Selecting power transformer for audio amplifier
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- čas přidán 25. 07. 2024
- This video touches on dual power supplies and selecting the right sized transformer for your power amplifier projects. I also experiment with how a transformer with the same output voltage but a different current rating effect the output power of the amplifier.
- Věda a technologie
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!
FIRST! :) Hey guys thanks for watching. I'll be uploading a few more videos soon. Stay tuned!
Can't you get more wattage using a smoothing capacitor or a filter?
JohnAudioTech
😂😂😂
MrBrymstond; Yes, but ONLY for a VERY short duration, as in "peak" or momentary "dynamic" power... Once the capacitor discharges then you have no more power available than what the transformer or power supply/power source can deliver on a steady basis, so if that transformer or power source cannot continually back up the power drain from the load then you're only gonna get as much as you put into the circuit, (from the power source), so that's why those extra large "add-on" caps that you see in a lot of car stereo systems don't (cannot) help any with the RMS/continuous power output of an amplifier, ONLY with the peak maximum (short duration) power output... And only then if properly installed, AND if using a good quality capacitor too, because many of the cheap junk ones made in China offer absolutely nothing, (or very little)!... I've seen some of those kind which have an actual value of only about 1/10 of their stated capacitance!... Pretty pitiful! LOL!
Basically, filter or "smoothing" capacitors only do just that; they smooth out the AC ripple that comes through a rectifier, (bridge, etc.), circuit, which in turn makes the output voltage have less AC on it and a more stable DC voltage... Capacitors do not "add" any power or wattage to the circuit.
Hi John! Hope you have time to respond. My dilemna,, is that most of the transformers I have, new and recovered, torroidal or EI core, have output voltages of 28 vac or more. Once you factor in the 122vac at the source, I have nothing short of 44vdc, theoretically. What's puzzling is that most of the older amps used this much voltage, when most SS amps I build require 35vdc or less? It's difficult to find mfrs. who make low voltage, hi current trannies. Thanks for your vids! Ill find your paypal!
Great video it shows how it just isn’t the size of capacitor but how important it is to size the transformer correctly!
Im getting into building my amps, and i find your videos very useful, keep it up! :D
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'.
The simplest way is with an oscillating op amp driving fets being manipulated by another op amp getting fed global feedback after the output filtering. Simplification, but it really is that simple.
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...
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.
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.
How did your project pan out?
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.
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
Sounds like a fun project. Thanks for the comment.
Great as always !! ⭐⭐⭐⭐⭐
Awesome video, thanks man
Thank you, helps me figure trans demand.
Great video
Thanks heaps john this was a big help in selecting the right transformer.
Glad it was useful to you!
very informative video. thanks
Great Channel John. If interested please do more on DIY Active speaker Build for cheapskates
Thanks for the details! Can you expand upon the dynamic power topic? Thanks
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!
Hi! I know this is old, but I had to respond. After ac voltage is rectified, the subsequent dirty dc is magnified by a factor of about 1.41. So, in building a LM3886 amplifier, I used a toroidal transformer with a secondary of about 19-0-19 vac, so 19X1.41 equals about 28 vdc, when you factor in I'm getting 122 vac at the outlet, another concern! The large capacitors "smooth" the dc somewhat. I think it was a 200 or so VA transformer, about the minimum. And of course, there's the voltage drop when the amplifier is driven, in my experience, just a volt or 2.
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?
I live next door to an electrical substation. I have like 15 pikachus.
Thank you for your time, Wish you well. Ta
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.
Regulated AC supplies are complicated and add impedance to the line. Most solid state power amps perform fine over a certain range of supply voltages and will lose peak power output but otherwise work fine on lower than rated voltage. Provided the filter caps and the output transistors are kept within the SOA higher doesn't bother them either.
So a properly designed solid state amp might work fine if its 120 nominal input voltage was anywhere between say 100 and 135 volts. Surges above that and spikes are potential killers though.
