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Old 28th April 2009, 07:40 PM   #211
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This is the only TA2020 based amp that uses an opamp, correct? Does anyone know what purpose it serves?
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Old 28th April 2009, 08:37 PM   #212
Gmorris is offline Gmorris  United States
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I'm assuming the opamp is acting as a pre-amp stage of sorts. People have reported better results when using a pre- with their tripath amps. If you already have a nice pre, I would guess bypassing the lepai input stage would result in the best sound.

I'm going more for high-quality portable sound so will probably leave the input section in place.
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Old 28th April 2009, 11:09 PM   #213
col is offline col  Australia
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I did remove the op-amp and replace it with a socketed LM4562.
Gmorris, did this make much difference to the sound? I'm considering doing the same to mine when it arrives.

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Old 28th April 2009, 11:41 PM   #214
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My MP3 player is powered by a single 1.5V AA battery so maybe the pre-amp is there to boost the voltage from the MP3 input and maybe the RCA inputs are fed directly into the TA2020 since the output of most CD/DVD player are above 1.5Vpk. This is pure theory since I do not have mine yet

Once I have it I will post my mods.

p.s. This is cheap fun

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Old 29th April 2009, 06:55 PM   #215
Gmorris is offline Gmorris  United States
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I only checked the amp functionality before replacing the opamp so I'm not sure how much of a difference it made. I figured it could only make it better and it was a fairly straight forward mod. I couldn't find my solder wick but that would have sped the process up. The socket makes it easy to swap in other dual opamps...I probably won't swap the original back in though.

The rca and mini inputs are both connected to the opamp. Also, I could barely hear sound using the mini input until I unplugged the rca cables.

I did some higher-volume listening last night and was impressed. I wouldn't mind dimming the blinding-blue LED down a bit though....
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Old 29th April 2009, 06:57 PM   #216
Bone is offline Bone  United Kingdom
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Default Lepai TA2020

Just bought one of these from iwannebuy. http://myworld.ebay.co.uk/iwannebuy/ . Good price and quick delivery.

Tracing the circuit it appears that the 'POWER' switch on the front is not an on/off switch but just mutes the TA2020. That is why the LED stays on when the switch is off. Think I will rewire it to turn off the supply instead.

There is also a circuit that mutes the TA2020 if the input (supply) voltage is >14v. This is what the 14v Zener is for. The max voltage for this chip being 16v. This is going to make it difficult to use in a car as the battery charging voltage can reach over 14v. It confused me until I traced out the circuit

The op amp is used as a preamp after the volume control with a gain of about 5 - presumably to compensate somewhat for the loss in the tone controls - about 20dB or some 10x.

I was quite impressed with the reproduction however ( Pink Floyd - Division Bell) but only into my bench speakers. I'll try it out on some proper ones after I have measured the offset.

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Old 29th April 2009, 10:34 PM   #217
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Would it be a simple matter to bypass the tone controls, and thus eliminate the need for an opamp as well?
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Old 30th April 2009, 12:35 PM   #218
aszu is offline aszu  United Kingdom
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I ordered this amp from export-genie, it arrived some time ago.

First thing: device was DOA ;/ - there was no sound at all.. It turned out that on/off switch area was completely messed up on the PCB (tracks were cut, drops of solder lead etc.). The only think this switch does is to ground pin 11(mute) on TA2020. This pin must be grounded in order to get any sound from the amp - so I was able to fix this switch pretty easily. I contacted the seller and was assured this won't happen again, however it clearly looks like quality control process of these amps is lacking at best

Second (much more important) thing: I hooked this amp to a pretty generic laptop psu (12V, 4A) and to my modest speakers set (Mission 560i). And.. WOW! This sounded really good! It was so clean and transparent. Not thinking much, I instantly replaced this inferior op-amp with LM4562, powered it up and.. was completely stunned..

I never thought it can make such a difference! Now sound is smooth as silk, so detailed and very addictive. I can''t stop listening to this little miracle-device! And soundstage... soundstage! Now I realize that before listening to this amp I didn't have idea what 'soundstage' exactly means. I was pretty sure that this is some wicked placebo effect, so I did A/B comparison with my old Yamaha 'natural sound' amp. Yamaha was completely devastated in this duel. It sounded so flat, dull, uninviting. I didn't understand how could I enjoy this amp so much before. Was tempted to throw it out of the window right away.

This cheesy, 30-buck chinese device changed completely my view onto the music. I stopped believing in high-quality cabling, audio-grade capacitors and other expensive audio-voodoo stuff.
I started to believe in real technology like this in TA2020.

I consider these 30$ to be probably the best spent money in my whole life (and definitely the best in terms of audio equipment). I never thought my old-fashioned speakers have such a potential. Smile appears on my face every time I look at this crappy-looking Lepai device

Worth to mention: I am using quite a decent source - HT Omega Claro Halo soundcard. When I connected my mp3 player, outcome was still very good, but all these subtle details and 'absolute-sound effect' disappeared somewhere.

My tips for the owners:

1. Get rid of build-in op-amp right away. Swap it out with something decent like LM4562. This will unleash full potential of TA2020. I guarantee you will be amazed with the result.

2. Tone controls are a bit tricky. Even a little manipulation changes sound signature completely. It takes some time to find an ideal position. I am thinking about bypassing them completely in order to improve sound even further (can't imagine how this device can sounds better).

3. This is obvious, but use good-quality source for the best effect.

4. Expect there might be some manufacture issues with your unit

I hope my mini-review will help someone. I am getting back to rediscovering my whole library
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Old 30th April 2009, 04:06 PM   #219
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"1. Get rid of build-in op-amp right away. Swap it out with something decent like LM4562. This will unleash full potential of TA2020. I guarantee you will be amazed with the result."

Is this something a complete novice can do (and if so - how?), or does it require soldering and such?

I bought one of these Lepai amps a while ago. I'm hoping it arrives today. I bought a power supply for it too, which just arrived yesterday (13.5V, 2.66A)
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Old 30th April 2009, 04:43 PM   #220
Gmorris is offline Gmorris  United States
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There is a lot of great diy electronics info on Tangent's site including de-soldering / soldering tutorial videos:

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