schiit commented that he likes the Lyr best with it (which makes sense, it was designed from the ground up for low impedence inefficient orthos) but for reasons even he can't explain, the low current Valhalla works well with them too.   Thus the all important "synergy" of gear.   Electrically, a pure OTL high-voltage, low-current amp shouldn't be a good match for K70x, but in some cases, other factors seem to make it a good match anyway.

K70x can take a lot of current, though the definitioin of "difficult to drive" seems to vary on these forums.  AKG's selling the rebranded Q701's (same drivers) as mobile device friendly.  A silly notion, but they're trying to cash in on the i-market.  Sure, you can "drive" the 701's from an ipod.  They might even not sound putrid.  But without sufficient power, they certainly won't be able to reproduce their full range and precision to the level they're capable of.   That's what amping is all about.  Sure, you can get sound feeding strained power into any can, even orthos, but the amount of power needed to fire the drivers with precise control and start and stop the driver "on a dime" is different than the amount of power needed to move it at all. 

So back to AVR headphone outs.  I haven't tried a Marantz 600x series.  I almost bought one but there were some known issues with the series so I bought a Denon instead.  I can't say if the Marantz falls into the same trap as most AVRs or not.  It's possible they don't and they have a real headphone out tied to the main amplifier section.  If so, your AVR may be a good option as-is.  If it's like most AVRs though, as good an amp as the main unit may be, the headphone out is usually not coupled to the main amplifier and is, on its own, a very cheap op-amp with horrible output-impedence.  Think, at best, something like a Fiio E9...but that may be wishful thinkng.  

 

PurpleAngel has a point though, since you have it in front of you, it's always worth a try!  You may like it.  Or not.  But at least you'll know.

 

My vote goes for Lyr...I'm running my HD650's and my K702's on it and am thrilled.  I bought my K702's specifically for use with Lyr so I haven't tried them on anything else yet.   My HD650s were "transformed" by it compared to my SS Headroom Micro Amp and all AVRs I've used it with.  But I haven't heard the other amps with them, and know only by reputation they are excellent amps.

Though I'm awaiting a response from Woo about a defective headphone stand, unfortunately. 

 

 

I think I learned a few things and someone 2nd my point, not a bad morning.

(Only four days left until John Carter comes out).
 

 

 

post #13 of 15
Quote:
Originally Posted by IEMCrazy View Post

 

All the amps you listed are good amps, though AFAIK all the Woo amps are OTL tube amps. 



The WA6 and 6SE at least, are transformer coupled. 

post #14 of 15

Hello Mr. Vintage Les Paul,

 

There are a few threads on Head-Fi where a few guys rave about using K701 or K702 or Q701s with the Lyr.

I own a pair of Q701 (basically the same 'phone as what you are buying).

You can actually drive them with an iPod or an iPad to a reasonable volume, just don't expect them to sound as good as they possibly can.

How much power do they really need?

The 'phones are speced at 106 dB @ 1 volt, what does that mean?  This works out to 16 mW at 106 dB. Not much power really.

How loud is 106 dB? This will be loud enough for any peaks you may encounter when listening to music at a reasonably loud listening level. 

Basically, if you want great sound out of them, you want a great sounding amp.

A low output impedance headphone amp would be more versatile, but I often use my Q701 with a tube amp which has a rather high output impedance; the La Figaro 336C. No harm is done, but I only use it for certain types of music: acoustic stuff, Jazz, etc. the bass is a bit loose and woolly with that amp. 

 

 

Efficiency:  an inefficient headphone needs more power than a more efficient headphone.

 

Low impedance:

a low impedance headphone needs a bit more current, a bit less voltage

a high impedance headphone needs a bit less current, a bit more voltage

 

It gets complicated because turning the volume control up and down really means you are turning the output voltage up and down.

 

Need more info?

try reading this;

 

http://www.head-fi.org/a/headphone-impedance

 

In closing, they are very nice sounding headphones, just try not to listen too loud!

 

 

post #15 of 15

The WA6 and CanAmp would be great choices.  Both are high current and can swing a good amount of voltage. Another option would be a used X-CANV8P, but they are so hard to find now. If you could get your hands on one you'd very much like it. IMO they drive the K702's better than the CanAmp can, but I think the WA6 may be better. I have not heard a K702 on a WA6 before, so who knows..

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