Bridging audio amplifiers explained, LM1875 example

I look at bridging amplifiers and some pitfalls to avoid. I set up an example and take measurements.
Correction: I said at 6:20, 45 volts, that should be 45 watts. I can't seem to add annotations anymore. I guess KZbin needs Flash Player for that and I refuse to install that garbage.

[@stevenstewart5980]

This video gave a great explanation of bridging amplifiers and the ramifications! Thanks John. Another great video!

[@markjosephnavarro7034]

Now that explains well for me...once again thank you sir...

[@omsingharjit]

4:24 can same apply with Bridge Amplifier too ? Can i combine two bridge channel of 4 channel car amplifier in single ic ? And then how can we replace single supply with split supplies ?

[@nef003]

Excellent video sir. How is one able manage the voltage input in order to avoid clipping in real life application if the transformer+ the rectifier if any bumps it. ?

[@pinghe2942]

Hi john, I'm new to analog electronics. So in the bridging experiment schematic, the left chip's output is fed into the right chip's neg-input, I expected something more obvious, like, feed the input into the right-chip's neg-input directly (swap + and -), what's the difference?

[@charlesklein7232]

i use a microphone that is plugged into a desktop computer in the microphone plug on the back of the motherboard and i use audacity in ubuntu 16.04. i can here the microphone but it is not loud enough. their is a thing called "48V Phantom Power Supply" but this is for Laptop which does not give the microphone its full 5 watt power. on my desktop it has that and so i was told that it would not allow me to increase volume. but could i use a "PRE-AMP" before i plug into the computer to increase its volume. or basically how do i increase volume.

[@MarcelOoms]

Hi John, came across this video now. I ordered 4 of those ebay LM1875 kit you tested. Good tip. Bridging them would be nice to try, but I have a question, why do you connect the output of the first amp to the second amps input instead of connecting the same input (to the inverting input of the amp also). Wouldn't that be cleaner, not having half of the signal go through 2 amps?

[@cassvirgillo3395]

Hi JAT, Great video on bridging. Uncle Doug on YT has a new series on power supplies where he discusses Peak and RMS power. The DVM internally converts peak to RMS. The values 0.707 and 1.414 were mentioned. You and Uncle Doug are always goto channels when you want to learn from people who know what they are talking about. All American Five Radio, and, one or two others. Thankyou for sharing your knowledge. I built a bulb current limiter as per an Uncle Doug video, works great. Be good, C.

[@mansionese]

how about making it Grounded-bridge power amp? Can it be done on a Chipamp?

[@tigerelectronics5966]

I have quite a few TA7205AP chips, can those be bridged too using the circuit you showed?

[@snaprollinpitts]

thanks John, didn't know that about bridging gives you less.

[@avi-tech-haifa]

can you explain what is this +12v / -12v power suply and wher to buy it?

[@MichaelBeeny]

Current limiting is the main issue on these small lowish powered chips. After all they were not really made for bridging. A good explanation of the principals of bridging however.

[@JohnAudioTech]

+Michael Beeny This is true. Bridging makes sense when you need more power when you are constrained by the supply voltage (such as when using batteries). 35 clean watts is not too shabby with +/- 15 volt rails. Bridging is also common with high power PA amplification where huge power is needed (over 1,000 watts in some cases) into common load impedances so the amp design doesn't have to resort on high voltage supply rails and HV solid state design or heavy output transformers in the lightweight gear they use now.

[@jamest.5001]

where can someone salvage a a torrid like the one you got there? I'd like to have a few of them!

[@ergindemir7366]

2 questions needs to be answered: Is the slew rate double, as expected? Is the power efficiency better or worse?

[@krishna0042]

A 6.5 inch subwoofer is enough for lm1875ic at 18 0 18 supply??

[@facundonu]

great video as usual. i'll only say that bridging "not so btl chips like 1875" could be useful when you already own several chips or a transformer with not enough voltage. those chips are way cheaper than transformers here, so if you want to add power to an existing system on a low budget, it's far more convenient to bridge or paralell some chips than to replace power supply.

[@spyko7z]

Can you explain of parallel mode works? :)

[@stephenodonnell6645]

Hi John... When you sayd "35 clean watts is not too shabby with +/- 15 volt rails", I think that is voltage +/-15 Volts under LOAD... In order to get more clean the wole picture, please, can you tell me about the transformer? I mean secundary Amperes and CA volts (VA transformer data) and after rectifier CC WITHOUT LOAD? As always, very instructive videos... Thanks a lot and Greetings from Spain...

[@omsingharjit]

9:49 and where is the audio inversed section ?

[@91rickstar]

What is the red square thing on the board is it a resistor pack or something

[@JohnAudioTech]

Those are 1uf film capacitors.

[@proutsos]

Great thanks I got it now! but how do you flip the signal?

[@JohnAudioTech]

Signal is fed into the inverting pin on the second amp so it is out of phase from the first amp.

[@proutsos]

Thanks!

[@andymouse]

Interesting tutorial...cheers.

[@Dazzwidd]

It's certainly worth bridging them if you want power from a lower supply voltage. I was thinking about doing it for an amplifier that runs from a single rail supply...22 to 24V from a rechargeable Li-ion battery

[@shaerodenaizen4375]

all you have to do to get around the current limitations is run the output of the op amp through a current buffer, and then take the feedback from the output of the buffer and you won't get any crossover distortion if your slew rate is high enough.

