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.
2012-3-21 23:15
2012-3-21 22:58
2012-3-21 22:58
2012-3-21 22:58
2012-3-21 22:57
2012-3-21 22:57
2012-3-21 22:57
2012-3-21 22:57
2012-3-21 22:57
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.
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2012-3-21 23:15
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2012-3-21 22:58
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2012-3-21 22:58
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2012-3-21 22:58
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2012-3-21 22:57
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2012-3-21 22:57
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2012-3-21 22:57
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2012-3-21 22:57
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2012-3-21 22:57
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An externally hosted image should be here but it was not working when we last tested it.
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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.
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.
Hi, listening experience is very pleasing, satisfactory. The sound was at least as good as a JLH class-A.
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.
jazzclassics,
the schematic is very difficult to read
what is the power supply requirements , power output and what the gain ?
thanks
kp93300
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.
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.
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Hi
How to adjust the gain?
This will be my next project after death of zen !
thanks
kp93300
Thanks for the updated schematic. Looks good, though you have added output drivers which the original JLH lacks. So the circuit is ever so slightly more complicated. It also has miller comp, something not needed by the original.
Have you checked the square wave performance into a capacitive load? All good?
Have you checked the square wave performance into a capacitive load? All good?
These two resistors decide the Ic of the output pairs, ie. the quiescent power of the amp. If you increase the R1 while decrease R14 by the same value, the total effect on the quiescent power should have no change.
The gain is decided by the ratio of R5/R4. Normally, it is between 10 and 40. The JC2012 open loop gain is over 70db, which is 15db more than Hood's 1969 simple Class-A. So you have greater freedom of make your choice of feedback factor. JC2012 design also allow you to build very efficient headphone amplifier, which has design constrains on battery voltage and power consumption.
The slew rate for JC2012 class-B is the only drawback of this design. I have not tested capacitive load. I will post such test result when available.
However, I should clarify that the slew rate of JC2012 class-A is as good as any of today's best commercial amp.
Thanks jazzclassics
Appreciate your comments. I am a great fan of jlh69 and looking for newer designs to try
The high and mid is very different from my other amps such as F5, aleph j and numerous tripath amps.
i am following this thread closely.
thanks
kp93300
Appreciate your comments. I am a great fan of jlh69 and looking for newer designs to try
The high and mid is very different from my other amps such as F5, aleph j and numerous tripath amps.
i am following this thread closely.
thanks
kp93300
Member
Joined 2009
Paid Member
Interesting, can you help me learn more ? ....The input device develops a voltage across R3 which is fed to the base of the phase splitter/driver device. But R19 kind of gets in the middle here, not sure the rationale for R19?
And I don't understand how this design is different from JLH other than the Darlington outputs - the JLH itself does not go nicely into ClassB so what is different here that I've missed which makes this suitable for use with low bias current ?
And I don't understand how this design is different from JLH other than the Darlington outputs - the JLH itself does not go nicely into ClassB so what is different here that I've missed which makes this suitable for use with low bias current ?
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