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Liquid Spark's ASR measurements do not match the manufacturer measurements..

LegionOfHell

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Notice that Liquid Spark's measurements indicate that at 300 ohms the max power output is 314mW and at 33 ohms, Max power is 2400mW:

Screenshot-2021-04-30-091940.jpg


Amir's measurements show that at 300 ohms, max power is 174mW and at 33 ohms, max power is 1540mW....

Can someone explain why this is ?
 

KSTR

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Amir defines the power at the point where distortions starts to rise significantly (kink in the curve) no matter how low that is in absulute terms, which is not according to "industry standard" of looking at the power where distortion has raised to 1%.
The difference is negligble in practice. A factor of two in power is a factor of 1.42 in voltage. In voltage terms this is only 3dB less and perception-wise its again less, some 2dB. This means twice the power is only perceived as 25% louder.
Plus, by the point you max out the power you're going deaf anyway.

EDIT: ASR measurement are in full accordance with Mfgr. spec here. -40dB is 1% and at the point where Amir's curve would intersect the -40dB line you'd have ~250mW and ~2.3W.
 

Cahudson42

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Purely subjective as I have no way to measure, but my LS drives my new 18 ohm HE5XX in low gain mode beautifully. IMO. No distortion I detect. Plenty of Headroom. Driven by LG V20 in 2v mode..
 

3125b

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"industry standard" of looking at the power where distortion has raised to 1%
I wouldn't necessarily call that an industry standard - every manufacturer seems to do it differently wich is kind of annoying.
Topping specs the power at 0.1% for their headphone amps, RME 0.001%. And it varies between categories, speaker amps are often specced at 1%, some at 10%. And then there are the companies that do whatever the hell they want like Denon who spec some devices at 0.08% and others at 0.7%.
 

KSTR

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@3125b, The whole concept of power specs is flawed IMHO. And why...because power goes with voltage squared and that makes it overly sensitive to even minor changes (like supply voltage in power amps). If we assume at full power/voltage we are a) dealing with levels that are deafening already and b) you don't have any headroom left for even the smalles peak it is clear that is not a good metric. Amir's way of rating falls apart for example with amps that have professionally designed soft-clipping. On paper, using either the start of the kink or an arbitrary threshold like 1%, 0.1% or whatever ,such an amp will always look like being inferior to the same amp design without soft-clipping and probably with a very nasty clipping recovery. But in actual use, it's the other way round, the soft-clipping amp has way more apparent (and actually usable) power output than the one without.
 
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LegionOfHell

LegionOfHell

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Ok, so I have a Creative X7 with the following power outputs:

Max power output at 32 ohms: 1,328 mW
Max power output at 50 ohms: 850 mW
Max power output at 300 ohms: 142 mW
Max power output at 600 ohms: 71 mW


Can X7 drive most of the audiophile headphones in the market ? Or should I consider buying a separate Headphone amplifier like Liquid Spark which has the following power outputs:

33 ohms: 2400mW
56 ohms: 1531mW
150 ohms: 614mW
300 ohms: 314mW
 

amirm

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Can someone explain why this is ?
What you post doesn't say if both channels are driven or just one. I always drive both channels. Note that there is incredible pressure for manufacturers to inflate these numbers as much as they can so it is not wise to put much stock in them. My measurements as noted show when a design starts to operate outside of its own criteria. Anything beyond that becomes marketing (within a margin).
 
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LegionOfHell

LegionOfHell

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What you post doesn't say if both channels are driven or just one. I always drive both channels.

It must be per channel, 314mW into 300 ohms...which means 2x314mW...your measurements is 2x174mW ?
 

amirm

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It must be per channel, 314mW into 300 ohms...which means 2x314mW...your measurements is 2x174mW ?
Why do you say it must be? If it is the other way around, then it is the same as what I measured (within accuracy error).
 
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LegionOfHell

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True. But this also happened with your Schiit Magni/Heresy review:

On Schiit's website, it is said that at 300 ohms the amp's power output is 410mW RMS per channel ... but your review says max power at 300 ohms is 274mW ??? Can someone explain why this is ?

I guess your measurement does not consider the power beyond a certain amount of distortion ?
 

MZKM

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On Schiit's website, it is said that at 300 ohms the amp's power output is 410mW RMS per channel ... but your review says max power at 300 ohms is 274mW ??? Can someone explain why this is ?

I guess your measurement does not consider the power beyond a certain amount of distortion ?
Correct. Amir states the power when the distortion starts to rise considerably, regardless of the distortion %.

The Heresy is rated at 410mW RMS into 300ohm, but has no mention of distortion level.

In Amir’s measurements, he states 274mW and that is at around 0.0005%, at 0.01% we actually see it does indeed reach 410mW.

I drew it in purple:
94F25E72-B578-4B7A-8370-99C54FEF7B8F.jpeg


Here is Schiit’s graph:
70D24ED9-F67B-4E69-8360-C821B7983DEB.jpeg



At 300ohm and if my math is right, 410mW would be 11Vrms, assuming 2Vrms input sensitivity (Amir fed it 2V and it output almost 2V).
 
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VintageFlanker

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I guess your measurement does not consider the power beyond a certain amount of distortion ?
I'm sorry, but you need to look a touch closer to understand THD+N Vs Power graphs.;) @amirm marks power as "before clipping", not "peak" power at <1% for exemple.

Your "410mW" are in there:
Schiit Magni 3+ and Heresy Headphone Amplifier Comparison High Gain into 300 ohm Audio Measure...png


Note that horizontal scales up to 500mW.

Édit : @MZKM just explained better!
 
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amirm

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On Schiit's website, it is said that at 300 ohms the amp's power output is 410mW RMS per channel ... but your review says max power at 300 ohms is 274mW ??? Can someone explain why this is ?
That is well within the measurement differences. The knee of the curve is quite sharp and you could inch forward little by little to squeeze a higher number. You can do that from my graphs yourself, visually interpolating. Or not bother since it makes little difference in practice.
 
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