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Help needed calculating wattage/voltage output...

post #1 of 14
5/17/10 at 6:20pm
Thread Starter 

Reading the specsheet for the Opera Consonance Cyber 20 headphone amp, I see that it is rated to output 1 watt into 32 ohms, while no specs are given for voltage output. I am a dummy when it comes to the ins and outs of amplifier design, so I ask: Is there a way to estimate what the Cyber 20's wattage/voltage output will be into a 120 ohm load? I'm wondering if the Cyber 20 will put out enough enough juice to drive my AKG K-1000 earspeakers (which requires about 1 watt and around 11 volts, I'm told)...  Thanks in advance for any help!

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post #2 of 14
5/17/10 at 6:50pm

1W = V * ( V / 32)

V = 5.66V

 

Since K-1000's sensitivity is 74dB/mW, @ 1000mW:

10log(1000) = +30 dB

 

Thus @ 1W, 104dB SPL.


Edited by udauda - 5/18/10 at 12:12am
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post #3 of 14
5/17/10 at 7:12pm
Thread Starter 

The capability to produce 104 db peak SPL should provide more than enough dynamic headroom, right? There is no doubt in your mind that the Cyber 20 will drive the K-1000's adequately? Is it possible that some aspect of the circuit design could cause the Cyber 20 to wimp out while driving the K-1000's? Sorry, but I've searched the archives and I cannot seem to find anything related to the synergistic match between the Cyber 20 and the K-1000's... Thanks, again.

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post #4 of 14
5/17/10 at 7:22pm

a0014291_4a71918902630.jpg

 

According to OSHA, the most moderate noise standard among others, you shouldn't listen to K-1000 @ 1W for longer than an hour per day. So yes, it is being adequately driven, at least power-wise. 

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post #5 of 14
5/17/10 at 7:42pm
Thread Starter 

I would probably do most of my listening at average SPL levels that are down in the 80's. If the Cyber 20 amp is truly capable of driving the K-1000's to peaks of 104 db SPL, that should leave enough dynamic headroom for the musical peaks present in a good recording. We might agree that, theoretically, the amp should work with these headphones. But, my final question would be: Do you know of any reasons why the "real world" performance of the amp might fall behind it's "theoretical" capabilities?


Edited by Michael G. - 5/18/10 at 12:44am
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post #6 of 14
5/17/10 at 8:00pm

 

We need to take a look at the full spectrum of objective parameters to determine that- but I do not see any reason why a conventional amp should fall behind unless it's defective. (watch out for clippings tho)

 

Yet, personally, I do not expect much linearity from a tube amp. :$

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post #7 of 14
5/17/10 at 8:03pm
Thread Starter 

Very good info - thanks so much for your help in this thread. I might give the amp a try...

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post #8 of 14
5/17/10 at 8:54pm

Michael, udauda, there is some misunderstanding…

 

Here we go…

 

 

1W into 32 Ohms is 5.657 V RMS (and it will draw a peak current of 250 mA)

 

5.657 V RMS applied to 120 Ohms (i.e. the K1000) is 267 mW (and it will draw a peak current of 67 mA)

 

267 mW applied to a headphone with a sensitivity of 74 dB at 1 mW will result in a sound pressure of approximately 99 dB

 

Hope this helps,

L.

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post #9 of 14
5/17/10 at 9:12pm

Oh yes! This certainly got me confused LOL:

http://wiki.faust3d.com/wiki//index.php?title=Image:K1000_2_Page_10.jpg

 

10log(1000( 5.657 / 120 ) * 5.657) = +24 dB

74dB + 24dB = 98 dB SPL

 

I guess we're good for 2 hours then.


Edited by udauda - 5/18/10 at 2:27am
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post #10 of 14
5/18/10 at 10:55pm

udauda, those charts refer to average sound pressure level, not peak. The calculation of 99dB SPL is the maximum SPL you can expect from that amp/can combo. In properly mastered music, the peak SPL can be more than 20db higher than the average.

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post #11 of 14
5/18/10 at 11:48pm

Quote:

Originally Posted by b0dhi View Post

udauda, those charts refer to average sound pressure level, not peak.

That's quite true, however 'calculating your exposure':

http://midimagic.sgc-hosting.com/spldose.htm

 

The peak level should be an adequate reference for hearing safety nonetheless, especially if the music you listen to are the victims of loudness war.

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post #12 of 14
5/19/10 at 4:00am

That's true, but my god I hope nobody is using the K1000 to listen to music which is so compressed

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post #13 of 14
5/19/10 at 11:30am
Thread Starter 

Thanks for the comments, bOdhi. BTW, 99 db is pretty loud for headphone use, don't you think? Do you think I am correct in making the assumption that "average" comfortable listening levels would be around 80 - 85 db. SPL? I think that I listen at volume levels similar to this in my home loudspeaker setup, which allows for approximately 20 db. of dynamic range expansion for musical crescendos (or "peaks"), above the average volume level. Anyways, if I buy the Cyber 20 amp and it works out well with the K-1000's, I will be sure to post something about it here at Headfi... Thanks.


Edited by Michael G. - 5/19/10 at 4:32pm
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post #14 of 14
5/19/10 at 5:39pm
Quote:
Originally Posted by Michael G. View Post

Do you think I am correct in making the assumption that "average" comfortable listening levels would be around 80 - 85 db. SPL?

 

 

Yes, seems about right. I would put an estimated guess at about 70 - 85 dB for most people.

 

Keep in mind though that the amp is likely to be quite distorted at peak output. I don't have any objective proof of that, just going on experience of cheap mass market asian tube amps in general.

 

Or maybe I just heard some bad examples. The guy at positive-feedback.com seemed to like the Cyber 20.

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