@@bugdrvr I used them in my DIY build amplifier with a bipolar switchmode power supply I designed as well (form factor was too small for a standard mains transformer). They work very well and don't have any real noticeable hiss, which is a bonus. The only downside is they require a positive and negative supply unlike a bridged class-D since they are basically an oversized op-amp, which can make things a little more challenging. Had a hard time finding an off-the-shelf SMPS transformer that would work for my application. Luckily I was able to find one from Wurth that could be repurposed.
Great video, my dude. Planning an amp build using LM3886 chip amps, so it’s good to see that even a poor design/implementation still gives more than decent results. Thanks for confirming the choice of chip for me. Keep ‘em coming, mate.
I spotted something even more egregious, potentially. They left the output relay off the board, so if there is compensation in the feedback network for eliminating the DC offset (which it appears there is), it will have serious turn-on thump issues while its charging the caps in the feedback network.
You convinced me to buy one of these and hear for myself. Its probably too late since that cap is cut open but I would love to see a video of you addressing the atrocious hum from an AC power input like a 25-0-25 transformer. I think the power supply needs rebuilding
It would be interesting to see how it would perform when a bypass cap is installed between VCC and ground right on the chip and a thiele circuit on the outputs
Another great review. I too would like to see inside those caps but also wondered, just out of curiosity, would it be possible to add the improvements you suggested? I'm guessing a decoupling cap near the LM3886 would be easy to add what about the network you mentioned on the output? Perhaps it isn't worth the effort for this amp. Thanks again for the great channel.
Its really only needed as at higher frequencies with the falling 6dB/decade response the amplifier looks inductive at its output, so if there is significant capacitance it can oscillate. With that said, I found these to be extremely sensitive to oscillations and RF interference if the layout is not done well. I kept the layout fairly minimalist with just resistors and RF/decoupling caps to avoid needing a relay on the output, but did include the inductor/resistor on the output side, just in case.
for this kind of Amplifier you can use a red of zobel or even a speaker protection, I guess, cause the diagram to certain point I think it's good, that's my opinion right, great video dude
I would like to know what the preamplifiers opamps do in this circuit. What is the circuit around them telling us? I think it it easy to operate the LM3886 directly from music player or line level outputs.
I'm into a lot of DIY audio amp stuff. But now i want to buy some good quality speakers. I'm buying them for my personal use and intent to use them for long time with good amplifier circuit. Please suggest me should i spend my money for 8 ohm speakers or 4 ohm speakers. Which is better? I know there's no definite answer for this but for which impedance would you spend your money? (Thinking of spending a little too much than usual) Please reply soon.
I do some diy home spkr. With 4ohms woofer you will usually get 2-2.5dB higher out at the same voltage comparing to 8ohm version of the same driver. Other than that Thiele-Small parameters will be a little different, Qes, Qts being usually lower for 4ohm. The coil inductance higher in 8 ohm and will limit upper freq resp. unless it uses Faraday rings in the motor. If you're building own X-overs, the hardest part that requires measurement set up and CAD program for designing proper crossover, inductor sizes for 4ohm woofers will be smaller and caps higher. Of course 8 ohm is easier to drive if something like 3886 is used, but unless you have something with 90dB+ efficiency the volume may not be satisfying (there's usually a 5-6dB drop in low mids, bass so correction for baffle diffraction is used in x-o). Rather than using passive crossovers, DSP based crossovers with multiple amps are really awesome since many of passive crossover limitations don't exist in DSP that have EQ, time alignment, variable slopes capability. Designing a really good passive X-over is a pain.
As said above, you will get a bit higher DB out with lower ohm speakers but also need to make sure your amplifier can happily drive them. My B&Ws drop into the mid 3 ohms at some frequencies and you can definitely hear the stress on some amplifiers with a lack of bass and shouty, bad sounding mid range. Give them good clean power and they sound amazing. I'm a big B&W fan and always suggest checking them out but everyone is different so I'd suggest listening to as many different speakers you can before making a choice. Not easy these days without too many hi-fi shops around and even harder with the virus keeping everyone away from each other but it's worth it.
Hey john, Based on your experience, among lm3886 and tda7294, which gives better bass response and overall better music dynamic. Its ok if its bit colored sound also.
