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Class D Switching Power Amplifiers and Power D/A conversion

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Old 26th September 2011, 03:42 PM   #921
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Join Date: Sep 2011
Quote:
Originally Posted by Motsey View Post
I recieved myNE5532's but i got the wrong ones! Duh! Im such a noob and didnt take any notice of the "dip 8" written on the listing

can i still solder these to the board but using wires to connect each leg or is it just not worth it?
Unbelievable! I did the exact same thing.. Apparently the pinout is the same so it's possible, but I guess it will be pretty hard..

Anyway, I ordered a lepai lp2020a+ for 21$ shipped on ebay, and I'll be getting it in a few days. I will probably mod it to death
I'll be back on here asking silly questions in a few days
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Old 11th October 2011, 07:48 PM   #922
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Join Date: Oct 2011
Hi everybody!

First of I have to thank you all for contributing all this amazing information on this forum!

I just registered an account here on DIY Audio, but I have been following this forum thread for a few years now, and now i finally have made my own portable stereo with this fantastic Lepai TA2020A+ and a 7,2Ah accumulator.

I am really satisfied with the result and I have been able to play constant for over 5 hours.

My really big concern was the power-cable and the power-connectors, but i solved that with a broken power-adapter from an old laptop (only the cable from the power-adapter).

I tested it and found out that the + was in the middle and the - was on the outside of the connector. I also put a 10A fuse on the +cable just in case and put cable shoes on the cables to ensure a simple way to connect them to the battery poles.

I use a aluminumcase from our local hardware store to put all the stuff in and i put two 4" full range speakers on one side.

When i have found out how to post images here i will do so.
Until then i will post a few links with the images here for you to see =)

Picture one (inside the case):
http://www.festivalstereo.se/images/...011_013201.png

Picture two (front of the case):
http://www.festivalstereo.se/images/img_20111011_012504.png

Picture three (Lepai TA2020A+ connected to battery with my home made cable):
http://www.festivalstereo.se/images/img_20111011_014013.png

Picture four (My home made power-cable with a fuse holder)
http://www.festivalstereo.se/images/...011_013845.png

I hope its not to early for me to post links, this is only to show my pictures, not as useless spam.

Cheers to all on this forum, you have given me a lot of useful information to get through with my home made stereo!

// Mogar123 from Sweden
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Old 12th October 2011, 11:02 PM   #923
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Join Date: Sep 2011
Ive made a huge mistake and connected the wire to my battery the wrong way round and now it all seems to work like normal except it does not output any sound and also does not click when switched on like it used to.
Any idea what it could be or what I should test? Could it be the replay/large black component with 12v written on it?

I have started a thread for it here

I hope someone can bring it back to life as ive just purchased a battery and was all ready to make my boombox doh!
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Old 27th October 2011, 02:54 PM   #924
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Join Date: Mar 2011
Ok I just got one without power adapter and going to use it with my PC. And Im going to get power from my PC power supply 12V rails

And In future im going to buy another and use it on my Bus. It got 2*12V 120ah Batteries and im going to tap a wire and get power from one battery. My concern is since the battery power is high (120Ah) will it be a problem for AMP?
Thanks
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Old 31st October 2011, 11:22 AM   #925
pkozul is offline pkozul  Australia
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Join Date: Feb 2011
Location: Melbourne, VIC
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, but the board inside is LP-2020B... It has the 'protection relay', surface mount components but only one op-amp. I mapped out the relay protect circuit, but I'm not convinced by it... Its still connected to the fault pin and looks like it will toggle the relay off if this goes high, but it is also connected to the mute/over voltage circuit. This will perform an automatic reset of the fault condition (see datasheet), which I don't think is desireable. Another thing - the relay only switches one side of each differential output - so for example, a short could occur on either pin and will not necessarily be disconnected by the relay. I'm not sure why this relay protect is necessary other than to prevent the switch on pop - but then why connect to the fault pin? From the tripath data sheet:
"The TA2020-020 is guarded against over-temperature and over-current conditions. When the device goes into an over-temperature or over-current state, the FAULT pin goes to a logic HIGH state indicating a fault condition. When this occurs, the amplifier is muted, all outputs are TRI-STATED, and will float to 1/2 of VDD."
What do other people think of this 'relay protect'? If I get time I'll draw up the schematic I have and post.

