I've wondered that myself. I also have an LCD-XC and it doesn't start to break-up or "fall apart" as quickly. But I'll have to admit I also have a Burson Conductor and it seems to control the Aeons a little better at high volume (vs the THX789). I think the Aeons pull quite a bit of current.
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WolfX700 Measurement of Topping A90 Headphone Amp
- Thread starter WolfX-700
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MRC01
Major Contributor
How loud an amp can cleanly drive a headphone depends on which limit the amp reaches first: voltage or current.
Method 1: Look at the headphone's voltage sensitivity. That will tell you how loud it is for any given voltage. Compare that to the amp's max voltage output. Then compute how much current the headphone would draw at that voltage (V=IR), and see if the amp can deliver that current. However, that impedance will depend on the frequency (unless the headphone is planar magnetic, which have flat impedance vs. frequency).
Method 2: Look at the headphone's efficiency, which tells you how loud it is for a given level of power. Then check how much power the amp has, at the headphone's impedance. Impedance is important, and leads to the factor that can throw off this approach: conventional headphones have varying impedance at different frequencies, even when they have flat frequency response (voltage sensitivity).
Regarding varying impedance, take for example the HD600. It's rated at 300 ohms, but it's almost twice that at 100 Hz. However, its response (voltage sensitivity) is relatively flat from 100 Hz to 1000 Hz. This means the same voltage produces the same amplitude and SPL at 100 Hz, and at 1000 Hz. But the impedance is twice as high at 100 Hz, so that same voltage draws only half the current, so half the power. If half the power produces the same SPL, it means it's twice as efficient at 100 Hz, as it is at 1000 Hz. Intuitively, you can think of this as the headphone's driver or voice coil wants to mechanically/electrically "resonate" at 100 Hz (more generally, at its impedance peak frequency), so a signal at this frequency doesn't have to work as hard to move it.
Just as good with 16ohm.
Thanks, John. Any more info on ETA?
I can't say for sure. It's in production. So shouldn't take too long.
Thanks so much. That really helped me to understand. Now Hifiman Susvara is a planar so this means that it has flat impedance vs frequency. It is impedance of 60 ohms so R=60. From where can I find that how much power this amp can provide at 60 ohms? Similarly how much current can it provide? From where can I get these values?
MRC01
Major Contributor
The bench test here used 8 V output and it was clean. How loud would that 8V be with the Susvara?
From what I read, the Susvara's efficiency is 83.5 dB / 1 mW and impedance is 60 ohms.
Power is i^2*r so 1 mW of power into the Susvara should be 0.2448 V and 4.08 mA of current, which produces an SPL of 83.5 dB.
8 Volts is 32.7 times more than 0.2448, so that's 20*log(32.7) = 30.3 dB louder. Plus 83.5 makes 113.8 dB SPL.
V = IR, so 8 = i * 60, which means driving 8V across 60 ohms takes 133 mA of current.
P = V*I, so 8 * .133 = 1.067, so this would be 1.067 watts of power.
My guess, the A90 can do that without breaking a sweat. I don't know about you, but my ears simply can't take 113.8 dB SPL, it is painfully loud.
Note: I showed my math so if the data I got wasn't right, you can plug in the right numbers and check for yourself.
From what I read, the Susvara's efficiency is 83.5 dB / 1 mW and impedance is 60 ohms.
Power is i^2*r so 1 mW of power into the Susvara should be 0.2448 V and 4.08 mA of current, which produces an SPL of 83.5 dB.
8 Volts is 32.7 times more than 0.2448, so that's 20*log(32.7) = 30.3 dB louder. Plus 83.5 makes 113.8 dB SPL.
V = IR, so 8 = i * 60, which means driving 8V across 60 ohms takes 133 mA of current.
P = V*I, so 8 * .133 = 1.067, so this would be 1.067 watts of power.
