Lepai T-Amp with TA2020 - Page 127 - diyAudio
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Old 25th October 2012, 05:36 AM   #1261
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I haven't changed the inductors or output caps. I have a 4700uf cap on order for the power input. I will do things bit by bit, its fun to hear the difference. Can you clarify a bit more the tone bypass, I'm not an electronics expert but can wield a soldering iron if I have clear instructions:

Quote:
You will then have 1.8 /2.2 UF input caps, metal film types, straight from input RCA's to the disconnected from the PCB Volume pot and then to the inputs on the board where C20, C21 were.
I've seen that red board 2020 amp for sale here in the UK. It costs a bit more here (18) but its still cheap, just bought one on your recommendation.

There's also a Yuang Jin 2022 board (claimed 90W) for about 30. Any good?

I've been playing about with the Lepai in lieu of getting two Helder 100W STA508 boards which cost about 80 delivered here. I just wanted to see if tripath was worth the fuss. My word, it is!
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Old 25th October 2012, 01:46 PM   #1262
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I recently bought a red PCB LP-2020A+, and have been modifying it. I've been documenting each stage, and before I started I reverse engineered the input schematic for everyone. Sometime this weekend I'll started a new thread (as the A+ seems different enough to warrant a new thread).

On the red PCB, there's a mistake in the tone control circuit, a capacitor connected in the wrong place. I'm not sure how much effect it would have (it's only wrong on one channel), and don't really care because I deleted that circuit anyway.

Mod #1: remove tone control op-amp, and resistors connecting it on the input side, leaving the rest of the circuit disconnected on both ends. Replaced volume op-amp with OPA2132.

Mod #2: remove volume control op-amp and capacitors/resistors, rewired volume pot to be just an attenuator, as I seem to never be pushing it above (or even near) a gain of 1, giving a clearer sound and more usable range on the knob.

Mod #3 (today or tomorrow when parts arrive: new caps to replace all electrolytics in the amp. The smaller value ones will be replaced with film caps. New inductors except the power input inductor, as it's already a nice toroidal type. Delete part of the output filter to create a "half filter" per TI documents SLYT198 and SLOA023.
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Old 25th October 2012, 03:29 PM   #1263
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A new thread for the red board would be good.

I just installed the 4700uf power cap. Not a great deal of difference in quality but does seem to go louder before copping out.

A bit worried about my speakers if it goes kaput as the early one doesn't have protection relays I think?

I'm still unsure of what components to change for the tone control defeat. Can't find any info on Lepai in the Wiki and the instructions I've followed from Calamaro differ from others I think. Here's the image he posted from p27, hope he doesn't mind me reposting.

Click the image to open in full size.
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Old 25th October 2012, 04:59 PM   #1264
Bare is offline Bare  Canada
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THIS one :
YJ TA2020 20W+20W Class D amplifier board | eBay
Note the red caps, all of them :-) they have Wima on them. May even be true Also note the simplicity of it.
NO inept "tone' controls, Which on the Lepai Must be bypassed for it to use the Ta2020 chip to it's best sound.
Regardless..The thing sounds Good "as is" ... true.
Don't! waste more $ on the lepai versions.. I did
All one gets is a metal box and the need to replace most/all ! of the discrete parts. And then there still is no DC output correction (important that) No ! bargain.

Last edited by Bare; 25th October 2012 at 05:08 PM.
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Old 25th October 2012, 05:04 PM   #1265
Bare is offline Bare  Canada
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Red PCB is essentially the same as the Blue one as far as I could tell and I did look.
Amplifier:Lepai T Amp - diyAudio
More here:
http://techtalk.parts-express.com/sh...e-Lepai-T2020A

Last edited by Bare; 25th October 2012 at 05:21 PM.
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Old 25th October 2012, 09:48 PM   #1266
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YJ TA2020 20W+20W Class D amplifier board | eBay

Yep that's the same one i bought but from a uk seller. Will be interesting to compare to the lepai. Seems funny to talk about wasting money when these amps are so cheap. The stock lepai is better in many ways than most amps I've owned yet costs as much a basic preamp valve! I just hope they last.

