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Old 21st November 2011, 12:05 AM   #971
tanker is offline tanker  Sweden
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Quote:
Originally Posted by htgeek View Post
Anybody knows how to add the OVERLOADB indicator? In the datasheet appears this:

Overload
The OVERLOADB pin is a 5V logic output. When low, it indicates that the level of the input signal has overloaded the amplifier resulting in increased distortion at the output. The OVERLOADB signal can be used to control a distortion indicator light or LED through a simple buffer circuit.

What kind of buffer circuit does it refer to?
A transistor as a buffer.
But I think a good LED will be able to drive directly:
+5V --->------[5k ohm]----->------[LED]---->----OVERLOADB
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Old 21st November 2011, 03:03 AM   #972
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Regarding the 2020 chip..

Is it considered as a easy to burn amp IC?

How does it compares to other amp IC's in terms of durability? (LA, TDA, STK etc..)
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Old 21st November 2011, 05:21 AM   #973
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Quote:
Originally Posted by Virpz View Post
Hello
I'm just a noob here and i'm trying to find awsners to the questions concerning the TA2020A+. Questions that have been already asked many times but not answered . I think bypass =no signal + no caps=no power

That way I would appreciate if you could point out exactly were from is this power/signal comming from ?
Running a jumper wire from the input caps to the TA2020 bypasses the volume control, op amps, and tone control. And so there is no audio signal for the op amps to act upon. But removing the caps still leaves power supply voltage to the op amps - there is power being consumed by the op amps. Cutting the traces for pins 4 & 8 of the op amps removes all power.
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Old 21st November 2011, 08:18 AM   #974
htgeek is offline htgeek  United States
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Quote:
Originally Posted by tanker View Post
A transistor as a buffer.
But I think a good LED will be able to drive directly:
+5V --->------[5k ohm]----->------[LED]---->----OVERLOADB
Yes, that is what I was thinking… but maybe driving it directly damages the chip. I will have to investigate about the transistor option.
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Old 21st November 2011, 10:27 AM   #975
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Quote:
Originally Posted by Optimusone View Post
Any Idea How to check whether the chip is still alive or not ? simple method will be fine.. Thanks
This is what happened to me... there was a short circuit after the op-amp modification .. there after the amp stop responding ..While checking the amp IC using multi-meter there was another elctric shortage between ic pins..After all this drama, the blue LED started to dim ..After inspection we decided there is a electrical short inside the circuit.. (standby current is way over 1 AMP)..now waiting for new ta2020..

What do you think?? your ideas highly appreciated..
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Old 21st November 2011, 10:53 AM   #976
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Quote:
Originally Posted by sofaspud View Post
Running a jumper wire from the input caps to the TA2020 bypasses the volume control, op amps, and tone control. And so there is no audio signal for the op amps to act upon. But removing the caps still leaves power supply voltage to the op amps - there is power being consumed by the op amps. Cutting the traces for pins 4 & 8 of the op amps removes all power.
You are right. But I might unsolder op amps and preserve the pcb for future mods, who knows.

Thank you for the awsner.
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Old 23rd November 2011, 03:44 PM   #977
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Quote:
Originally Posted by Virpz View Post
Hello

By doing the bypass I posted for the ta2020a+ you are disconnecting the input signal from the tone, volume control and two op amps.
You are essentially comming from the input then r36, r37,r35 ,r34 to coupling cap then r8, r10, r9, r11 to IC TA2020 pins 9, 10, 11, 13.
As you can see on the pic of my post I even removed the caps from the op amps circuit. That means op amps have no power and are just sitting there, not being feed and not connected.

I think you can and must use 2.2uf mkp instead of electrolytic 1.75uf,
I have had only used the 1.75uf because I don't have 2.2uf caps right now. If you want your lepai to be more like the tripath suggested circuit you can also replace the resitors on r37,r36, r35, r34, r8, r10, r9, r11 and them go to the inductors, output caps etc.

[]'s
as per what u mention in the previous post, are the polarity of c20 and c21 printed wrongly?? so i should go opposite when putting in new caps for c20 and c21??

i tried to change a 2.2uf cap on c20 and c21 following the polarity of the printings.. indeed it sounds better and i notice higher clarity of the output..
but on the highs, i got distortion on one side of the speakers..

i change back the 1.75 uf caps and the distortion disappear..
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Old 25th November 2011, 02:29 PM   #978
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Quote:
Originally Posted by actinium View Post
as per what u mention in the previous post, are the polarity of c20 and c21 printed wrongly?? so i should go opposite when putting in new caps for c20 and c21??

i tried to change a 2.2uf cap on c20 and c21 following the polarity of the printings.. indeed it sounds better and i notice higher clarity of the output..
but on the highs, i got distortion on one side of the speakers..

i change back the 1.75 uf caps and the distortion disappear..
Yes, you should connect it to the positive on the PCB for the best using bipolar 2.2uf MPK's .

Click the image to open in full size.
You got distortion even at low volume ? If it happens only when you go up with the power that may be your speaker wires that are fault.



I replaced inductors and that was the best mod so far, improved all aspects of the SQ. I am addicted to this thing cause I can't wait to give it another try.
Click the image to open in full size.

[]'s

Last edited by Virpz; 25th November 2011 at 02:36 PM.
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Old 26th November 2011, 02:07 PM   #979
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I would like to buy a Lepai Lp-2020a+ from this ebay shop "earphones_uk". I wondered if anyone else has tried one from him and checked that the board is the 2020a+ and not the 2020B in the wrong box!

Regards

Chris
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Old 27th November 2011, 11:48 AM   #980
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Quote:
Originally Posted by Virpz View Post
I replaced inductors and that was the best mod so far, improved all aspects of the SQ. I am addicted to this thing cause I can't wait to give it another try.


[]'s

care to share what inductors you replaced with and how u replaced them??
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