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Old 15th February 2013, 03:48 AM   #1371
blossom is offline blossom  New Zealand
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Quote:
Originally Posted by talladega View Post
This is what my full plan is to do.

Hopefully my poor mspaint drawing is understandable.

Click the image to open in full size.

I've been told by some people that EMI may cause an issue if I dont shield the amp from the raspberry pi and wifi adapter and the power supply.
Got my attention here as well.... Looking forward to see how it turns out, do post here when your all done wont you.
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Old 15th February 2013, 05:49 AM   #1372
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Looks like that item is for 220v and from your flag you're in Canada?

Quote:
Originally Posted by talladega View Post
Hi, I'm looking to get another one of these Lepai amps to mod. I'm wanting to put it in a new enclosure and would like to have the power supply inside the enclosure.

Will a power supply like this work?
12V 5A 60W Switch Switching Power Supply Driver for LED Strip Light Display USA | eBay

Or is there something better out there? For my use, having a power brick external of the amp enclosure will not work.
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Old 19th February 2013, 02:21 PM   #1373
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Hi all.

I have a question, hopefully someone can help. I have this amp and want to incorporate the existing on/off toggle and volume functions into a single potentiometer. I have modded several other lepais, but just basically moved the on/off switch to a different spot. I recently bought an on/off volume pot from parts express (see pic) and want to use this. I believe I would run the two power lines into the two leads at the bottom of the pot. The other three would be for the volume. How do I wire those? I assume I'd de-solder the existing volume pot and rewire each of the three leads into the three leads on the new pot? Is it as straightforward as that? Or am I leaving something out? Thank you so much for any help you could recommend. Also, what is the wire soldered to the outside of the volume pot in the circuit board pic earlier in the post? Is that a ground that I would need to solder to the new pot? THANK YOU!
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File Type: jpg pot.jpg (39.4 KB, 320 views)
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Old 19th February 2013, 02:58 PM   #1374
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Yes, it's that straightforward. Just make sure the new pot is connected so a clockwise turn increases the volume.
Yes again. That's a ground wire.
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Old 19th February 2013, 03:38 PM   #1375
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Thank you, so much. Now I just need to hope my soldering skills are OK
I appreciate the help!
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Old 21st February 2013, 03:10 PM   #1376
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Quote:
Originally Posted by Virpz View Post
If you want to correctly bypass and adjust the gain on your lepai then you need to connect directly to the RCA inputs instead of pads on R35 and R34 ( C31 and C 30 on pcb 120305 ) you should know that:

R8 and R10 and the Rin resistors while R9 and R11 are the Rfeed resistors. These are the resistors that adjust the gain. Look into the TA2020 datasheet to get the full explanation.

- For ipod and portable players with built in volume control use 22K for Rin and 39K for Rfeed

- If you want to play it safe with and set your lepai for general use you should use 22K for Rin and 22k for Rfeed.

- For signals coming from a pre-amplifier you can go for 56K for the Rin and 22K for the Rfeed

I will post an definitive mod list for the lepai in a few days . I just need the time to do it correctly with pictures and everything else.
I will also show how to make the "switch" button work as it should; bypassing tone controls for real.

[]'s
Thanks for sharing this info!

I am wondering if similar/same info is available to do the same thing to the 2020B.

I have successfully bypassed the tone controls and opamp by installing some nice caps as per this post Lepai T-Amp with TA2020

In the future, however, I would like to bypass the volume control and use the 2020B as a power amp, with a DIY tube pre-amp. I am wondering what resistors I need to change (if any) to achieve optimal gain.
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Old 27th February 2013, 04:18 AM   #1377
lolek is offline lolek  United States
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Hello everyone,

I got hold of my second 2020A+ amp - 111129 PCB - got it used, not in a best shape, broken volume potentiometer, etc....
here is my ( and its ) problem: when the tone switch is pressed, the right channel goes away - left one is good. I checked the switch, it is fully functional on both positions, and both channels. checked for cold solder, re-soldered a few locations, no difference...
checked the potentiometers, they also good...
when the tone is set to "direct", both channels are fine....

