chip amps are built from transistors too. So the knowledge is for all kind of amps.

Step response tests are great for finding amplifiers that are on the verge of instability. It is a great tool recommended by many amplifier designers.

This could have been a great amplifier! But this is what you get when you copy directly from the datasheet, it's not a readymade solution, you have to actually read the datasheet to find out where you are going to need to put in a lot of research and development, the Chinese must be wondering why no one else is building this? The circuit is right there for everyone to see! But if I build this exact thing, which I could have easily, I have the software, I have all the tools necessary too, but do I have the time and skill to get it working correctly so that it doesn't destroy your speakers? Where I'm from, I would have to replace your speakers and provide you with an amplifier that works or refund your money, then there's compansation for the inconvenience that my product has caused you... Does any of this apply to the Chinese? I'm guessing that the answer is no! If you are lucky, you might get a 50 cent refund! But at least you can keep your speaker killing device with your toasted speakers... Nice 👍

That would be awesome. Heard the older Uber version and I did like it, but I'm very interested in less expensive regular UCD400 or ICE amps for DIY multi channel amp.

They use a 100uf and 100k resistor in the mute circuit for delay. The time constant seems to be enough to eliminate the turn on pop.

@@JohnAudioTech Ah! Missed that when I looked at it the first time.

Most probably an old, used capasitor. I have found similar, even dryer ones... in new chinese gear...

It probably wouldn't matter, but I'd treat them as if they're not bridged.

@@JohnAudioTech Thank you

I don't have a scope but I added those components to my point to point build as without those amps sounded grainy. Adding those helped, on TDA2030As I used only caps those muffled highs noticeably.

@@Tegelane5 There's a trade-off between actually getting the gain down far enough to allow some immunity to oscillations and RF interference, and actually killing the gain in the audio band. If the impedance of the compensation network is low at audio frequencies, it will kill off the high end gain. You can use free spice simulators to see what the response of the amps will be, and help with selection of any external compensation. Another approach is to include RF decoupling capacitors at the input. These should be chosen to be about 10x the impedance of the input network to the amplifier at 20kHz. If your using something like a 20kOhm volume potentiometer, the impedance will be about 10kOhms. A suitable capacitor would be 47pF across the input to each channel of the amp IC. That will usually provide good RF rejection above about 200kHz, keeping noise out of the amplifier and combined with the 1uH inductor at the output will help prevent RF oscillations.

@@Tegelane5 I used the simple RF decoupling caps at the input on my build, which also has a flyback switch mode power supply integral to the amplifier PCB I made, and that seems to do a good job of keeping the hash out of the audio when suitable star-point grounding is used.

Probably a pretty bad ground loop.

To elaborate a bit more, since the PSU is powering both the PC and the amplifier you will have severe ground loop issues as the sound card and the amplifier will share multiple ground paths thru both the audio cable and the power supply itself at both the amplifier input and power supply. The resulting offset in ground voltage will appear as an input, and at the very least will be amplified as though it were a signal. Combined with poor decoupling of the power supply this will cause it to oscillate wildly. Since the other power supply you tried it with is likely isolated, the input of the amplifier will be floating, so there is no DC path for ground loops at the input. If you just want it to work you can include an audio isolation transformer to break the coupling between the sound card and the amplifier input, but if its noise from the PC bus thats the issue it wont help much. A more involved solution is to use an on-card isolated DC-DC converter to create a local isolated supply for the amplifier, but thats somewhat involved. But from my experience since the PC generates so much noise its best to use an external amplifier with its own fully isolated supply, so there is no easy path back to ground for the noise and DC currents. Also watch out for using a large 50/60Hz transformer as the shunt capacitance is easily high enough to allow higher frequencies through and cause interference in the audio. Best bet is to either use a screened transformer, or a clean SMPS that will fully isolate the power.

In most cases (not all), they copy the sample circuit from the data sheet and remove those extra components, (e.g. standby) then make the board without measuring or testing, they know a few component missing or value not correct usually didn't affect the operation, they definite need to send the boards to John (same cases for Siglent sent an oscilloscope to Dave Jones for test), a FREE ADVISER for them!