Sometimes i think we have reached the end of the road for analog electronics.....Switching amps (class D) seems to be the trend. As a matter of fact, anything you can do with analog electronics can be done with switching circuitry. Having said that, the LM 3886 is going to be the classic solution for analog amplifiers....Some people prefer them for low distortion audio. Kind of like Compact Discs versus 33 rpm vinyl records.
Hi John. Hope you and your cat are OK. I have tried your LM3886 circuit. Seems to work fine. I have 2 questions. First is, can we use a resistance type inductor instead of coil inductor at the output ? And second is, the circuit is working but sound is very faint. Iam using 21-0-21 volts supply. Is more voltage required for high power output ? Datasheet suggests 28 volts or higher but just a difference of 8 volts is decreasing the sound this much ?
I wonder if there's a nice board made for 4 Ohm Subwoofers. Couple it with a nice 3116 board for Mids and High's I could Make a nice little inexpensive sound system that uses low power but has a big impact
The coil has higher impedance at high frequencies (well beyond audio range) which prevents the amplifier from driving capacitive loads at high frequencies. That can cause instability. Because the coil and capacitance will have resonance, a resistor is connected across the coil to reduce the Q of the circuit.
Thank you very very much Sir !!!Sir can you please do a review of TDA 7498 & also I suggest you sir to do a comparison video series about audio qality, true maximum rms etc. TDA AB class vs TDA D class amplifiers (ex - TDA 7295 vs TDA 7498) Again thank you very Sir !!!I got a great knowledge about audio amplifiers through your attractive explanations included videos !!!
Yay the Gainclone. Had a couple of new Dynaudio Pro studio monitor active speakers being used in an onair sound suite part of a TV News production facility that would randomly suddenly motorboat at full volume.... Caused utter hell live... Anyway they're a warranty job but on account the rohna i replaced the three LM3886 set with GENUINE chips from Digikey. The problem solved. The chips i pulled out had bad smudged labels compared to the clean sharp replacements from DigiKey... Fake chips for sure....
The entire time you are looking at traces ans PCB this horrible noise is coming through.. I keep wonder why you didn't just remove that hard clear film
Are your numbers in peak to peak or RMS? For us guitar players; can something like this function as a guitar amplifier? Could we feed the guitar signal into one channel of this amplifier and use it as a boost to get us to proper input levels for the other channel and end up with a mono instrument amplifier with about half the output wattage? For many of us this would be plenty of watts for a practice amp and we don't need full frequency response given the range of our instruments. It would be cheap guts for homebuilt project.
Instrument amplifiers are different than reproduction amplifiers. There's more to it than just output Watts. I think it is down to the bias? An amp made for playing music is just too neutral. So they tend to lack presence and sound very thin. An instrument amp just has a richer more direct sound to it. Like you're actually there playing. Playing through a stereo it sounds like you're channeling a ghost. John should feature some musical amplifiers to tell us what the secret sauce in them is. But I guess that's not his thing?
@@1pcfred It's called impedance balancing. The simplistic version of a device that does this is a transformer. I have one I use for a microphone to switch from low to high impedance and vise versa. Older record players needed help to get their small signal heard by an amplifier. The record arm pickup outputs about the same as a guitar pickup.
@@1pcfred I made an adapter to plug my guitar into the phono input of a stereo back in the 80's. It worked but it's clean sounding without some pedals in the signal chain.
@@tenlittleindians clean is definitely one way I'd characterize the sound. A bit too clean. It is one of those works but it doesn't deals as far as I'm concerned. Tone is pretty important to a lot of players and one thing stereos don't give you is any tone whatsoever. Any stereo that did add color would get laughed out of the market. So they're designed to not do that. Maybe an old tube amp would be OK? Those are naturally "warm". There's no way around it really. The tube sound is real. I hear some early transistor circuit topographies were pretty bad. They were basically making tube amp circuits and using transistors. There's reasons solid state had a bad rap. Early transistors were pretty bad by themselves. But all of that changed over time. I've made some transistor amps that I think have nice tone. I biased the circuits hard to get it. Made them hot. Not hi-fi at all. More like hi-db Made to play loud at low volume. Had nice feedback. I got a little Marshall amp too and I like mine better. www.instructables.com/id/Transistor-Amplifier-Build/
We know what's inside. Still would be funny to see it though. Cut them WIMAs open too. They're fakes. Like John said the power amp ICs are real. That's probably the only real parts on the board. I suppose imitation is the sincerest form of flattery. They should have made them Black Gate caps. If you're going to go then go all the way.
