Lepai Tripath LP-2020A+ mini Amp dissected

No real reason to short the pot. All that will do is change the volume taper a bit.... could be better, could be worse.... but, a very slight difference at any rate.

I don't think you have any 10uF ceramics... unless they are SMD. Normally, that value would be an electrolytic. So, you can just use a 10uF electrolytic, with the + terminal towards the opamp. (No need for a NP cap, since the amp is biased up from ground. In fact, the amp should work fine even with a 1uF in that spot if, for some reason, you want to use a film cap. Have fun!

-k
 
No real reason to short the pot. All that will do is change the volume taper a bit.... could be better, could be worse.... but, a very slight difference at any rate.

I don't think you have any 10uF ceramics... unless they are SMD. Normally, that value would be an electrolytic. So, you can just use a 10uF electrolytic, with the + terminal towards the opamp. (No need for a NP cap, since the amp is biased up from ground. In fact, the amp should work fine even with a 1uF in that spot if, for some reason, you want to use a film cap. Have fun!

-k

The reason I was thinking of shorting the pot was to make the HP filter cutoff fixed rather than variable. But if I don't really need to roll off the low frequencies then I can just make the cutoff very low as you suggested previously. So it's a tradeoff between having fixed filter cutoff or having higher input impedance. Or I could change the pot to larger value, increase the input resistance, and short out the pot.

The 1uF and 10uF caps I have are indeed ceramic smd. Pretty much all the parts I keep on hand are smd, which helps for messing around with this thing.
 
Is there any good reason to mod the later version?

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Well, just with regard to the volume circuit, with pot turned to full volume the input resistance is just 1K and your source probably won't like that! But the Lepai has so much gain that you would never turn this thing all the way up unless the source was very, very low level. So I think you can make the case that there is no need to change it for normal use. But I don't like it that way. I wanted more appropriate overall gain and so then the volume circuit needs tweaking.
 
Well, just with regard to the volume circuit, with pot turned to full volume the input resistance is just 1K and your source probably won't like that! But the Lepai has so much gain that you would never turn this thing all the way up unless the source was very, very low level. So I think you can make the case that there is no need to change it for normal use. But I don't like it that way. I wanted more appropriate overall gain and so then the volume circuit needs tweaking.
Thnx for response.
I'm not seeing 1k loading in the skiz, what am I missing?

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Hi everyone -I've been an audio enthusiast my entire life and am shocked at how it has changed. I am new to this site so bear with me.. Now that I'm older I am trying to acquire a more up to date system. In the process I purchased a Dayton Audio DTA-1 Class T Digital AC/DC Amplifier 15 -WPC . I was shocked at the power and fidelity. I hooded them up to some older 2 way JBL's and they sounded very good. Nice punchy bass. So I tried it with some Paradigm Monitor 11's and it worked very well also. Keeping in mind it was 35.00 on amazon. I wouldn't use it as my primary power source but for 35.00 - hey, its a deal.
 
Thnx for response.
I'm not seeing 1k loading in the skiz, what am I missing?

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Are you looking at the one in the attachment on post #92? That is the circuit in the new ones. If the pot is turned all the way up then only the fixed 1K resistor and the capacitor remain in the input path.
 
Are you looking at the one in the attachment on post #92? That is the circuit in the new ones. If the pot is turned all the way up then only the fixed 1K resistor and the capacitor remain in the input path.

That's what I'm looking at, I see 1k into 47k to ground. Then to the pot across the input/output of the chip thru a cap.

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You are right about the loading. The main current path has to go through the full 20K of the pot, so I blew that. Sorry! I'm not sure if there are other reasons that a low impendance in the input section of the op-amp circuit might be a problem for the source. Maybe Ken can chime in here.

The other points remain:

1. The HP filter cutoff frequency changes (so does the LP filter but not much can easily be done about that). Input cap is 2.2uF so and input resistance varies between 1K and 21K so fc of the HP filter varies between 72Hz and 3.4Hz (someone check my calcs!). So changing R37 makes this range in the corner frequency not as broad. Shorting out the terminals labeled pins 2 and 3 of the pot gives a fixed fc; I haven't decided whether to do this or not.

2. The total gain of the Lepai is extreme overkill. Maximum gain of the volume circuit is 20 and gain of the TA2020 is 16.5, so 330! A gain of not much more than 12 will begin to clip a 2V p-p input. So I wanted to reduce overall gain, and I'm doing this in the volume circuit.
 
