TPA3255 Class D Amplifier and SMPS Part 1

[@MarcelOoms]

Hi Michael, hope you get better soon! You've been quite busy none the less. Strange, that noise issue. In my experience (ie PC speakers), most class D chips suffer from hiss, or rather a faint, annoying crackle. So I keep to class AB in my proper set. Maybe that is a power supply issue I now wonder. The hypex modules on the other hand are extremely noise and distortion free, but pricey! The TPA3255 is suppposed to be rather good. Look forward to your further measurements!

[@makarov138]

So, I did the math. I'm using this power amp, preceded with a tube preamp of my liking. And with 36V at 10 amps I have what I need in my living room in my home. What more could I want?

[@10100rsn]

I've been working on some designs using this TPA3255 class-D chip and other similar class-D chips. Something I've noticed in simulations and testing is that when the devices are in BTL or PBTL mode they really don't like any imbalance in the audio inputs, by which I mean the inverting input needs to be exactly 180 degrees out of phase from the non-inverting input or you get strange overcurrent protection issues. I've started using an OPA1632 on the inputs to these chips to ensure that the non-inverting and inverting inputs are a perfect 180 degrees out of phase at all times and this has eliminated the over-protective overcurrent protection issues and some other noise issues I've had here. I have a few different boards with the TPA3255 that I've used for testing while I design my own board. That particular board you have isn't one I have here but I'm certain the noise issues you might have are more to do with the TL072 chips on the input stage and the power regulator they are getting power from. Here in my designs I've been using a switching regulator to get the voltage to about 15 volts and then a linear regulator to bring it down to 12 volts for the audio circuits (and a 3.3 volt regulator for the LEDs and an OC and OT reset circuit) and this is also what the EVM from Texas Instruments does as well. That board you have seems to be using just a single switching regulator for 12 volts which is probably where most of the noise comes in. On the EVM from Texas Instruments the switching regulator is only used to bring the voltage down to an acceptable level so the linear regulator doesn't get too hot and a fast linear regulator is really what you need to get that power supply noise down flat.

[@MichaelBeeny]

Interesting thoughts. I see the point of a linear regulator, makes sense. The choice of a TL072 does seam an odd choice, not really known for it's low noise. Maybe I did not make it clear but when supplied with 48 volts, noise was very low indeed, best so far for a class D. Over protection is an issue, particularly on lower supply voltages. I found you cannot get to clipping before the clip or the fault light comes on. Keep in touch if you have success with a new PCB layout and modified circuit, or even make a video about it. Good luck and thanks for your input, most appreciated.

[@MasterBlaster220]

So would it help to use the OPA1632 on this board here?

[@10100rsn]

@@MasterBlaster220 different pinout. You would need an adapter I believe... OPA1632 is a fully differential opamp and you need 2 for stereo. My personal designs use an opa1632 on the input whenever there are two or more of the outputs linked. If you use the TPA3255 in 4 channel mode it doesn't matter but as soon as you link 2 or more channels it makes a difference to ensure they are balanced.

[@MasterBlaster220]

@@10100rsn Ah, thanks. I misunderstood that.

[@KKMan20xx]

I have had a cheap version of that since 2018 outputing to a pair of Monitor Audio Bronze 2. , it is great. :D The cheap version said the large capacitors are ELNA but I didn't trust that so I replaced them with Nichicons with higher values and relocate them to the bottom.

[@MichaelBeeny]

Relocating the caps probably does make sense. I have have found Elna caps quite good really. Nichicons or Panasonic might be better overall.

[@KKMan20xx]

@@MichaelBeeny Elna is good, but I don't trust them to be authentic ones. :D It was the cheapest one I found listed after all.

[@nakfan]

All the best to you 🙏 Started binging on your many videos and they just contain soo much information. Thanks a lot for sharing.

