Selecting power transformer for audio amplifier 

FIRST! :) Hey guys thanks for watching. I'll be uploading a few more videos soon. Stay tuned!

Thank you - great video. Now I know exactly why current is so important in an amplifier transformer. Best video I have seen explaining it. Bravo!

Im getting into building my amps, and i find your videos very useful, keep it up! :D

Great video it shows how it just isn’t the size of capacitor but how important it is to size the transformer correctly!

I keep coming back to this video. Some I am not too clear on but it has helped a lot. PLEASE do one on SMPS for Class D Amplifiers. Nobody seems to have covered this as it's a rather 'sticky field'.

A very concise presentation. As you say, if money was not an object, the toroidal transformer would be the choice to get maximum output power per unit space (that the transformer takes). I constructed a kit which used a 'C-core' transformer, which is somewhere between the E-I type and the toroid in efficiency...

This is an excellent video right mix of theory and practice Many thanks !

Nice video, I bought a few LM3886 chips a few years back and never got around to building my amp circuit. Today seems like a good day.

Amazing video! Could you make one explaining in detail how eliminating coupling capacitors influence on sound quality, and how speaker is working when we don't have split supply. There are a lot of amp projects that doesn't require split supply and knowing how to choose right transformer would be helpful.

Thank you, that was fantastic. Very informative.

Good video as always. I have just stripped (disassembled - awful word) a Monicor PA 900 line amp that got a sudden cooling in a pub by a pint of beer. Vents top and bottom didn't help much. The DC supply is fine as are most of the 'gubbins'. The amp is rated at 120W RMS and the mains 230V transformer is 40VDC at about 7A that's 280W That's more than double the output. It's being converted into an LM237 - 2N3055 x 4 bench power supply - I'll try anyway. The beer stains on the transformer are going to stay there as they look quite content. I do hope you get a power supply sorted young fella, you deserve one. Regards

Thanks again. As I have been delving deeper in audio amps more and more things pop up and the last for effective use seems to be power supply. This is one of the more clear videos I have seen and really explains it well.

Thanks heaps john this was a big help in selecting the right transformer.

AC voltage x √2 = DC voltage when rectified. I have always wondered why hifi buffs dont spend the money on a regulated quality power supply for their amplifiers instead of hundreds of $ for one meter of cable. 😁 Good video.

Great video! Thanks for sharing. Can you explain the function of the extra diodes, transistor, ceramic cap, and resistors on the bread boarded power supply? I understand the bridge rectifier and big electrolytic smoothing caps... but what's the other stuff for? It's not just to for the indicator LED, right?

Thank you, helps me figure trans demand.