[@markjosephnavarro7034]

Sir..what is the main purpose of bridging amplifiers?thanks for you response in advance..

[@JohnAudioTech]

+Mark joseph Navarro More output power.

[@markjosephnavarro7034]

But it won't affect or reduces the life span of the amplifier sir?

[@JohnAudioTech]

+Mark joseph Navarro Not if properly done. This is why I selected 30 volts (+/- 15v rails) with the LM1875 so that the output current is kept around 2 amps max when bridged. This gives some current headroom for dealing with most speakers' reactive loads. Running the chip bridged at a higher voltage would certainly stress it more.

[@PetruV]

Just in time as I was experimenting with this chip,bridging them is not worth it, not enough current What I tried doing(and succeded) was adding some transistors to boost the current of the lm1875,thus making 2 ohm operation possible.Ask me you want more info or a schematic.

[@JohnAudioTech]

+PetruV I used an LM1875 driving an output stage in my Kinter MA-150 amp review as I was planing to make a video on it at some point.

[@mikeab1yk911]

John, I left a similar comment on another video... Are you at all involved with armature radio?

[@JohnAudioTech]

+Mike AB1YK Hi Mike, I never had much interest in it. It seems to be an expensive hobby and I my meager salary permits limited resources to my hobbies. That said, I would like to play more with RF and transmitter circuits.

[@mikeab1yk911]

+JohnAudioTech John I would Google "BitX" "farhan" and check out his website. your videos have helped me in my home brewing... Most likely you already have everything you would need to get on the air. Please look into getting licensed. Very little money is required. Send me an email struzikmp at gmail dot com and I will send you some links.

[@TomStorey96]

JohnAudioTech you have solid content and people really like your videos. You may find some success with a Patreon account which seems all the rage these days. At the least it may provide some pocket money for components, tools etc.

[@antonrnnedal7797]

How do you get genuine chips?

[@TomStorey96]

Buy from a reputable source. I use a combination of RS and DigiKey. I tend to prefer RS as where I am, in the UK, they have free next day shipping, whereas DigiKey ships from the US and only offers free shipping if you buy above a certain dollar value.

[@joohop]

Badboy thanks man

[@benli3065]

The constant camera movements, especially for static scenes like the whiteboard, is distracting and makes it more difficult than necessary to pay attention to the substantive information. See bigclivedotcom, techmoan, or eevblog for good examples of how to handle the camera to show different bench and instrument elements, without risking motion sickness.

[@Rivalgamesbg]

I don't get the purpose of signal generators. Every android phone can be such(up to about 22KHz). I can't see a reason investing in one.

[@JohnAudioTech]

+Rivalgamesbg A true wave form generator is far more versatile. Higher amplitude, low distortion, RF frequency, modulation options, arbitrary waveform, dual channel, frequency counter and so much more. I have no excuse for not having one on my bench besides the money needed...

[@HillOrStream]

+JohnAudioTech Yes indeed, something I have wanted for decades now... Also a good dual power supply and scope like you have.

[@Rivalgamesbg]

JohnAudioTech It can do all those stuff you mentioned. The only thing it can't do is high frequency. The app is called waveform generator. The app+ a proper op-amp amplifier circuit can save you a lot of money. It is perfect for your audio testing needs.

[@prasadhlyalkar9746]

Mihail Tochev I was using android app like you said but it has its own limitations if you are serious about building you're power amp,preams and crossovers you need real thing it helps a lot money well spent.

[@martinda7446]

Mihail, what you said, no it doesn't. Unless you just want a toy to play with, then it's OK.

[@steveone]

Twenty minutes . I think thats a record for your channel John .

[@JohnAudioTech]

+Steve Smith Yes it is! It was pushing 22 but some of it ended up on the cutting room floor as they say.

[@hendryparman3782]

John. I dont understand why you stuck on tnose chipamps its no challenge. At least build descreet component amplifier with separate transistors. I dont mean to be rude but that would be a Better challenge than those chipamps.

[@JohnAudioTech]

+Hendry parman Discrete amps are beyond what a lot of people are interested in and don't attract as many views as the chip amp videos. Despite that, I am interested in discrete designs and do have a video in the works.

[@jeremyhankenson7335]

His voice strikes me as Bill Gate-ish

[@JohnAudioTech]

I wish my bank roll was Bill Gates-ish.

[@jamest.5001]

I also wish I had money!

[@watup110875]

I never liked the sound that comes from bridging car amplifiers! It just didn't sound right! To me it was like a whole lot of speaker movement, without the bass matching it! 😎 It is as if a switch was being cut on and off to mimic what was suppose to sound better, but didn't! But I don't care much for dual-voice coil speakers either! To me a mono block amp is far better than a stereo to bridge mode amp, because it is made for stereo to out put mono! To where the other, has to be rewired to get the same effect! Plus I think there is more bang for the buck going mono vs a tri-bridge configuration! 😎

[@keithalexander36]

i likw amp

[@kulamario2]

ale masz tam kurwa bajzel na tym biurku prawie jak ja