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JLH 10 Watt class A amplifier
JLH 10 Watt class A amplifier
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Old 6th June 2021, 02:28 PM   #8061
hanair is offline hanair  United States
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JLH 10 Watt class A amplifier
Looks like my amp is oscillating even with TIP41C. Anybody here used the following PCB with any NPN power transistors? Next I need to replace my switched power supply with a regular one.
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Old 6th June 2021, 04:12 PM   #8062
OldDIY is offline OldDIY
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2sc2705 e-k-b npn https://static.chipdip.ru/lib/310/DOC000310064.pdf
2sa970 e-k-b pnp https://static.chipdip.ru/lib/947/DOC005947869.pdf
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Old 7th June 2021, 02:33 AM   #8063
hanair is offline hanair  United States
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JLH 10 Watt class A amplifier
I could remove oscillations by shorting R1. R1 is in series with the input coupling capacitor (coupling capacitor is C1 on this board which is actually C4 in JLH's original schematic). I used some arbitrary (but low k) for R1 and apparently that is not required as per JLH! Before I can test it with speakers, I need to re-assemble the board that I was playing around with.
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Old 14th June 2021, 09:41 AM   #8064
bistvan1980 is offline bistvan1980  Hungary
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JLH 10 Watt class A amplifier
Default Join the team.

Hello! I will join the team.
Original Motorola 2N3773 is the output. (saved from old industrial power supply)
My test version schematic:
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File Type: jpg JLH 4W.jpg (137.1 KB, 314 views)
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Old 14th June 2021, 11:26 AM   #8065
OldDIY is offline OldDIY
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At 12V and 8 ohms, it is enough to set the current to 0.8-0.9 A. The power will be 1.5 watts.
Some used BD911.
MJE13007 can also be used at the output. For a driver, their characteristics are not quite suitable. But it will work)))

Last edited by OldDIY; 14th June 2021 at 11:35 AM.
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Old 14th June 2021, 11:47 AM   #8066
bistvan1980 is offline bistvan1980  Hungary
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JLH 10 Watt class A amplifier
Hello! It is currently in an experimental phase.
I haven’t measured it yet, I roughly calculated 4W music peak power.
I put it together quickly based on the circuit diagram.
It sounds good and 1.5W RMS is enough for me. I'll replace the transistor in it, that's all it was at home.
I'm sending some pictures:
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File Type: jpg DUT 4W Class A.jpg (299.7 KB, 266 views)
File Type: jpg MOT 2N3773.jpg (65.9 KB, 267 views)
File Type: jpg not finished double reflex.jpg (121.2 KB, 261 views)
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Old 14th June 2021, 12:00 PM   #8067
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Suitable radiators, correct position (vertical). If you want and use a more powerful power supply and a higher voltage (up to 27 V), you can build an amplifier according to the author's specification.
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Old 14th June 2021, 12:11 PM   #8068
bistvan1980 is offline bistvan1980  Hungary
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JLH 10 Watt class A amplifier
The 24Vac can be used with these transformers. Can be used up to 2.5A.
Voltage regulator is not a problem. LM317T (or 7824 (?)) with PNP power transistor.
I'm interested in the thing.
I have 6pcs 100VA 230V/30Vac hypersil transformer. 30Vac is too much, I can to make lower voltages.

Last edited by bistvan1980; 14th June 2021 at 12:23 PM.
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Old 14th June 2021, 12:37 PM   #8069
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24V AC will give 32V DC (no load). The surplus can be used to operate a stabilizer or a capacitance multiplier. Or DC-DC converter.
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Old 14th June 2021, 01:36 PM   #8070
bistvan1980 is offline bistvan1980  Hungary
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JLH 10 Watt class A amplifier
Maybe unwind from the secondary to about 22Vac(100VA 30V hypersil).
I am thinking hard about bringing step-down SMPS into the system.
Result: negative. 3-7V drop analog regulator is more sympathetic.
IQ=1,3A is enough for 24V(dc) stable / 10W 8 Ohm?
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