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.
Hi all,

I have the same Lepai as padgettr. It's has LP-2020A+ on the case, but the board inside says LP-2020B. It has the protection relay and some surface mount components, but only one op-amp.

Candoumi previously linked to the photo of the board:

Lepai LP-2020A+ - My Photo Gallery

I made a few mods the amp, and now it sure sounds better to my ears... cleaner, faster, more detailed, sweeter...

- Bypassed the op-amp and tone controls
- Replaced the input caps with 2.2uF 250V film
- Replaced the reservoir cap with 2 x 2200uF 25V (Panasonic)

For bypassing the op-amp and tone controls, the photo below shows how I did it. After replacing the input caps (big yellow caps on the right), I left one side "floating" and then soldered on those yellow hookup wires, one for each channel. On the other end of these wires, I removed the pair of caps near the TA2020 chip (they are marked 2.2uF on the board, but 1.75uF were actually installed). I then soldered the yelloy hookup wires to the unshaded side of the solder pads where the caps were removed.

Click the image to open in full size.

If and when I get time, I might look at changing the output inductors to toroids as others have reported better bass response.

I've learnt so much on these forums... thanks to all of you who contribute!

Cheers,
Pete
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Old 2nd November 2011, 09:19 PM   #926
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Join Date: Jan 2011
Location: Maine
Nice post, Pete. I may try this as a winter project. I guess it's spring for you.

Oh yeah, I may be the one who mentioned the thump. That's good to hear that it's minimal.
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Old 4th November 2011, 03:54 PM   #927
Largol is offline Largol  France
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Join Date: Dec 2008
Purchased a Lepaļ LP2020A+ amplifier. I'm satisfied with the amplifier, good sound, but I don't like the soft-start circuit: I explain why.....

when you turn up the power everything went well. No pop, no click noise, the relay works fine.

When you shut down the power supply, it's another story: I hear a HUGE pop

How to improve the soft start circuit in order to avoid a pop at shut-down of the unit ?

Regards.
Largol.
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Old 7th November 2011, 11:37 AM   #928
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Join Date: Nov 2011
Default Lepai LP-2020A+

A+ Version: Just got myself one of these and thought I'd take a look inside as I'm getting a little distortion at around 11 o/clock. See the attached picture of R29 (Nr Op Amp). It was totally shorted and not reading it's 10K across the points. It now is
I also found quite a few dry joints throughout and while it will work with these now, it may not down the road. I have re-touched more than a few using solder wick braid to clean joints where I had to. SMT work looks a bit iffy in general - rushed probably but I wasn't expecting much for the money
I will have a hunt about for some better Op amps and may upgrade them if I still have the distortion.
I see the circuit board layout has allowed for bigger caps to be fitted on the imput - C32,33,36,38 positions. I'm not gonna mess with it too much though. Famous last words lol
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Old 7th November 2011, 09:26 PM   #929
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Yes, very nice Pete. My two amps are still going stong, and I still think they sound fantastic!
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Old 9th November 2011, 09:37 PM   #930
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Join Date: Sep 2011
Hey guys.

Just finished doing the first set of mods to the lepai. I don't have proper speakers right now where I am but testing on a spare driver with no box I think it is better
I changed the 16v input cap to a 4700uf samwha SD series 25V cap, the output caps to 250V philips 0.47uf 5% caps and the stock inductors to 3A 10uh inductors. They are a straight coil with some stuff (ferrite?) inside. I placed them so that they point upwards. I wonder if this will make them interract in a bad way but whatever I have 50v 2,2uf film caps for the input decoupling, to install where the C30 and C31 caps are. Will buy some opa2134's off ebay (or ne5532). Just gotta remember to get the smd package this time

The problem that has arisen is that the right output is noticeably louder
I measured a sine wave output with my multimeter and when the right channel is reading 2.03V the left one is only 1.53V..
Didn't check this before but I didn't notice it until now... Sort of bummed about this so does anyone have a known solution?

PS. pics will follow at some point
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