Thanks. That means you can fine tune them. Yes I used to use data books and piece together circuits. Was lots of fun. Look up lm3900 in a national semi book. Hundreds of things you can build with comparators. Looks like a winner

nice little amp and decent price for not being a kit build. This one is nice having treble and bass controls and the option of running up to 24v @ 50w. i caught their 80w error last month when i looked up the TI chip. still a nice lil amp. i built the TDA7297 amp kit from IC station and i like it really well to. i built it for a portable guitar amp, which Im still trying to find a small suitcase to install it in and 2x 8" speakers, for traveling. Thanks for sharing !

Appreciated with your awesome video project, thanks very much. :)

Ebay and low prices were so damn seductive lol. Most of these little amps are pretty awful, but I've had a few that were surprisingly decent. For a battery powered boombox or guitar amp, I got good results. In hindsight having gone to college for E. engineering though, slopping something together class-a will ultimately give better fidelity and *useable* volume from just a couple dozen watts.

How do you connect the scope to a bridge output amp? Do you remove the ground on the scope or use differential input on the scope?

should have done a comparison on the scopes, one showing the line in from the phone and the other scope showing the output of the amp, what frequency does the bass and treble controls of this amp actually adjust? on mine bass is 55Hz and treble is 12Khz, pair one of these up with a pair of jbl control1 or wharfedale diamond 9.1 speakers and prepare to have your mind blown with the sheer clarity.

I've noticed some artifacts with this chokeless design while using long speaker cables. If I connect no longer than 10 inches of wire from amp to speaker this oscillations and artifacts go away.. Also some popping and crackling while reaching near full power at 8 ohms load. Could be that speaker wire induction messes up the modulation or something? I've also noticed in TI's datasheet that they sudgest short speaker wires with filterless design.. I was curious if you maybe noticed this too with you're module. Mine doesn't have op amp and tone controls on the input, just decoupling caps and pot

I'm using same type of amplifier but I noticed that when a sudden strong vocal input or strong music kicks in it causes the power amplifier to go in some kind of protection causing muting of audio output. I'm using 4Ohm drivers also tried with 8Ohm drivers but having same result. I can't set in higher volumes. Can you help me to fix this? Thank you!

Ive got one very similar to this powering a pair of JBL Control-1 pro speakers, i tell you what it really does sound excellent. in fact so good i fitted the amp inside it and use the control1's for music making. what frequency range do the bass and treble controls affect on this particular amp?

@12voltvids

6 жыл бұрын

I didn't check that, and I don't believe it is in the specs. I didn't know what to expect as I have tested a few amps, and some sound better than others, but the last TI amp I tested, in the SMSL SA50 also had a Texas Instruments chip, and it also sounded fantastic, and this one was also a winner. It does pop when powered up, but not very loud, but other than that for what it cost I don't think you will find a better little amp for the money. I am going to get some speakers at the second hand store and mount this amp inside the box. I really like this one because of the volume, bass and treble controls. I will mount it inside a speaker box, with the controls sticking out the back. This is better than amps that use buttons for volume. Always nice to be able to just reach over and turn the volume up or down.

@Synthematix

6 жыл бұрын

thats exacly what ive done with a pair of jbl control1 speakers, the sound is amazing, deep bass and sizzling highs, great set of monitoring speakers now! mines powered with a 12v 7amp transformer

@markanderson350

6 жыл бұрын

Are the bass and treble done in digital or analogue domain?

Nice!!

It's hard to tell how good they sound coming from your speakers into a microphone, then through my KZread TV speakers.

Hi Old man, have you any idea of fixing a PS4? or a Mac-Min (i have a mac mini 2011, one socket of RAM not work, when i put RAM in first socket i ear 5 bip, and the screen be black, but when i put it in second socket and i keep first empty it work fine) any idea about this problem?