Using a regulated supply for preamps, CD players, and other low current devices could be beneficial. Most have internal DC regulation so higher voltages will cause their linear regulators to run hotter. HOW you regulate the AC is crucial. many schemes like ferroresonant transformers produce a distorted waveform which will result in higher noise.
@@wamgoc3637 I think he meant regulated DC.
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.
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?
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!!!!
thank you! Can you help me determine the optimal current when losing parameters on transformer.
Hi John. Nice video you got there... What size are the two capacitors on that power supply you build? 25volt dc ? thanks you
In a stereo setup, would the transformer secondary need to have a separate winding for each channel plus center tap?
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.
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?
oh yeah, I'm tuned in. I like a toroid transformer, I prefer winding them myself.
good stuff
It´s quite possible to use Switched power supplies instead of bulky transformers. I´m using them for my home built Quad amps.
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
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?
I might do this. My latest video (to be uploaded soon) shows a modification of a power supply I built a while ago.
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?
I used free audio editing software called Audacity. It can generate tones that can be saved to WAV files. I had a potentiometer connected to the input of the amplifier to vary the signal. Scope was connected across the 4 ohm load resistor on the output.
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.
Max voltage is √2 times the secondary output.. ie 35 volts
Could you recommend a introductory fo totally clueless guys like me trying to understand
Hi John , Just wanted to know what chip or amplifier it was you used in the testing ,, thanks ..
hi is it possible those diods are not placed right?
So I would need a 4000va transformer for a 2000w mono amp?
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?
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
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
please help me with output coupling capacitor
@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?
Nice
Great videos. Thanks! Did anyone tell you, you sound like Tobby Maguire :)
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?
I'd have to watch the video to remember but those are probably not part of the circuit. I have a lot of stuff "parked" on my breadboards.
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?
Is it a small click or a larger pop? These solutions likely won't correct the problem. It is normal to have some click at power up / down. The solution would require a relay on the outputs, time delay and voltage sensing circuitry. This is a lot of circuitry to correct for, what is in my opinion, a trivial issue.
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.
Why? Burning speakers is part of the fun
Respect
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!
There really wouldn't be any change to the sound quality, although the bass can roll off sooner depending on the size of the output capacitor used. If you mean that you want to see a video on how to connect them in single supply mode, I could do that at some point.
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.
As a kid, my friend gave me a new 5HP 3 phase motor. It was heavy and I took it home in my red wagon. At some point I dissembled it and eventually threw it away. I can just kick myself now. Those were expensive!
The more I learn about circuits and electronics, the more convinced I am that I’ve thrown away enough gear to have contained at least one of every component I’ve ever bought :)
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.
What are you powering with it? It is 15-0-15 secondary. After rectification and filtering, it would put out about +22 & -22 volts relative to the common lead at no load.
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.
Yes, That is a mono block design and is fine.
Nice to see someone using real maths rather than fictitious BS claims. Well done.
sir i did not understand why in AC or transformer rating we use VA instead of WATTS am kinda confused ? please help me out
Bahi proton xt 4000 watt ka input output board kitne ka mile ga
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!!!
haha FULL BRIDGE RECTIFIER he said the FUNNY THING
Electroboom is smiling.
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.
The AC audio waveform goes above and below zero volts. If you have a dual (plus and minus) power supply, it's possible to do this and have the amplifier output sitting at 0V DC. If you use a single supply, the amplifier output will need to be at 1/2 of the supply voltage. Because of this, a capacitor is needed on the output.
This DC blocking capacitor impacts the performance of the amplifier in a negative way (phase shift, impedance, as well as a
Non linear element in series with the output) and could just as easily be used as a filter capacitor for a dual supply amplifier.
In short the answer is performance. No modern high quality amplifier will use an output capacitor and a single ended supply.
Thanks! That helped
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.
Nearly all modern amps can be improved by adding more capacitance to the power reserve. With enough dynamic power, you can get away with being a bit starved.
