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  • #31
    Re: Lepai T2020A+ Repair/Upgrade

    Originally posted by passexperts View Post
    Be careful with those output inductors. You must use shielded types or cross-coupling effects rise dramatically and you will negatively affect SQ. Even toroids couple badly if parallel to each other. Also, you have to use the correct material to avoid saturation. You'll need to know the filter's corner frequency.

    And the best output filter capacitors are X7R. Lowest DA and lead inductance for the application.
    Any idea where I can get the X7R capacitors? Are these just ceramic caps? Since the inductors may require a bit more research, I can start with the capacitors and go from there.

    How do I find the filter's corner frequency. Rather, what is the a filter corner frequency?

    Still learning here.
    Modding the Lepai T-Amp

    Comment


    • #32
      Re: Lepai T2020A+ Repair/Upgrade

      Just ordered one of these:

      http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWNX:IT

      We'll see now how well it works and if it makes any difference at all.
      Modding the Lepai T-Amp

      Comment


      • #33
        Re: Lepai T2020A+ Repair/Upgrade

        I'm learning that X7R is the temperature coefficient and that the ones made with an X7R temperature coefficient are ceramic. I'm finding a good variety of these at reasonable prices so I think I'll go with them.
        Modding the Lepai T-Amp

        Comment


        • #34
          Re: Lepai T2020A+ Repair/Upgrade

          Alright, I found superior audio grade replacements for all of the caps on the board with the exception of the ones above the heatsink labeled "474 Z"

          These don't have a voltage rating written on them, so I have absolutely no idea what to buy. There are 100V versions available in the 5% tolerance variety, but they're $3.19 apiece, which is quite expensive compared to the others and will end up costing me almost as much as the entire amp since I need 6 of them. These do appear to be output caps based on their proximity to the terminals, but I'm not an expert so what do you guys think?

          The "Z" rating on these represents a tolerance rating of -20%/+80%. Anyone have any idea what this means?
          Modding the Lepai T-Amp

          Comment


          • #35
            Re: Lepai T2020A+ Repair/Upgrade

            Originally posted by XtremeRevolution View Post
            Alright, I found superior audio grade replacements for all of the caps on the board with the exception of the ones above the heatsink labeled "474 Z"

            These don't have a voltage rating written on them, so I have absolutely no idea what to buy. There are 100V versions available in the 5% tolerance variety, but they're $3.19 apiece, which is quite expensive compared to the others and will end up costing me almost as much as the entire amp since I need 6 of them. These do appear to be output caps based on their proximity to the terminals, but I'm not an expert so what do you guys think?

            The "Z" rating on these represents a tolerance rating of -20%/+80%. Anyone have any idea what this means?
            It means it's not what you want to use in the output filter. "Tolerance" is a searchable term.

            Audio Grade does not equal "superior", but maybe it does...sometimes. You'd have to be an engineer to know what's important (or conversely, and sometimes more importantly what's not) and choose accordingly. I don't know what you really want, so I can't help you there. Changing a bunch of parts doesn't make it sound better. Sometimes it sounds worse, but different. Different might be what you're after...

            Corner Frequency: http://lmgtfy.com/?q=corner+frequency

            The output voltage swing won't exceed 12V - don't spend unnecessarily. Solder the SMD (surface mount) caps to the pads where the through-hole caps are now. If they don't reach, use a short piece of wire from the cap to the pad - bent in an "L" shape.

            Still, none of this bullsh*t is going to make much sonic difference. Lower radiated emissions, lower variation in filter response over a wide temperature range. But SQ? Not so much.

            Comment


            • #36
              Re: Lepai T2020A+ Repair/Upgrade

              Originally posted by passexperts View Post
              It means it's not what you want to use in the output filter. "Tolerance" is a searchable term.

              Audio Grade does not equal "superior", but maybe it does...sometimes. You'd have to be an engineer to know what's important (or conversely, and sometimes more importantly what's not) and choose accordingly. I don't know what you really want, so I can't help you there. Changing a bunch of parts doesn't make it sound better. Sometimes it sounds worse, but different. Different might be what you're after...

              Corner Frequency: http://lmgtfy.com/?q=corner+frequency

              The output voltage swing won't exceed 12V - don't spend unnecessarily. Solder the SMD (surface mount) caps to the pads where the through-hole caps are now. If they don't reach, use a short piece of wire from the cap to the pad - bent in an "L" shape.

