biuro74
New Head-Fier
- Joined
- Jun 5, 2012
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Hello,
So I'm in progress of doing my 2.1 project. I've done few steps, some of them works, some of them need some rework. Today I need help with my amplifier "build" - it's done just to see how it works with my configuration (vintage computer + 12V + 4-10W speakers). Later it will be put on own-etched PCB, together with rest of components (like second ampli for bass speaker and 2x audio mixers... known as summators).
First issue is: I've got just computer stereo out (2x cinch) and TDA connected directly to it & to speakers. No volume pot, no preamps. And quality of sound is weird, really weird:
* it's too loud, I have to use software volume set to minimum, or 1-2 steps above to hear sound with to distortions (as far as I understand, I need pot soldered directly to audio in on my temporary PCB ?)
* even when volume is lowest, sounds like some freqs are not passed through (basses & some trebles),
* there are some noises, but I presume it's due to 8-bit nature of my computer DACs... anyways I didn't expect such exposing of them - on other speakers they are more "natural", probably due to higher freq range passed through.
Second issue: it's totally HOT. I feed it with 12V, wherever typical voltage is 14.4V. Looks like I have to put some huge radiator here, is it any workaround ? Or which IC to use ? I've seen super-slim Amp topic, so it's possible to have cold chips inside
And third issue, most odd. Once stopped playing sound, I can hear in speakers some FM radio channel (??!), It's very quiet, but IT IS PRESENT. What is going on ? I enclose picture of my temporary PCB and environment: vintage computer in front of it, and 350W PSU on righ-hand-side, just next to speakers (cut on photo). Computer has got TV modulator, does it influence of anything ?
And some explanation
It was totally my first build, so first time I turned it on, some light smog appeared. Close investigation revealed it must have been melted glue - see that blue mute cable behind top-right TDA corner ? It has been glued (like all cables) to avoid cable crack. Anyway, I thought I've done some short circuit, because I put too much solder to TDA pins, but I was lucky at the same time as my molex was "flipped" to 5V (instead of typical 12V). In the meanwhile I thought TDA was fried, so I take out some solder not bothering the soldering temperature and time. You can see some brown places there - too many resin left, but majority solder came out.
So once I noticed 5V molex, I decided to give it one more try changing voltage to 12V... and surprise ! It worked. But how it works - it's different story
Do you think TDA was broken anyways, or rather it is typical noisy-hot-piece-of-silicon ? BTW, I've bought it on Ebay - and as I read, not everyone trusts Ebayers who might sell fakes or damaged items (mine was sent from HongKong), caps come from RS.
Thank you for any clues.
I'm learning electronics & audio subjects in express ratio, so far I've read one huge 'brick", still reading second one, and looking at hundreds of schematics, mostly audio amps. So please be tolerant, I'm just coming into this world.
Update:
Accidentally I unplugged one stereo cinch "Audio in" and some noises appeared. Plugged it back - everything was fine. Unplugged both = silence. And since then it's neverending silence. Is my ampli dead ? It would be ridiculous, it's not funny to burn out the device once unplugged audio source...
So I'm in progress of doing my 2.1 project. I've done few steps, some of them works, some of them need some rework. Today I need help with my amplifier "build" - it's done just to see how it works with my configuration (vintage computer + 12V + 4-10W speakers). Later it will be put on own-etched PCB, together with rest of components (like second ampli for bass speaker and 2x audio mixers... known as summators).
First issue is: I've got just computer stereo out (2x cinch) and TDA connected directly to it & to speakers. No volume pot, no preamps. And quality of sound is weird, really weird:
* it's too loud, I have to use software volume set to minimum, or 1-2 steps above to hear sound with to distortions (as far as I understand, I need pot soldered directly to audio in on my temporary PCB ?)
* even when volume is lowest, sounds like some freqs are not passed through (basses & some trebles),
* there are some noises, but I presume it's due to 8-bit nature of my computer DACs... anyways I didn't expect such exposing of them - on other speakers they are more "natural", probably due to higher freq range passed through.
Second issue: it's totally HOT. I feed it with 12V, wherever typical voltage is 14.4V. Looks like I have to put some huge radiator here, is it any workaround ? Or which IC to use ? I've seen super-slim Amp topic, so it's possible to have cold chips inside
And third issue, most odd. Once stopped playing sound, I can hear in speakers some FM radio channel (??!), It's very quiet, but IT IS PRESENT. What is going on ? I enclose picture of my temporary PCB and environment: vintage computer in front of it, and 350W PSU on righ-hand-side, just next to speakers (cut on photo). Computer has got TV modulator, does it influence of anything ?
And some explanation
It was totally my first build, so first time I turned it on, some light smog appeared. Close investigation revealed it must have been melted glue - see that blue mute cable behind top-right TDA corner ? It has been glued (like all cables) to avoid cable crack. Anyway, I thought I've done some short circuit, because I put too much solder to TDA pins, but I was lucky at the same time as my molex was "flipped" to 5V (instead of typical 12V). In the meanwhile I thought TDA was fried, so I take out some solder not bothering the soldering temperature and time. You can see some brown places there - too many resin left, but majority solder came out.So once I noticed 5V molex, I decided to give it one more try changing voltage to 12V... and surprise ! It worked. But how it works - it's different story
Thank you for any clues.
I'm learning electronics & audio subjects in express ratio, so far I've read one huge 'brick", still reading second one, and looking at hundreds of schematics, mostly audio amps. So please be tolerant, I'm just coming into this world.
Update:
Accidentally I unplugged one stereo cinch "Audio in" and some noises appeared. Plugged it back - everything was fine. Unplugged both = silence. And since then it's neverending silence. Is my ampli dead ? It would be ridiculous, it's not funny to burn out the device once unplugged audio source...
