L12/2 version 5
Many hours later, we have a provisional circuit. Still need checking, we don't want to publish an inaccurate circuit. Don't worry about testing. It's more of an instability rather than an oscillation. Not the kind that draws amps. A major influence on use is C2 a 100pf cap. If reduced to 47pf, the board becomes much more stable. Please don't start modifying your boards. The problem has not yet been solved we are still working on it. I welcome input from anyone that is actively working on this problem. I wonder if LJM knows?? He should be the one to sort it really. More as available. The layout on this board is dreadful.
Many hours later, we have a provisional circuit. Still need checking, we don't want to publish an inaccurate circuit. Don't worry about testing. It's more of an instability rather than an oscillation. Not the kind that draws amps. A major influence on use is C2 a 100pf cap. If reduced to 47pf, the board becomes much more stable. Please don't start modifying your boards. The problem has not yet been solved we are still working on it. I welcome input from anyone that is actively working on this problem. I wonder if LJM knows?? He should be the one to sort it really. More as available. The layout on this board is dreadful.
Hello Michael,
I'm already looking forward to the circuit miracle - please post the proposal.
All this hype always reminds me of the sudden appearance of disposable lighters in supermarkets in the late 1970s.
Take it and throw it away, that was the motto.
Furthermore, you are absolutely right, the Asian kits should always include the correct wiring diagram /the schematic - that's the way it should be.
Have fun with reverse engineering,
greetings
HBt.
I'm already looking forward to the circuit miracle - please post the proposal.
All this hype always reminds me of the sudden appearance of disposable lighters in supermarkets in the late 1970s.
Take it and throw it away, that was the motto.
Furthermore, you are absolutely right, the Asian kits should always include the correct wiring diagram /the schematic - that's the way it should be.
Have fun with reverse engineering,
greetings
HBt.
Good afternoon .. I have just been testing these boards and got about 90 watts out of them @ 8ohms but I did not see any oscillation on the scope.. I have not used square waves yet only sine waves but they seem clean to me..
Any pointers on what to look for, I did hear a muted crack from somewhere when I pushed the boards but did not see any smoke etc. Probably the dummy load resistor as it got real hot!!
Thanks Wayne+
Any pointers on what to look for, I did hear a muted crack from somewhere when I pushed the boards but did not see any smoke etc. Probably the dummy load resistor as it got real hot!!
Thanks Wayne+
Quick update. I did more testing with square waves and fried the NJW0281G transistors.. Will order some new ones and finish the testing.. Not sure why but I was not really pushing the amp board that much.. I will wait to see what Michael Beeny comes up with and go from there.. Happy New Year to all.. Cheers Wayne
I was making enquiries to a seller on AliExpress. I did not want the VERSION 5 as I have read many warnings about it on this site. Here is what he says.
As far as I can make out, the seller is saying WHAT IS ACTUALLY DIFFERENT on the version 5 boards, rather than suggesting component changes in points 1-6?... Here, below, is a direct paste of what I was told:
VER5 version is improved compared to VER4
1 Replace the low-power transistors B649 , D669 with the medium-power transistors A1837,C4793,2.
2 Increase the quiescent current of the driving power transistor from 6MA to 18MA.
3. Add a radiator to the medium power tube.
4. Add the static current adjustment function of the output power tube to make the static current of the two circuit boards on the left and right channels equal.
5. Use an electronic filter to replace the previous RC passive filter to reduce input stage interference.
6. Change the input stage mode to increase the input impedance. Improved low-frequency performance.
Maybe the Version 5 IS BETTER?
As far as I can make out, the seller is saying WHAT IS ACTUALLY DIFFERENT on the version 5 boards, rather than suggesting component changes in points 1-6?... Here, below, is a direct paste of what I was told:
VER5 version is improved compared to VER4
1 Replace the low-power transistors B649 , D669 with the medium-power transistors A1837,C4793,2.
2 Increase the quiescent current of the driving power transistor from 6MA to 18MA.
3. Add a radiator to the medium power tube.
4. Add the static current adjustment function of the output power tube to make the static current of the two circuit boards on the left and right channels equal.
5. Use an electronic filter to replace the previous RC passive filter to reduce input stage interference.
6. Change the input stage mode to increase the input impedance. Improved low-frequency performance.
Maybe the Version 5 IS BETTER?
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More information in the other thread.
Thanks for the link jxdking. Yes it seems I have chosen the wrong thread to put my message on. The L12-2 Ver 5 thread has taken off elsewhere rather than on this one.
L12-2 version 4 is a fine amplifier, but appears that version 5 is a failure.
Here is the real problem: boards are produced and have to be sold. Both boards are sold as L12-2. What if you get version 5 instead? Are you going to complain. Would you send it back to China? Are you eligible to refund?
But you've got your L12-2 they might reply, even the latest, improoved version, they could argue.
Anyone experienced this?
I think the version 5 is the end of otherwise fine product.
Here is the real problem: boards are produced and have to be sold. Both boards are sold as L12-2. What if you get version 5 instead? Are you going to complain. Would you send it back to China? Are you eligible to refund?
But you've got your L12-2 they might reply, even the latest, improoved version, they could argue.
Anyone experienced this?
I think the version 5 is the end of otherwise fine product.