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Lepai T2020A+ Repair/Upgrade

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  • #91
    Re: Lepai T2020A+ Repair/Upgrade

    Originally posted by neildavis View Post
    It doesn't matter. The bulk capacitor doesn't do much to ensure stability or minimize switching noise. In fact, Tripath specifies a puny 180uF cap on the TA2020 or TA2024 data sheets--so that 2200uf cap is fine. A far more important cap is the ceramic or tantalum cap that is very near the chip power pins. This link explains why: http://www.eetimes.com/design/audio-...s-D-amplifiers . It turns out that at high switching frequencies, the inductance from the circuit board traces will decouple that low ESR cap--so it is a waste of money to make it a higher quality part.

    If you want more details, ST has a nice PCB design tutorial that even shows waveforms with good and bad decoupling. It is for a higher current device (STA317b), but the concepts still apply. I can post that tutorial for you if you like.
    Thanks for the info and the link! Reading...

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    • #92
      Re: Lepai T2020A+ Repair/Upgrade

      A gentleman with a Class D amp site in Italy suggests these are great inductor replacements. I may give them a try along with an Alps volume pot, because the stock pot does not track very well L/R in my Lepai.

      http://www.ebay.com/itm/4-pcs-Choke-...item3cbb0a551e

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      • #93
        Re: Lepai T2020A+ Repair/Upgrade

        Also, this may make a good replacement for the volume pot, no?

        http://www.mouser.com/ProductDetail/...ujRSOS7sDss%3d

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        • #94
          Re: Lepai T2020A+ Repair/Upgrade

          Originally posted by xoaphexox View Post
          A gentleman with a Class D amp site in Italy suggests these are great inductor replacements. I may give them a try along with an Alps volume pot, because the stock pot does not track very well L/R in my Lepai.

          http://www.ebay.com/itm/4-pcs-Choke-...item3cbb0a551e
          I would go with the ICE inductors that Mouser is selling: http://www.mouser.com/search/refine....aign=128304187

          The Ebay inductors appear to be the powdered metal core variety ("type 2") that Tripath originally specified for the mid-sized amps. They are "fairly" linear and low-loss, and were widely used several years ago for class D amps. However, most newer class D amps are using the shielded gapped ferrite cores, which are even more linear (L vs I). The new inductors designed for audio amps are supposed to overcome some of the quirky properties of ferrites such as hysteresis distortion. I haven't seen hard data that compares the two types in real amps, but the literature that I've read suggests that the "class D audio inductors" such as the ICE products should be better (lower distortion).

          Also, nothing wrong with the Alps pot other than the price. The tracking is guaranteed to be less than 3db over the entire range, which is pretty good for a mechanical control.
          Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

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          • #95
            Re: Lepai T2020A+ Repair/Upgrade

            Originally posted by neildavis View Post
            I would go with the ICE inductors that Mouser is selling: http://www.mouser.com/search/refine....aign=128304187

            The Ebay inductors appear to be the powdered metal core variety ("type 2") that Tripath originally specified for the mid-sized amps. They are "fairly" linear and low-loss, and were widely used several years ago for class D amps. However, most newer class D amps are using the shielded gapped ferrite cores, which are even more linear (L vs I). The new inductors designed for audio amps are supposed to overcome some of the quirky properties of ferrites such as hysteresis distortion. I haven't seen hard data that compares the two types in real amps, but the literature that I've read suggests that the "class D audio inductors" such as the ICE products should be better (lower distortion).

            Also, nothing wrong with the Alps pot other than the price. The tracking is guaranteed to be less than 3db over the entire range, which is pretty good for a mechanical control.
            Thank you very much for your analysis. I haven't ordered anything yet, so I will give these ICE inductors a look. Just need to find out some lead spacing. When I make a decision and do any part swaps I will update this thread with pics.

            Comment


            • #96
              Re: Lepai T2020A+ Repair/Upgrade

              It seems like the channel imbalance I was experiencing is due to the treble pot. When I wiggle it, it seems to come back a bit. They are 16mm shaft B50K dual pots. The volume pot is a B20k dual pot.

              The Alps pots at Mouser are about $12 each which does seem very expensive.

