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Old 11th November 2007, 09:42 PM   #1
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Join Date: Dec 2003
Location: brussels
Default CK2III headphone amp problem

hello,

i have just completed my ck2III;

listing to it revealed a flaw.

i have on the left channel beautiful sound
on the right i have a dc of -11v (which is less beautiful).

i have eliminated everything exept the parts on the pcb (so it is not an input, volumepot, or output phone plug problem)

i use 2sc2238 and 2sa968 and not the standaard ones.

what could be the cause of this ?

(the led burns, and the +15/-15 test path is okee).

thanx a lot people
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Old 11th November 2007, 10:14 PM   #2
Gordy is offline Gordy  United Kingdom
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I don't know enough about discreet circuits to help, however for anyone wanting to help the schematic of the amp can be found here:

http://www.amb.org/audio/ck2/
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Old 12th November 2007, 06:38 PM   #3
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Location: brussels
thanx gordy,

i don't know exactly what caused it, but i found three problems, a wire was broken to the headpone plug (probably from flexing to much in my search for the problem)
(the opamp was not giving good contact, so i sometimes had sound and somethimes not.
(i replaced bjt's to see if that was the problem, but soldered them wrong, oeps, no prob, replaced them and everything was okee)

but everything is working fine now

greetings
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Old 13th November 2007, 10:09 AM   #4
awpagan is offline awpagan  Australia
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then_dude

What output devices are you using?

If BD's are hard to get, you could try 2sa1930/2sc5171.

allan
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Old 13th November 2007, 04:11 PM   #5
00940 is offline 00940  Belgium
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Location: Paris
Quote:
Originally posted by awpagan
If BD's are hard to get, you could try 2sa1930/2sc5171.
In Brussels, you can get BD139-BD140-BC560-BC550 from cotubex.
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Old 19th November 2007, 04:26 PM   #6
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i order with rs components.
i had ordered an extra pair.
just for in case (and i have 3 extra ck2III pcb) i lost them in moving, but after unloading everything, they are back. woehoe, but now ? maybe built another ck2III, or a few ?
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Old 19th November 2007, 06:03 PM   #7
awpagan is offline awpagan  Australia
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Quote:
Originally posted by then_dude
(and i have 3 extra ck2III pcb) maybe built another ck2III, or a few ? [/B]

It makes a good preamp too.

allan
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Old 20th November 2007, 11:49 PM   #8
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a good preamp,

indeed that must be the case, i'm really impressed by this little thing. everyday even more, listing like 5 hours a day headphones the last 10 years, this should have come along long time ago.

gotto love the diy people who did all the designing and distributing; great thanx again
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Old 21st November 2007, 04:14 AM   #9
awpagan is offline awpagan  Australia
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Join Date: Nov 2004
Location: sydney
Quote:
Originally posted by then_dude
a good preamp,

indeed that must be the case, i'm really impressed by this little thing. everyday even more, listing like 5 hours a day headphones the last 10 years, this should have come along long time ago.

gotto love the diy people who did all the designing and distributing; great thanx again

The original by Benny
http://hjem.get2net.dk/bencar/kumisa..._headwize.html

Redone by Alex (Runeight) and others.
http://headwize.com/ubb/showpage.php?fnum=3&tid=6605

allan
ps
Did you use 2sa/2sc's instaed of bc's?
Did you match the input pair?

With the preamp, I used the 2sa1930/2sc5171's (pinout 180%) for outputs.
BC were all "C"s and close gains, within hfe of 5
input pair same gain.

different power supply
Used LM317/337's then through JLH filter.
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Old 21st November 2007, 11:52 PM   #10
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well there they are the glorious, the magnificant 2.

yes i used a 2sa968 and a 2SC2238, indeed reverse polarity. i have an akg 500, not a bass monster. i was been told that the original bjt sound warm and bass, but i like the sound more of clear and refined. i was advised the ones i use, and good god, it is a lot of bass, not like all over the place bass, but thight extremely well controled bass, impact all over the headphone, i can hear very silent bass lines or deep organ notes that i never knew that they were there. it is a bit like an electrostatic, no blazing bass, but a very realistic sound of a bass. i'm delighted with it. more bass would be not great, at least not with the akg.

the jfets are matched nothing else.
maybe i should pay attention to that, i think my right channel is a tad louder than the left, but it could be my hearing. i will measure and see if there is a measurble difference,

probably i'll make some new headphone amps, i don't need a preamp at this time. i was thinking on making a balanced CK2III, but people at head fi told me that it sounded worse than the single. maybe i give it a try anyway. but i'll pay attention to the matching of the parts.

at this moment i'm trying to get the best out of my tda1545 dac; it is monica; i have made an ss stage, and fed it 21v, monica gets 12 volt, it is quite impressive the sound.

Still with this combination: monica + CK2III i think i'm seeing the horizon of what is capable sonicly. i mean it is all there, the sound is good, spacious, clear.... still the music isn't there, i mean it is not like i'm into it. maybe speaker has more chance of doing it. but what i mean is: it sounds very very good, : i can listing all day without frustration or headache, but i miss involvement.
maybe it is not airy enough, not real enoug, i donno.

probably i'm gonna look for a new headphone, not that i don't like the akg, i'm an akg fan from the first hour i got a headphone, and this is already like 15 years. but i need one that portrays the details even when it plays silent, maybe i need something better then the 5OO (something like the 701) or i need something closed, cause i hear to much from the outside world.

anyway i'm hacking my own tread. not a good thing.
so i will order some new parts. but i live in belgium, not a great place to source parts you know. getting a dale RN55D is a nightmare. i'm not a freak in these things, but i wanna use good non boutique stuff. like dales, panasonic fm, polyprop caps roederstein. well that's about it for tonight

bye
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