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Old 7th October 2011, 12:12 PM   #11
rjm is offline rjm  Japan
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Quote:
Originally Posted by davygrvy View Post
See the chart (hope it is readable) ->
I see an I-V plot with constant-power curves indicated, but the individual headphones would plot as straight lines on such a graph (as V = I Zheadphone) rather than individual points, unless a output level was specified (120 dB for example) which I don't see written anywhere.

My calculation (for the record) went as follows:

Typical line level is 2 V rms. Max. My "very loud" volume setting on the headphone amp, for line level input with the HD600's, is such that together with the amp gain, the total signal gain is unity. So the "typical music power" (-20 dB) is 0.1 mW, with clipping peak (0 dB) at 13 mW. For 16 ohm phones, the current required is 6 times larger but the power will be the same provided the sensitivity is comparable. Some headphones are less sensitive than average, but a push-pull class A amp can always slide into class AB to cover the peaks.

So most of the time I'm using less than 1 mW, but 10-20 mW could conceivably be required on transients. 50-100 mW is already overkill, but diy'ers are rarely put off by that word.

Enjoy your amp, it looks like fun.
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Old 7th October 2011, 05:25 PM   #12
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Yes, a straight line from zero (assuming pure resistive) to the points indicated. The data came from here. I took max power and impedance and plotted for volts and current. In essence, a headphone amp to handle any set of phones needs to do 9Vrms and 275mA.
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Old 7th October 2011, 06:03 PM   #13
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For HD600s, 300ohm @ 80mW calculates to 4.9Vrms and 16mA
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Old 7th October 2011, 07:14 PM   #14
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Listening level I don't like to exceed has 5V peaks (that's 10Vp-p if you're counting) and measures around 1Vrms into my 25 ohm Denons. That's 200ma peaks.

From that, calculate power if you want to, but I've never found power as a measure of any significance except to derive back to V and I, which are the important ones. I called a local sound company once to rent some amps and spec'd him volts at a minimum load and he couldn't understand me until I talked watts.

I don't exceed that level because I can hear the distortion of my crappy CD player smearing the mids

Guess what my next project is?
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Old 8th October 2011, 12:27 AM   #15
Mikett is offline Mikett  Canada
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I'm out. I was planning to use some older Improved Sulzer regulators to power the headphone amp. The Sulzers can't supply that kind current.

I found I had a couple AD844 while rummaging through the stuff and a couple AD811. I guess I'll go the composite op amp route per Walt Jung on this one. I imagine coupled with the Sulzer power supply it should sound half decent.
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Old 8th October 2011, 12:49 AM   #16
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you shouldn't need a regulated supply
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Old 8th October 2011, 12:57 AM   #17
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Mikett, I can spare some chassis parts if you want: heatsink, sides, to-3 mounts, and a top and bottom. There doesn't appear to be enough room for the power supply though, but I haven't tried yet
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Old 8th October 2011, 01:02 AM   #18
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shoot.. after i'm done with this version, I'm going to have to sell it to recoup expenses
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Old 8th October 2011, 03:31 AM   #19
Mikett is offline Mikett  Canada
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Thanks

but the thought was interesting before I came to my senses with a headphone amp with a large current draw. Shucks these days I'm switching off my printers!

I gotta pass , too much "stuff" that was what prompted me to go through my stash of stuff left over.
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Old 8th October 2011, 04:04 AM   #20
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Quote:
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I'm out. I was planning to use some older Improved Sulzer regulators to power the headphone amp. The Sulzers can't supply that kind current.

I found I had a couple AD844 while rummaging through the stuff and a couple AD811. I guess I'll go the composite op amp route per Walt Jung on this one. I imagine coupled with the Sulzer power supply it should sound half decent.
composite multiloop amps can have high loop gain which translates to high PSRR

further, you can sub regulate the input op amp supply which doesn't see any load with simple Zener shunts for even more ridiculous PSRR in the composite amp

silly complex PS regulation should be reserved for "simple" discrete circuits that have no PSRR of their own
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