My guess, the A90 can do that without breaking a sweat. I don't know about you, but my ears simply can't take 113.8 dB SPL, it is painfully loud.
Note: I showed my math so if the data I got wasn't right, you can plug in the right numbers and check for yourself.
Thanks so much for taking the time to explain this and doing the calculations. Much appreciated. Yes I don’t listen to anywhere close to 113db, for me 80-85db is enough. I like to preserve my hearing.
MRC01
Major Contributor
PS: @solderdude measured the Susvara and shows efficiency much lower than what I found: 74 dB / 1 mW. That's a big difference: 9.5 dB!
So an 8V signal would produce an SPL 9.5 dB lower than what I computed above, which is only about 104 dB SPL.
If you listen with average levels around 83 dB, you may hear dynamic peaks in the range of 104 dB SPL. As an audiophile you want your peak listening levels to be within your equipment's continuous ratings. So, 8 V output could be considered marginal or barely sufficient for the Susvara, which is a very inefficient headphone.
So, whether the A90 would be sufficient is no longer a slam-dunk. It depends on its max output.
So an 8V signal would produce an SPL 9.5 dB lower than what I computed above, which is only about 104 dB SPL.
If you listen with average levels around 83 dB, you may hear dynamic peaks in the range of 104 dB SPL. As an audiophile you want your peak listening levels to be within your equipment's continuous ratings. So, 8 V output could be considered marginal or barely sufficient for the Susvara, which is a very inefficient headphone.
So, whether the A90 would be sufficient is no longer a slam-dunk. It depends on its max output.
Yes it is one of the most hard to drive / inefficient headphones since the diaphragm is very thin. So the voltage will be the limiting factor then? Because at 60ohms there would be 3-3.5w of power available through this amp? No?
MRC01
Major Contributor
Yah, from what I see in the review, the A90 can put at least 3 W of power into 50 ohms with negligable distortion. If the Susvara is 74 dB at 1 mW, then 3 W is 10*log(3000) = 34.8 dB louder, and 74 + 34.8 = 108.8 dB SPL.
That should be loud enough even for transient dynamic peaks. Anyone who wants it louder should have his hearing checked
The Susvara is unusual, much like the prior HE-6, in being one of the least efficient headphones out there. I don't think that's from having super thin membranes on the driver. It's more about the driver's construction: its wiring and the magnets around it. Essentially its low efficiency comes from low voltage sensitivity requiring high voltage to make it respond, and lowish impedance making that voltage draw more current. The drawback is you need a powerful amp. The benefit is that it is immune from the microvolts of noise that can become audible with sensitive IEMs, and you'll probably be using the upper half of the volume knob range where the pot has the best performance.
For example, consider the 50 mV output test. With normal full-sized headphones like the HD-600 or LCD-2, this produces an SPL in the high 70s to low 80s. With the Susvara, it's only 60 dB - that's a HUGE difference.
That should be loud enough even for transient dynamic peaks. Anyone who wants it louder should have his hearing checked
The Susvara is unusual, much like the prior HE-6, in being one of the least efficient headphones out there. I don't think that's from having super thin membranes on the driver. It's more about the driver's construction: its wiring and the magnets around it. Essentially its low efficiency comes from low voltage sensitivity requiring high voltage to make it respond, and lowish impedance making that voltage draw more current. The drawback is you need a powerful amp. The benefit is that it is immune from the microvolts of noise that can become audible with sensitive IEMs, and you'll probably be using the upper half of the volume knob range where the pot has the best performance.
For example, consider the 50 mV output test. With normal full-sized headphones like the HD-600 or LCD-2, this produces an SPL in the high 70s to low 80s. With the Susvara, it's only 60 dB - that's a HUGE difference.
JohnYang1997
Hello. One question please. You are the right person to ask. Although the rest of opinions will also appreciate them.
I have read opinions of all kinds.
When it comes to powering a headset like the one I have 300 Ohms, an HD800. I am going to combine it with the D90 that I already have.
