i completely isolated all the caps in the input signal path, replaced it with a single known-good 560nF coupling cap connected directly to my source and got no change in distortion what so ever. Therefore all the people in this thread reporting a massive transformation from changing the 2.2uf coupling caps to a much more exotic cap are simply experiencing a placebo.
The ripple on my powersupply is small enough and on short enough leads that the main inductor and 2200uf cap on the input aren't getting a work out. Replacing the 470uf cap could make a difference, but i doubt it. In my experience mediocre caps don't cause -40dB distortion products (-25db at low volume! - which people have noted with listening tests).
I can also reliably doubt that the capacitors on the outputs aren't causing the distortion because the distortion products completely change in phase when i heat up the heatsink on the TA2020.
Maybe if the distortion products were all down at -70dB changing the caps would do something, but the distortion is just too high and too unpredictable to be caused by the caps IMO. Note how some harmonics are very prominant at -40dB to -50dB then on certain tests they can suddenly jump down to -80dB. This is behavior that can only be caused by the chip if you ask me. The massive distortion at low volume is also consistent with Class-D behavior.
I can see how some people may find the distortion 'tube-like' or pleasant, but that is besides the point. The linear performance of the TA2020 is too far gone to warrant installing ridiculously exotic caps. Even if you enjoy the distortion of the amp, changing the caps probably isn't going to change anything because the internal distortion of the TA2020 just dominates everything by a huge margin.
The ripple on my powersupply is small enough and on short enough leads that the main inductor and 2200uf cap on the input aren't getting a work out. Replacing the 470uf cap could make a difference, but i doubt it. In my experience mediocre caps don't cause -40dB distortion products (-25db at low volume! - which people have noted with listening tests).
I can also reliably doubt that the capacitors on the outputs aren't causing the distortion because the distortion products completely change in phase when i heat up the heatsink on the TA2020.
Maybe if the distortion products were all down at -70dB changing the caps would do something, but the distortion is just too high and too unpredictable to be caused by the caps IMO. Note how some harmonics are very prominant at -40dB to -50dB then on certain tests they can suddenly jump down to -80dB. This is behavior that can only be caused by the chip if you ask me. The massive distortion at low volume is also consistent with Class-D behavior.
I can see how some people may find the distortion 'tube-like' or pleasant, but that is besides the point. The linear performance of the TA2020 is too far gone to warrant installing ridiculously exotic caps. Even if you enjoy the distortion of the amp, changing the caps probably isn't going to change anything because the internal distortion of the TA2020 just dominates everything by a huge margin.
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-40dB is plainly audible, especially when you have 8th and 10th order harmonics up at that level.
Here is the 1khz test tone untouched:
1khzuntouch.mp3
And played through the TA2020 (1W @ 8ohm):
1khzlepai.mp3
The lower distortion your speakers are the more likely it is to be audible. Decent speakers can approach -50dB to -60dB THD across most of their usable range. Average speakers are around -40dB and rubbish speakers are -30db and above. The difference is that the harmonics in speakers are going to be predominantly 2nd and 3rd order. Not even really crappy speakers manage -40dB 6th-10th order harmonics.
I put together some music recordings. There are 3 samples of each song - One is recorded through the Lepai 2020A+, one is the original recording and one is a wildcard which i have done something to with software. They are not necessarily in that order. Tell me which one you think each is.
Incubus - Drive
Sample A IncubusA.mp3
Sample B IncubusB.mp3
Sample C IncubusC.mp3
Cog - Run
Sample A CogA.mp3
Sample B CogB.mp3
Sample C CogC.mp3
I would recommend listening to those with something better than a TA2020 amp for unbiased results.
Here is the 1khz test tone untouched:
1khzuntouch.mp3
And played through the TA2020 (1W @ 8ohm):
1khzlepai.mp3
The lower distortion your speakers are the more likely it is to be audible. Decent speakers can approach -50dB to -60dB THD across most of their usable range. Average speakers are around -40dB and rubbish speakers are -30db and above. The difference is that the harmonics in speakers are going to be predominantly 2nd and 3rd order. Not even really crappy speakers manage -40dB 6th-10th order harmonics.
I put together some music recordings. There are 3 samples of each song - One is recorded through the Lepai 2020A+, one is the original recording and one is a wildcard which i have done something to with software. They are not necessarily in that order. Tell me which one you think each is.
