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/HTB1zVAz...ifier-module-High-power-TDA8932-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?
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.
the chip has a + input terminal and a - input terminal. i thought the wiring was as simple as this:
https://ae01.alicdn.com/kf/HTB1zVAz...ifier-module-High-power-TDA8932-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?
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.
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.
Internal on the small board, I believe power "-" is connected to signal ground. You just do as indicated in the sketch you link to.
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...)
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.
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?
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?
You should tell us if you want any modification. If it sounds good don't fix it. 
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.
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.
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 don´t 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 it´s 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 Ohm´s law. Without it better stick to changing light bulbs if the are brocken, but only for the same value!
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 don´t 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 it´s 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 Ohm´s law. Without it better stick to changing light bulbs if the are brocken, but only for the same value!
On the site you refer to, I see 5 suggestions for improvement of that board. I have listed them in order of importance:
1) The power supply line decoupling capacitors are insufficient for bass reproduction. There is in total 5x100uF decoupling on the board. The supply current can be several amperes. The suggestion is to add 4700uF-15000uF capacitance external of the board. This suggestion must be for a stereo version with two boards.
The photos show no such extra capacitors. For one board and feed from an SMPS, 4700uF (50V) should be sufficient. There is no extra place for further capacitance on the small amplifier board. The external capacitor should be placed near the supply terminals of the board, eventually on the supply terminals and pointed away from the other components
2) The output filter chokes are insufficient in current rating to handle the output current. They are simply too small. If they saturate, it can have serious consequences for the output. Filter chokes that can handle the output current safely are necessarily larger in physical size. From the photos you see two different replacements with toroidal chokes. Another option is to move the output filter (chokes and capacitors) to an external board, placed close to the amplifier board and connected with short wires.
3) The output filter capacitors are of the ceramic SMD type with poor linearity. There is no space on the small board for replacement by foil capacitors with better linearity. If you anyway move the filter chokes to a board external of the amplifier board, use foil capacitors instead. If the chokes stay on the small amplifier board, leave the SMD capacitors as they are.
4) The chip cooling is poor and the chip will be hot above 20V supply. Luckily it is possible to mount a heatsink on top of the IC and this way leave operation up to 36V supply possible. The first photo shows two small green heatsinks mounted on top. You may add a small fan to ventilate the heatsinks. Another possibility is to use a heat-bridge from the IC and to the board edge and there connect a larger heatsink.
5) The input coupling capacitors are of a small ceramic SMD type with poor linearity and noisy. As you use the amplifier for a guitar, a slight increase in THD is not problematic. The noise level is anyway low. From the photos it seems not to be easy to replace the small SMD capacitors with foil capacitors (the blue ones), and I suggest you leave the SMD capacitors as they are.
As Think says, do not “repair” something that you actually find works quite well. And, remember the statement of Turbowatch2 that start modifying a cheap board designed for simple use, if you really want something better, is not worth the effort. Then buy something that is better implemented,
In my view, the TDA8932 chip has an enormous potential if implemented right but this very cheap board only allows simple performance.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.