Now I need to find a suitable case that will also fit the two 100w helder mono blocks and meanwell psu when I eventually upgrade!
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Old 26th October 2012, 01:50 AM   #1267
Bare is offline Bare  Canada
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Great! hopefully it will be a 'good one'.
Hey! these are Chinee product with the world famous reputation for quality control.
Yes.. certainly inexpensive amps.
But a bare Ta 2020 chip is $5 delivered to your door.
Follow the Tripath Data sheet and one can diy a surprisingly good rendition of the amp.. at least as good as any premade product.
Diy'rs don't have to justify mere pennies in parts quality :-)
The Lepai is initially seductive.. pricewise, but the in hand reality reveals it to be a shoddy bit of kit ( although the latest version is markedly better built than the early contraptions) Upgrading the thing to it's chip's potential ends up costing more than the silly thing's purchase price.

A wall wart setup of 12 v 5 amps is 'fine' or perhaps fit a 12v Gel battery for the ultimate in a clean power supply.
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Old 26th October 2012, 06:18 AM   #1268
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I agree, it's not exactly high-end build quality! But I'm no DIYer either. I'll have a go if I have idiot proof instructions, as I have no electronics education or training. So for a few quid extra I'm happy to pay for chifi-assembly I look at modding more as a bit of fun - in truth I could happily listen to the stock Lepai all day. I've bought an extra one as a spare (though will probably use it in my AV system), plus I'll have the YJ board soon. Maybe getting a couple of 2020 chips might be a good safeguard against future when supplies dry up? Still don't understand why Tripath went bust...

Realise I'm taking a bit of a risk with the Mk1 board: if it blows up so will my speakers! I take it the YJ has speaker protection?
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Old 26th October 2012, 11:29 AM   #1269
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Quote:
Originally Posted by hozepipe View Post
YJ TA2020 20W+20W Class D amplifier board | eBay

Yep that's the same one i bought but from a uk seller. Will be interesting to compare to the lepai. .....
Hello
I may surprise you but I tried this amp and I prefer the Lepai (old version).
I read somewhere that the TA2020 had a better sound if it was preceded by an operational amplifier (a good one of course). This is what I also found when comparing the two amplifiers.
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Old 26th October 2012, 11:53 AM   #1270
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Quote:
Originally Posted by Bare View Post
The Lepai is initially seductive.. pricewise, but the in hand reality reveals it to be a shoddy bit of kit ( although the latest version is markedly better built than the early contraptions) Upgrading the thing to it's chip's potential ends up costing more than the silly thing's purchase price.
Couldn't agree more with the first part. Upgrading is fun though, sometimes more fun than making your own from scratch because you have something functional out of the box (hopefully) and you can hear each little (and cheap) change.

I'm using mine for desktop speakers from about 170Hz to the top, no crossover. I'm changing the 2.2uF caps to smaller ones to high-pass the input. That said, I don't need more than a 2A PSU. It's going to cost me $60 total for the amp, the parts I want and shipping on all. I can't complain, as it's light years ahead of anything I could make for that price, and blows away the crappy Creative computer speaker amp I had been using.

Quote:
Originally Posted by hozepipe
Realise I'm taking a bit of a risk with the Mk1 board: if it blows up so will my speakers! I take it the YJ has speaker protection?
The speaker protection is gimicky at best. It reduces turn on/off thump and that's about it. From all the reading I've done, the biggest risk seems to be that pulling the speaker cables out while playing is instant death to one or more channels of the chip. I presume because the inductors have no load and dump their power back into the chip.

Do you have a LP-2020 (no B or A+ revision)? Check here: http://www.diyaudio.com/forums/#Amplifier_Revisions

Quote:
Originally Posted by killmister
I read somewhere that the TA2020 had a better sound if it was preceded by an operational amplifier (a good one of course). This is what I also found when comparing the two amplifiers.
I found a huge improvement when upgrading the volume control op-amp, but I found the sound quality slightly better yet, with a wider sound stage, when I removed that and set up the volume pot as a simple attenuator. I was using the trusty OPA2132. In the blue and red boards, the volume op-amp is set up as a variable gain amp, with volume settings below about half on the knob being attenuated, and settings above amplified. As I could never ever see wanting a pre-amp gain over 1, I saw no reason to have extra amplifiers in the signal path, no matter how good.
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