Incubus - Drive
Sample A IncubusA.mp3
Sample B IncubusB.mp3
Sample C IncubusC.mp3
Cog - Run
Sample A CogA.mp3
Sample B CogB.mp3
Sample C CogC.mp3
I would recommend listening to those with something better than a TA2020 amp for unbiased results.
Valid question. When no input is present the only sound coming from the output is some residual 50hz mains hum and the noise floor at -110dB that you see in all the previous measurements.
The harmonics on the 1KHz tone via Lepai are quite obvious. The ones in the car (PCB 2020s from ebay) also have audible noise like that with nothing playing. A glassy HF. Not noticeable when driving or playing.
Not heard that on the Lepai itself on my home speakers, but i haven't had it as loud as the car. I'll have another listen!
Of the three MP3s, I think the mid/high has been boosted on one as it sounds livelier. But I am no expert at all.
Please remember I'm comparing standard Saab audio of 12 years ago and Goodmans cheap sub of similar vintage with the Lepai.
Not heard that on the Lepai itself on my home speakers, but i haven't had it as loud as the car. I'll have another listen!
Of the three MP3s, I think the mid/high has been boosted on one as it sounds livelier. But I am no expert at all.
Please remember I'm comparing standard Saab audio of 12 years ago and Goodmans cheap sub of similar vintage with the Lepai.
Exactly. It's a cheap amp and you will get what you pay for. For me, being a relative noob, modding it was fun as well as a learning experience.
I have the latest double-relay Lepai+. I'm wondering two things:
Is it really worth upgrading the caps? Unlike reports of the awful appearance of caps from previous threads, this one seems to look pretty good. Perhaps they are just fine, or at least good enough. Should I even bother doing anything else to it? It doesn't seem so clear cut, reading this particular thread.
Is it worth correcting the dc offset? I have 79mv on one channel which I'm lead to understand is well in to distortion territory. The problem is that I'm not knowledgeable at electronics and the original dc offset correction guide is for a much earlier version, and no one has seen the need to do it for late versions.
My version is the attached pic, with the double relay.
Is it really worth upgrading the caps? Unlike reports of the awful appearance of caps from previous threads, this one seems to look pretty good. Perhaps they are just fine, or at least good enough. Should I even bother doing anything else to it? It doesn't seem so clear cut, reading this particular thread.
Is it worth correcting the dc offset? I have 79mv on one channel which I'm lead to understand is well in to distortion territory. The problem is that I'm not knowledgeable at electronics and the original dc offset correction guide is for a much earlier version, and no one has seen the need to do it for late versions.
My version is the attached pic, with the double relay.
Attachments
Ok, but I've already got it and I don't mind making a few cheap mods/upgrades. And if I destroy it in the meantime, well tant pis, as the French would say.
While you are surely entitled to your opinion, please remember that this IS a "LP-2020A+ mod thread". While I agree modding these amps isn't money well spent, there still are reasons people want to do it. For myself, it was the first amp I had modded and would rather fry a $20.00 amp than a $200.00 one, if I had messed up.
If, in fact, the tests done by TMM are valid and the problems and noise are centered around the Korean made clone TA2020, then what would be the point in buying a "properly made and laid out TA2020 amp" when they will have the same Korean made clone TA2020?
If you had bothered to read through the thread you would see the TA2020 itself is full of overwhelming distortion.
I wonder why the clone is so noisy. Surely a die-copy is a copy? The packaging should have a negligible effect.
Unless they reverse engineered it somehow??
Or they reverse engineered the firmware (if it has any)?
Yes. If I had a new one, the main change I would make is to change C20/C21 from electrolytic to a film cap of any kind. Besides bypassing the garbage preamp op-amp section again.
I agree. I learned a lot from modding these things. Bypassing the op amps and replacing the input caps helped a lot.
I also noticed a big difference with replacing the output inductors/caps. Inductors were hand wound to 10uH +- 1%. The ones that came with the amp were garbage and the eBay ones I bought were 6-12 uH... All over the place.
Only problem I have now is the DC offset. Anyone know how to fix this? I have about 100mA on one channel and about 40mA on the other.
I also noticed a big difference with replacing the output inductors/caps. Inductors were hand wound to 10uH +- 1%. The ones that came with the amp were garbage and the eBay ones I bought were 6-12 uH... All over the place.
Only problem I have now is the DC offset. Anyone know how to fix this? I have about 100mA on one channel and about 40mA on the other.
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