Awesome video, thanks man

very informative video. thanks

Great video

Extremely interesting video JohnAudioTech! I was intrigued by the simplicity of the maths! I know now exactly how to work these things out for myself WHICH I THANK YOU FOR! I've watched some videos about simple amplifier circuits using the TDA2822M & LM386 by ardwenone and he said that you can use +12 & -12 Volts to get a 24 volt supply in one of his videos about stripping old discarded or broken electrical items down for parts, but i'd never even heard of a negative supply rail! He said something about positive and negative voltages referenced to a virtual ground so that the ground is kind of the mid point of the total voltage as one option for a split supply and you can do this from batteries by (something along the lines of) measuring the voltage from a different point or taking the ground from half supply voltage or something by using resistors of equal values or something about using a divider circuit?? Which really didn't make much sense to me as I never knew voltage could be divided using resistors (if it can I don't know about it because I'm just starting to learn about electronics!), but your diagram made it a lot easier to understand! That visual stimulus made it make sense in a way that I understood, it's great being told the information but sometimes you need that little extra explanation or like your graph to actually understand it. I do kind of get it now about the negative voltage because I now realise that music is an AC current rather than DC is that right? Ardwenome linked to your channel in one of his videos and that's how i found myself here. He was correct you do supply a wealth of information & I'll subscribe to your channel too now between the information in his video & your video I now understand a lot more about amplifier IC's which is what I'm trying to build as my very first electronics project. So basically yohu could have a voltage of an infinite number of volts with half of the voltage being positive and the other half being negative if you take your zer or ground voltage to be half the total supply voltage yeah? But wouldn't that break anything you connected to it if it was wantinf zero volts as a ground?? So basically you're saying that +50 & -50 would make 100V total supply, So could i run an lm386 or tda2822m or tda2050 or similar on a dual / split supply? obviously a lot smaller voltage 9 or 10V for the TDA2822m +&-5V, then say +&-6V for the LM386 and +&-12V for the TDA2050? Or is it not possible to run all amplifier IC's on a split / dual supply?? I think I'll try and replicate ardwenome solar powered amplifier so I can have a portable speaker and like he did use a battery pack for when there's no sun but I want mine to recharge itself from the solar panels too but he said something about balancing the batteries and charge or battery protection circuits built into the cells, I'll have to look into it all and see what sense I can make of it. As i've never heard of balancing batteries when there's more than one being used, surely you just charge them up and away you go? Something to do with lithium ones and over charging he said it can be dangerous and you need to have a balancing board to prevent it catching fire or to stop the batteries exploding or something. And is it possible to just connect the solar panels directly to the batteries and have them charge or would it be better to use op-amps to boost the voltage of the solar panels before the power gets to the batteries? which is something else he mentioned when talking about a solar power bank he had that broke but I thought op amps were for music? I'm quite confused about it all and I suppose I need to do some research now before I build it. I guess you guys on here know what you're on about or you'd not be making videos about these things. Which is why I'm kinda asking for your advice i suppose. Anyway Loved the video you explained it in a way I actually understood (only because of the graph!) Look forward to hearing your answer JohnAudioTech!

Thanks for the details! Can you expand upon the dynamic power topic? Thanks

Great Channel John. If interested please do more on DIY Active speaker Build for cheapskates

Thank you for your time, Wish you well. Ta

Great as always !! ⭐⭐⭐⭐⭐

In a stereo setup, would the transformer secondary need to have a separate winding for each channel plus center tap?

Hi John. Nice video you got there... What size are the two capacitors on that power supply you build? 25volt dc ? thanks you

Toroids have a lot of advantages but one thing that gives them fits is that any DC offset on the AC line will put them into saturation very rapidly. There are ways around this but this is something to consider.

thank you! Can you help me determine the optimal current when losing parameters on transformer.

Can I just switch an AV receiver transformer for a larger torrodial one (same otput specs of course) or is there more to it than that. Would love to experiment with a Yamaha receiver I have.

To Mr. John Audio. Really enjoyed your video. Thankyou very much for making the video for us all. Say i have a shorted toroid the voltage is 240/120 56v-0-56 15-0-15. Can i replace with 68v-0-68/15-0-15....or perhaps slightly lower 42-0-42/15-0-15...btw I'm learning a lot from you. Thanks again!!!! Cheers!!!!

Hi John , Just wanted to know what chip or amplifier it was you used in the testing ,, thanks ..

the power peaks that one wants is based on how much is the peak power a speaker can take or is it based on the watts RMS desired?

Am very certain to select the appropriate transformer for an audio amp. Would need to know its power consumption then add a little on top for overhead. This would include voltage and amps. Am guessing 1 would need to know how much the transistors are consuming? Interesting video on differences in performance of amp with different transformers though.

sir-i have a query i have 2 transformers same type-15 v 6a each made by same manufacturer-- i join the 0 v of each to make dual rail supply of 15-0-15 v 6a ac for amplifier tda 2050 --The turns on transformers i guess they are same as made by same manufacturer 1----------if i connect like this in parallel do i get 16-0-16 v @ 6a--w.r.t to each rail now what do you think can it be done without any issues ? ------thank you

U hav a classic knowledge of electronics.. R u an electrical engineer ?? I should learn from you sir

shouldn't there be high wattage resistors on the power rails between the capacitors and transistors? like 100 ohm 10 watts

On Regulated Power Supplies - they will many times use a 2n3055 Power Transistor to increase the Output Power. What would the output of the small transformer be if you added one 2n3055 transistor to it?