              The lead spacing on the stock inductors is about 7mm, which is great, because there are 10uH ICE Inductors at Mouser with 7mm lead spacing. They are OOS right now but should ship in about two weeks.

              Any ideas on a good place to get a replacement pot without spending as much as the whole Lepai?

              Thanks!

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              • #97
                Re: Lepai T2020A+ Repair/Upgrade

                The voice of reason spoke to me last night... I am not going to persue 'polishing the turd' any further. Life is pretty full and this little amp is a neat toy and curiosity and will be just fine in the computer sound environment that I am using it for.

                As my last hurrah, I removed the poly bypass cap on the 5600uF cap and got four of those 10uH ICE Inductors. They were inexpensive.

                All further tweaks are cancelled. Thanks for everyone's input. I learned a lot.

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                • #98
                  Re: Lepai T2020A+ Repair/Upgrade

                  Originally posted by xoaphexox View Post
                  I learned a lot.
                  That's the real spirit of DIY--getting your hands dirty, figuring out how stuff works, discussing the technology and acquiring the information to judge what is true and false along the way. $25 is a good deal for that much learning.

                  ...and it is also why the tag fairy should be caught and banned. The mean-spirited tags on this thread are have no place in the DIY community.
                  Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

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                  • #99
                    Re: Lepai T2020A+ Repair/Upgrade

                    Say what you will about diminishing returns - these ICE inductors along with swapping out the stock SMD caps with some nice Wima polypropylene caps has turned this tea bag in to a silk purse with chrome spinning rims! This little amp gives me goosebumps now listening to my favorite recordings!

                    :D

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                    • Re: Lepai T2020A+ Repair/Upgrade

                      to be fair, to my novice ears i was mighty impressed with what this amp could do for its price. Admitidly im no audiofile but certainly like improving upon what is already there and have very much enjoyed this thread.

                      I have two A+'s and intend modding one of them as a comparison experiment, but first i need to scrub up on my soldering technique!

                      any advice would be appreciated!

                      Comment


                      • Re: Lepai T2020A+ Repair/Upgrade

                        Originally posted by xoaphexox View Post
                        Say what you will about diminishing returns - these ICE inductors along with swapping out the stock SMD caps with some nice Wima polypropylene caps has turned this tea bag in to a silk purse with chrome spinning rims! This little amp gives me goosebumps now listening to my favorite recordings!

                        :D
                        Could you please post the exact part numbers you used for the ICE inductors and Wima caps? Thanks.
                        Craig

                        Comment


                        • Re: Lepai T2020A+ Repair/Upgrade

                          This may be a silly question but is this the T2020A+ ?

                          http://www.parts-express.com/pe/show...r=310-300&FTR=

                          I ask because it only says T2020. I assume the A+ is this newer version with the tone defeat feature.
                          Craig

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                          • Re: Lepai T2020A+ Repair/Upgrade

                            Originally posted by PWR RYD View Post
                            This may be a silly question but is this the T2020A+ ?

                            http://www.parts-express.com/pe/show...r=310-300&FTR=

                            I ask because it only says T2020. I assume the A+ is this newer version with the tone defeat feature.
                            Yeah, its the same one. I just picked one up 2 weeks ago.
                            Modding the Lepai T-Amp

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                              • Re: Lepai T2020A+ Repair/Upgrade

                                Originally posted by jmw0403 View Post
                                I’m hoping one you can help me. Since reading this thread I’ve been playing with my lepai. Somehow I’ve lost the right channel output. When you press the cap in the photo below, (I colored one of the top panes orange) you get static out of the right speaker and at one point I got a little sound for a moment.

                                Is this a bad cap I tried to de-solder, re-solder but it did not help. Any thoughts?

                                Also, removed the direct/tone switch and the two related potentiometers, that's why they are missing.
                                Could be a bad cap. I'd recommend replacing all of them anyway. As I mentioned in this thread and the one below, the quality control on these is terrible, and consistency is poor. It is recommended that these caps be replaced if you have the ability to replace them.

                                http://techtalk.parts-express.com/sh...d.php?t=226235
                                Modding the Lepai T-Amp

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