Hello,
This is my second shot on a chip amp, the first one was TDA2050 which worked really well. I have some simple pc speakers with a dead amp lying around and thought about doing this 2x10W simple amp. So i downloaded the datasheet, etched my pcb, soldered all the components and it came out pretty good. Definitely not one of my first diy projects, i've built a dozen guitar effect pedals
However, i noticed this strange behavior:
1. when i use an old short cable stripped from the dead amp, from the PC output directly soldered on the PCB i get amazing sound, no noise at all.
2. when i use a common 3.5mm audio cable (1.5m long) and solder it directly on the board, i get noticeable noise
3. when i use a jack to connect the audo cable, and then solder the jack to the PCB, i get some huge buzz/clapping sound, and as you can guess, no music at all. The TDA also overhears very fast, in about 2-3 seconds!
(There was no big heating at all in the other 2 cases)
So what could it be, is there anyway i can fix this?
Thank you for this great forum
This is my second shot on a chip amp, the first one was TDA2050 which worked really well. I have some simple pc speakers with a dead amp lying around and thought about doing this 2x10W simple amp. So i downloaded the datasheet, etched my pcb, soldered all the components and it came out pretty good. Definitely not one of my first diy projects, i've built a dozen guitar effect pedals
However, i noticed this strange behavior:
1. when i use an old short cable stripped from the dead amp, from the PC output directly soldered on the PCB i get amazing sound, no noise at all.
2. when i use a common 3.5mm audio cable (1.5m long) and solder it directly on the board, i get noticeable noise
3. when i use a jack to connect the audo cable, and then solder the jack to the PCB, i get some huge buzz/clapping sound, and as you can guess, no music at all. The TDA also overhears very fast, in about 2-3 seconds!
(There was no big heating at all in the other 2 cases)
So what could it be, is there anyway i can fix this?
Thank you for this great forum
Vagos21,
Is your circuit (schematic and PCB) the same as page 4 of the datasheet?
Can you attach a picture of each cable with your PCB? It may be no problem for someone else, but I cannot visualize noise sources from words only.
I had similar issues with a recent chip amp build. My issues were all due to grounding on the prototype stripboard, which were fixed when I laid out final version. But just because the symptoms are similar, I cannot be sure that the cause is the same.
Is your circuit (schematic and PCB) the same as page 4 of the datasheet?
Can you attach a picture of each cable with your PCB? It may be no problem for someone else, but I cannot visualize noise sources from words only.
I had similar issues with a recent chip amp build. My issues were all due to grounding on the prototype stripboard, which were fixed when I laid out final version. But just because the symptoms are similar, I cannot be sure that the cause is the same.
Thank you for your prompr quick answer!
Here are some images of the 3 cases i listed above. the schematic and pcb is taken from here, which i guess is taken from the datasheet (matced it)
Power Amp 20w With IC TDA2009 - HQEW.net
maybe i need some kind of preamp buffer in the input to straighten things out?
Here are some images of the 3 cases i listed above. the schematic and pcb is taken from here, which i guess is taken from the datasheet (matced it)
Power Amp 20w With IC TDA2009 - HQEW.net
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
maybe i need some kind of preamp buffer in the input to straighten things out?
thanks for your kind answer, yes ofcourse there's no preamp in there, the pcb is just a trace of a pdf image in photoshop, it's really a prototype, that's why it looks like that?
Do you have a pcb to suggest? i'm in need of some more constructive criticism here... it's my first time in amps i'm no pro or anything
Do you have a pcb to suggest? i'm in need of some more constructive criticism here... it's my first time in amps i'm no pro or anything
If your audio jack's ground is not insulated from the chassis, that would not be good.
And what are the other jacks etc, there? Some have only one wire, indicating that you are using the chassis. That is usually not a good thing.
ALL pairs of conductors should always be kept as close together as possible. Otherwise, they make ANTENNAS, and have currents induced in their loops by any time-varying magnetic fields there, in proportion to how much geometric area they enclose.
