This is not L20SE, is it.
There won't be any issues with L20SE.
Additionally, I do not recommend purchasing 2SA1943 2SC5200. 99% of the 2SA1943 you want to purchase in China is fake.
And there are many authentic TTA TTC 5200 products.Of course, MOUSE should be no problem.
In fact, fake power tubes are almost impossible to measure the difference.
If the oscilloscope can detect a problem. That must be a problem with the circuit. It's not the difference between true and false transistors.
This is a design issue. It's not a matter of authenticity. Basically, counterfeit products will have cheaper models modified to sell with higher power. This cannot be measured using an oscilloscope to distinguish.
You can only distinguish it by breaking it open and looking at the chip.
I have done tests before. Fake goods even perform better than genuine goods. Because its power is smaller.
The characteristics of transistors determine. Transistors with lower power. There are better performance indicators.
For example, TO92>TO220>TO3P。
So we don't want to use an oscilloscope. Or instruments. To determine the authenticity of the power transistor.
Because this method itself is wrong.
Because of different transistors. It cannot change the performance indicators of the amplifier.
Even cheap transistors. It has better specifications than expensive transistors.
For example, A 1941 performs better than A 1943.
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What problem do you need me to help you solve。
I've been saying it all along. I don't understand English.
I use Baidu translation software.
If I could help any of you. I would be happy to.
I've actually built a few of these and some others from LJM and have had zero problems with them. They have been in operation since 2021. Mine do not get hot and sound comparable to some of my old school audio equipment. So if you want to criticize, have a solution, please!
https://www.diyaudio.com/community/threads/power-amplifier-ljm-l20se.321025/post-6864660
The only problem i had with ljm boards for many years now was with this KEC power transistors,they burned very easy,don't sound good & have so little cpacitance when measure C-E pinouts <1nf (very small die).Unfortunately can't change the output transistors without modifications to other components.Mr Ljm recent years following the advice of some experts from this forum became more mature,with very good schematics.L20 V10 is one example but what a shame that using the useless KEC transistors.So we need an L20 V10 with good brand name transistors.
I usually comment from the perspective of a third party.
Actually, the KEC power transistor was just a transistor that I accidentally purchased. After measurement. Medium quality.
And there are no counterfeit goods. It is still acceptable.
In addition, there are also versions of L20V10 that use other power transistors. For example, NJW0302G and NJW0281G.
You can see the NJW power tube version at the agent. Perhaps some agents did not provide this version.
But regardless of the use of any transistor. They have no effect on the effect.
Because the function of the output power transistor is only a current buffer. That is, the current amplifier.
It does not have the function of voltage amplification. It will not affect the effect.
So as long as the quality is good, it's fine. There is no difference if it is not damaged.
No,no....the power transistor affect the sound quality...at mx50 se board years ago i change the KEC transistors to some Toshiba i had at hand & the sound improved a lot..
Charles Kettering:
“A problem well-stated is a problem half-solved"
What I have made public isn't criticism at all, just plain facts. Yet, you have the right to perceive it as criticism.
Meanwhile, I have performed more tests and measurements and do intend to publish them. The problem still exists whether we want to be aware of it or we ignore it. It is still there.
Perhaps, there is someone among us who can solve the problem in hand.
If testing at lower voltages
Current sources are not going to be ideal.
So only assuming DC offset could be negative voltage.
Non inverting amplifier likely to ring on negative rail.
Amplifier rings on positive rail.
What is DC offset on output?
Non inverting amplifier should have positive offset
You have mentioned experimenting with different
transistors. Did you change T0-92 packages?
I see schematic with NCC pinout for N package 5551
maybe used for layout reason.
If you have changed transistor, not recommended
unless you use correct pinout.
NCC has ECB pinout.
different from other 5551
which is usually EBC
If you plan to use amplifier at 34 volt rails.
Would likely need to change some resistor values
to make currents sources at correct value.
Current sources are not going to be ideal.
So only assuming DC offset could be negative voltage.
Non inverting amplifier likely to ring on negative rail.
Amplifier rings on positive rail.
What is DC offset on output?
Non inverting amplifier should have positive offset
You have mentioned experimenting with different
transistors. Did you change T0-92 packages?
I see schematic with NCC pinout for N package 5551
maybe used for layout reason.
If you have changed transistor, not recommended
unless you use correct pinout.
NCC has ECB pinout.
different from other 5551
which is usually EBC
If you plan to use amplifier at 34 volt rails.
Would likely need to change some resistor values
to make currents sources at correct value.
I know what you mean.
90% of people believe that the output transistor has an impact on the effect.
But I still have to say. Don't focus on the output transistor.
We can ignore it. Because its impact is very small. We should focus on areas with greater impact.
For example, input transistors. Input capacitor. Or on the voltage amplifier. Instead of a current buffered output transistor.
Don't worry LJM, I will publish more measurement results so you will be able to see real deficiencies of L20SE. Diverting attention with nonsense conversation will not deprive people of important information.