Wait, Snickers let you plug in the soldering iron without inspection. I swear mine know that the moment I plug it in, they need to do a close up inspection. Long haired cats and soldering irons, wtf ?
those are my favorite chips it is sad that texas instruments does not produce them anymore. So I don't think they were original so as capasitors. P.S. good review.
Experience with MANY fakes tells me that fake audio chips have much smaller output trannies, which for whatever reason tends to cause oscillation issues into 4 ohm loads.
I wish I could find an honest review made on amplifiers with an excellent sound quality....NOT reviews made on scraps! I know it's a really good thing to be warned NOT to buy those AWFUL amplifier boards but I REALLY wish to see something different even if I had to spend more than $100.00 on a board so I could build that Boombox and see everyone want to enjoy some nice music.
@@amitghosh6966 - I am having problems with my internet connection and have lost TWO detailed replies to your question. In summary, the answer depends on the power supply's current capabilities and also whether it is regulated (eg: electronic) or unregulated (transformer based). Power equals Volts SQUARED divided by Ohms... so a bit more voltage provides a LOT more power! On a regulated (electronic) power supply of sufficient power, the peak voltage for music and sine wave will be the same. Therefore (max) power output will be the same for both. On a more realistic regulated power supply with less power, there won't be enough current for continuous sine wave, so voltage will droop under continuous sine wave. Yet the big power capacitors will store enough amps to allow max power on music peaks. Therefore, "peak music power" will be higher than continuous power. On an unregulated power supply, the nominal (rated) voltage is only supplied under full load. When power draw is lower, the voltage rises - the difference can be considerable on a small power transformer. Because the AVERAGE power of music is always lower than for a sine wave, the voltage across the capacitors will rise up much higher accordingly-- this means on music peaks there's lots more power available (because of the V-squared in the equation). I hope that makes sense, as it's hard to answer quickly in a RU-vid comment LOL
@@johncoops6897 1. Does an audio amplifier operated on Single supply and Split supply output same power on both configurations ? 2. How much current can a 12 -0-12 v, 2 Ampere transformer provide ? 50℅ or 75 ℅ of the rated Ampere ?
Why don't you try to address the issues if it is a quick fix and show us how it get improved with simple measures . That would be more of educational and we learn from your skills. After all it is only a 30$ Amp .
7:05 puts capacitor on meter and says "about what they should be".... UMMM - NO. (EDIT, actually YES, read below) The cap is rated 10,000uF and the meter reads 9.463uF. That's only off by a factor of one thousand LOL EDIT TO ADD: MY ERROR - There was a video cut at 7:05 and the multimeter range changed fro uF to mF. I didn't notice, so my comment above is not correct.
I thought the same, but on rechecking the meter reads 9.463mF, which is if I'm not very much mistaken 9463uF - so close enough. I'm sure if it were only 9,463uF John would have come back and commented on this or his follow up video.
@@slm60uk - well spotted, and you are correct! I missed the jump-cut at 7:05, so he started on the uF range and I had remembered that. Then after the cut it displayed 9.463 but the range had been changed to mF. Unfortunately I didn't even look at that part of the display. I have edited my comment above to correct my error.
Nice vid but 5 adverts in a 20 minute vid I just lost track of what was going on so lost interest in what was being taught. Can you imagine an advert every 4 minutes while in college. Untenable. I'm unsubscribing from all content makers that have introduced mid roll adverts. I quit tv because of too many adverts and if the greedy tube doesn't change its policy it will be going the same way as the tv. E.g. lose viewers. Greedy, greedy tube.
Counterfeit Chinese parts and low quality workmanship turned what could have been good into something of questionable quality. Can we buy good Japanese parts separately?
Next week it is fingernails on chalkboard. All you non-hackers need to be driven off! Elvis Costello used to pump white noise into the auditorium before the show to clear the venue of all non-fans. There is no room for the weak!