The main one to worry about is the input signal and input signal ground. Those two must be tightly (4 turns per inch) twisted together, ALL the way from the jack to the PCB, and the input signal ground must not connect to the chassis, at the jack.
Also, on the PCB, they should stay as close together as possible, and ideally you should use a ground plane in the signal input area (but separate from the power grounds).
Also keep all other pairs tightly twisted. If the AC transformer is anywhere nearby, make sure that both the primary and secondary pairs are tightly twisted, everywhere.
And what are the other jacks etc, there? Some have only one wire, indicating that you are using the chassis. That is usually not a good thing.
ALL pairs of conductors should always be kept as close together as possible. Otherwise, they make ANTENNAS, and have currents induced in their loops by any time-varying magnetic fields there, in proportion to how much geometric area they enclose.
The main one to worry about is the input signal and input signal ground. Those two must be tightly (4 turns per inch) twisted together, ALL the way from the jack to the PCB, and the input signal ground must not connect to the chassis, at the jack.
Also, on the PCB, they should stay as close together as possible, and ideally you should use a ground plane in the signal input area (but separate from the power grounds).
Also keep all other pairs tightly twisted. If the AC transformer is anywhere nearby, make sure that both the primary and secondary pairs are tightly twisted, everywhere.
I followed your advice gootee and also added 10K resistors at the input like Mihkus suggested and the noise really went down (not very silent but quite good) and no huge buzz when using the input jack. But when connecting the external wire to the PC the noise comes back at a considerable level again...
(i tried various power supplies and the result is the same)
maybe i do need a preamp after all? is there a preamp with positive only (12V) power requirement? thank you for your suggestions
(i tried various power supplies and the result is the same)
maybe i do need a preamp after all? is there a preamp with positive only (12V) power requirement? thank you for your suggestions
If you need a way to control the volume, you could use either a passive or active preamp. Lowering the input level somewhat might make it sound better. You could try it by making a temporary two-resistor divider for each channel. For example, If you put 3k in series with each input, before the 10k to ground that you added, that would cut the input level to 10k/(10k +3k) or 10/13ths of what it is now, roughly.
I don't really understand why it was suggested to put the 10k to ground. If the input impedance was too low, putting 10k in parallel with it would lower it further. But if it made a noticable improvement then you should keep it that way.
If you want to see if buffering would help you could try it with a single dual opamp, with outputs tied directly to negative inputs, and 10 uF in parallel with 0.1uF to ground from each power pin. That would give you two buffers for the two channels. You could put another set of buffers ahead of those and put a dual volume pot between them and have an ideal preamp.
But it sounds like your main problem is grounding or cables, between the two systems. Is there some other source you can try? Maybe a battery-operated source?
I don't really understand why it was suggested to put the 10k to ground. If the input impedance was too low, putting 10k in parallel with it would lower it further. But if it made a noticable improvement then you should keep it that way.
If you want to see if buffering would help you could try it with a single dual opamp, with outputs tied directly to negative inputs, and 10 uF in parallel with 0.1uF to ground from each power pin. That would give you two buffers for the two channels. You could put another set of buffers ahead of those and put a dual volume pot between them and have an ideal preamp.
But it sounds like your main problem is grounding or cables, between the two systems. Is there some other source you can try? Maybe a battery-operated source?
The first issue that I see are the connections to pin 7 and pin 11. These are clearly "NC" - no connection - in the datasheet. I do not know if this relates to your issues, but it is not a good thing.
Gootee gave good advise to avoid noise.
Mihkus gave partial advice, I think. TDA2009 has a minimum input impedance of 70kohm (datasheet again). Something like a 10kohm potentiometer volume control would be the simplest "preamp". It looks like there is one mounted on your enclosure, but not connected in the picture.
Gootee gave good advise to avoid noise.
Mihkus gave partial advice, I think. TDA2009 has a minimum input impedance of 70kohm (datasheet again). Something like a 10kohm potentiometer volume control would be the simplest "preamp". It looks like there is one mounted on your enclosure, but not connected in the picture.
Thank you all for your advice.
