Modding the Lepai T2020A+

[neildavis]

Re: Modding the Lepai T2020A+

Where were you when I posted my first thread, lol.

Not trying to spoil anyone's fun :D.
I didn't post until someone questioned whether the cap replacement was worthwhile...

The power supply was a concern area with previous models. Previous models operated at 13.2V, and units were shutting down as a result...

That makes sense, because according to the diagram that someone posted, there is an overvoltage protection circuit. In order to use a higher supply voltage you would have to change a resistor in that circuit, or else use a different zener diode. Also, the TA2020 chip requires additional shottky clamping diodes for supply voltages above 13.5V (see the note on page 5 of the TA2020 data sheet). So using a higher supply voltage gets more complicated, but it's not hard to do.

When I asked about this earlier on three forums (this one, diyaudio, and diyma), it was recommended that I leave the inductors alone as they are shielded. That's the biggest reason I never messed with it.

You can buy larger shielded inductors. However, the shielding is primarily for RFI/EMI, and if the amp is in a metal case it probably won't make much difference whether the inductors are shielded. The "low-distortion" ferrites from Icecomponents or the Sagami's from inductor.com would be even better, but they are usually hard to get in small quantities.

Where is the op amp, how expensive are they, and how easy are they to replace?

Looks like there are two of them: U1 and U2. The "secret" to replacing SMD IC's is to cut the legs off near the body and then remove the legs with solder wick. However, you will need a good quality temperature-controlled iron with a fine tip to solder on the new part. "Easy to replace" is relative: if you have the right equipment and some experience, it is easy. Otherwise, don't do it.

Are you recommending that the red film caps I mentioned first are not worth replacing?

Again, from an engineering perspective, the answer is "no". These are filter caps to remove the 60KHz to 90KHz carrier, and a stacked metallized film cap is well suited for that application. The distortion from those film caps should be much lower than the distortion from the output inductor. I can't dispute that you heard a difference--I'm just saying that from an EE perspective and as someone who has done a lot of reading about capacitors, there shouldn't be any benefit from replacing them.

[XtremeRevolution]

Re: Modding the Lepai T2020A+

Not trying to spoil anyone's fun :D.
I didn't post until someone questioned whether the cap replacement was worthwhile...

That makes sense, because according to the diagram that someone posted, there is an overvoltage protection circuit. In order to use a higher supply voltage you would have to change a resistor in that circuit, or else use a different zener diode. Also, the TA2020 chip requires additional shottky clamping diodes for supply voltages above 13.5V (see the note on page 5 of the TA2020 data sheet). So using a higher supply voltage gets more complicated, but it's not hard to do.



You can buy larger shielded inductors. However, the shielding is primarily for RFI/EMI, and if the amp is in a metal case it probably won't make much difference whether the inductors are shielded. The "low-distortion" ferrites from Icecomponents or the Sagami's from inductor.com would be even better, but they are usually hard to get in small quantities.



Looks like there are two of them: U1 and U2. The "secret" to replacing SMD IC's is to cut the legs off near the body and then remove the legs with solder wick. However, you will need a good quality temperature-controlled iron with a fine tip to solder on the new part. "Easy to replace" is relative: if you have the right equipment and some experience, it is easy. Otherwise, don't do it.


Again, from an engineering perspective, the answer is "no". These are filter caps to remove the 60KHz to 90KHz carrier, and a stacked metallized film cap is well suited for that application. The distortion from those film caps should be much lower than the distortion from the output inductor. I can't dispute that you heard a difference--I'm just saying that from an EE perspective and as someone who has done a lot of reading about capacitors, there shouldn't be any benefit from replacing them.

Thanks for the advice. I'm intrigued regarding the inductors. How expensive are we talking here?

I certainly don't have the right equipment to replace the opamps, so I'm thinking I'll pass on that mod, lol.

As for those film caps, it would be neat to send one of these amps out to someone who can test the differences.