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Meanwhile, LJM has injected in this thread 9 (nine) completely unrelated posts and consequently, has shifted important information into the state of the complete oblivion at the penultimate page. People usually read the first and the last page
I understand him, he has tangible interest to maintain turn-over, but you, future and past clients, members of this community, have the Right-to-Know.
There were several posts in this thread that indicate problems with this amplifier board. Earlier, it was reported that quiescent current should not be increased over 15 mA. Rallyfinnen has indicated that:
Below, I have shown a couple of representative measurements. Before publishing this I have assured that the presented results are really objective and repeatable. I have measured four boards, one was pre-built with all components provided by the seller. In all other boards I have replaced "genuine" TTC/TTA output devices with original Toshiba 2SA/2SC transistors purchased from Mouser. In one board I have replaced practically everything with genuine components. I have even tested the use of TIP31C/TIP32C in place of the original drivers. Everything has ended with the same result.
At low power the amplifier behaves normally but the increased output power results in asymmetric oscillation. This board oscillates at the positive side of signal. Quantitatively, the oscillations are quite substantial.
Now, please refer to two snapshots shown below. Measurements were taken at 17.8 Vrms, RL 8 Ohm and rails +/-34,5 V. I have presented enlarged snapshot of oscillations (in blue color) to show the real nature of the problem. You can observe significant distortion of the signal.
For me, this amplifier is useless.
More measurements follow.
Quote
I understand him, he has tangible interest to maintain turn-over, but you, future and past clients, members of this community, have the Right-to-Know.
There were several posts in this thread that indicate problems with this amplifier board. Earlier, it was reported that quiescent current should not be increased over 15 mA. Rallyfinnen has indicated that:
Indeed, this board suffers from serious deficiencies. I am sorry for bringing bad news, but it is what it is: this board was sold by presenting fake-news, almost perfect "measurements". My measurements indicate that his is far from the truth. Quite the contrary.
Below, I have shown a couple of representative measurements. Before publishing this I have assured that the presented results are really objective and repeatable. I have measured four boards, one was pre-built with all components provided by the seller. In all other boards I have replaced "genuine" TTC/TTA output devices with original Toshiba 2SA/2SC transistors purchased from Mouser. In one board I have replaced practically everything with genuine components. I have even tested the use of TIP31C/TIP32C in place of the original drivers. Everything has ended with the same result.
At low power the amplifier behaves normally but the increased output power results in asymmetric oscillation. This board oscillates at the positive side of signal. Quantitatively, the oscillations are quite substantial.
Now, please refer to two snapshots shown below. Measurements were taken at 17.8 Vrms, RL 8 Ohm and rails +/-34,5 V. I have presented enlarged snapshot of oscillations (in blue color) to show the real nature of the problem. You can observe significant distortion of the signal.
For me, this amplifier is useless.
More measurements follow.
Quote
Meanwhile, LJM has injected in this thread 9 (nine) completely unrelated posts and consequently, has shifted important information into the state of the complete oblivion at the penultimate page. People usually read the first and the last page
I understand him, he has tangible interest to maintain turn-over, but you, future and past clients, members of this community, have the Right-to-Know.
There were several posts in this thread that indicate problems with this amplifier board. Earlier, it was reported that quiescent current should not be increased over 15 mA. Rallyfinnen has indicated that:
Indeed, this board suffers from serious deficiencies. I am sorry for bringing bad news, but it is what it is: this board was sold by presenting fake-news, almost perfect "measurements". My measurements indicate that his is far from the truth. Quite the contrary.
Below, I have shown a couple of representative measurements. Before publishing this I have assured that the presented results are really objective and repeatable. I have measured four boards, one was pre-built with all components provided by the seller. In all other boards I have replaced "genuine" TTC/TTA output devices with original Toshiba 2SA/2SC transistors purchased from Mouser. In one board I have replaced practically everything with genuine components. I have even tested the use of TIP31C/TIP32C in place of the original drivers. Everything has ended with the same result.
At low power the amplifier behaves normally but the increased output power results in asymmetric oscillation. This board oscillates at the positive side of signal. Quantitatively, the oscillations are quite substantial.
Now, please refer to two snapshots shown below. Measurements were taken at 17.8 Vrms, RL 8 Ohm and rails +/-34,5 V. I have presented enlarged snapshot of oscillations (in blue color) to show the real nature of the problem. You can observe significant distortion of the signal.
For me, this amplifier is useless.
More measurements follow.
Quote
I didn't realize the problem you mentioned.Meanwhile, LJM has injected in this thread 9 (nine) completely unrelated posts and consequently, has shifted important information into the state of the complete oblivion at the penultimate page. People usually read the first and the last page
I understand him, he has tangible interest to maintain turn-over, but you, future and past clients, members of this community, have the Right-to-Know.