Good day I just wanted to ask what is the lowest impedance it can handle I would like to know because what I have is one sub 100 watts 8 ohms and will add two 90 watts 4 ohms connected in parallel, I hope someone can answer if what I am doing will be just fine. Thanks in advance

So are the speakers (wires) emitting a 1Mhz signal into the surrounding air ? This is a cool amp system ....need more info on distortion specs.

@12voltvids

6 жыл бұрын

Yes they will emit some RFI, and this is one of the problems. Long speaker wires will certainly radiate, and according to data I have read, this needs to be mitigated with ferrite chokes placed on the speaker wires when long runs are used. Now, remember, ADSL and VDSL telephone lines use RF in the AM and shortwave bands as well, and these lines can be up to a KM or more in length. House wiring is not shielded, and modems can and do cause RFI and do cause a considerable amount of interference to AM radios that are near the walls with DSL signals. With an AM radio I can pinpoint where the wires are that carry my DSL signal from the demark, to where they enter the house, traverse my workshop and head to the closet where the modem is located. The noise generated by a class D amp will not be any worse than from other unintentional radiators except in very high power systems and over long speaker runs.

@packratswhatif.3990

6 жыл бұрын

Ok good stuff thanks. Guess we could just add some proper chokes here (maybe abit overkill). What is your favourite class D amp that you have seen and would like to use.....Ross

@12voltvids

6 жыл бұрын

Yes chokes to the speaker wires (those snap on box suppressors would be fine) would remove any remaining noise and would be recommended for long speaker runs. To date the 2 class D amps I like are is the one in that SMSL amp / digital madia player, and this one. All the boards I have tested have been pretty good except for that 100 watt mono amp that had all the noises in the audio. That one certainly didn't sound as good as the others. I will probably do a video some time where I will compare the different amp boards I have and we can do an A/B/C comparison. I will play the same track, at the same volume, on the same speakers and give them a fair comparison. I will likely have a few more ones sent to me to check out. When I do this I will use the same power supply for them all too, so that they will all be tested under the same operating conditions.

@packratswhatif.3990

6 жыл бұрын

Again thanks for the info. By the way, that D amp that you just tested, what was THD numbers for it. Guess I am getting picky in my old age and have nothing better to do !! Want the best ....

@12voltvids

6 жыл бұрын

You can look up the specs to see measured specs. They claim 0.1% THD+noise, but of course that changes with frequency and power levels. On most of the graphs it is closer to .01% until the frequency gets up to 10KHz

I wonder what the current waveform going through the speaker would look like, since the frequency is so high the speaker might not even be passing the perceived noise. Plus its got that processor so it could be doing other magic and exploiting what a speaker can and cannot reproduce.

@mrjohhhnnnyyy5797

6 жыл бұрын

I was thinking the same, at 1.5MHz the inductive reactance will be so high that there won't be any significant current flowing. Plus, speakers have inertia, cone physically can't move all that fast. Engineers at TI exploited the limitations of the speaker to their advantage, nice job.

@12voltvids

6 жыл бұрын

The switching frequency is 1.2MHz, and there IS a low pass filter, it is just I didn't see it initially as I was looking for conventional components, however this uses very small ceramic SMD capacitors and SMD ferrite inductor. The reason they get away with this is because the frequency is so high, and well above what any tweeter would be able to act on. The carrier present is actually quite low, but again it is so high in frequency, and the coil effect of the tweeter is going to suppress RF radiation, but I would imagine that running it close to an AM radio is going to have some audible noise being picked up by an AM radio. Even at 24V, the carrier would be less than that, and this is not about to radiate very far. The AM transmitter I built puts out 400 mW, which is enough to make it about 1 block when fed into a wire antenna. I measured the RF voltage coming out the antenna terminal, and when tuned for resonance the P-P voltage on the antenna measured up at about 165 volts. (Remember this is RF into an antenna, not a load. 165 volts results in about 400 mW of radiated power (about 4X the FCC level for unlicensed operation in the USA) and that makes it only about 1 block. So a switching carrier frequency which is less than 20v, into a terminated load isn't likely to cause interference unless the receiving radio was very close to the speaker lead. That is another video though to actually prove if it does cause any interference.