              Still, none of this bullsh*t is going to make much sonic difference. Lower radiated emissions, lower variation in filter response over a wide temperature range. But SQ? Not so much.
              Tolerance is indeed a searchable term, but it won't give me what I want to know nor will it be relevant. Tolerance in respect to output capacitors on an amp is not something I can search or find easily. What difference does that tolerance make, and was -20/80 chosen because of cost or because of a specific purpose? As far as I can tell, tighter tolerance caps are more expensive.

              I'm coming from the perspective that this is quite possibly the cheapest amp that money can buy at this performance level (or really any for that matter) and that consequently, corners were cut here and there to make it cheaper. You won't be getting the best quality parts in the cheapest 40W RMS amp on the planet. Based on that, I figured why not give it a try because in a worst case scenario, it will sound undesirable so I'll solder the old ones back on and I'll have learned my lesson and wasted nearly nothing. So far my cart on mouser electronics is up to $10.68, and that includes parts to upgrade 3 Lepai amps including the large cap that blew on mine, so after I fix the bad cap I'll have lost $9. This is a loss I'm willing to risk and chalk up as a learning experience either way. If it sounds audibly better, crisper, and cleaner, I will report my impressions as such.

              That being said, I'd like to know if I can even replace the output caps in question and if so, with what. Whether or not it may not make an audible difference, I want to at least try it and see if it will sound any different and in what way. There are literally pennies I'm playing with. However, I'd at least like to go into this not being completely blind, and not knowing why the tolerance on those output caps is -20/80 and whether or not I can use a different tolerance cap has me at a roadblock right now.

              Edit...looks like -20/80 are the lowest possible tolerances on a capacitor that you can get. It doens't get much looser than that. They also happen to be the cheapest. Were these chosen for a purpose, or just to save money?
              Modding the Lepai T-Amp

              Comment


              • #37
                Re: Lepai T2020A+ Repair/Upgrade

                I ordered all of the caps. High quality "audio grade" electrolytic to replace the current electrolytic capacitors, and Panasonic polypropylene film caps to replace the rest.
                Modding the Lepai T-Amp

                Comment


                • #38
                  Re: Lepai T2020A+ Repair/Upgrade

                  Originally posted by XtremeRevolution View Post
                  They also happen to be the cheapest. Were these chosen for a purpose, or just to save money?
                  Sorry, I've been visited by the occasional hate-filled members from this board lately. It got to me earlier and I was a little short with you. My sincerest apologies.

                  Bingo. They'd build them out of Dixie cups and duct tape if it could work.

                  I'm a little surprised they used a double sided PCB...maybe this is their high-end.

                  Tolerance of that sort means variance in percentage of its printed value. So, a -20% / +80% would put a 1uF capacitor at 0.8uF or up to 1.8uF. That's huge and really affects filters and other, critical stages of circuitry. Bypassing and decoupling are much more lenient in a (relatively) low speed circuit such as this.
                  Last edited by passexperts; 04-22-2011, 01:47 AM. Reason: Math...what's that?

                  Comment


                  • #39
                    Re: Lepai T2020A+ Repair/Upgrade

                    Originally posted by passexperts View Post
                    Sorry, I've been visited by the occasional hate-filled members from this board lately. It got to me earlier and I was a little short with you. My sincerest apologies.

                    Bingo. They'd build them out of Dixie cups and duct tape if it could work.

                    I'm a little surprised they used a double sided PCB...maybe this is their high-end.

                    Tolerance of that sort means variance in percentage of its printed value. So, a -20% / +80% would put a 1uF capacitor at 0.8uF or up to 1.8uF. That's huge and really affects filters and other, critical stages of circuitry. Bypassing and decoupling are much more lenient in a (relatively) low speed circuit such as this.
                    That's pretty much what I was thinking; that they used such low quality parts because they're cheap. Those are some extremely loose tolerances.

                    Not sure how much this affects the particular amp I'm using, but the 5% tolerance caps I bought to replace these will be an interesting experience.

