Modding the Lepai T2020A+

[gychang]

Re: Modding the Lepai T2020A+

There is a switch on the front of mine that allows me to turn off the tone controls.

sorry, I know that, what I meant was to get rid of (remove) the tone control circuit on permanent basis...

[XtremeRevolution]

Re: Modding the Lepai T2020A+

sorry, I know that, what I meant was to get rid of (remove) the tone control circuit on permanent basis...

It might be more trouble than its worth to be honest with you, especially for such a cheap amp.

[gychang]

Re: Modding the Lepai T2020A+

It might be more trouble than its worth to be honest with you, especially for such a cheap amp.

I will just concentrate on improving the sound. I took mine apart and picture of parts seem little different, will plan on putting up some pictures soon.

[benhinkle711]

Re: Modding the Lepai T2020A+

It might be more trouble than its worth to be honest with you, especially for such a cheap amp.

$22.80 for the amp + ? Shipping
$9.13 for the capacitors + $6.95 shipping
$10.25 for the power supply

Total: $49.13.

Total for only mods: $26.33

These are cool mods on a cheap amp and it's fun to tinker but your response to gychang's question, especially in light of the money and effort you've put into yours, well I have to admit I LOL'd. :p

[XtremeRevolution]

Re: Modding the Lepai T2020A+

These are cool mods on a cheap amp and it's fun to tinker but your response to gychang's question, especially in light of the money and effort you've put into yours, well I have to admit I LOL'd. :p

I think the difficulty in entirely eliminating the circuitry to disable the tone controls would be significantly higher than de-soldering and re-soldering a few cheap capacitors. I'd imagine you'd need considerably more knowledge of this amplifier's architecture to even attempt it, especially when in the end, you'll have gained nothing since you can bypass the tone controls with the push of a button.

[benhinkle711]

Re: Modding the Lepai T2020A+

I think the difficulty in entirely eliminating the circuitry to disable the tone controls would be significantly higher than de-soldering and re-soldering a few cheap capacitors. I'd imagine you'd need considerably more knowledge of this amplifier's architecture to even attempt it, especially when in the end, you'll have gained nothing since you can bypass the tone controls with the push of a button.

No I totally get your point, especially since Lepai has provided a disable circuit, but I hope you can see where your response might strike my funny bone.

[XtremeRevolution]

Re: Modding the Lepai T2020A+

No I totally get your point, especially since Lepai has provided a disable circuit, but I hope you can see where your response might strike my funny bone.

I see it quite well.

It is a bit amusing that I've sunk more money into these amps than they cost out of the box.

[gychang]

Re: Modding the Lepai T2020A+

mine has slightly different color caps... Do I still replace as suggested??

[XtremeRevolution]

Re: Modding the Lepai T2020A+

mine has slightly different color caps... Do I still replace as suggested??

Yep. The first one I modded had those blue caps. As I mentioned in the first post, the consistency is terrible. Out of the 4 I've opened, none of them had the same output caps.

[Taterworks]

Re: Modding the Lepai T2020A+

Reading this thread inspired me to open up one of the two Dayton DTA-100 that I picked up from the Tent Sale. I had to remove a lot of hot-melt glue to find anything, but I found film capacitors in the output stage that are very much like the ones you show above. However, the mod I've usually seen done to Tripath amps is to upgrade the single DC decoupling capacitor in series with both line inputs, but on the DTA-100 (as on your Lepai, it appears) these capacitors are surface-mount. Still, I think I have a way to upgrade these caps to some nice Teflon-dielectric caps if my research shows the surface-mount caps to be unsuitable. I just need to look around and see if it's really necessary.

[neildavis]

Re: Modding the Lepai T2020A+

...I found film capacitors in the output stage that are very much like the ones you show above... I just need to look around and see if it's really necessary.

It shouldn't be necessary. These caps are in the output filter circuit and they provide low-pass filtering at around 40KHz-90KHz, depending on their value and the load impedance. The originals are stacked metallized poly caps, which are fairly low distortion. The fact that their tolerance is 10% vs 5% is not an issue. From an engineering perspective, it makes no sense to replace these.