When is the next VCR video? I love when you repair them.

@12voltvids

6 жыл бұрын

I actually have a little TV / VCR combo unit sitting on the shop floor awaiting it's turn on the bench. Have no idea what is wrong with it at this time. Has a note on it that says "Broken" whatever that means.

@TheVCRKing

6 жыл бұрын

Oh sweet! Please make a video of you fixing it. I also review VCRs taken apart. Check out my channel if you'd like. I've also learned how to clean mode switches because of your videos. Thank you so much!

I might be wrong but isn't that Texis instrument amp a PWM amplifier, if its pwm you expect it to be squirewaves that chopped up to make the sound, very short bursts.

@12voltvids

6 жыл бұрын

HPZeta It is pwm however the frequency of this one is in the 1200 khz and doesn't use the conventional lpf. Very small capacities /inductor network is used and HF components are detectable on the output.

Even though it sounds good, the high frequency noise is a problem. It may burn tweeter elements for instance. The TI Typical Application schematic does have two stage LC/RC snubber circuits.

@12voltvids

6 жыл бұрын

thulinp Looking at the layout there some smd chip components out the output that make up the snubber circuit. Because the frequency of this amp is much higher than the typical class d which is around 400 KHz and this one operated up around 1.2 mhz the LC/RC circuit can be laid out on the board and be very effective. The camera mic doesn't do this amp justice but to my ears this unit sounds fantastic. Also throwing a ferrite bead around the speaker lead would clean this high frequency noise up, but again it is so far up there in frequency it isn't going to be an issue. I am sure that it will disturb AM radios nearby, and that will be the focus of another video.

@12voltvids

6 жыл бұрын

Read this: www.maximintegrated.com/en/app-notes/index.mvp/id/3977 As you can see, modern class D amplifiers do not require the low pass filters as in the past.

@valentinocolaon6060

6 жыл бұрын

i's not an issue at all, I'm experimenting with this particular chip for some time now. frequency in which it operates is higher than anything we had in audio/amp equipment in the past so it's kinda odd to observe this kind of design at work.

@12voltvids

6 жыл бұрын

Right on. Yes I haven't seen this type of frequency before and it was a little unnerving to see the switching signals present on the scope, but it certainly is not in the reproduced sound. I just got some BT boards and I think a project with this amp board and a pair of speakers is in order for a future project.

@davidgriffin79

5 жыл бұрын

@@12voltvids It sounded ok but ramping up the treble made my ears bleed.

Well you cant hear that h.f, but the low pass filter is still needed, cost cutting :-(. Have you listened to the 1.5mhz on a comms receiver?

@12voltvids

6 жыл бұрын

Not according to the latest data I have read. There are filter less designs out now. This one actually does use a LPF, it is just very small. The components are tiny SMD chips, and they use the board layout for the filter. You don't see the tiny ferrite indictors because they are actually under t he heat sink right next to the chop. you can see them from a side view. The capacitors are small ceramic caps, and they are between the heatsink and the speaker terminals. You can see them at 6:29 between the green heat sink and the blue speaker terminals. 4 little chip capacitors. The inductors, also SMD are just under the green heatsink next to the chip. Just little black SMD chips. Because of the high frequency they get away with very small parts. That noise you see on the scope is residual carrier, but due to it's high frequency is not in any ay going to impact the audio. Even sub harmonics are still going to be many times higher in frequency that any reproducible sound.

@zx8401ztv

6 жыл бұрын

Im supprised its not been jumped on for the ipossible nterfearence to the mediumwave band and perhaps ham band. I react to the problem because i had a brother that was a ham, he was rather strict with unwanted emmissions, i was into c.b radio repair and he didn't like me for that, silly sod, it was good for learning all the circuits. I also repaired ham radios, like kenwood yaesu, complex synth but basic radio methods were still usefull.

