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Class D Switching Power Amplifiers and Power D/A conversion

Help on input wiring on TDA8932 amplifier.
Help on input wiring on TDA8932 amplifier.
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Old 20th September 2019, 12:31 PM   #1
Lysergium is offline Lysergium
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Join Date: Sep 2019
Default Help on input wiring on TDA8932 amplifier.

I'm having trouble figuring out how to connect a mono jack socket as the input.
the chip has a + input terminal and a - input terminal. i thought the wiring was as simple as this:
https://ae01.alicdn.com/kf/HTB1zVAzc...-low-power.jpg

However, in another thread ( strange buzz problem with input stage of home-made chip amp. | All About Circuits ), i was told, that i need to connect the - input terminal to ground. is this correct? haven't seen anyone else do this when using this chip.

I've read the schematics of the amp board, and they confused me even further.
where are the terminals in these schematics? one has one input, the other has two, but it's the same chip. also, there are multiple connections to ground in the schematics, but my amp chip isn't connected to ground anywhere, so that would imply that i do need a connection to ground somewhere. so is my solution as easy as connecting the negative input terminal to ground?
i dont get it.PNG
i dont understand.PNG

If I understand correctly, this is what i should do:
1. connect the + lug of mono jack socket, to + input terminal on chip, with shielded wire
2. connect the ground lug on the mono jack, to the - input terminal, via the shielding of the shielded wire.
3. connect the - input terminal to the ground on my power source.

is this correct? please help, i'm completely lost.
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Old 20th September 2019, 12:53 PM   #2
FauxFrench is offline FauxFrench  France
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Location: The mountains, calm and quiet.
Quote:
Originally Posted by Lysergium View Post
..... i thought the wiring was as simple as this:
https://ae01.alicdn.com/kf/HTB1zVAzc...-low-power.jpg

This is correct. "-" input to signal ground and "+" input to the signal wire.
Unless for extended knowledge, do not start wondering why they configured the board circuit like that.
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Old 20th September 2019, 01:01 PM   #3
Lysergium is offline Lysergium
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so, i do need to connect the - input lug to the ground connection on my power source?
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Old 20th September 2019, 01:10 PM   #4
FauxFrench is offline FauxFrench  France
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Join Date: Dec 2017
Location: The mountains, calm and quiet.
Quote:
Originally Posted by Lysergium View Post
so, i do need to connect the - input lug to the ground connection on my power source?

Internal on the small board, I believe power "-" is connected to signal ground. You just do as indicated in the sketch you link to.
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Old 20th September 2019, 02:07 PM   #5
Lysergium is offline Lysergium
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ok, so the negative (-) input terminal functions as the ground for the signal, i do not need to connect it to the ground of my power source. finaly.

you are seriously helpful.

additional question - if i put the amp circuit in a metal enclosure (without contacting it), and run a wire from that to the ground connection on my power supply, that will function as a farady cage and will eliminate RF and EM interferance, right? no problems?

it's obvious, but building this simple amplifier made me realise, i know less about electronics than i thought (fricking dunning-kruger effect...)
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Old 20th September 2019, 02:37 PM   #6
FauxFrench is offline FauxFrench  France
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Join Date: Dec 2017
Location: The mountains, calm and quiet.
Quote:
Originally Posted by Lysergium View Post
ok, so the negative (-) input terminal functions as the ground for the signal, i do not need to connect it to the ground of my power source. finaly.

you are seriously helpful.

additional question - if i put the amp circuit in a metal enclosure (without contacting it), and run a wire from that to the ground connection on my power supply, that will function as a farady cage and will eliminate RF and EM interferance, right? no problems?

it's obvious, but building this simple amplifier made me realise, i know less about electronics than i thought (fricking dunning-kruger effect...)
Many thanks.

Yes, putting it in a metal enclosure will shield the amplifier against certain electrostatic and electromagnetic fields. Magnetically conductive MU-metal is the best but difficult to find. Aluminum or sheet iron is often used.

Yes, you have to connect the metal chassis to one point in the amplifier. Normally you use input signal ground as this is also the reference for the amplification.

You seem to be in the same situation as many slightly less experienced DIYs - you may know many details but you lack the overview. Then, you are not sure how to fit the details in when facing an actual situation. Theoretical studies of electronics bring good knowledge of the details but you normally need "hands-on" practical experience to gain the overview. Overview means what is important and what is less relevant in a particular practical situation.

Good luck with your project and future DIY experiences.
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Old 20th September 2019, 03:46 PM   #7
Think is offline Think  Netherlands
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Help on input wiring on TDA8932 amplifier.
Click the image to open in full size.

Is this your board?

Then schematic 2 applies but this does not matter as these connections are in the board.
This is a mono or 1 channel board with an unbalanced input, so just put audio + (left or right) to audio + input and the - to the - input.
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Old 20th September 2019, 05:21 PM   #8
Lysergium is offline Lysergium
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thanks guys.

So it's fine if i connect the faraday box to the negative input terminal, not the ground (earth) on my power supply? both of these would work, right?

But grounding it to the negative input terminal seems both safer and simpler.

thanks for the help, i now have a working amp. volume not too high, acceptable, but i'll probably add a preamp to this circuit, so that's fine currently.

one more thing, if you have the time and interest:

I found this interesting page on modifying this amp board ( http://diybudgetaudio.com/TDA8932.htm )

most of the recomended modifications, i know, are a bit out of my league right now, but the page says this -
"The power-line decoupling capacitors need some attention as well /.../ With the potential of the TDA8932 chip, a further 4700uF-15000uF should be added externally through low impedance wiring."

seems simple to do. but the page gives zero instructions.
What modifications do you think i should/could do?
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Old 20th September 2019, 05:52 PM   #9
Think is offline Think  Netherlands
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Help on input wiring on TDA8932 amplifier.
You should tell us if you want any modification. If it sounds good don't fix it. :P

Sound quality is best upgraded by upgrading the weakest link in the audio chain. And that is most often the speakers or speaker location in the room.
Adding huge power caps will not do much if anything at all, maybe some better caps do. With an SMPS power supply of batteries, shortening or upgrading to thicker wires from the power supply to the amp is one of the first things to do if you experience voltage drops.
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Old 21st September 2019, 03:24 AM   #10
Turbowatch2 is offline Turbowatch2  Germany
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You can not measure voltage drops with the usual digital hand held multi-volt-meter.
It only averages for about half a second. To see dynamic voltage drop you need an oscilloscope, so you can see fast changes. With your tiny amp, about 1000-2200uf (voltage of capacitor at least what you run the amp on) connected over the + and - at the boards power input, could make it a bit more capable with low level signals, if the loudspeaker can reproduce them. But donīt expect too much.
It does not make sense to "improve" on a weak amp, if it would be cheaper to get a better, stronger one. This one is limited by itīs output filters to less than 2 ampere, so this should be the limit. How much power this is, depends on the speakers impedance.

R=U/I and P=UxI for a very, very rough calculation. (This would right be only with DC, but gives you a first idea)

So U=RxI which makes 4ohm x 2amp = 8volt and 8volt x 2amp = 16 watt.
With 8 ohm this looks better, it can use 16 volts. You see, as it is the current (A) that limits the small inductor.
This magic formula "R=U/I" is Ohmīs law. Without it better stick to changing light bulbs if the are brocken, but only for the same value!
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