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Per-Anders QRV-03
May 23, 2003 at 11:25 AM Thread Starter Post #1 of 23
hwmj0024

hwmj0024

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Hi, everyone!!
I'm Hyun Joon Rho, DIYer in South Korea.
It is my first post in Head-Fi.
Several Weeks ago, I saw Per-Anders's QRV-03 at his homepage.
I was very curious about its sound, So I had made up my mind to build it... and built.
I just mention what I have modified and result shortly due to my English.

1. I used +/- 12V power
(virtual configuration using TLE2426 and JRC4556 Op amp)
and omitted Input DC coupling capacitors.
2. replaced R11,R12 with 1K trim pots to adjust current..
3. replaced BD139, BD140 with 2N2905A, 2N2219A..
(I built another QRV-03 using BD139, BD140)
Compared both QRV-03s, I think later is more stable
and better sound.
4. replaced LT1115 with OP07CP Op Amp.
(It is hard to get LT1115 in Korea)
5. set output-current(idling Current) with 30mA approximately.
adjusted value of R17(10R) and R18(10R) with 60R.
(This value was set by increasing step by step, 10R~60R)
6. A measured value of the Headphone Terminal's DC is 0.2mV~0.6mV.
It is comparatively difficult to adjust Headphone Terminal's DC,
but It's possible to set minimum DC by balancing two R11, R12(1K trimpots).
7. - Listening QRV-03 -
Although it is very subjective and hard to describe my experience in English, Sound is so clear and rich... In a single word, Excellent!!!
This QRV-03 gives me the most satisfaction among what I have built 19 kinds of DIY Headphone amps.

Lastly, I am very grateful to Per-Anders.

-- QRV-03 Link (Per-Anders Homepage)
http://home.swipnet.se/~w-50719/hifi/qrv03/

-- QRV-03 Link (Korean Website, QRV-03 pics that I built)
http://www.headphoneamp.co.kr/bbs/vi...esc=asc&no=188

http://www.headphoneamp.co.kr/bbs/vi...sc=asc&no=1038
 
May 23, 2003 at 12:06 PM Post #2 of 23
Nice pictures you got there. Too bad I am a Chinese not able to read the comments on your forum!!

Well done!
biggrin.gif
 
May 23, 2003 at 2:53 PM Post #3 of 23
Hyun, glad you liked the design but I'm also amazed that this design is totally dismissed by others. I can't see why if it's done right.

Have you "tweaked" the compensation parts anything? My values were only start values (220R and 22 pF).

I helped a friend to make an Alexander amp similar to the original . The amp worked really good and I still think the idea is good.

It's a shame though that this design is protected by a US patent 5097223. Send me a message if you don't can get hold of it by yourself.

Before I get permission from Analog Devices to use this design I have a low profile in make professional pcb's. I doubt that I never will get permission because american lawyers are many and keen on making money and the guys at AD are really slow if they are at home at all.

Hyun, could you give links to your other projects? It's hard to navigate at your "home forum".
 
May 23, 2003 at 3:53 PM Post #4 of 23
 
May 23, 2003 at 4:23 PM Post #6 of 23
I am drooling.Make one for me free?
biggrin.gif


Kidding, look at how it is connect, very expert terminating points.
 
Sep 2, 2003 at 7:15 PM Post #9 of 23
You guys get some nice, unique casework, knobs, jacks, etc in korea. Is any of it internationally available?
 
Sep 2, 2003 at 7:45 PM Post #10 of 23
Quote:

Originally posted by Nisbeth
P-A, there was an article about building a Mark Alexander-amp in High Fidelity around 1994-1995, have you read that?


Yes, but I got very quite about this amp. Didn't they use IGBT's which many at diyaudio.com don't like. I am also a little bit skeptic over this type of transistor.

The pros about the "Alexander amp" is that it's very easy to get going. The korean guy used my "desktop design" and succeeded right away. The only thing that need some thought is the current offset adjustments.
 
Sep 10, 2003 at 8:03 AM Post #11 of 23
I have now got permission from Analog Devices to your their patent of the "Alexander amp" so maybe there will more people than Hyun Joon Rho in South Korea who can get excited....

Quote:

Although it is very subjective and hard to describe my experience in English, Sound is so clear and rich... In a single word, Excellent!!!


The thing which is left is to tweak the offset current in the current mirrors. Some kind of current servo will fix that.
 
Jan 28, 2004 at 11:57 AM Post #14 of 23
Some reviews would be great.

Peranders, on your webpage I saw that the component-list for the QRV-03 you can donwload is called qrv02 and in e.g. the exel-file also the name QRV-02 is used. Is that OK or is there some mistake?
 
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