@JohnAudioTech I just so happen to have two different toroidal transformers without a center tap. Their specs are as follows: First one, Primary 120V 60Hz 350VA / Secondary 26.3V 12.55A and the Second one, Primary 0-100-110-115-127 50/60Hz 360VA / Secondary 26.3V 13.1 / Autoxfmr Output 120V 8.5A. Now I'd like to use these as I can get them for free. Do you think I could use either of these. Most of the transformers you show have a center tap?

hi is it possible those diods are not placed right?

oh yeah, I'm tuned in. I like a toroid transformer, I prefer winding them myself.

It´s quite possible to use Switched power supplies instead of bulky transformers. I´m using them for my home built Quad amps.

Another question John. I have two toroidal transformers and am looking at using 1 each to power an lm1875 kit. With a few quick testes it seems that I would be ok to have both connected to the AC mains with each powering a single kit each. Is that advisable? Alot of Googling hasn't come up with much in the way of an answer.

Great video! I'm new at this. New tricks for an old dog. I've got a Eico 147A Signal tracer. Change the audio in jacks, install a 4" or 5" Eminence speaker and viola! A self diagnosis guitar amp with the evil green eye equalizer?

Hello. thank you for your answer. I have one more question. I have a poweramp straight to the speaker (8ohm), its causing a pop when turning on. I want to know if I should add a decoupling capacitor? or should I add a discharge resistor? or a zobel network? or the 3 solutions?

Hey! Excellent content and knowledge! Question... I have my dad's Sansui RA-500 Reverberation Amplifier The illumination output is going out and im looking for a replacement transformer. Where can i find a transformer for this application? Output 6.3v 1.5ma illumination 21v × 2 150ma

So I would need a 4000va transformer for a 2000w mono amp?

I live next door to an electrical substation. I have like 15 pikachus.

Thanks, your video is great and helpful, but how do you get that sinusoidal signal out of the music player? And how do you increase or decrease the amount of power and the oscilloscope connections?

john, great as always! i am just in the middle of building my first power amplifier , just missing the connection to the power line (220V) . would be very helpful to show how to connect power line to transformer, build an rectifier and connect everything to the amplifier (LM 1875). because of safety reason i am hesitating at the moment. any plans to publish a video in the near future regarding this topic?

Max voltage is √2 times the secondary output.. ie 35 volts

sir i did not understand why in AC or transformer rating we use VA instead of WATTS am kinda confused ? please help me out

Could you recommend a introductory fo totally clueless guys like me trying to understand

please help me with output coupling capacitor

what other elements do you have in your rectifier board? I see some didoes, an interesting blue electrolytic capacitor and an interesting and rather large ceramic capacitor?

good stuff

Im kicking myself for throwing away some of the parts i used to pull out of dead audio gear when i was a kid, i had quite a few box's of pretty nice stuff, high power toroidal transformers, lots of transistors and other goodies from a bunch of dead yamaha PA amps I had gotten my hands on, i still didn't really know what i was doing at that age, just really liked pulling apart electronics trying to figure out how they worked. Now im looking at building a nice high power ( 20-25 Amps at 13-15 volts) low noise linear power supply and with the power supply components from a couple of those amps would have made a killer power supply for the high power RF transmitter im playing with for ham radio stuff.

If one Transistor goes short circuit then bye bye loud Speaker If you have expensive Speakers always put a protection circuit between amp and speaker.

