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Old 12th October 2007, 12:00 PM   #1
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Default headphone amplifier

Hi to all,
i have MBQuart QP400 dinamic heapdones
http://www.mbquart.com/en/produkte/p....php?nr=qp_400

i want to make extremely good amplifier for them....
so far i know that they are 300 ohm phones that are extremely hard to drive......
so far i have tried few desings that wer not good enough to drive them..... (some of them were tube designs, some of them were solid state using bjt's and some of them also using opamps)....

if someone would like to make extremely good amplifier to drive 300ohm headphones what should he look after in order to make it....what design approach (i would like bjt's to keep things small)......
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Old 12th October 2007, 12:15 PM   #2
00940 is offline 00940  Belgium
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This: Audiovalve RKV schematic (hybrid headphones amp) will drive your headphones without a sweat (it drives the AKG K1000 with ease). But it's neither bjt nor small...

Btw, the crappy opamp they use can be changed for an opa627 with some compensation cap. Make a search on head-fi for this.
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Old 12th October 2007, 12:16 PM   #3
paulb is offline paulb  Canada
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Pick one of these:
http://headwize.com/projects/index.htm
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Old 12th October 2007, 12:34 PM   #4
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the problem is that i do not know what to pick.....

i do not know if my headphones will work the best with high current class A or some class AB project.....or what...this is the problem....
they need something that is very dinamic with hugh soundstage and that can drive without a problem 300ohm headphones - not to be loud but to "drive" them..... i can make a small power amplifier to drive them but would this be o.k.
i am lost here that is the problem....and i am trying to seek a solution on a more quicker way (i hope),..
they like tubes on a high current (for tubes)... but something that has tubes is very big - i need something smaller.....
using bjt's or mosfets or combo....or something...
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Old 12th October 2007, 12:38 PM   #5
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nice project that one with tubes and opamps......


i would like the guys that are using headphones with 300ohm impedance to tell me what they are using for amplifiecation...something good and mean

that can drive 300ohms.........and is physically smaller if possible than 20kg monster i made last....
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Old 12th October 2007, 12:48 PM   #6
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Not sure what would make them that hard to drive. 300 ohms is easy, unless they have some huge inductance or something. I'm pondering the same question right now, but our answers will likely be quite different. I want class A, and to try some circuit topologies I haven't tried before.

Something you might try- if you have a power amp in your system that you really like, with a common ground, make up a voltage divider/pad with a very low value to ground, say 0.1 to 1 ohm. For the upper resistor use something around 10 to 30 ohms. The output impedance of the pad will be the two values in parallel, essentially the lower resistor. The idea is to run your power amp at a more normal level to get out of the grunge, plus present a low Z to the phones. Use 2W resistors for testing. Connect the phones and see how that sounds. If you have a conventional amp, and don't like the sound, you should probably build a class A something-or-other, or maybe even question if you have the right phones for your taste.

BTW, 300 ohms is high enough you could even parallel two or three of the new National opamps (with some low value sharing resistors) and drive them to about any level you wanted with no problem. Or any other opamp of your choice.
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Old 12th October 2007, 01:00 PM   #7
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Thanks Conrad,
i have tried opamps - i do not like them ....i do not know why....i like discrete better.....

the idea with the resistor and power amplifier is interesting - i will try it during the weekend....will see what will pop out....

i am also not sure why they are so difficult - they have very nice sound but constantly i feel that they can open more and have more air in the sound ....and when i make something that is better than some easy-made headphone amplifier i can hear the difference very clearly but i have never stumbled on a circuit that will make them breed fully.....and they accuse them for being to much bright - where, how?...i do not know - since i need to have them be brighter (actually open)..i do not need tone controls....

i really need monster of headphone amplifiers - a mother of them all.......
Grado still beats them regarding being open...they are not open like Grado - why.... but i like more their type of sound ... it suits me better but again they need to open just a bit more.....and using something reasonable in size....

probably i am not clear at all....man!!
hard to tell what is still a feeling.....



maybe better to say....gimme a monster in quality, in detail, in stage in performance and gimme that to drive my 300 ohm headphones.....
something like that - suggestions.....

maybe something to construct - a topology - an idea what might work but was not done (maybe using bjt's).....oh man....
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Old 12th October 2007, 01:29 PM   #8
Zen Mod is offline Zen Mod  Serbia
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why don't you ask few days ago..........

solution is brutally simple

HERE

you can even make jfet version - known as Aleph J Mini , or Babelfish mini

btw- driving 300 ohms is easy, comparing to ,say, 70 ohms of AKG K270 Studio
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Old 12th October 2007, 01:42 PM   #9
00940 is offline 00940  Belgium
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300 ohms is neither easy nor difficult to drive, it all depends how sensitive the headphones are. The 400ohms AKG K340 I had for long was way more difficult to drive than my Grado SR225 (32R).

Links towards "monsters" :

http://www.amb.org/audio/beta22/
http://www.djgardner.com/headphone/gilmore/ (scroll down to Dynahi)
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Old 12th October 2007, 01:47 PM   #10
paulb is offline paulb  Canada
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Quote:
Originally posted by Zen Mod
...solution is brutally simple ...
Maybe you could post a link to the schematic for our friend, instead of just a review.
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