JC2012Doomday - The High Efficiency Version of JLH1969 Class-A - diyAudio
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Old 21st March 2012, 03:30 PM   #1
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Default JC2012Doomday - The High Efficiency Version of JLH1969 Class-A

Hi,

For those interested in JLH1969 but dismayed by the difficulty of designing the PCB and handling the Heat, here is some good news. The modeling, experiment and listening result is very encouraging. I name it JC2012 Doomday. JC2012 distinguishes from JLH1969 in that the former can work in Class A and/or Class B. While JC2012 maintains nearly all the good characteristics of JLH1969, it is much more efficient than JLH1969. Just like JLH1969, JC2012 uses only 4 discrete semiconductors. The -3db frequency is from 20Hz to > 5MHz. The distortion component is predominantly 2nd harmonics. The quiescent current through the output pair is only 35mA. If anyone is interested in this design, please feel free to contact me or reply this post. Enjoy DIY. Click the image to open in full size.

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Old 21st March 2012, 05:01 PM   #2
La Mer is offline La Mer  China
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here say hi. read your post in hifidiy. this schematic was started by millwood already many years ago. it came with one pair FET as output.
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Old 22nd March 2012, 12:30 AM   #3
kp93300 is online now kp93300  Malaysia
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Hi

I am interested in this circuit .
How is the sound compared to the JLH 69?
thanks

kp93300
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Old 22nd March 2012, 12:54 AM   #4
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What is more, this design doubles the gain of a JLH class-A. So that you can get rid of a pre-amp and get more than 50W directly from a CD other portable music source.
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Old 22nd March 2012, 12:55 AM   #5
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Hi, listening experience is very pleasing, satisfactory. The sound was at least as good as a JLH class-A.
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Old 22nd March 2012, 01:12 AM   #6
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Quote:
Originally Posted by La Mer View Post
here say hi. read your post in hifidiy. this schematic was started by millwood already many years ago. it came with one pair FET as output.
This does not use a mosfet output pair, although the PCB alows both mostfet, and BJT or darlington. This is an improved design of John Linsley Hood's simple class-A. Thanks for your interest.
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Old 22nd March 2012, 02:08 AM   #7
kp93300 is online now kp93300  Malaysia
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jazzclassics,
the schematic is very difficult to read
what is the power supply requirements , power output and what the gain ?
thanks

kp93300
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Old 22nd March 2012, 02:50 AM   #8
GregH2 is offline GregH2  Australia
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Yes, looks interesting. Please post a larger schematic
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Old 22nd March 2012, 03:50 AM   #9
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Quote:
Originally Posted by kp93300 View Post
jazzclassics,
the schematic is very difficult to read
what is the power supply requirements , power output and what the gain ?
thanks

kp93300
A clearer schematic. This is the one that use to verify the prototype. It basicly leverages the advantages of darlington to archieve better current gain at the output stage, such that the amp works fine in class A/B. JC2012's close loop gain can be varied from 20db to 40db, although I found that 29db to 30db would be satisfactory. This is one of the major advantages over Hood's simple class-A.
JC2012DarlingTon2N3055.JPG
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Old 22nd March 2012, 04:46 AM   #10
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With JC2012, you can get rid of the pre-amp along with the bulky heat sink. That said, I have to recognise here that class-A has its own merit. So if you want to hear the best sound and not mind to waste some power on heat, then go for JC2012 class-A. You can also make a little change arround R1 and R14 so that it can switch between class-A/class-B at your will.

Last edited by jazzclassics; 22nd March 2012 at 04:49 AM.
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