There were several posts in this thread that indicate problems with this amplifier board. Earlier, it was reported that quiescent current should not be increased over 15 mA. Rallyfinnen has indicated that:
Indeed, this board suffers from serious deficiencies. I am sorry for bringing bad news, but it is what it is: this board was sold by presenting fake-news, almost perfect "measurements". My measurements indicate that his is far from the truth. Quite the contrary.
Below, I have shown a couple of representative measurements. Before publishing this I have assured that the presented results are really objective and repeatable. I have measured four boards, one was pre-built with all components provided by the seller. In all other boards I have replaced "genuine" TTC/TTA output devices with original Toshiba 2SA/2SC transistors purchased from Mouser. In one board I have replaced practically everything with genuine components. I have even tested the use of TIP31C/TIP32C in place of the original drivers. Everything has ended with the same result.
At low power the amplifier behaves normally but the increased output power results in asymmetric oscillation. This board oscillates at the positive side of signal. Quantitatively, the oscillations are quite substantial.
Now, please refer to two snapshots shown below. Measurements were taken at 17.8 Vrms, RL 8 Ohm and rails +/-34,5 V. I have presented enlarged snapshot of oscillations (in blue color) to show the real nature of the problem. You can observe significant distortion of the signal.
For me, this amplifier is useless.
More measurements follow.
Quote
Has anyone else noticed any issues with L20SE. It seems that no one has ever told me.
Many people in China use it. They all have oscilloscopes.
Or you want to tell me. How can L20SE be modified better? Or is there a problem?
This is also a lot of people. Including the reason why I did not reply to you.
Because we don't know what you want to express.
If you have any methods to make L20SE better. It can be said directly.
It doesn't need to be so complicated. Nowadays, people rarely use BBS because their time is limited.
Also, I want to remind you. Do not purchase pirated L20SE
There are many blue and red L20SEs online that are fake.
L20SE uses many non-standard parts. Fake goods do not work properly.
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Actually, 90% of amplifiers. Cancelling the output transistor can also be used normally.
For example, the MX50SE uses B649+D 669 to drive B817 and D1047.
If we cancel 817 1047 and only use 649 669. Actually, it can still work normally. And the effect won't change much. Just don't output too much power.
So we can judge. The impact of the output transistor on the amplifier is very small.
No, I do not think I can improve anything, my knowledge is too modest to do that.
You are the expert and I appreciate that. I just wanted to report my observations, nothing more. Additional observation, good or bad doesn't hurt, just widens our knowledge. I have always been honest and straightforward in expressing myself. Based on my experience, it can be painful, but in longer run people respect frankness.
Now let's get back to the measurements because I have observed some progress.
Fortunately, oscillations occur at higher power. Perhaps people listen and test at lower power and this problem went unnoticed.
However, the good news is that I have observed tendency that oscillations fade slowly with time, especially when I push the amplifier really hard. I can really push it very hard on a large heat sink and 400W dummy load. I hope that this is the sign that L20SE just needs more time at higher temperatures to burn-in.
I will leave the amplifier at 100W output overnight. I hope this is just a case where it takes longer to burn-in the amplifier. That would be a great news.
It is late here and I will go to sleep now. Soon it will be morning in China, so:
Good morning my dear LJM, with all due respect
Believe me. I really didn't realize what you said.
L20SE is a very simple circuit. Its main structure comes from the amplifier circuit of SELF
The output structure adopts the three-level output structure of LME 49810. So theoretically, I can't find any problems.
Also, do not replace the components. Especially TIP41C cannot be used,The driver transistor can only use the following three types. 2SA1930, KTA1659, KTB1369, 2SC5171, KTC4370, KTD2061。
There are no requirements for output transistors. You can use any transistor you can find.
It is also not recommended to replace the output transistor. There won't be any difference.
I usually use TTA1943 or NJW0302G
and some capacitors may have aged.
Try not to use capacitors with early production dates. I usually use the Electrolytic capacitor produced within 3 years.
Some customers prefer to use capacitors produced in Europe decades ago. This is likely to cause a malfunction.
Especially at different temperatures.
I suppose the blame for any oscillations should fall onto the manufacturer, but also to some extent - on a potential buyer (DIY-er).
Have a look at the PCB layout and see if you are happy with the way things are laid out. If you're not happy, don't buy the PCB.
If you can't/don't know how to tell.... examine very closely the Japanese amps' PCB layouts - their (Marantz, for example... especially the phono stages... but also the power supplies/power supply/regulator sections) PCB design is perfect.
Have a look at the PCB layout and see if you are happy with the way things are laid out. If you're not happy, don't buy the PCB.
If you can't/don't know how to tell.... examine very closely the Japanese amps' PCB layouts - their (Marantz, for example... especially the phono stages... but also the power supplies/power supply/regulator sections) PCB design is perfect.
There are many agents here who purchase goods and sell them to various countries.
So I don't specify a specific merchant. You can find your own merchants. Just email me his website for confirmation.
My email is LJM_LJM@FOXMAIL.COM
Because the address I sent may not be the cheapest.
When you receive the product. You can also take photos and confirm with me via email. Is it genuine. If not. You can apply for a refund.