[nelsonvandal]

Re: Modding the Lepai T2020A+

There's a long thread at Diyaudio.com http://www.diyaudio.com/forums/class...mp-ta2020.html . I haven't read it since I don't have a Lepai, but there's probably something useful there eg this schematic http://img23.imageshack.us/img23/1586/scan10006k.jpg .

I think there's room for polypropylene input caps, and I think cheap polypropylene sounds better than expensive electrolytic. Bypassing the tone controls is probably easy (see schematic) and beneficial to the sound. Replacing the opamp should also be a major improvement. NE5532 is very cheap. Not the best but OK and used everywhere. Here's a desoldering tutorial http://tangentsoft.net/elec/movies/tt04.html . Cutting pins often leads to destroyed PCB traces. There seems to be a coupling cap between the opamp and the output amp, and a polypropylene cap here might also be beneficial.

[Wolf]

Re: Modding the Lepai T2020A+

(unless you have ears like Wolf and can hear up to 40KHz* ).

*Disclaimer: Neil's kidding. I never even remotely claimed that, however, my dog may be able to... ;)

Thanks for the laugh, Neil!
Wolf

[Bob Brines]

Re: Modding the Lepai T2020A+

OK, Ill be the devil's advocate here: Why do you want to remove the EQ anyway? A little EQ can often salvage a truly bad recording, and if you removed the EQ, you are SOL!

Bob

[nelsonvandal]

Re: Modding the Lepai T2020A+

OK, Ill be the devil's advocate here: Why do you want to remove the EQ anyway? A little EQ can often salvage a truly bad recording, and if you removed the EQ, you are SOL!

Bob

I never use it and I don't like unnecessary parts in the audio pathway. Wherever there are tone controls there should be a "Direct" button. I like it when different records sound different.

[neildavis]

Re: Modding the Lepai T2020A+

...I'm intrigued regarding the inductors. How expensive are we talking here?

The price is reasonable. I came close to ordering some of the Sagami's from inductor.com and the price quote I got was in the $2-$3 range for quantities of 100. Unfortunately, I don't know where to buy them individually.

To be honest with you, I don't know why some coils are branded as "low distortion" or for "class D". The three major vendors that have a dedicated line of inductors for class D amps are Toko, Sagami and Coilcraft. And if you look at the major class D chip vendors--TI, ST and IR, their application notes or reference designs usually specify either these Toko or Sagami parts. So there is something special about these coils, but I don't know the details.

So much for the high-end stuff. For upgrading the Lepai amp, you just want to make sure the coil is being used in its linear range and is not anywhere near saturation. If the coil on your board is 10mm in diameter and 10mm high, it is probably adequate (I can't tell from the photo). If it is smaller than that, it may not be suitable. I'm basing that size estimate on the specs for the Murata 1200RS available at Digikey for $.85. If you look at the data sheet for this coil, it shows a nice flat I vs A curve out to at least 3A for the 10uH part. Other shielded ferrite coils that are about this size should have comparable current-handling ability. Another indicator is the coil resistance--something in the .025ohm range for a 10uH part should be OK. However, measuring these low resistance values can be tricky.

Link to Murata coil: http://www.murata-ps.com/data/magnetics/kmp_1200r.pdf

[daveinva]

Re: Modding the Lepai T2020A+

Can anyone look at the tripath chip in their Leapi and see if one of the end pins looks like its not soldered. I have a bad one that only one channel has sound. That one pin doesn't look like it has any solder on it. It may not be used, and I'm hesitant to go applying heat if thats not the problem. If other peoples are the same (no solder on that pin) I'll leave it alone.

Any one else get a lepai w/ only one channel working? PE sent me a replacement in one day so I'm not complaining. It would just be fun to fix it.

Thx.

[Sam N.]

Re: Modding the Lepai T2020A+

So I have two non-functional lepais that I was considering modding/fixing. I also have two boards that came from an Onkyo cd player that went out on me.