@12voltvids

6 жыл бұрын

Don't get me started on HAMs. They are are a strange bunch. I can say that because I am one, and have had my license for over 30 years. I can't use HF here due to all the noise from plasma TVs, ADSL and VDSL tel lines, these eithernet extenders that use house wiring, also known as PLE or power line ethernet donglels), CFL and LED light bulbs. The big one is VDSL though. The phone co is using VDSL 17A profile which uses frequencies up to 17MHz, and just kills the 80, 40 and 20 meter bands with constant noise. They are building fiber to the house right now though, so the DSL noise will drop substantially as people migrate from copper to glass. Then it will just be the dam plasma TVs that some people insist on hanging onto.Some of those one ones throw so much noise onto the HF bands.

@zx8401ztv

6 жыл бұрын

Yes it's a world of digital noise, i wonder how manufacturers get away with it, switchmodes need to be in a thick earthed box with plenty of input/output filtering, laptop supplys work well but they screw up radio reception, should be in a diecast earthed box really. That's the reason i don't mind the old linear supplys, no noise :-) My brother was up his own arse, if you know what i mean.

@12voltvids

6 жыл бұрын

zx8401ztv Oh I know what you mean. Myself I am not that active on the ham bands. I occasionally use 2m or 440 in the car and the 224 band from home once in awhile but only talk to a few people. Many hams have gone digital but I haven't jumped on that bandwagon yet but from what I understand it is superior and eliminates many of the noise problems.

Is it because the scope,s are picking up higher/RF noise from the amp that speakers are not damping out, because there is not a ground on the psu?

@12voltvids

6 жыл бұрын

I believe this is just leakage past the LPF. This unit uses much higher frequencies than other class D modules I have testes. One owas down at around 100KHz, but most have been in the 400 KHz range. This one is operating at 1200KHz, so this dispenses with the need for large filters.

I can imagine that device as a active crossover, with 10watt boost, similar to a Eq but with soft clipping for when distortion is detected in the frequencies like sub bass, bass kick , mid and treble .. 4channel out put for 4 amps ..... thats what sound system's have ,oh well Just a idea

That sounds as good as the audio from my SONY Sound Bar and Sub Woofer, what about using two low pass filters on the output of the PWM amp to clean up the signal.

@12voltvids

6 жыл бұрын

Those Texas Instruments TPA and TAS class D chips sound fantastic. That SMSL SA-50 audio payer also uses one, and it too sounds incredible. They have pushed the switching frequency up into the 1.2MHz range, and this reduced the size of the LPF filtering needed, and even though there is still some HF noise present, it is well above frequencies that tweeters can operate at even in sub harmonic ranges. Looks strange on the scope as it, being a high impedance device can see it, but the speakers don't respond, and they sound very good.

No Mute circuit so turn on pops are to be expected. Does it use the the speakers as inductors then?

@12voltvids

6 жыл бұрын

No they are actually on the board, under the green heat sink. They are tiny SMD inductors, and SMD ceramic caps. You can see them between the heatsink and speaker terminals. I commented that it didn't have any, as I was expecting to see large ones as on the other amp I showed, but this one is much higher in frequency, and the parts are much smaller, but they are still there. The residual RF leaning through will be taken care of by the voice coil. Yes it does thump when powered up, but it not not a loud pop, noting that is going to cause any damage.

@masanders19781

6 жыл бұрын

12voltvids Is there something that can be done about the popping?

where is the faultz and sdz pins?

Just bought one of these and have horrible noise, specially when touching the treble adjustment knob, any ideas on whats could be wrong?

@alextsirint758

5 жыл бұрын

Hello, same with my XH-M577 (same amp with 1 more potensiometer). Have you found a solution ?. Thinking of replacing input volume pot with a 10K.