This is why it's always good to slightly "overbuild" your amplifier power supply!... This is also the exact main reason that most modern home theater "receivers" simply cannot put out high wattage in any kind of sustained manner, because they are all essentially being powered by only the smaller transformer in this video (relatively) because of size and space and cost considerations, instead of the larger transformer, (again relative sizes, not exact), like the kind you would see in a truly dedicated separate component power amplifier.

I got curious to know what that toroidal transformer would do to the amplifier's power delivery. Also, I noticed that between the transformers tested and those big capacitors there was a FULL BRIDGE RECTIFIER!!!

Can you please make a video comparing the use of chip amps (like tda2030/tda2050) on dual supply and single supply? Its a request from a big fan of yours!

That would be great!! but for some reason I have seen most people ( including you) use dual supply more often then single supply though single supply is commonly available.

John, can you please check a 'MT 2130 toroidal transformer' it has a VA300, the crew at Jaycar (Australia) said it wouldn't do the job. They stated it wouldn't go into the -12 and that both 12 outputs were +, I have been watching a heap of builds and cant get a sold understanding...... Getting through your vids, learning a lot.

Can a transformer be too powerful for the amplifier? I've built this push pull amp ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-mQuvMrJXDoI.html which works fine using a 20V wall adapter or my 18V bench supply with a rail splitter . However, I would like to use a large speaker like this ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-wapHGDgNHlM.html without clipping. You can see it clipping in this video using the 20V wall adapter with the large speaker and woofer filter. However, when I hooked it up to a big 20V CT transformer I got a very loud hum and the transistors got hot. I add a 50 Ohm resistor in series with the speaker to eliminate the hum, but it still sounded bad unless I turned up the volume to crazy floor-shaking loud. It simply didn't work at low volume even with the gain adjusted. Is the transformer just to powerful? Can I add current limiting resistors somewhere? Any thoughts would be appreciated.

Hey what about the Toroidal transformer... explain man

Great videos. Thanks! Did anyone tell you, you sound like Tobby Maguire :)

which type of transformer will eliminate humming in an amplifier? besides that which combination of capacitors will eliminate transformer humming in an amplifier?

I have a big toroid like that in an amp I just recently blew something on in the amplifier stage. The transformer is fine, and still powers up the rest of the amp, but blows out the amp stage fuses if I replace them. I just got the idea to power other amplifiers that are not as powerful as the one this came out of, maybe getting an overall output increase from it. Also I would fix the amp it's in already if I knew what exactly is blown/shorting, but it's hard for me to tell. If anyone has any suggestions as to what I should check out and look for on an amp thats speaker outs were accidentally dead shorted while putting out full power feel free to tell me. The amp is relatively simple in its layout and I'm sure i could replace any component that's bad on it. Just not sure what to replace, what to test and what I'd be looking for in testing it

Few days ago i tried to power up my amp and the capacitor exploded. i used 3 3300uF cap 50V rating. 12V supply. Could you please make a video on why capacitor explodes!! i searched online but didn't find any source talking about this. Thanks in advance.

Nice video, well explained ! I have a Bass Amplifier with rating 120VAC, 60Hz, 210VA Average, bought in Canada. I am presently in India and therefore have a 230VAC, 50Hz source. Can you kindly suggest, what need to be the VA rating of a 230VAC to 120VAC step down toroidal transformer ? Thank you in advance !

Bahi proton xt 4000 watt ka input output board kitne ka mile ga

Nice to see someone using real maths rather than fictitious BS claims. Well done.

Thank you for all your answers. I'm trouble shooting a PSU and i'm getting +9.6v and -8.3v. What causes the voltage difference of 1.3v between +VCC=9.6v and -VCC= -8.3V in a PSU? a) the coil has a central tap wrongly placed? b) the rectifier (diode bridge) is fried or cheap quality? c) one of the capacitors (3300uF 25v) are damaged and should be replaced? thanks again

my speakers are 40+40+75 Watt rated (2.1 system) I drive them with 3 amplifiers rated for 100Watt each I wana power all of the amplifiers with a single 100VA transformer can I expect a total output of at least 80Watts? (20+20 and 40 for the sub)?

