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Class D Switching Power Amplifiers and Power D/A conversion

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Old 10th June 2011, 05:25 AM   #801
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Join Date: Aug 2010
Location: Örebro, Sweden
Quote:
Originally Posted by lithoc View Post
Hi All,

This morning I got a stranger issues on my Lepai TA2020A+ (2011 release)

Previously, It was working fine with 12V 2A adapter. After I plug in, the relay will switched on and started to play music.

This morning I changed it to 12V 5A adapter. There's no sound and the relay didn't seems able to switched on.

This is weird. Anybody have this issues before.

Thank you
Hi. Sorta the same problem. I tried a bigger 12V adapter and the relay switched off. Did some measurements and it turned out the adaptar delivered close to 17 V. So try measuring your adaptor

Best regards /Bo
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Old 10th June 2011, 12:56 PM   #802
gychang is offline gychang  United States
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Join Date: Feb 2005
Location: Davis, California
Quote:
Originally Posted by padgettr View Post
I got another one off ebay arrived a few days ago. Its an LP-2020A+ on the case

I've made the following mods to the new one:
1. Removed overvoltage circuit and relay circuit - tied mute to gound and added an LED to the fault pin.
2. Removed tone control/volume control and op-amp
4. Replace input caps with 2.2 uF (they were 1.75uF)

I'm very pleased with the result - it does sound much better without the tone controls as an earlier post suggested - better bass response, and I think the treble sounds sharper too. Using a 12V regulated power supply I don't need the protection circuit, or the extra diode on the output (data sheet says they are only needed for voltages >13.5V). The switch on 'thump' is minimal once the op-amp/tone control is removed, as an earlier post suggested.
Being a newbie and schematic-dumb but have 2020A+... Like to follow your mod, will it be possible to show the steps in a picturial form? (desolder-here, solder here etc.? where can I get the 2.2uF cap that will fit in US?, Partsexpress?

thanks,
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Old 11th June 2011, 07:33 PM   #803
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Join Date: Mar 2011
Quote:
Originally Posted by gychang View Post
Being a newbie and schematic-dumb but have 2020A+... Like to follow your mod, will it be possible to show the steps in a picturial form? (desolder-here, solder here etc.? where can I get the 2.2uF cap that will fit in US?, Partsexpress?

thanks,
Hi, I'm afraid I didn't take any step by step pictures... also, you need to know which circuit board you have, the newer ones are all surface mount I think and it may be more tricky. Best thing is to look at the schematic on the datasheet for the TA2020 chip (easly found using a search engine) then trace the circuit on the board you have. When you have located the input caps, take them out and add 2.2uF (yours may already be 2.2!) There is no need to remove all of the tone control/op-amp circuits - you could bypass these by connecting the input to the capacitor and cutting the track to the op-amps... I removed the whole lot to try and save power as I am running my amps from a 12V lead acid charged by solar. For those interested quiescent I measured 130mA with the Lepai as supplied, went down to 70mA after removing relay circuit/op-amps.
As for the 2.2uF, I just re-used two that I'd removed from the op-amp/relay circuits. Probably not the best quality, but sounds as good if not better than an LM1875 based amp I made several years ago...
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Old 17th June 2011, 09:36 PM   #804
Sigrm is offline Sigrm  Norway
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Hi there,

I'm a bit worried about getting the power input wrong. Can anyone confirm that the DC connection is 'standard' with ground on the outside (barrel/sleeve) of the plug?

Thanks
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Old 17th June 2011, 09:51 PM   #805
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Location: San Antonio
You can see it on the Parts Express Lepai TA2020 page. It shows 12V2A center-positive for the power jack.
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Old 18th June 2011, 08:14 AM   #806
Sigrm is offline Sigrm  Norway
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Quote:
Originally Posted by sofaspud View Post
You can see it on the Parts Express Lepai TA2020 page. It shows 12V2A center-positive for the power jack.
Thanks, I can see it on the amp now, I must have been temporarily blind :P
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Old 19th June 2011, 01:00 PM   #807
Sigrm is offline Sigrm  Norway
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Default Changing low voltage cutoff

Btw, is there a way to make the amp cut off at 11V instead of 9V?
I have it running on a 12V SLA battery, and it would be nice to have a battery protection circuit integrated in the amp

Cheers
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Old 21st June 2011, 10:15 PM   #808
ontelo is offline ontelo  Finland
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How you remove the front plate safely?
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Old 22nd June 2011, 11:42 AM   #809
toxaris is offline toxaris  Sweden
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Join Date: Jun 2011
Hello.
I have searched this thread but I cant find an answer to my question.

I have bought a Lepai TA-2020A+ amp and its driven by a 12V 55Ah carbattery.
If I want to add a fuse between tha battery and the amp, what is recommended?
From what I know a 6A fuse is just 1A above specifications.
Will that work or should I go higher or lower?

Thanks.
Daniel Persson.
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Old 23rd June 2011, 01:53 AM   #810
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Default Accidently switched positive and ground!

Have a 2011 model but without tone switch (relay and one JRC op-amp)
My brother accidently switched a power supply so that ground was in middle and positive in ring. There was some smoke, then he was real sad. Does anybody know if it could be fixed?
With correct power supply I get the blue led light and I can just about hear the input music if I keep my ear very close to the board and all knobs are turned to max.
Any ideas?
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