Lepai T-Amp with TA2020

[chinesekiwi]

Hello, you guys probably dunno who I am nor care but I plan to buy one of these soon for my new speakers.

Anyway, has anyone tried the LME49720NA with this as I plan to buy this opamp along with 2 LT1057's for my Asus Essence STX?

I know that the LME49720NA is supposedly the same as the LM4562 but of course there's debate about this etc....

Any opinions on the LME49720NA or LT1057 in this speaker amp would be great!

TIA.

[totoelettro]

hi to all,

djnemesi , the power switch is on the mute in my lepay, but i use a battery with another power switch on the line and i put on the switch on lepay before that i start the battey.
the lepay go in sleep for five secon, but after this time i have the pop and the ampli works.

sorry for the english.........

thanks

[Dreas89]

I'm quite new here, been reading in this thread for maybe a month. I got my Lepai today, now i need a set of speakers to my Lepai.

How big speakers can they handle?

My eyes is right now set on these ones http://www.fynda.se/index.php?prodid=2434

I'm from sweden so if you have a better suggestion, please let the shop be in the Nordic countries.

[DrLex]

Well, I couldn't resist trying the Lepai 2020 so I bought one from the Bay. It's the same one as the right one in this photo by MikeHunt. It works pretty well out-of-the-box but being a seasoned hacker, I have made some modifications in the meantime. Here's a list:

1. Grounded the volume pot casing: it wasn't grounded due to the plastic ring with the LED separating it from the case, and a hum could be heard when touching the volume knob. I guess they just forgot to solder the grounding wire in my amp.
2. Added a 'mute' switch (which is connected to the IC's standby pin). I use this to avoid the turn-on pop.
3. Replaced the opamp with a NE5532AP. Also started to replace some of the tone circuit components, but this is still a work in progress.
4. Added some more decoupling capacitors and replaced some of the existing bulk capacitors with larger values.
5. Added DC offset correction with the circuit shown by Lostcause. I trimmed the DC on the speakers from a whopping 120mV and 60mV to near zero. This is a highly recommended mod. There's just enough space on the underside of the board to fit the trimmers if you sand them down a bit.
6. Dimmed the blue LED by giving it a larger series resistor.
7. Corrected the swapped L/R channels on the 'MP3' input.

Now, the amp performs very well but I have the impression it lacks slightly in bass output. I have to crank the bass control all the way up to get decent bass on good speakers, so on inferior speakers I can't reach a satisfactory bass level. What would be the most likely cause of this? I guess I'll try replacing the inductors and further cleaning up the tone controls...

[msj965]

Any pictures on your moded lepai?

[col]

drlex, that sounds like an impressive list of mods. I found that changing the inductors made the biggest improvement in bass. Another mod that is totally worthwhile but I seem to be the only person to do it so far, is to replace all the resistors with 1/2 W metal film. This lowers the noise floor considerably.

col.

[DrLex]

Originally Posted by col

drlex, that sounds like an impressive list of mods. I found that changing the inductors made the biggest improvement in bass. Another mod that is totally worthwhile but I seem to be the only person to do it so far, is to replace all the resistors with 1/2 W metal film. This lowers the noise floor considerably.

col.

Here are some pictures. The trimmers in the second photo are sanded to about 4mm thickness and glued to the bottom.

The third image shows some frequency responses obtained through an improvised set-up. I fed the amplifier a constant amplitude sweep from 16Hz to 20kHz, and recorded the speaker terminals' output in Audacity with a 6Ω load (didn't have any 4Ω resistors handy). This was done through a transformer, which causes the small bump at the lowest frequencies and the 'wobble' at the highest frequencies.
There seems to be an overall loss of bass indeed: with both treble and bass set to max there's only a +6dB bass boost while there's a +12dB treble boost. With both controls set to min, bass is attenuated much more than treble.

I have followed col's advice and ordered 10µH 3A toroids from arjenhelder. I'll repeat this experiment when they arrive. To get the tone controls truly balanced I may need to replace those components too

[UltimateX86]

Hi

Can I use 10000µF cap in this LEPAI 2020 ?

thx

[jkeny]

I'm expecting a Lepai TA2020 in about a week & was invesitigating mods. Are there further mods in addition to Dr lex's ones? Can anyone give a link to the dc offset correction mod schematic? I have some 10uh toroid inductors which I intend to try - is this the correct value?

[zlab]

Originally Posted by UltimateX86

Hi

Can I use 10000µF cap in this LEPAI 2020 ?

thx

Already done with a Rubycon 25V 10000µF which help to boost the base a bit.