                    Here are the replacement parts I ordered:

                    3x Polypropylene Film Capacitors 0.10uF 450VDC 5% (to replace the red one to the right of the Tripath chip)
                    https://www.mouser.com/Search/Produc...-ECW-F2W104JAQ


                    18x Polypropylene Film Capacitors 0.47uF 450VDC 5% (to replace the blue 474 low tolerance ones)
                    https://www.mouser.com/Search/Produc...-ECW-F2W474JAQ


                    1x Aluminum Electrolytic Capacitors - Leaded 16VDC 5600uF (for fiddling around with as a larger input cap than the 4700uf)
                    https://www.mouser.com/Search/Produc...67-EEU-FR1C562


                    6x Aluminum Electrolytic Capacitors - Leaded 50volts 2.2uF 20% (direct replacement)
                    https://www.mouser.com/Search/Produc...47-UKW1H2R2MDD


                    6x Aluminum Electrolytic Capacitors - Leaded 50volts 1uF 20% (direct replacement)
                    https://www.mouser.com/Search/Produc...47-UKW1H010MDD


                    6x Aluminum Electrolytic Capacitors - Leaded 25volts 220uF 20% (direct replacement)
                    https://www.mouser.com/Search/Produc...47-UKW1E221MPD


                    3x Aluminum Electrolytic Capacitors - Leaded 16volts 470uF 20% (direct replacement)
                    https://www.mouser.com/Search/Produc...47-UKW1C471MPD


                    6x Aluminum Electrolytic Capacitors - Leaded 16volts 100uF 20% (direct replacement)
                    https://www.mouser.com/Search/Produc...47-UKW1C101MDD


                    3x Aluminum Electrolytic Capacitors - Leaded 16volts 4700uF 20% (input cap replacement)
                    https://www.mouser.com/Search/Produc...47-UKW1C472MHD



                    These should ship out tomorrow via UPS so I'll be able to get started next week. Since I happen to have two identical amps that have not been used, I'll be able to report back the results after I mod one of them.

                    I've decided against replacing the inductors btw. The polypropylene capacitors I've read are great around heat compared to ceramics and a few other kinds, which is good considering they're right next to the heatsink, and the electrolytic capacitors are apparently "audio grade," whatever that means.
                    Last edited by XtremeRevolution; 04-22-2011, 11:31 AM.
                    Modding the Lepai T-Amp

                    Comment


                    • #40
                      Re: Lepai T2020A+ Repair/Upgrade

                      Originally posted by XtremeRevolution View Post
                      That's pretty much what I was thinking; that they used such low quality parts because they're cheap. Those are some extremely loose tolerances.

                      Not sure how much this affects the particular amp I'm using, but the 5% tolerance caps I bought to replace these will be an interesting experience.

                      I've decided against replacing the inductors btw. The polypropylene capacitors I've read are great around heat compared to ceramics and a few other kinds, which is good considering they're right next to the heatsink, and the electrolytic capacitors are apparently "audio grade," whatever that means.
                      But those are HUGE. You'll have fun putting them in. There's this property called "lead inductance" that comes into play with these high frequency filters. Sticking an enormous capacitor in place of a smaller - though less accurate - capacitor is kind of like replacing a too dim nightlight with a too-bright searchlight. You're not achieving results you want - and you're hurting your chances of success. Higher lead inductance has a negative effect on the capacitor's ability to do its job.

                      I might as well have not even given you advice... I think your success can't be measured. You haven't stated what you want to achieve...so....it's anyone's guess.

                      Comment


                      • #41
                        Re: Lepai T2020A+ Repair/Upgrade

                        Looks like all of your links are there, but are associated with the wrong component descriptions.

                        Comment


                        • #42
                          Re: Lepai T2020A+ Repair/Upgrade

                          Originally posted by passexperts View Post
                          Sorry, I've been visited by the occasional hate-filled members from this board lately.
                          It is a shame that happens

                          There are also a couple members who seem to only post sarcastic "know it all" comments but never really add any useful content, and usually follow it with one of these: :rolleyes:
                          Last edited by PWR RYD; 04-22-2011, 10:48 AM.
                          Craig

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                          • #43
                            Re: Lepai T2020A+ Repair/Upgrade

                            Originally posted by passexperts View Post
                            But those are HUGE. You'll have fun putting them in. There's this property called "lead inductance" that comes into play with these high frequency filters. Sticking an enormous capacitor in place of a smaller - though less accurate - capacitor is kind of like replacing a too dim nightlight with a too-bright searchlight. You're not achieving results you want - and you're hurting your chances of success. Higher lead inductance has a negative effect on the capacitor's ability to do its job.