[@MichaelBeeny]

Good luck with the binging, make sure you have a nice cuppa T available lol

[@impuls60]

Fun to see you dipping your toes into some of the best of class D chip. I think you must have bought the most barebone card on the hole Aliexpress site hehe. The step down solution is quite awful on some of these boards. It also deliver the power to the opamps and the poor voltage quality to the op amps I assume is the reason for the hiss. If you have a balanced dac you should try to solder the balanced signals directly to the TPA3255. The 4 electrolytic silver caps on audio signal side of the pcb is the line in, so just solder the wire to them leaving the caps in the circuit(if you dont have dc blocking caps elsewhere). This way you skip the terrible op amp circuit and the sound will improve drastically. The chip impedance is about 20kOhm so it would be interresting to see a video of you trying a dirt cheap balanced dac connected to it this way. I have a highend dac connected to it directly and it works so much better than the stock SE mode. That heat pad is way to thick! All of us modders use cpu thermal paste and direct contact which is so much better at higher power levels. I would not be surprised if the chip shuts itself down in your wattage test.. The heatsink solution is also a joke compared to what TI recommends so I usally put a temperature controlled fan on it. Anyways these board can become quite usefull with some small mods applied to them and thats why they have such a large following :) This chip series also has an interesting sound character which seperates it from other class D chips in a good way. Some prefer the 3251 because of the sound vs the 3255.

[@MichaelBeeny]

Yes that heat transfer pad did strike me that it was a little on the thick side. I think with sine wave testing the heatsink will get VERY hot. I don't think I would even try 4 ohms. In high powered music, into 8 ohms it gets to about 46c without a fan, probably OK. It's early days yet for me to experiment but overall I think its got good possibilities. I welcome input from my viewers, most appreciated.

[@peteytwofinger]

Hey pal , i have a fair amount of experience playing with chinese class d amp boards . My wife and i have a family band and we live in a 2 bedroom apartment .we have been using class d amp boards with sealed lead acid batterys and lithium ion batterys . apart from the amp boards , we get everything used including the batterys. there was a popular internet service that came with a back UPS device with a 12v 7 mah cell and al lot of these units showed up at resale stores for about 5 years you could get them . more recently we are converting over to lithuim ion batterys we recycle from lap top power packs . we have a E-Bike battery which is li ion @ 48 volts , its a large battery , i looked it up and it retailed for 500 usd . i paid 5 for it at a goodwill store . right now we are using a class d board that is rated at 600 watts .a 2.1 board that runs a 300 watt sub woofer channel and then the sattalites are 150 watts each . we have a dual ten inch sub and a pair of 10 inch [a speakers with 1 inch comression horns . the amp board is inside a small brifcase chassis which has a pair of 12.5 li ion packs with buck boards to drop 12 to 9 volts . so dual 9 volt packs run the mixer which is designed to run off a pair of regualr 9 volt batterys . the brifcase hoilds a mp3 decoder board so we put drum tracks or canned backing tracks which i will control from a footswitch i hacked off the mp3 boards pcb connectors . there is a bbe sonic maximizer pcb inbetween the oputput of the mixer and inpu of the amp as i like to allways run an eq qith a bit of a smile curve . we have been doing this sort of thing since 2009 and have video of songs going all the way back and up to present . earlyer our kids played in the band and we each had our own set of speaker cabinets and the drum machine we used to use had a pair of 15 inch speaker cabs ... so that was a lot . now the digital multi effects have amp and cabinet simulators in them that sound very good so we use those for the duo and play thru that 2.1 pa . so we have been doing this for a long time . we had one board fail on location (?) and one board arrive doa . i have built a lot of these amps though . a lot . typicallyi would find a neato old speaker then install an amp board and battery inside that . in my opinion the sound is very good . especially the newer stuff using these nice digital multi effects . now i am in my mid fiftys so i have tube amps and tube gear but ... there is no ac outlets in the forest . i have had people make comments when i type about this stuff like " tube amps are better" , but to ME thats nopt the point when playing remote out of respect for neighbors and landlord . the whole analogue vs digital thing is a tired way to use our com skills imo . anyway i am the guy who LOVES class D amps . i really do . they have enabled us so many wonderful days of fun in the outdoors making our music (we like to make our own music and not play copy songs so much but to each their own) . right now we have a small toyota and we fill it up pretty good . we will go when the weather is tollerable and after getting the gear set up , i get this overwelming sense of happyness . like all this work has come together . we have been using a line out direct to a old two track digital recorder an syncing this board mix with the camera footage . would you care to see this mess ? i will share two links , one old full family band song and something newer . these will more than likely be not line in rather mic recordings but you will get the idea . hey thanks pal , and be well ! - - kzbin.info/www/bejne/qJzCZGp8dqhgh5I - - kzbin.info/www/bejne/qmKUqHyuqqhkf8U -- enjoy and mind you this music would not exist if it were not for the efficiency of class d amps . does this make me less of a musician that i play thru these amps ?