can this be one of the two 4558's on the op-amp?

thanks in advance.
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Old 27th February 2013, 12:21 PM   #1378
lolek is offline lolek  United States
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nice, how about adding an USB port in the back or front, for audio storage unit ( usb stick, etc ), or for a RF remote control - I am also curious why are you adding an USB DAC if R-PI has already one built in ( usually it defaults to the HDMI audio, but this can be switched ).
Your project is perfect for getting on-line radio streams, from ShoutCast.for example.
I have done something similar with an ITX board, and re-did GeexBox basically from scratch, than I put all the guts in a vintage ( 1970s ) receiver.enclosure.... still got it

Good Luck!


Quote:
Originally Posted by talladega View Post
This is what my full plan is to do.

Hopefully my poor mspaint drawing is understandable.

Click the image to open in full size.

I've been told by some people that EMI may cause an issue if I dont shield the amp from the raspberry pi and wifi adapter and the power supply.
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Old 27th February 2013, 12:35 PM   #1379
hax is offline hax
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Quote:
Originally Posted by Diverted View Post
Hi all.

I have a question, hopefully someone can help. I have this amp and want to incorporate the existing on/off toggle and volume functions into a single potentiometer. I have modded several other lepais, but just basically moved the on/off switch to a different spot. I recently bought an on/off volume pot from parts express (see pic) and want to use this. I believe I would run the two power lines into the two leads at the bottom of the pot. The other three would be for the volume. How do I wire those? I assume I'd de-solder the existing volume pot and rewire each of the three leads into the three leads on the new pot? Is it as straightforward as that? Or am I leaving something out? Thank you so much for any help you could recommend. Also, what is the wire soldered to the outside of the volume pot in the circuit board pic earlier in the post? Is that a ground that I would need to solder to the new pot? THANK YOU!
Not all three wires I think.

The ones on the outside are generally signal in, if you wire both of them the pot will read max at full and min turn and half it's rating in the centre, I've only wired LED's myself but you only need to connect one side. And which one depends on the direction of the pot you want to low the low resistance. I think.

Please correct me if I'm spouting ****, this is what I've deduced while working with pots and LEDs.
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Old 2nd March 2013, 09:24 PM   #1380
aj982 is offline aj982  United States
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Hello fellow DiY-ers... This is my first post. I've been reading a bunch and I've been learning a ton about these little gems. Thanks to all the contributors.

Currently, I have replaced all my caps with audio grade and changed my inductors. I also removed, cleaned and re-installed my heatsink with better thermal compound.

I am at the point where I want to bypass my tone controls and opamps but i want to keep my volume control.

I understand that I need to run wires from C20 and C21 to C30 and C31 with 2.2uF caps inline to bypass all of this.

I also understand that I need wires from C20 and C21 to the volume pot with 2.2uF cals to enable volume again.

My question is... Do i need a total of 4 wires and 4 caps coming off of C20 and C21 to enable bypass and volume?

Thanks in advance. Anyone have any pictures of this?

Quote:
Originally Posted by Virpz View Post
I did the last mods on m lepai's lp2020a+. Looking at the output stage noticed that there is a smd cap just after the inductors. Well I have no clue what they intended to anchieve with that cap there but my guess is that it is their EMI output filter and they placed it right there before the output caps. Also the zobel cap on mine had one 0.47uF cap instead of 0.22uF. there we go:

Click the image to open in full size.

I used 10000pf 5% polystyrenes that I had around for C40 but you can use multilayer ceramics.
If you're going to use it as power amp you better replace R8 and R10 with 22k or 39K low noise resistor. Much better now .

On one of my units I did the bypass and added a volume pot following Pano mod for sonic impact. Great reading there.
If you want add the volume pot after you did the bypass on Lepai Lp2020A+ you should look at the image bellow.

Click the image to open in full size.
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