Sooo... I recently mistakenly ordered an amplifier board that requires dual AC power. I don't have any AC transformers but I do have TONS of DC power supplies. I even have PC power supplies with negative and positive output. My question is, can I power the amplifier that calls for a center tapped 24VAC transformer using DC instead??? I really hate to spend $40-$50 just to see what 0.003% distortion sounds like instead of the 0.5-1% I'm used to!

Dayton for the win!

oh, thanks... I have soldered a couple of LM1875 mono boards up, The ones in your vid 'LM1875 IC audio amplifier board kit test and review' I will be making a stereo Amp with them. Jaycar have toroidal's for sale 12-0-12, 24v - $27 18-0-18, 36 - $17 25-0-25, 50v - $17 all reduced from $87 ...The link I sent you was supposed to be a 12-0-12. I don't really understand how you got 15-0-15....... but i'm learning. Will the 12-0-12 'MT 2130 toroidal transformer' be a good addition to the bench?

Nice

I always wondered why transformer power output was specified as VA rather than W.

I've been designing amplifiers for over 10 years now, and I've read many places that say that your transformer needs to be at least double your total rated output power. I've found this to be a myth. I've found that if you about get a transformer with VA equal to total output rated power (and a well regulated transformer), you're perfectly fine, and still have reserves. No audio signal can sustain rated output of an amplifier. A 100 W amplifier will typically sustain an average of 20 W. The 100 W rating allows the necessary headroom. The capacitors provide the energy for the high power transients. Am I wrong?

Respect

John Can you not make a video about making a proper ground connection to the frame. From where is the ground best to make the connection? What if there are several power supplies?

This transformer available indai

( I love this stuff... lol) You do a really great job John!! Very good bench testing/proof... really helps in the learning process by practical hands on. I'd be interested to have you review or build any of my 3 (easy-build, home-brew )great-sounding little HIFI audio tube-amps. ( www.pbpix.com/amp/ or www.balazsy.com/amp/ ) 1.) 5902 PP integrated amp 2.) 6v6 PP integrated amp 3.) 12Ax7-6v6 SE amp Primarily I'd like to see you discuss some of the technical benefits and other aspects of the interesting approaches I took for some of the circuit elements: ie : 1.) Voltage dropper capacitor used for filament supply in the first amp and again in the 2nd alt version used for the dual supply to the opamp driver. 2.) Use of LM317 as CCS for cathode bias

good

i live in columbus

measuring the output voltage without measuring the line voltage,... ?

100 Watts x 2 at 8 Ohms.

your formula to double va works good for you but not for my wallet as im looking for tf for my 1000w amp :)

Sound standard ka 2000 ka transformer ka prize kya hai

Can you help me chose a good toroidal transformer for this amplifier board??? I will be driven 8 ohms speakers. www.thanksbuyer.com/tda7293-power-amplifier-board-100w-100w-ne5532-op-amp-audio-diy-kit-unassembled-53073 Thanks in advance.

1:00: but how am I going to find Pikachu then?

Well this one is an Abdu Amiderrr man lol...What I knew..one of the last few around there..wound the secondary right and thickkk wire real wire...it is high resistance from it...and all the lawless shit running HOT in only and all that old school shit...I think it's alright but I did kill a rec...

Pokemon go. Is 7years old!!!!! The fuc

Pokeman is why I quit riding a motorcycle. People were looking at their phones and not the road looking for imaginary thing that had no reward in finding them. I don't understand it and I hope I never do. I think all of those people are voting age now by the looks of things.

What's with the add skip button? If you don't watch the stupid commercial you just keep getting commercials until you finally watch one all the way through . Most of the time viewers are looking to see something they might be interested in and don't have time to wade through stupid commercials . I was subscribed and now I'm not