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These still decent 2 years after the original post? Are there different models on ebay/amazon that i should be picking up? $20 seems like a bargain.

Need a little sound in the new baby room, have speakers, have no amp.
 
I am sure you will find it to be just fine for that. If not then no big deal, right? I think if you buy a new one it will have the tone defeat. LP-2020A+
 
These still decent 2 years after the original post? Are there different models on ebay/amazon that i should be picking up? $20 seems like a bargain.

Need a little sound in the new baby room, have speakers, have no amp.

My Lepai is more than two years old, has the cap mods and has power from a 12V 5A PS brick purchased for way cheep off Ebay. MCM blew these amps out at a ridiculous low price about a year ago, so I bought a couple more and a stick of the Tripath 2020 chips. Well worth the effort. :music:
 
I received the parts to do the Co capacitor mod for 8-ohm speakers, changing cap values from 0.47uF to 0.22uF. All seemed to go well - inspecting my soldering it looked good and clean. But I got no sound out of the amplifier. So I put the original caps back and still no sound. Somehow I think I killed the TA2020 but I can't imagine what I did. Looking on a scope I have signal going into the TA2020 IC but nothing coming out, just flat 6V.

The only thing I found is that I did break the ground connection on the cheap RCA input (fixed now). But I can't imagine that has anything to do with blowing the tripath IC.

Any troubleshooting advice? Probably best thing is to just buy another one.
 
I have done three of these. All the electrolytics were replaced and each of the power caps had a major upgrade.

When done, check closely for solder bridging, then thoroughly clean the board with IPA. I had no problems, all three sound incredible given their initial price and crap components.

Several of the larger electrolytics were leaking onto the board before replacement. Assume that any major brand caps attached to the Lepai board are counterfeit. Some of the smaller caps were all over the map spec wise, compared to their listed spec as shown on the part.

The Parts-Express has several interesting Lepai modding threads in their Tech Forums.
 
The soldering looks clean, no bridges. I cleaned the board in the area where I soldered but only the area around the soldering on the bottom side (top side looked clean). There is only so much troubleshooting that is worth it when a replacement is $20.
 
OK I want to do this again... but now I am reconsidering changing Co for the 8 ohm speaker load. I wonder if this makes much difference. Ignoring the quality of the components supplied with the lepai, and looking only at the issue of capacitance of Co, what is the reason to change this from 0.47uF to 0.22uF? Is it mainly to reduce the peaking at the resonant frequency of the filter? Using 0.47uF with 8 ohm speakers gives a Q=1.7, kind of high. But the filter's resonant frequency is at 70-80KHz, way above audible and way below the switching frequency. So is the peaking really a problem? Also, by reducing the value of Co the cutoff frequency moves higher so the attenuation of the switching frequencies is less - so there is that tradeoff for the less peaking.

Thanks to anyone with a better handle on this than me who can answer this question!
 
5A Power Supply, not an alternative!

Hi, just wanted to chime in, that I bought the Lepai or Lvpin amp being discussed a coupla weeks ago and also upgraded to the heftier power supply. Well, I don't know why everyone is saying that it upgrades the amp, it doesn't. In fact, I talked my neighbor into buying this amplifier also and he purchased a different 5A power adapter also. Yeah, his didn't sound any better either.

So, please stop referring to this mod as a better alternative, its not, in fact, it actually sounded a bit worse. The 2A that came with out, works fine, straight shot to the electrical outlet, too. Oh, but thanks for advising on the amp, works great, DR
 
Couple of points:
Lepais are a messed /inept bungle of the Tripath Data sheet Amp circuit.
Even worse; virtually ALL the parts on the messed up circuit are FAKE (cheap/poorly made imitiations. Even (especially) the Ta2020 chip).
Lepai's Do Not sound ...Anything... like a genuine Tripath circuit/chip amp.. which were surprisingly Good Amps.
So good that the vermin fake builders flourished like Mushrooms after Tripath ceased to exist.
Clearly you have Not yet heard a True Tripath,, tricky to do though these days as the type is long extinct.
On a Real ta2020 fitting a 5 amp ps (that in itself isn't a piece of Junk !)
Makes immediate Audible improvement.. as it should.
You are only speaking from your own Clearly limited experiences.
 
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a piece of Junk !)

You are only speaking from your own Clearly limited experiences.

Perhaps you should do a little background checking of who has contributed to this thread and what their credentials are in the audio world before you appoint yourself the Supreme Exalted One.

You might be surprised at what you learn, and by what you don't know.
 
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