I would like to know what your opinion in terms of sound quality, if we look only at the output impedance between the A90 or for example the HDVD800 with its output impedance of about 40 Ohms, which is supposed to be the ideal for this headset or at least, the one devised by the manufacturer
¿Could it somehow not take the 100% advantage of the HD800's quality with the A90 for this reason?
Otherwise, I have no doubt that I will be very happy with your purchase for the excellent measurements.
Thank you.
Hello. One question please. You are the right person to ask. Although the rest of opinions will also appreciate them.
I have read opinions of all kinds.
When it comes to powering a headset like the one I have 300 Ohms, an HD800. I am going to combine it with the D90 that I already have.
I would like to know what your opinion in terms of sound quality, if we look only at the output impedance between the A90 or for example the HDVD800 with its output impedance of about 40 Ohms, which is supposed to be the ideal for this headset or at least, the one devised by the manufacturer
¿Could it somehow not take the 100% advantage of the HD800's quality with the A90 for this reason?
Otherwise, I have no doubt that I will be very happy with your purchase for the excellent measurements.
Thank you.
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The difference on hd800 from 40ohm output impedance vs 0.1ohm is very small. Not mentioning the balanced output and unbalanced output of hdvd800 have different output impedance. Meaning, it's not really part of the design of hd800.
One step back, hd800 is not really a good sounding nor accurate headphone to begin with. Hd800s is much better and can sound good on most amps. If you have any other headphones or iems with wobbly impedance you'd better go with low output impedance route. Otherwise if you like the sound of hd800 you mostly wouldn't hear major difference between amps the characteristics of hd800 will remain the same.
Do I really need 6W of power for headphones? I own (and love) HifiMAN Arya which are considered to be inefficient HP (90dB/1mW@1kHz) with 35 Ohm impedance. In the past I used it with Marantz HD DAC-1 which offers less than 1W and I never used hi gain. Currently I am using it with Schiit (don't ask ) Asgard 2. It offers 1W and I set vol knob on 12 o'clock during listening. When i go 100% at low gain it is uncomfortably loud. going close to max at hi-gain causes audible bass distortion - it is too much for Arya. And it is 1W. What's the point of such power from headphone amp? I am just curious. From my point of view it is unwanted possibility of damaging headphones. Currently I am considering either DX7Pro or D90+A90. I find second option really cool because of way it looks like but is there any sensible reason of this choice over DX7Pro in my case (I am not going to use Susvara)?
) Asgard 2. It offers 1W and I set vol knob on 12 o'clock during listening. When i go 100% at low gain it is uncomfortably loud. going close to max at hi-gain causes audible bass distortion - it is too much for Arya. And it is 1W. What's the point of such power from headphone amp? I am just curious. From my point of view it is unwanted possibility of damaging headphones. Currently I am considering either DX7Pro or D90+A90. I find second option really cool because of way it looks like but is there any sensible reason of this choice over DX7Pro in my case (I am not going to use Susvara)?
MRC01
Major Contributor
That power can be useful for headphones that are less efficient than yours, like the HE-6 or Susvara. These headphones are the exception, and 1 W of power -- even 250 mW -- is sufficient to drive most full size headphones to ear bleeding levels. Keep in mind that power to volume is not linear. 6 W is only 7.8 dB louder than 1 W, which is only 6 dB louder than 250 mW.
What I find most impressive about this A90 is its low noise, especially at low to moderate volume settings where it matters. Looks like it has the highest 50 mV SNR we have yet seen. Significantly better than the DX7Pro, and a difference you might actually notice. That's probably closest to a "sensible reason" as one can get with any audiophile purchase.
Yeah, I am aware that power is not linear but as you said - most of headphones will be ok with milliwatts. But ok, there are few headphones that will not - maybe A90 is aiming them. Regarding low noise - good point, thanks.
shadymilkman
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Will the A90 and D90 be sold together as a set?
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