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 !
You might want a transformer with at least a 250 to 300 VA rating. Too many unknowns for me to give solid advice here. Going from 60 to 50Hz may also be an issue with the amplifier. The amplifier may be configured for 230v operation internally. You have to hack it at your own risk.
@@JohnAudioTech 1. The average is 210 VA, therefore the peak could be at least 3 times that. What do you think ?
2. The European models are configured for 220 V AC.
3. What I had mentioned above is the name plate rating.
Hey what about the Toroidal transformer... explain man
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.
( 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
Dayton for the win!
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
Sounds like the output transistors are shorted. You should check the drivers for damage as well.
@@JohnAudioTech okay, I know what my transistors are. By drivers I would assume you mean the speakers that were hooked up, if not tell me what that is lol. My driver was fine though, the amp was powering a sundown sa12 subwoofer, which is quite robust. I actually have another identical amplifier that still powers that subwoofer
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?
I might have seen the wrong one. 12-0-12 ones are fine if you are going to use 4 ohm loads. You can go with the 18-0-18 if you use no less than 8 ohms speakers because you will get good power output, around 25w per channel. The 25-0-25 is too much voltage for the LM1875 after rectification and filtering. Those are very good prices. You can use 300 watt (VA) transformer but you really only need 100.
great...So now,I'm guessing it's not as easy as just plugging it into the V- G V+ inputs of the board. "LM1875 after rectification and filtering." any direction on this matter :)... it's 5am and my solder iron is running haha... Thanks again
where on earth do i go from here... got my 18-0-18 toroidal, connected to 240 main, but, do you think i can get any response with my multimeter with the remaining red, blk, yellow, orange wires... Nope... lost! if you can help... awesome thanks
PRI:240V AV 50Hz (130C) Blu-Blu
SEC:18V ACx2 Red-Blk+Yel-Org
...thats all the spec's I have.
Thanks again ;)
.................hope to here from you. cheers
With your meter set to AC voltage, you should get around 20v (a bit higher than 18v because the transformer is not loaded) across the proper leads. red to black and yellow to orange, I guess (Jaycar site is down for maintenance as I type this). Do NOT connect this direct to the amplifier. You need a full wave rectifier bridge and filter capacitors to make a dual DC supply for the amp board. Connecting AC direct will ruin the amp if it is the same LM1875 board I reviewed as it requires DC.
Much appreciated :)
Can a transformer be too powerful for the amplifier? I've built this push pull amp czcams.com/video/mQuvMrJXDoI/video.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 czcams.com/video/wapHGDgNHlM/video.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.
which type of transformer will eliminate humming in an amplifier? besides that which combination of capacitors will eliminate transformer humming in an amplifier?
If you mean humming coming from the transformer itself, the toroidal transformer would be the best. Amplifier designers like to use as much filter capacitance as possible but that means a high current crest factor drawn from the transformer. Putting an inductor between the fullwave bridge and filter caps would reduce that and perhaps make the transformer quieter. I don't know for sure since I haven't tried this.
I always wondered why transformer power output was specified as VA rather than W.
Short answer is that the VA is what the transformer is capable of, but once connected to a bridge rectifier and load, the current is no longer a clean sine wave as the voltage, nor is it in phase any longer, so the actual power delivered to the load is not has high as the VA (power) that the transformer is putting out. Power out is not equal to power in, and I'm not talking about efficiency, although that's part of it, I'm talking about power factor. Apparent power versus real power (VA versus Watts).
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?
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
It might be because the coil has a misplaced center tap, or there may be differing loads between the positive and negative sides.
If the mismatch is causing problems, try using voltage regulators, although that will lower the effective supply voltage and require more heatsinks. Look for low-dropout (LDO) regulators.
A few possibilities. Could be a center tap not being center due to shoddy transformer construction, could be a bad rectifier, uneven loading, bad smoothing cap. If those rails are regulated, it might also be a bad regulator.