                            I might as well have not even given you advice... I think your success can't be measured. You haven't stated what you want to achieve...so....it's anyone's guess.
                            Yes, they are larger, but I don't believe they're prohibitively larger. They're half an inch wide, which given the massive amount of clearance I have from all directions where the original caps are, shouldn't be an issue. I'm not changing the actual values; they're still .47ohms, and from what I've read these are supposed to be excellent for high frequency circuits. That being said, I'm not arguing with you, just figuring this out. Does the fact that they're physically larger make that much of a difference?

                            I wanted to improve sound quality. What that means, I'm still not sure of. At an absolute minimum, I wanted to find a way to keep the front LED light from dimming under harder bass beats and keep the unit from shutting down when the voltage drops to unstable levels as a result of said dimming. It was clear to me that there was a power delivery issue as I was driving a 20W speaker and the amp couldn't keep up despite it being rated for 20W RMS. Either the power supply can't keep up with the load, or the input cap is too small, hence the attempt with the larger input cap and the 5A power supply I ordered. I will also be looking for ways to increase the size of the heatsink.

                            As far as the other output caps, I simply wanted to see if I could improve the way the amp sounded in general. A more flat response, a more detailed high end, and better tone controls.

                            Your advice may not have changed my mind, but don't think I won't be remembering everything once I'm done and trying to explain why it does or doesn't sound the way I want it to. To me its more of a learning experience than anything since I can very easily solder the old parts back onto the board.

                            In a worst case scenario, I'll come back to say that everything sounds exactly the same and at minimum I'll have put in higher quality parts that have a lower chance of failure, at least with regard to the electrolytic caps.

                            Originally posted by Leroy R View Post
                            Looks like all of your links are there, but are associated with the wrong component descriptions.
                            Just fixed them.

                            Originally posted by PWR RYD View Post
                            It is a shame that happens

                            There are also a couple members who seem to only post sarcastic "know it all" comments but never really add any useful content, and usually follow it with one of these: :rolleyes:
                            I've seen them here and there, but scarcely on this board. I generally ignore them and move on. We have a LOT of them over on diyma.
                            Modding the Lepai T-Amp

                            Comment


                            • #44
                              Re: Lepai T2020A+ Repair/Upgrade

                              Alright, status update.

                              Got the crossover parts in. The 4700uf "audio grade" caps and the 5600uf "low ESR" cap are the exact same size, and they both fit in the location of the old one as a direct replacement. There's definitely enough vertical clearance.

                              The replacement power adapter also arrived, and I got to test that just now. Previously, the amp's lights would start dimming and the amp would shut down at just over the 1/2 volume point when testing an Aura NS6 off of one channel. Now, I can crank it past the 3/4 point and the lights don't even dim.

                              I have concluded that the 2A power adapter these things come with is insufficient by a long shot. It should be thrown away immediately and replaced with a larger unit that can actually provide the rated power. The one I got provides up to 6A at 12V. I've already ordered 2 more power adapters.

                              I didn't get a chance to replace any of the caps, but I figured I'd share my findings.
                              Modding the Lepai T-Amp

                              Comment


                              • #45
                                Re: Lepai T2020A+ Repair/Upgrade

                                Ok, so I've replaced all of the blue caps on one of them and the broken input cap and fired it up. I now have a song playing and I have the left and right channels split between two amps, each amp connected to a speaker. Each are connected to a Peerless India 3" buyout driver in a mini cube made of oak.

                                The test was to fire up one amp, then fire up the second, wait for the relay delay, then turn the first one off. That's pretty much a seamless way to hear the difference.

                                The tests were done with the unit I fixed, and a brand new unit fresh out of the box. My wife was the one switching them and I was listening across the room. Now, my wife isn't the kind of person to notice things, but she noticed a difference, and I noticed one too between the two amps.

                                Its hard to describe it, but the stock amp that wasn't modified sounds more...hollow. It almost sounds as if you're playing it in the bathroom, while the other amp sounds more rich and more full. The music sounds more wide and clear. The stock amp lacks some midrange clarity as well. Its not very noticeable, but its definitely there.

                                I'll replace the rest of the caps tomorrow and see if it makes a difference at all. So far so good.
                                Modding the Lepai T-Amp

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