Latest news is:
I used this preamp i had built a month ago,
Clean boost for guitar (or bass) | jer00n.nl
and connected the output straight to the amp, using a pot to control the volume. Now the signal is dead silent, no noise at all, and only a tiny bit when the volume is really up (which is not noticeable due to the music playing really loud too)
So it is ok to keep this configuration with preamp+amp?
Thank you guys for all the support, and the tips will be remembered for future reference for sure
Latest news is:
I used this preamp i had built a month ago,
Clean boost for guitar (or bass) | jer00n.nl
and connected the output straight to the amp, using a pot to control the volume. Now the signal is dead silent, no noise at all, and only a tiny bit when the volume is really up (which is not noticeable due to the music playing really loud too)
So it is ok to keep this configuration with preamp+amp?
Thank you guys for all the support, and the tips will be remembered for future reference for sure
Excellent!!
Sure, it should be OK to keep it that way.
Don't change it if it's working fine, but, for future reference, on the preamp PCB, I am surprised that there is no bypass or decoupling capacitor from the op amp's pin 7 (9V) to either the grounded pot pad (by the "C" in "Clean" on the PCB) or to the op amp's pin 4. I would have at least put a 0.1 uF X7R ceramic, probably in parallel with a 10 uF or larger electrolytic, there. Without them, there is some risk of instability (especially without the 0.1 uF), and some risk of transient distortion of fast edges, and a slight risk of thinner bass, and possibly some risk of feedback problems (maybe mainly if trying to cancel distortion at high frequencies). The last three probably wouldn't be any problem, unless the 9V wire was more than several inches long.
I would probably also use a polypropylene film or polystyrene cap for C1 (the input cap).
I would also flood-fill much of the left side of the PCB with the ground copper, especially under and around R1, R3, and C1, and the traces that connect to them. That would lower the enclosed loop area of the loop formed by input and input ground, making a worse antenna, so less interference and noise would be picked up "over the air".
And I would probably put a 1k resistor in series with the trace to the "+" op amp input, close to the op amp's input pin, with 470 pF to ground from the + input pin, which would make a low-pass RC filter, to keep out RF (Radio Frequency).
Sure, it should be OK to keep it that way.
Don't change it if it's working fine, but, for future reference, on the preamp PCB, I am surprised that there is no bypass or decoupling capacitor from the op amp's pin 7 (9V) to either the grounded pot pad (by the "C" in "Clean" on the PCB) or to the op amp's pin 4. I would have at least put a 0.1 uF X7R ceramic, probably in parallel with a 10 uF or larger electrolytic, there. Without them, there is some risk of instability (especially without the 0.1 uF), and some risk of transient distortion of fast edges, and a slight risk of thinner bass, and possibly some risk of feedback problems (maybe mainly if trying to cancel distortion at high frequencies). The last three probably wouldn't be any problem, unless the 9V wire was more than several inches long.
I would probably also use a polypropylene film or polystyrene cap for C1 (the input cap).
I would also flood-fill much of the left side of the PCB with the ground copper, especially under and around R1, R3, and C1, and the traces that connect to them. That would lower the enclosed loop area of the loop formed by input and input ground, making a worse antenna, so less interference and noise would be picked up "over the air".
And I would probably put a 1k resistor in series with the trace to the "+" op amp input, close to the op amp's input pin, with 470 pF to ground from the + input pin, which would make a low-pass RC filter, to keep out RF (Radio Frequency).
sorry to keep you waiting guys, i did a "quick reply" but it never came up here.
I used a preamp based on the TL071 i had built a couple of months ago, and all the noise is gone, dead silent it seems to be an impedance problem after all, so a low gain preamp works, and even with a volume control. I guess i could just use a buffer too?
Thank you very much for all the tips, they will be remembered in future builds!
I used a preamp based on the TL071 i had built a couple of months ago, and all the noise is gone, dead silent
it seems to be an impedance problem after all, so a low gain preamp works, and even with a volume control. I guess i could just use a buffer too?Thank you very much for all the tips, they will be remembered in future builds!