No one is going to give you the circuit that's already been perfected! If that were the case, you would only be able to get the datasheet accompanied with a license. Everything that you need to get this amplifier up and running is in the datasheet, if you read closely, you will also find the key areas where you need to pay special attention to make it work properly, but you are going to need to do some experiments and a lot of testing to get it to work correctly! Some Chinese person took a look at the datasheet and thought, oh wow they just gave us the complete amplifier! I just have to copy it and before you know it, it's on eBay! It takes a lot of work to get an amplifier circuit working correctly, that's why no one else was building them and palming them off on eBay, but the Chinese don't care if you destroyed your speakers! It's not like you can do anything about it! And that's why videos like this are extremely important! Supporting channels like this keeps the bastard's honest! They will keep making this junk until we stop buying it.

@@PeterMilanovski I agree with you 100% Peter, my channel is full of faulty amplifiers PCBs that claim the world and often offer little. But once in a while I find something that's really quite good, it can happen. Probably 1 in 5. The sad thing is with just a few minor changes can make all the difference. I guess we never learn, we keep buying. It is a very steep learning curve.

@@MichaelBeeny I just might have to give your channel a visit then... There's no such thing as a topic being repedative as long as the content provider can add at least one thing that someone else didn't, then that's good enough for me!

@@PeterMilanovski Thanks Peter, hope you find something of interest.

It's not. They are not the same behaviour.

@@johnyang799 I meant the clipping at the bottom of the waveform, after all oscillation and bad behavior is removed at the end of the video. I've seen other LM3886 clip the bottom of the waveform the same way, and assumed it must be the protection circuit activating

@@maxhifi1232 I know what you mean. But that's not the behavior of SPiKe. It's power supply decoupling related. SPiKe behaves much more aggressively. It also activates at or after the voltage peak. It works by sensing the temperature of a internal resistor as a better equivalent of SOA protection.

They can run in parallel with v small resistor at the output of each chip, no bridging option as far as I know. But I didn't try it. The notes should show the schematics.

Both channels of the dual NE5532 opamp chip are used. The jumper appears to bypass only one of them. To eliminate the preamp from the circuit you would have to remove the NE5532 chip and input the signal where the final preamp output was.

@@JohnAudioTech thasnk you for the prompt reply! this particular board has some hissing on it. its barely noticeable in the listening chair. but i wanna mod it to see if i can lower it down still . so i was wondering if its the opamps gain is the source or there is a problem with the design of the power supply section . i already removed the fake main filter caps and swapped in 2 genuine 8.2 k uf nippon chemicons. and i also added the LC network at the output.

if its not too much to ask. im a noob to this so excuse my ignorance. but i was wondering if you can show me where to solder the input underneath to bypass the preamp section completely?

Bypassing the feedback resistor with the cap alone might make the amp oscillate at high frequencies as they are not compensated for low gain. I'm sure they had good reason for adding it. It cuts the gain in half at high frequencies, probably at the the cost of phase margin.

Oh how much times have not changed.

The only thing real was the new plastic wrapping on the capacitor.... Nah, that was fake too!

They are truly artists at faking capacitors. The fake one measures just like the real one =))

No effect observed.

@@JohnAudioTech it's about sqare wave test with lower, real life loads, 4 ohms or less... Btw are you a member of diyaudio.com? This is not a platform for "chating" 😁 cheers.

I've heard that in China, there are "domestic" version of these ICs.

Systematic.

@@1959Berre I figured no one would get the reference.

Why it destroys speakers like lightning ⚡. Oh look at what you have done now! Can't get the bloody song out of my head...

Ring is a form of damped oscillation.

Genuine CE (China Export) quality.

As explained in the last video, ICs weren't fake.

@@johnyang799 it was conjectured. They could just be very good fakes though.

@@1pcfred hmmm

@@1pcfred I can't be 100% sure but I believe these are authentic. The Chinese use counterfeit die of smaller size for less cost. Not having the room for proper output transistors on the counterfeit die, I find the fakes struggle with heavy loads. Since these were delivering 90w at 4 Ohms, +/-32v supply, they were doing the business. I also see the same notch at clipping in authentic LM3886 ICs.