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Valhalla 2 review coming soon! - Page 9

post #121 of 824
Quote:
Originally Posted by MrTechAgent View Post
 

Valhalla 2 :

 

Peak DC Voltage when turning
on: -0.103v ~ 2.799v
off: -2.246v ~ 0.971v

 

That's a figure I got from a person on YouTube , unless you want to massage your headphone diaphragms I would suggest un-plugging your headphones before turning it off , its like going for a back massage and then coming out with a broken spine 

 

Again , I'm not bashing it , I own and love it but just keeping you guys updated for the safety of your headphones , take it or leave it ....

 

Not a big deal for me since my 150s suffer , not all

If I see numbers like that I suspect the guy has a ground issue in his measurement set-up. Maybe he should download the internet and search for "ground loop" and "common-mode".

post #122 of 824
Quote:
Originally Posted by MustelaNivalis View Post

If I see numbers like that I suspect the guy has a ground issue in his measurement set-up. Maybe he should download the internet and search for "ground loop" and "common-mode".

Maybe , the numbers seem dubious to me too.
post #123 of 824
Quote:
Originally Posted by MrTechAgent View Post
 

Valhalla 2 :

 

Peak DC Voltage when turning
on: -0.103v ~ 2.799v
off: -2.246v ~ 0.971v

 

That would almost certainly be unloaded, or over a 10M DMM input, DSO probe, or something.  As soon as you add a load that voltage likely disappears.  It's purely nominal and perfectly normal.

post #124 of 824
Quote:
Originally Posted by sandab View Post
 

That would almost certainly be unloaded, or over a 10M DMM input, DSO probe, or something.  As soon as you add a load that voltage likely disappears.  It's purely nominal and perfectly normal.

 

Well .....interesting to see you assume it was unloaded , when in fact it was (Partly my mistake , I didn't mention it)  , he used a HD-600 while measuring , so if we know our impedances , the load was 300ohms 

 

But according to a reply he got from Schiit , the high voltages might have been because of leaky tubes..... Schiit sent him a new pair , I don't know if that is the real cause though , until he re-measures them we will not know , anyways I noticed my membrane being sucked at "off" and that was only with the DT-150s so its not a huge deal any more , and it is not a huge deal anyways since you can remove your headphones first and nobody is gonna keep tubes running all day long 

post #125 of 824

If you want to measure the contribution of the Valhalla, you need to disconnect the headphone and terminate with a resistor. The headphone is a coil, if you try to get DC through it, it fights back by creating a high voltage in the opposite direction.

 

Also to prevent a ground loop or short circuit via mains, it is best to use a battery powered scope (disconnect the optional mains plug).

post #126 of 824

BTW, the voltage created by the coil does not result in a movement of the membrane, it tries to avoid the movement that way... That is what coils do, try to keep everything the way it was.

post #127 of 824
Quote:
Originally Posted by MustelaNivalis View Post
 

If you want to measure the contribution of the Valhalla, you need to disconnect the headphone and terminate with a resistor. The headphone is a coil, if you try to get DC through it, it fights back by creating a high voltage in the opposite direction.

 

Also to prevent a ground loop or short circuit via mains, it is best to use a battery powered scope (disconnect the optional mains plug).

Well , that doesn't look like a lot of fightback to me 

 

 

 

And that's around 2.20v on the original Asgard , this gentleman seems to get 2.246v peak 


Edited by MrTechAgent - 8/9/14 at 11:16am
post #128 of 824

I wish I could show you the membrane being sucked on my 150s but since the baffle has the acoustic soak , I ain't screwing that up ..

post #129 of 824
Quote:
Originally Posted by MrTechAgent View Post
 

Well , that doesn't look like a lot of fightback to me 

 

 

 

And that's around 2.20v on the original Asgard , this gentleman seems to get 2.246v peak 

LOL, not much fighting there.

 

Please do not mix up things. Valhalla produces a little DC current due to the single ended end stage. The HP coil responds with relative high voltage to prevent movement.

