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Old 16th January 2002, 03:01 AM   #1
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Location: boston
Default DOZ Headphone amplifier

Hi!
Has anyone built the ESP project 70?
http://sound.westhost.com/project70.htm
It is a headphone amplifier based on the Death of Zen preamp from the same author. Only the output transistors are changed. I'm building a preamp (the Doz preamp...) with a headphone amplifier. Since they both operates at the same voltage, it would simplify things a lot if I choose those two circuits.
I'd like to make sure that the DOZ for headphone is a VERY good design. I'm not going to build thousands of those so it has to be good the first time!!! Any other circuits/ideas are welcome.
Thanks alot
David
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Old 16th January 2002, 04:42 AM   #2
paulb is offline paulb  Canada
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I'm going to try building the DoZ headphone amp (I have the boards already). Note that it draws a lot of current for a headphone amp, I think about 300 mA. I really want a Class A amp for my headphones, though, so I'm going to try this and compare it with a Class A FET design I've already built (the "Szekeres" amp). The FET amp also draws about 300 mA, but it runs from a +15V supply.
For my DoZ headphone amp, I'm building one channel using complementary transistors and reversing the electrolytics so I run both channels from a +/- 25V supply (slightly less than the 30V recommended).
An alternative you might consider is just an audio grade op-amp like the OPA2134. The headphone amp I'm currently using is based on this and performance is excellent, at least into my 300-ohm phones. You can run these op-amps from a single supply if you use an output capacitor and derived ground arrangement.
If you aren't aware of it already, this site has a wealth of information on headphone amplifier projects and a discussion group similar to this one:
www.headwize.com
The Szekeres amp I mentioned comes from here, and there are tutorials on amp design, etc.
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Old 16th January 2002, 04:59 AM   #3
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I saw the headwise site but all the design there are not using the same power supplie as the DOZ preamp I'm building with this headphone amplifier...I would need either two transformer or use a bunch of regulator. The DOZ headphone has the same power requirements as the DOZ preamp. I'd just like to make sure it's a good choice
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Old 16th January 2002, 05:21 AM   #4
paulb is offline paulb  Canada
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Okay, just be aware that the headphone amp uses a Lot more current than the preamp, so the power supply requirements may be the same voltage but you would have to size it a lot bigger to handle both.
You could run an op-amp based headphone amp from the same power supply if you have a small power supply.
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Old 26th February 2002, 06:11 AM   #5
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I just found this site/forum and am actually listening to a DoZ Headphone Amp - ESP P70 that I finished building over the past couple of weeks. I'm using it with Senn HD580's and can honestly say I love this thing!!! When warmed up, it is sonically superb! It's built on Rods PCB's. Trannies used are; input: NTE159, drivers:- NTE373's and outputs are TO3 2N3055's. All transistors were matched between the channels, and the output transistors Q5 were selected to have a slightly higher gain than the current source Q3. All resistors were Dale RN55D 1% metal. Power comes from a 2x8.1V 4A toroid ($6 surplus) with 12000uF cap followed by a capacitance multiplier, which gives the amp a 24V rail when set at the 330mA per side quiescent point. It's absolutely silent with or without an input connected. Comfortable listening level for the high impedance HD580's is about mid way on a 100K input volume pot - there's bags of overhead if you want to go deaf.
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Old 26th February 2002, 01:21 PM   #6
paulb is offline paulb  Canada
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Thanks for the report, I may build one of these someday - I have the boards already.
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Old 1st March 2002, 11:32 AM   #7
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A little more detail on the amp I built and pictures at: -

http://www.head-fi.org/forums/showth...?threadid=8443
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