First thing I'd do is disconnect the transformer from the board, hook it up to the multimeter on AC, and check the readings - if it's a bad tap, that'll be obvious right away. If nothing is out of the expected readings, that's the first problem eliminated.
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?
I can agree because, like you say, most music signals have the bulk of the power far below the peaks. The transformer can handle the low average power and the filter caps the peaks. There are those who like the type of music with heavy sustained bass notes and played at high levels. This places great demand on the power supply, so I would recommend a stronger transformer. It can also help with reactive loudspeaker loads that can dip well below their nominal impedance at certain frequencies.
Thanks for the reply. I agree about the impedance dropping significantly, so I design for that as well, but I think this accounts for much less of a demand on the power supply because it happens only at certain frequencies, so the power is very little, even if the impedance dropped to 3 ohms for an 8 ohm load.
At the moment I'm designing for rated 330W in 4 ohms, but it will most often be doing about 180W rated in 8 ohms. I'm using a 625VA transformer. If the supply had to drop 10%, it would sustain a 260W sine wave in 4 ohms. Not many speakers can handle this sort of continuous power. I think over-rating a transformer is a bit more relevant for lower power amps. I would be very glad to test how the 625VA holds up for two channels driven with a sine wave, but I don't have a capable 4 ohms load! :)
www.ebay.com/p/500-watts-4-ohm-audio-power-amp-amplifier-dummy-test-load/1784886370?_trksid=p2047675.l2644
Thanks. That's one, I would need two, and then it's going to cost me a lot to get it here, and risk it getting lost. :) If I want a 4 ohm load, I'll build one; I don't see the need for one at the moment.
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)?
It is not so straight forward to calculate. If you like you music loud with such an undersized transformer, it can overheat.
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!
BTW the amp has rectifier on board so does it convert the AC to DC anyway? It's one of those TDA 2030x2 and 2050 for subwoofer output. Thanks
You could hook up dual DC if you can bypass the bridge rectifier. What country do you reside? If you live near a Radio Shack, they sell a 25.2v 2A transformer (same as used in the video) for around $15. They are good quality and would power the amp fine. If it is an eBay special, it will probably work but I doubt the ICs are authentic, especially the TDA2050.
This transformer available indai
i live in columbus
measuring the output voltage without measuring the line voltage,... ?
Sound standard ka 2000 ka transformer ka prize kya hai
1:00: but how am I going to find Pikachu then?
100 Watts x 2 at 8 Ohms.
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...
your formula to double va works good for you but not for my wallet as im looking for tf for my 1000w amp :)
its good for small stuf like this for that a 1200va transformer shuld be perfect or even 1100va and also why not wind it yourself get a 1200va ups broken since u dont need it working and wind that transformer up ...
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.
I'd get a transformer with a 56 volt secondary that is center tapped (or two 28v secondaries). Sometimes notated as 28-0-28. Volt-amp rating should be no less than 250 (250 VA). It says the kit doesn't include a heatsink or capacitors. I'd get two 10,000uf 50volt capacitors. The heatsink must be fairly large. Roughly 18cm wide x 10cm tall with 5cm vertical cooling fins.
JohnAudioTech
Your information is gold to me brother. I appreciate your time.
Could you link me to the best option ( Transformer)
AS you can see this amp is dual chanel 100w+ 100w.
I will be running 8 ohms speakers .
The toroidal transformer will be working in the USA. AC110V
Link me to the best toroidal transformer you can find.
Thanks a lot man.
Gio.
Please link
JohnAudioTech
TELL me I found it.
Look at this:
www.amazon.com/dp/B071SJZQNG/ref=asc_df_B071SJZQNG5222080/?tag=hyprod-20&creative=395033&creativeASIN=B071SJZQNG&linkCode=df0&hvadid=216534554317&hvpos=1o3&hvnetw=g&hvrand=14769108606621420209&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9004398&hvtargid=pla-351409043017
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