Headphone amplifier for HiFiMAN HE-6

[jimvibe]

heaveno,

I have been very interested in QRV08, considering it can drive AKG K1000 as stated in the other forum post. I accidentally came across this article: http://www.changstar.com/index.php/topic,1395.0.html The person states that QRV08 wasn't quite able to drive HE-6 headphones. Is this technically true? It's surprising it can work with AKG K1000 just fine (which should require more power), but not with HE-6.

Thanks,
Jim

[peranders]

I'll have to check what 83 dB means in sensitivity. Is it at 1 mW or? The question is how many dB's you think is enough.

[jimvibe]

We have two amps, one of which can drive the headphones reasonably loud and the other can do twice as loud. We matched the volume levels and the first one was clearly lacking a bit of bass. My friend was able to blindly tell which one is which even if I changed the volume slightly to confuse him before switching an amp. Also the first amp could be adjusted louder so that its bass level was equal to the second amp, but it's treble and mid-range was unbearably loud. Why does the bass degrade even though the volume is pretty high from the technical perspective?

[peranders]

When you mean twice as loud, do you mean at clipping level or? If the gain is too low you can easily change it.

Driving the headphone with 100 ohm output impedance will create a bass hump and create a certain sound.

[jimvibe]

Yes, the second amp was able to drive these headphones twice as loud at the clipping level. So the first one had the volume almost all the way down, the second one only half the way and they sounded equally (based on loudness). They have different gain levels also as far as I understand. But it's interesting that the one that was close to maximum amount of gain (the less powerful amp) wasn't able to have as much bass as was required, so it sounded thin (although still loud enough) I am not sure if it couldn't supply enough current or voltage.

[peranders]

When I do my calculations...

83 dB at 1 mW

93 dB at 10 mW

103 dB at 100 mW

113 dB at 1 W

116 dB at 2 W (clipping level at QRV08)

You mean you listen to sound levels around 120 dB and over?

I checked a Sennheiser headphone and that one has 114 dB at 43 mW (1 Vrms /23 ohm), quite a difference. If you compare those products you have a huge difference.

[jimvibe]

I believe I compared those two amps at around 90dB. I am confident QRV08 will be able to drive HE-6 to high level, I am just worried that the bass might be lacking since I have witnessed that with another amp already. When do bass frequencies suffer? Is it voltage or current lacking?

[peranders]

You have  of course current limits which also has to do with the overall design including the power supply. I think also this can be connected to the headphone itself and possibly psycho acoustical effects.