 

Asgard is capable of high current and has a push pull end stage with a DC servo. The DC servo cannot be fast other wise it reduces low audio frequencies. Apparently the push pull stages start a bit uneven. I think the Asgard 2 already has an output relay.

 

Please come up with a video where a Valhalla 2 is used.

post #130 of 824

Just removed the ear pads from my Shure SRH1840 and switched the power of the Valhalla 2 on and off, not the slightest movement of the membrane could be seen. Also using my Sennheiser HD558 which is see-through, not the slightest movement. (Sorry no videos.)

 

That is it for me. I'm out of this discussion and back to plain music listening.

post #131 of 824
Quote:
Originally Posted by MustelaNivalis View Post
 

If you want to measure the contribution of the Valhalla, you need to disconnect the headphone and terminate with a resistor. The headphone is a coil, if you try to get DC through it, it fights back by creating a high voltage in the opposite direction.

Yeah, like this:

 

That's 220 ohm.

Funny you should mention this, because i just set this up to run a bunch of sinusoidals through to see what the output spectrum looks like...  Also created to RCA plugs terminated with 220 ohm (should perhaps be higher come to think of it) so I can check a line level source or output.  While at it.


Edited by sandab - 8/9/14 at 3:46pm
post #132 of 824
Quote:
Originally Posted by sandab View Post
 

That's 220 ohm.

Funny you should mention this, because i just set this up to run a bunch of sinusoidals through to see what the output spectrum looks like...  Also created to RCA plugs terminated with 220 ohm (should perhaps be higher come to think of it) so I can check a line level source or output.  While at it.

The 220 [Ohm] depends on what you want to see. White cathode followers have their max distortion at the lowest load impedance. Or maybe you want something that is closest to the load you are going to use, 300 [Ohm] for example. Anyway I think you are going to find most (but little) distortion on the second harmonics especially in high-gain mode.

 

Big question remains how measured figures translate to perception...

post #133 of 824
Quote:
Originally Posted by MustelaNivalis View Post
 

The 220 [Ohm] depends on what you want to see. White cathode followers have their max distortion at the lowest load impedance. Or maybe you want something that is closest to the load you are going to use, 300 [Ohm] for example. Anyway I think you are going to find most (but little) distortion on the second harmonics especially in high-gain mode.

 

Big question remains how measured figures translate to perception...

Yeah, but speaker impedance is complex (reactive), not predominantly resistive so a resistor is not a representative load anyway.  So I don't think it terribly matters if it's 220 or 300 or 470, as long as it's not 22 or 1.2k.  Ballpark is close enough.  Ideally, I'd measure the RMS current and use an adjustable resistance so for any given test frequency the current is matched at a particular volume and gain setting using a particular set of headphones.  But that's too much work.  I wanted a set of characterization of my Aune T1 before and after I replace the power caps.

 

The Valhalla 2 and Bifrost combo driven either by USB or optical form my MacBook Pro is indeed very clean, with a scattering of minor distortion products, mainly harmonic.  This is unlike the Aune T1 which starting at 1kHz has harmonic distortion at 2x and 4x, but worse has non-harmonic distortion almost equal to the harmonic at 3x and 5x.  These are at about -50dB give or take 5%.  This is undoubtedly why it sounds shrill.  At 8kHz it behaves as if it's starting to take on a step shape; the frequency spectrum diffuses and it shows a hint of warbling.  This then continues up the scale and at 10kHz the warbling is quite obvious in the wave shape.  It also has a spike at 320kHz and another spike further up, I didn't pay too much attention but it might be 1.5MHz.  The Bifrost Uber and Valhalla 2 with Telefunken E88CC tubes by comparison is a marvel of signal fidelity and spectral cleanliness!

post #134 of 824

If you like to consider complex loads too, you could measure the output impedance against frequency. All the reactiveness is ideally sinked by a low output impedance. That is actually one of the improvements between Valhalla and Valhalla 2, the update can sink more current from the load.

post #135 of 824

I'm not really going to spend much time on the Valhalla 2... it sounds great to me so why bother.  No reason to go looking for things wrong with it.

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