@jeremymtc

3 жыл бұрын

@@alextsirint758 @CesconetoG I know that your questions are a year or two old respectively, but they seem to be common questions about this board and its 4-knob sibling. I've found a solution that has worked in my application and may be of use to you. Try adding a jumper wire from the audio input ground to the potentiometer cases. The treble, mid and bass potentiometers on my board (XH-M577) did not have a ground path to the cases when checked with a multimeter. In my application the amplifier board is mounted to a plastic fascia panel, so I used a strip of tin foil mounted between the potentiometers and faceplate to create a common ground plane for the pots, and then connected a single short wire from that groundplane to the AGRND solder point at the input on the back of the board.

@alextsirint758

3 жыл бұрын

@@jeremymtc Thanks for your answer. Until today due to limited free time, I have left it as is. I will try your solution as soon as I disassemble my speaker. I have also found in a webpage (but I can't find it now) that a resistor grounding the audio input is misplaced under the heatsink. That leads to a very high input resistance leading to oscillations. Thanks again.

@jeremymtc

3 жыл бұрын

@@alextsirint758 That is very interesting regarding the potentially wrong resistor application/placement. Grounding the pots to AGRND made a huge difference on mine. Previously it had a noticeable quiescent hum, and would also make noise in reaction to just touching the potentiometers, or even hovering your hand slightly near them. After grounding all of those noises are gone. Hope it works out for you!

Which small form factor amps allow a common ground? I am working on jukeboxes and they all have common grounds it seems on the internal speakers.

@12voltvids

4 жыл бұрын

You can always run a new wire to the speaker and unground the lug that is grounded.

@thasickest

4 жыл бұрын

@@12voltvids It's not that simple, the volume control for the wallboxes goes through a set of resistors and that whole thing has to be resoldered and adapted to unground it. I'd rather not change something that has worked for 60-70 years if I don't have to. Are there any amps that support a common ground that you know of? Thanks so much for your knowledge and reply. Love your content.

@12voltvids

4 жыл бұрын

@@thasickest Yes use an audio transformer. Sometimes called a 70 volt pa speaker transformers. Pa amplifiers used them to step up the voltage from the amp to feed multiple speakers so the speaker inmpedience from multiple speakers wont load the amp down. The original amp was probably a tube amp and all tube amps use an audio output transformer. The primary transformer goes to the amplifier and the secondary to the speakers. This way all the speakers can use s common ground and they are isolated from the amplifier. The BTL output from the amp just looks into s single isolated load, the audio transformer. You need one of sufficient size for the power you plan to drive it with. Your other option is to just use a class ab type amp as they will be common ground for speakers. It is just the small class d that use BTL. output to increase power.

@thasickest

4 жыл бұрын

@@12voltvids it was a 70v system. If I run 2 discrete mono amps, would they be able to "share" a ground? I have read somewhere there's a couple digital chips that support it but I failed to bookmark the page.

@12voltvids

4 жыл бұрын

@@thasickest if you put in some 8 ohm to 70 volt transformers then you can.

A test signal is not very similar to a music signal. The digital amps will be able to deliver only half or less of the specified power within a few tenths of a second of full power, where a conventional amp will continue to give off its full power.

@12voltvids

6 жыл бұрын

Yes this is knows as music power, or peak music power. RMS is totally different, and is what we all refer to as old school power. A big class AB amp will deliver rated power all day long, but are large, heavy, and not very efficient. These little class D amps are very efficient, can drive an incredibly low impedance load and handle music signals very well, and for everyone outside of the audiophile world are perfectly acceptable. I am a tube nut myself. I love firing up my class A and AB tube amps to listen to music,. and I enjoy watching the dollar bills fly out of my wallet to pay the power company for the privilege. But hey, I can turn the heat down a bit because all those tubes heats the room up quite nicely.

I was told Class D amps require a very high speed (150mhz or faster) scope to display the wave forms clearly. The pulses are FM modulation with a mix of time delay reflectometry. I don't have a scope that fast to verify it.

@12voltvids

6 жыл бұрын

The Tektronix is a 300 MHz. Looks like it was a 400 at one time, but I guess they swapped boards before I got it because the 400 had 300 written over it, and there were 300 and 400 mhz versions available.