[@SheikhN-bible-syndrome]

Jesus Christ no one's going to read all of that

[@Unker_Spunkanathan]

I think if you are listening at moderate volume, there's very little difference between the 3255 and a class ab amp. Most of the chinese factories try to squeeze everything into a small footprint, caps with little headroom n small heatsink so it kind of creates a constraint on a very competent chip. Then again, it costs so little and could easily match up with AB Amos at 2~3 times that price

[@phillipmain6475]

Excellent write up sir, thank you.

[@supercompooper]

I'm so glad I found your channel!

[@MichaelBeeny]

I'm also pleased Anthony, welcome.

[@KR1IS]

I think it's coming from the 12 V regulator harmonics

[@davidokon2988]

Just Bought the TPA 3255 Amplifier with 48v 7amp power. I will give you my own feedback soon but for now it sounds great😊😊

[@MichaelBeeny]

Which version did you get David? Same as mine or a different one?

[@davidokon2988]

@@MichaelBeeny the amplifier was same same as yours and power was Mean Well HRP-300-48

[@davidokon2988]

@@MichaelBeeny I am building a case for it and i will sent you the finished image

[@New-England-HiFi-Guy]

@@davidokon2988 how would you say this would drive 4ohm Elac Unifi 85db? I bought the premade Aiyima amp the A07 first real venture into class D. This little guy is the real deal. Using stock 32v 5amp. Looking for better psu. Also stock caps are 50v. Not much headroom if feeding 48v

[@ssiowi]

Splendid insights Michael; thanks. Working through your channel. Should you share the interest, post a series on custom, class d powered, FRFR guitar cabinet with integral power supply. cheers and thanks from WA state.

[@MichaelBeeny]

Sorry David my channel has now closed down. I am no longer uploading videos.

[@josue7769]

hello, I don't understand your video, I only know Spanish, I'm using the translator, I wanted to know what the real power is without distortion and how much impedance was measured

[@joeneticchan9640]

Hi Michael, thanks for detail review, what is your comment of compare on sound quality of TPA3255 amplifier and LJM L20D amplifier?

[@dshnt1893]

Even i bought extra pairs of class ab amps ic for the future 😊

[@edverbeek6292]

You have a great caracter. Best wishes from the Netherlands

[@MichaelBeeny]

Thank you ED, but was the video any good?

[@robertwestinghouse4098]

Your are excellent

[@klepp19]

Hi everyone, is it better to have a linear power supply with toroidal transformer vs a SMPS power supply to run a TPA 3255 chip?

[@MichaelBeeny]

If you use a SMPS you can set the voltage to exactly what you want. They are stabilized and keep that voltage almost exactly. The main issue for me is reliability. I have NEVER had any issues with a conventional power supply. However, I have had a number of SMPS fail. Often as complete right offs. I tend to use SMPS on test simply because I can current limit and change voltage easily. For a complete finished amplifier, it's a transformer every time.

[@JMJM75257]

Got a question. Can you bridge this amplifier? If so how is it done?

[@MichaelBeeny]

Not as it stands as each channel is in fact already bridged.

[@dshnt1893]

Sir it's still better to have class Ab amp like lm3886 and tda7294 ...

[@rhenry74]

Do take care of your health. We need more measurements.

[@CarlosGuzman-cu7yy]

No hubo 2da parte por k el tio se vacuno cntra el covi y manco

[@RioTintoGoAwayFromDrinaRiver]

The biggest difference between AB and D class is wave form. AB have 100% sinusoide curve and D class have square wave form. You can google forward... Great video!

[@klepp19]

Is the latest class D like Purifi and Hypex Nilai better than the TPA 3255 chip?

[@klepp19]

So square wave is more true to the analog music wave form?

[@RioTintoGoAwayFromDrinaRiver]

@@klepp19 No, it is totaly opposite. Class D is Digital. AB is analog, true HI-FI.