TDA1562SD question

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Hello,

I've made an amplifier using TDA1562SD chips using this schematic and PCB layout. Only used on one channel single 4700uf caps for lift supply, second one 2x2200uf banks. It works and sounds nice, but main problem is when i use PC speaker output, it has very loud hissing/background noise. Changed the signal source form PC to a source from my phone (Samsung galaxy s3), and the hissing was gone. Amp went fully unnoticable when no audio playing, instead of giving out loud ssssssssszzzsss all the time.

Amp is fed by computer PSU (not from the one used as a signal source).

Any ideas why that could be so?

*forgot to take out old pics of schematic*
 

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Unless you upgraded your soundcard, that's probably your problem. Stock sound cards work OK for YouTube videos and times when sound quality is not an issue. You might want to look into a USB DAC. You can find some for less than $100 that do a great job. When I run music out of my laptop, I use either an HRT Soundstreamer or if I'm using headphones I have a Parts Express DAC and a Creative Soundblaster X-Fi. I use one or the other. Both work well.
Mike
 
So it means the integrated audio is c***. Well i knew it, but didnt think it's so bad. My daylydriver - Sure 2x100W has almost no hiss at all. Its there, but barely unnoticable. Tho the Sure is running from transformer, rectifier and few caps, not for a SMPS. It means the TDA's are more sensitive to input quality than the Class-D Sure amp?
 
I can't really answer those questions. I would say the sound card doesn't put out the same sound quality as the Sure. It's pretty typical of on board sound cards. It's probably cheaper to buy a USB DAC than it is to mod your computer with an equal value sound card. Others may feel differently. Are you using a desk top or a laptop? If you Google USB DAC you'll find a lot of options at a lot of prices.

I would recommend a DAC that has RCA-out jacks and a headphone-out jack. If you never listen to headphones, then the headphone out doesn't matter. But if you do, a DAC is a huge improvement compared to the computer headphone jack.
Mike
 
Im using desktop (motherboard Asrock 970 Extr3, with Realtek ALC892 Audio Codec). Headphones, hmm yes, usage is 50/50 time speakers/headphones. Sometimes even headphones are used more.

Maybe try and "nail" together a DIY DAC something like this?
 
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Well my pcb's aren't anything spectacular, just toner-transfer and etching bath. Design in ExpressPCB, print with laser printer on laminate film. Nothing fancy. For theese TDA chips, I used kinda retarded thing - designed pcb, printed in ink printer, then scanned to PDF, then printed with laser printer. Came out lets say good. Only the 0.3mm traces got a bit messed up. And the etching bath didnt go quite as smooth too. Maybe ill take some pics and post them later. Good thing about Expresspcb, it prints high DPI, so it eliminates saw-tooth edges on traces.

For now, TDA1562SD board added.
 

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Pics would be good. I've not done any work making my own PCBs. I've read about it, but haven't gone that route yet. I've got a laser printer and access to a scanner. What would you estimate it cost for supplies to do your for first board? In other words, the cost of the chemicals?
Thanks,
Mike
 
Sorry for late reply ;) Since I bought my supplys few years ago, don't remember exact prices but

- A4 (1mm thick, single sided) sized sheet of copper laminate ~ 6$
- FeCl3 for etching 250 gramms ~ 4.5$
- Set of HSS drills (1mm, 0.8mm, 0.6mm, 0.4mm) ~ 4$.
- Transfer film A4 size, 2$ a piece.

On topic:

Since I'm using my Sureelectronics amp on it's lowest gain setting, the hiss is barely noticable. Today ramped the gain all the way up, and hey presto we've got a mosquito hive in speakers. Conclusion - Some other input source needed. Oh, and tried to run my TDA1562 from monitors headphone output (GPU -> HDMI to monitor -> Monitor out to TDA's) - hiss is less but still loud enough to be annoying when music is quiet or not playing at all.
 
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Quite honestly the problem description (hiss with computer or monitor, no hiss with phone) makes me suspect a ground loop related issue. Even a lousy ALC892 implementation should be good for 85-90 dB of SNR. That normally makes a good enough line-level source.

Do your amps connect signal ground and safety earth? If so, that would complete the ground loop, as the computer definitely does.
 
Quite honestly the problem description (hiss with computer or monitor, no hiss with phone) makes me suspect a ground loop related issue. Even a lousy ALC892 implementation should be good for 85-90 dB of SNR. That normally makes a good enough line-level source.

Do your amps connect signal ground and safety earth? If so, that would complete the ground loop, as the computer definitely does.

I really don't know about the Sureelectronics one (amp is widely discussed in this forum), but TDA1562sd deffinetly has power ground and signal ground connected together.

The schematic used for TDA's
An externally hosted image should be here but it was not working when we last tested it.
 
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