@MidnightVisions

6 жыл бұрын

Perhaps because the music is always changing, that's making the waveform look unrecognizeable. What do fixed tones look like?

The cat likes it ;)

@12voltvids

6 жыл бұрын

That cat likes everything. She is sitting on my shoulder right now purring in my ear. Thats my new cat, and she behaves so much like the old cat. I turn on music and she comes running.

@GustoTheGamer

6 жыл бұрын

Lol :okay ) i like your special guest keep up the good work!

That's amazing, an amp for the price of a PC board. Now it seems the power supply is the expensive part.

@12voltvids

6 жыл бұрын

Yes a power supply could cost more than this. I am going to try it on an old laptop supply. I have a few old 19V supplies from old laptops that have long been recycled kicking around.

@markanderson350

6 жыл бұрын

Very impressive what you get for the buck. My only worry, what will this do to tweeters? Wont it heat the voice coil?

@12voltvids

6 жыл бұрын

Mark Anderson Not at all. This is 1200 khz low level rf. What gets to the voice coil will have no effect on it. Most of the switching signal is filtered by the low pass filter which is a ferrite inductor and ceramic chip cap. What showed on the scope is what gets past the filter and it is very low level and we'll beyond the frequency the tweeter can handle.

@markanderson350

6 жыл бұрын

How come it looks so bad on the scope then? This is a mystery amp.

@12voltvids

6 жыл бұрын

You are right it does not look great on the scope, however the scope very sensitive, and will display the residual RF left on the speaker wires. The speaker, being a mechanical device will not respond to this RF. It is well beyond what the speaker will respond to, and any that makes it to the tweeter will just cancel out in the voice coil. The RF is there but there is no current at that frequency. All the current is in the audio frequencies which are what drives the speaker.

What is the maximum number of amperes it can give?

@12voltvids

3 жыл бұрын

Couldn't tell you

What is the real RMS Power of each channels?

@12voltvids

2 жыл бұрын

Running at 26 volts and a 4 ohm load it will put out 50 watts per channel or 100 bridged according to the datasheet published by Texas instruments. Lower supply voltage or higher speaker impedence reduces the power.

Poor people that are worried about colors of wires. The wires are unaware of what color they are. They do not know if they are brown, black, yellow, green or purple

@12voltvids

4 жыл бұрын

Yip, some people eh.

Its a shame we cannot play our own music anymore and has to be pretty rubbish I know the 2001 song though. that thing is so small to.

@12voltvids

6 жыл бұрын

Well you can play pretty much any music these days, but the copyright owner will make a claim and then they take the advertising revenue. That kinda defeats the purpose. Believe it or not I actually do try to make money from the channel. I am getting close to retirement from my day job. I am at the age where I could retire in a few months now, but can't afford to do that yet. I don't have enough years to get my full pension, and that is where youtube comes in. I am not there yet, but in another couple of years I may be able to do this full time and that is the goal. So I need to make sure that my videos are monetized, and I need to make sure that I don't have any claims against videos, otherwise I am working for free and lining someone else's pockets. I already have to keep an eye out for people that download my videos and post them as their own. That has been an issue. I did publicly out one person that has done this, but I have caught several others, and taken action to have my videos removed from other channels. Unfortunately content ID doesn't work for me in this respect, as that is a service only available to the big studios, so I rely on users tipping me off by sending me links of my videos that have been stolen. To date close to 100 people have had their accounts terminated by youtube for this. The kicker is the majority of them are not even monetized, and likely done by kids, but every view one of my videos gets from someone else's account is 1 less view from my channel, and that is where the problem lies. Now with this reply, I am probably going to generate a ton of hate mail, from the freeloaders and trolls on the internet that believe everything should be free. They are just the losers that don't have the incentive or the drive to succeed. There will be those that say things like "i don't do this for money, I do it for fun, or to share knowledge" I know a few people like that. One is 55 years old, lives in his mothers basement. Never had anything than odd jobs.