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Lepai T2020A+ Repair/Upgrade

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  • #76
    Re: Lepai T2020A+ Repair/Upgrade

    Originally posted by Sydney View Post
    You can find a Tantalum in 1.7ufd.
    I appreciate the suggestion but I am against using Tantalum caps in the signal path. The last amp I restored that had tants in the signal path of the tone controls was a Yamaha CA-1000. The unit sounded great once I switched them out for polypropylenes - specifically Panasonic ECQ-P(Z) - but they are obsolete now, not to mention physically larger.

    Not much elbow room in this Lepai, that's for sure!

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    • #77
      Re: Lepai T2020A+ Repair/Upgrade

      I just finished doing some recapping with the Lepai using Nichicon Muse KW caps that I had on hand - I see they are the same ones you used. Two exceptions were the 100uF and 1uF caps - I used Elna Silmic II for those...

      Thanks to your handy parts list I am placing an order for the 5600uF cap - looks like the FR series replaced the FM which I was so fond of. I am also picking up the .47uF caps on your list - when I got to my workshop I realized I was out of the ECQ-P(Z) jobs.

      Thanks for putting the info in a convenient place.

      Let me know if you ever replace those inductors and what you plan to use. I would love to slap some Burr Brown Opamps in here but surface mount technology is a PITA with my tools (and eyes).

      Thanks again for the thread...

      Ohh yeah - forgot to give my impressions - I think the little guy sure packs a punch! The imaging and clarity definitely sounds better with the "direct" mode on - when I put the tone controls in circuit things sound muddy and veiled. I am thinking about trying two Nichicon Muse ES Bipolars in place of those 1.75uF bipolar caps to see if that helps things out. Not much else I can do without going crazy on surface mount parts - no thanks!

      Rob

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      • #78
        Re: Lepai T2020A+ Repair/Upgrade

        I finished my Lepai upgrades today.

        I replaced all the parts you mention with two exceptions:
        • Added a .56uF bypass capacitor across the 5600uF cap
        • Replaced the two 1.75uF bipolar caps in the tone controls with 2.2uF Nichicon Muse ES bipolars


        I am listening to the unit now and I think it sounds fabulous - with or without tone direct depressed.

        I wonder if the distortion you noticed when trying to replace your caps was due to a solder mishap or bad replacement parts.

        Comment


        • #79
          Re: Lepai T2020A+ Repair/Upgrade

          Originally posted by xoaphexox View Post
          I finished my Lepai upgrades today.

          I replaced all the parts you mention with two exceptions:
          • Added a .56uF bypass capacitor across the 5600uF cap
          • Replaced the two 1.75uF bipolar caps in the tone controls with 2.2uF Nichicon Muse ES bipolars


          I am listening to the unit now and I think it sounds fabulous - with or without tone direct depressed.

          I wonder if the distortion you noticed when trying to replace your caps was due to a solder mishap or bad replacement parts.
          I don't recall, but I know it was something I was able to measure as well. I suppose those two capacitors wouldn't make or break it.

          What's the purpose of the .56uf bypass capacitor?
          Modding the Lepai T-Amp

          Comment


          • #80
            Re: Lepai T2020A+ Repair/Upgrade

            Originally posted by XtremeRevolution View Post
            What's the purpose of the .56uf bypass capacitor?
            From what I recall, bypassing the cap provides a lower impedance over the mid to high frequencies than the electrolytic cap would alone. This gives a quieter, stiffer supply at all frequencies, giving lower distortion.

            It is a habit I got in while restoring vintage gear. I realize this isn't quite vintage - nonetheless, I had the caps on hand. It fit nicely under the PCB and doesn't prevent it from sliding back in the metal housing.

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            • #81
              Re: Lepai T2020A+ Repair/Upgrade

              Originally posted by xoaphexox View Post
              From what I recall, bypassing the cap provides a lower impedance over the mid to high frequencies than the electrolytic cap would alone. This gives a quieter, stiffer supply at all frequencies, giving lower distortion.

              It is a habit I got in while restoring vintage gear. I realize this isn't quite vintage - nonetheless, I had the caps on hand. It fit nicely under the PCB and doesn't prevent it from sliding back in the metal housing.
              Wait, which cap are you talking about specifically? You said you bypassed the 5600uf cap. Isn't that the input cap?
              Modding the Lepai T-Amp

              Comment


              • #82
                Re: Lepai T2020A+ Repair/Upgrade

                Originally posted by XtremeRevolution View Post
                Wait, which cap are you talking about specifically? You said you bypassed the 5600uf cap. Isn't that the input cap?
                Yes, the 5600uF cap. I assumed the largest cap in the unit was the power reservoir. Force of habit I suppose.