They are covered in blue Nichicon capacitors and small red film style capacitors. I can figure out what the blue ones are but the red ones the markings seem to be proprietary. For exapmle the most commone one on the board says 222J. Also there are two that are 0Z8 474.

Anyone have any clue as to how to decipher them?

Also does anyone know if the blue Nichicons are decent quality?

[Ronkayes]

Re: Modding the Lepai T2020A+

So I have two non-functional lepais that I was considering modding/fixing. I also have two boards that came from an Onkyo cd player that went out on me.

They are covered in blue Nichicon capacitors and small red film style capacitors. I can figure out what the blue ones are but the red ones the markings seem to be proprietary. For exapmle the most commone one on the board says 222J. Also there are two that are 0Z8 474.

Anyone have any clue as to how to decipher them?

Also does anyone know if the blue Nichicons are decent quality?

I think 222J stands for 2200pF according to this website. http://www.electronicsteacher.com/capacitor-chart.php

Found a 222J on ebay.

http://cgi.ebay.com/50pc-PEI-PE-Plastic-Film-Capacitor-222J-2200pF-100V-5-/130296095723#ht_1224wt_1163

[gychang]

Re: Modding the Lepai T2020A+

I would set the following priorities in modding this amp:

3) The op amp. 4558's are not low distortion or low noise. There are many good options, but even the low cost TL082 would be a major upgrade.

thanks ordered the op amps... thanks for a nice suggestions.

[meeotch]

Re: Modding the Lepai T2020A+

I've seen a few discussions about bypassing the tone controls. But my 2020+ (new version) sounds a bit "tin can-ny" with the bypass button set to Direct. Too flat? I don't know - all I know is it sounds better with the treble boosted.

Problem is, with the tone controls enabled, I can't crank the volume much past halfway without distortion. (In Direct mode, I can generally get up to about 2/3). This is into a 6 ohm satellite/sub set, and it seems to be pulling less than an amp at this volume - so maybe not a power supply issue?

Which of the discussed mods, if any, will allow me to operate the thing with the tone controls enabled?

(Unfortunately, I have neither the time nor the skillz to mess with any of the SMD components right now. Leaving for a desert trip in two days, and will be running the amp off at 12V battery.)

[nige838]

Re: Modding the Lepai T2020A+

2 Questions:

1. Are the two surface mounted capacitors closest to the inputs the coupling capacitors and if so what are their values. marked C30/C31.

2. I'm interested in coupling the two channels into one after the input. On the older ones, I used (2) 10k resistors and then joined them together and fed them into the 2 decoupling caps (2.2uf I think). This amp looks a lot different. Do you have any suggestions on how to do this? (that's really the only reason for the first question. Also, I used to replace these caps with better, poly caps.)

Thank you very much,
Nicholas

[XtremeRevolution]

Re: Modding the Lepai T2020A+

2 Questions:

1. Are the two surface mounted capacitors closest to the inputs the coupling capacitors and if so what are their values. marked C30/C31.

2. I'm interested in coupling the two channels into one after the input. On the older ones, I used (2) 10k resistors and then joined them together and fed them into the 2 decoupling caps (2.2uf I think). This amp looks a lot different. Do you have any suggestions on how to do this? (that's really the only reason for the first question. Also, I used to replace these caps with better, poly caps.)

Thank you very much,
Nicholas

Someone more knowledgeable will have to answer that question for you, as I'm not as technically inclined as others to be able to answer that question for you.

[gychang]

Re: Modding the Lepai T2020A+

3) The op amp. 4558's are not low distortion or low noise. There are many good options, but even the low cost TL082 would be a major upgrade.

I tried to replace my op amp, and messed up. I tried to cut the legs off first and PCB board came up... I have soldered amp6basic (41Hz) without difficulty, so unless u r very good with a solder gun, should reconsider...