I have build a working prototype of the TDA2009 Op amp with a dual A10k pot on the input to ground. I find that when listening to my ipod, however, the output is rather distorted, or not present at all. I suspect this is because I am using two small of speakers: 8 Ohm rated for 2W. I am powering it at 9V at the moment.
For background: In addition to building analog modular synths, I am also a conceptual artist. I recently got a grant for a project that involves many portable amps and speakers (boom boxes, essentially) to be used outside. I was hoping to make 15-20 of these loud speakers that would be loud enough to be heard a block away in an urban area.
I was originally looking at using a TDA2009 and 9V batteries, but I don't think this is going to be loud enough. I was hoping to spend less than $30 per boom box.
Any hints as to a circuit I might use? Mono is OK. I know this isn't synth related, but it is audio related. I'm pretty good at building stuff from a schematic/pcb combo, but know nothing about circuit design...
For background: In addition to building analog modular synths, I am also a conceptual artist. I recently got a grant for a project that involves many portable amps and speakers (boom boxes, essentially) to be used outside. I was hoping to make 15-20 of these loud speakers that would be loud enough to be heard a block away in an urban area.
I was originally looking at using a TDA2009 and 9V batteries, but I don't think this is going to be loud enough. I was hoping to spend less than $30 per boom box.
Any hints as to a circuit I might use? Mono is OK. I know this isn't synth related, but it is audio related. I'm pretty good at building stuff from a schematic/pcb combo, but know nothing about circuit design...
I build a TDA 2009 based amplifier, and added the stereo A10k pot to the input. When I listen to my ipod via the amp, the sound is either distorted or not-present. I suspect the distortion is caused by using under-powered speakers (8 Ohm/ 2 Watts). I am currently powering the amp via a 9V battery.
Do I need a pre-amp?
For background: In addition to building modular synths, I am also a conceptual artist. I recently got a grant for a project that involves many portable amps and speakers (boom boxes, essentially) to be used outside. I was hoping to make 15-20 of these loud speakers that would be loud enough to be heard a block away in an urban area.
I was originally looking at using a TDA2009 and 9V batteries, but I don't think this is going to be loud enough. I was hoping to spend less than $30 per boom box.
Any hints as to a circuit I might use? Mono is OK. I know this isn't synth related, but it is audio related. I'm pretty good at building stuff from a schematic/pcb combo, but know nothing about circuit design...
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Do I need a pre-amp?
For background: In addition to building modular synths, I am also a conceptual artist. I recently got a grant for a project that involves many portable amps and speakers (boom boxes, essentially) to be used outside. I was hoping to make 15-20 of these loud speakers that would be loud enough to be heard a block away in an urban area.
I was originally looking at using a TDA2009 and 9V batteries, but I don't think this is going to be loud enough. I was hoping to spend less than $30 per boom box.
Any hints as to a circuit I might use? Mono is OK. I know this isn't synth related, but it is audio related. I'm pretty good at building stuff from a schematic/pcb combo, but know nothing about circuit design...
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9 volt batteries won't work. The IC's minimum voltage is 8 volts and the little 9v batteries can't supply the current which pulls the voltage down and can cause the amp to shut down on the peaks and cause distortion. Output power is directly related to supply voltage. If you need any power, you need 18 - 24 volts and efficient 4 ohm speakers to get it loud.
Results may still be surprisingly decent, however, when using 2x 9 V in series with about as much buffer capacitance as you can possibly get (I'm thinking 10000-20000+ µF at 25+ V).
That being said, output impedance for 9 V batteries tends to be a few ohms, which is a bit impractical if you're trying to drive a load in the same order of magnitude. (Cheapies may also be somewhat strained by the ~60 mA idle current draw already, alkalines or rechargeables should fare better.) A battery type with some more oomph is definitely recommended.
That being said, output impedance for 9 V batteries tends to be a few ohms, which is a bit impractical if you're trying to drive a load in the same order of magnitude. (Cheapies may also be somewhat strained by the ~60 mA idle current draw already, alkalines or rechargeables should fare better.) A battery type with some more oomph is definitely recommended.
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