I would set the following priorities in modding this amp:

1) Power supply. The provided 2A supply isn't sufficient, but a decent 3A supply should do the job. Also, if you can find a low-cost 13.5V supply you could get about 25% more power. If you add the extra diodes shown in the TA2020 data sheet, you can use a 14.5V supply, or a 15V supply with a series diode.

2) The output inductors. The inductor should have a high enough current rating to make sure the inductance vs current is linear and to ensure that the core doesn't saturate. The originals look a bit on the small side. If you unsolder one and accurately measure the resistance, you could determine whether they are adequate.

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.

4) C30 & C31. They look like they could be low quality XR5's and they are ceramic caps that appear to be in the signal path (hard to tell for sure from the picture).

5) Coupling electrolytics

6) Filter caps (the large electrolytics). With a decent power supply, changing the filter caps is probably not necessary, although it might help with high current output.

[Ronkayes]

Re: Modding the Lepai T2020A+

Very nice write up and images. Thanks for sharing it with us. I'm going to order the caps.

I was wondering if any body found a suitable replacement binding posts for the speaker connectors. Changing the speaker connectors to binding posts should make it look nicer if nothing else. I searched the web but couldn't find a binding post connector that is about the same size as the current speaker connectors.

[Soundslike]

Re: Modding the Lepai T2020A+

Thanks for the write-up and photos..., very helpful. I'm planning a portable system using PE's USB/card reader with a Lepai amp and I've been concerned about the meager power supply, which will have to power both.

But, before I dive in, I have to ask: The fun of modding the amp not withstanding, is there a better choice of amps in the $50 - $60 range?

Neil,
Your suggestions following the line:

I would set the following priorities in modding this amp:

are in reference to the DTA-100 I presume?

[neildavis]

Re: Modding the Lepai T2020A+

Neil, Your suggestions following the line: ...are in reference to the DTA-100 I presume?

Nope -- the Lepai T2020A+

And my priorities would be about the same for upgrading the DTA-100. First address the power supply, then make sure the output inductors are properly sized, and then make sure the op amp is at least minimum quality (low distortion/noise specs). After that, look at the coupling caps and the filter caps. Changing the output caps should have no audible effect, unless they are ceramic types, so I wouldn't even put those on a "to-do" list (unless you have ears like Wolf and can hear up to 40KHz ).

[XtremeRevolution]

Re: Modding the Lepai T2020A+

It shouldn't be necessary. These caps are in the output filter circuit and they provide low-pass filtering at around 40KHz-90KHz, depending on their value and the load impedance. The originals are stacked metallized poly caps, which are fairly low distortion. The fact that their tolerance is 10% vs 5% is not an issue. From an engineering perspective, it makes no sense to replace these.

I would set the following priorities in modding this amp:

1) Power supply. The provided 2A supply isn't sufficient, but a decent 3A supply should do the job. Also, if you can find a low-cost 13.5V supply you could get about 25% more power. If you add the extra diodes shown in the TA2020 data sheet, you can use a 14.5V supply, or a 15V supply with a series diode.

2) The output inductors. The inductor should have a high enough current rating to make sure the inductance vs current is linear and to ensure that the core doesn't saturate. The originals look a bit on the small side. If you unsolder one and accurately measure the resistance, you could determine whether they are adequate.

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.

4) C30 & C31. They look like they could be low quality XR5's and they are ceramic caps that appear to be in the signal path (hard to tell for sure from the picture).

5) Coupling electrolytics

6) Filter caps (the large electrolytics). With a decent power supply, changing the filter caps is probably not necessary, although it might help with high current output.

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

The power supply was a concern area with previous models. Previous models operated at 13.2V, and units were shutting down as a result. PE's solution back them was to send people 12V power supplies, which solved the problem. Newer models are now shipped with 12V power supplies for that reason. If anyone can find a capable power supply for a cheaper price than the one I listed, I think it would be quite beneficial.

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.

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

Are you recommending that the red film caps I mentioned first are not worth replacing? Those in fact made the biggest difference in sound quality from the tests I ran. Even my wife, who doesn't have anywhere near as critical of an ear as I do, heard the difference quite clearly when I switched between a modified and a non-modified amp with only those capacitors replaced. The other electrolytic caps made little difference if any at all. I only replaced them as a "while I'm in here" thing to ensure consistency and reliability.