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                • #83
                  Re: Lepai T2020A+ Repair/Upgrade

                  Originally posted by xoaphexox View Post
                  Yes, the 5600uF cap. I assumed the largest cap in the unit was the power reservoir. Force of habit I suppose.
                  I'm just learning here, so how does bypassing the power reservoir cap help anything? I thought that was way far down in the power supply chain.
                  Modding the Lepai T-Amp

                  Comment


                  • #84
                    Re: Lepai T2020A+ Repair/Upgrade

                    Originally posted by XtremeRevolution View Post
                    I'm just learning here, so how does bypassing the power reservoir cap help anything? I thought that was way far down in the power supply chain.
                    Frankly I can't explain the science behind it. It is just a habit that I got in of bypassing large caps with a value 1/10,000th the size (hence the .56uF).

                    If you look in high end gear from Sansui, Luxman, Nelson Pass, etc - they use bypass caps, and when it comes to restoring/upgrading audio I like to stick with what I see pros doing - I'm not a trailblazer myself.

                    Comment


                    • #85
                      Re: Lepai T2020A+ Repair/Upgrade

                      Originally posted by xoaphexox View Post
                      Frankly I can't explain the science behind it. It is just a habit that I got in of bypassing large caps with a value 1/10,000th the size (hence the .56uF).

                      If you look in high end gear from Sansui, Luxman, Nelson Pass, etc - they use bypass caps, and when it comes to restoring/upgrading audio I like to stick with what I see pros doing - I'm not a trailblazer myself.
                      Have you heard a difference when bypassing this cap before?
                      Modding the Lepai T-Amp

                      Comment


                      • #86
                        Re: Lepai T2020A+ Repair/Upgrade

                        Here is a quote I stole from a bypass cap thread on Audiokarma on a reason why bypass caps are used on larger caps:

                        "Attenuate the inductance [and] add some low ESR energy storage"

                        Comment


                        • #87
                          Re: Lepai T2020A+ Repair/Upgrade

                          Originally posted by xoaphexox View Post
                          Here is a quote I stole from a bypass cap thread on Audiokarma on a reason why bypass caps are used on larger caps:

                          "Attenuate the inductance [and] add some low ESR energy storage"
                          This is something I'm quite curious about, because it makes very little sense to me. The caps I picked out were low ESR caps to begin with.
                          Modding the Lepai T-Amp

                          Comment


                          • #88
                            Re: Lepai T2020A+ Repair/Upgrade

                            Originally posted by XtremeRevolution View Post
                            Have you heard a difference when bypassing this cap before?
                            This is the first (and only) Class D amp I've ever heard. I've spent the last 6 years inside amps from the 1970's. I auditioned the amp with the stock cap in place, and again with the 5600uF cap in place, and again with the 5600uF bypass cap in place and I do think it sounded better each go-around. I will say, however, that I did replace other parts at the same time as adding the bypass cap and by gut tells me the improved sound quality came more from removing those two cheap Chinese bipolars and replacing them with Nichicon Muse than it did from adding that bypass cap. Like I said, I just did it out of habit and because I have a large stockpile of caps from my vintage restorations.

                            Comment


                            • #89
                              Re: Lepai T2020A+ Repair/Upgrade

                              Originally posted by XtremeRevolution View Post
                              This is something I'm quite curious about, because it makes very little sense to me. The caps I picked out were low ESR caps to begin with.
                              I wonder what the ESR of the original Chinese 2200uF cap was compared to the new Panasonic cap - then compared to the bypassed Panasonic cap...

                              If I go back in to change out the inductors or SMD input coupling caps I may do some measurements.

                              Did you try your hand at replacing either of these? I am curious to hear about it. I'm a bit obsessive - all my gear takes turns on the bench trying out different parts. Economic? No... Fruitful... not always. Fun? Yes!

                              Comment


                              • #90
                                Re: Lepai T2020A+ Repair/Upgrade

                                Originally posted by xoaphexox View Post
                                I wonder what the ESR of the original Chinese 2200uF cap was compared to the new Panasonic cap - then compared to the bypassed Panasonic cap...
                                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.
                                Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

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