LP-2020A+ mod thread

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#161
Here's pictures of my caps, "temporary placement"

Honestly I don't think I can fit everything in the case... :shhh:
 

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#164
Here is my plan to use the Lepai as a final stage with and without DC blocker.
First of all I will play with the Lepai volume control to find the correct input impedance (R) that optimizes the pre-lepai coupling.
Remove all caps, opamps and pots (volume, bass and treble) on the left side of the pot (see schematic).
Remove C20 and C21 and shorten tracks (in the output stage of my pre I have already two paper-in-oil 2uF caps).
Connect the inputs directly to pin # 1 of the switch.
Connect the inputs directly to pin # 3 of the switch through a 2uF film cap (I do already have a couple of clarity caps).
In this way I can use the tone/direct switch for excluding the DC blocker.
 
#165
Fukinagashi said:
Here is my plan to use the Lepai as a final stage with and without DC blocker.
First of all I will play with the Lepai volume control to find the correct input impedance (R) that optimizes the pre-lepai coupling.
Remove all caps, opamps and pots (volume, bass and treble) on the left side of the pot (see schematic).
Remove C20 and C21 and shorten tracks (in the output stage of my pre I have already two paper-in-oil 2uF caps).
Connect the inputs directly to pin # 1 of the switch.
Connect the inputs directly to pin # 3 of the switch through a 2uF film cap (I do already have a couple of clarity caps).
In this way I can use the tone/direct switch for excluding the DC blocker.
Click to expand...

Hey fuki, why do you want to do this? 😀

just to test out between the "difference" of with/without dc block caps?

it'd be easier to just buy a second lepai if you want to compare, vs all the work that you'll put in just to "do this" :joker:
 
#167
cigar box amp

tp4tissue said:
Here's pictures of my caps, "temporary placement" Honestly I don't think I can fit everything in the case... :shhh:
Click to expand...

TP - Consider finding a really nice cigar box, big enough that you could fit your modded board into. Cut a rectangular opening in the front of the box and just screw the amp's faceplate to it to mount.

Like this guy does with the birchwood cabinets.

Modified Lepai T-Amplifier | nsmt loudspeakers
 
#168
Scratch built from Japan

Not a Lepai but an interesting page on building a TA2020 from scratch.

making Digial Amp -- TA2020-20 --

Near the bottom of the page the builder claims a difference in sound when he disconnects pin 30 (5v out) and connects pins 2 & 8 to an external 5v regulator. Take it with a gain of salt but if you like experimenting it's something else to play with.

Someone earlier asked about a tube preamp using the 6111WA tube. I found this (bottom of page): Quad Amplifier 4 You can find the kit on Ebay by searching 6111 preamp.

Got a pic of my homebrew of it here: http://www.diyaudio.com/forums/tubes-valves/173084-ge6111-preamplifier-5.html
 
#170
Fried!

Something's gone fried:

Yesterday I made the mods but something has gone wrong.
I made the basic mods, removed the tone controls, the pot, capacitors and opamps.
I wired the inputs directly to the right side of C20 and C21 (as seen in pics).
I did short inputs and use a couple of 6ohm resistors output side.
After a while the resistors got very hot and then I measured about 12V DC at the outpus of the Lepai!
First question is:

1) Is the 2020A irremediabily gone?
2) What was wrong in my config? The only differences respect to original schematics is that I did not use any DC blocker as I'm sure that pre-amp has not any residual output DC.

On the first try indeed I took the input directly from the RCA plugs (see pic) and connected the Lepai to my pre instead of shortening inputs. Could this been dangerous for the Lepai?

Please help me!
TX

7d44Nep.jpg
 
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#171
Fukinagashi said:
After a while the resistors got very hot and then I measured about 12V DC at the outpus of the Lepai!

The only differences respect to original schematics is that I did not use any DC blocker as I'm sure that pre-amp has not any residual output DC.
Click to expand...

Measure your pre-amp, don't guess! Then multiply what you measure by 20 and that's about what your speakers will see.

Where did you measure the outputs with respect to? + to - or + to ground? This is a bridged amp with a single supply, there's probably +12V on + AND - with respect to ground, which gives 0V between + and -.
 
#172
Redshift187 said:
Measure your pre-amp, don't guess! Then multiply what you measure by 20 and that's about what your speakers will see.

Where did you measure the outputs with respect to? + to - or + to ground? This is a bridged amp with a single supply, there's probably +12V on + AND - with respect to ground, which gives 0V between + and -.
Click to expand...

Unfortunately I measured 12V on + AND -.
I've ordered another Lepai: in case I want to remove the pot should I get the signal directly from the RCA inputs or between R37 and R34?
 
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#175
Fukinagashi said:
Unfortunately I measured 12V on + AND -.
I've ordered another Lepai: in case I want to remove the pot should I get the signal directly from the RCA inputs or between R37 and R34?
Click to expand...

Take a Look at the datasheet, there is a fault pin, check the voltage there, to be sure that the chip its gone... If its gone... You always can order only the TA2020 IC, and change it... It Will be always cheaper than ordering a new lepai... Its what I did with My first lepai that blew cause I desoldered without discharging the input big cap... And now I have that one working with a total tone/volume components removed ... And its has a great sound...
 
#176
danzz said:
Take a Look at the datasheet, there is a fault pin, check the voltage there, to be sure that the chip its gone... If its gone... You always can order only the TA2020 IC, and change it... It Will be always cheaper than ordering a new lepai... Its what I did with My first lepai that blew cause I desoldered without discharging the input big cap... And now I have that one working with a total tone/volume components removed ... And its has a great sound...
Click to expand...

danzz I see on the data sheet that fault pin is #18 but which voltage should I expect to exclude possible failures?
 
#178
Redshift187 said:
From looking at the datasheet it says 5V for fault, and I would presume 0V for no fault.
Click to expand...
Also can check pin 6 Which its the overloadb pin, you should have 5V in there as it says in the datasheet...

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.


About the fault pin...

Fault Pin
The FAULT pin is a 5V logic output that indicates various fault conditions within the device. These conditions include: low supply voltage, low charge pump voltage, low 5V regulator voltage, over current at any output, and junction temperature greater than approximately 155°C. The FAULT output is capable of directly driving an LED through a series 2KΩ resistor. If the FAULT pin is connected directly to the MUTE input an automatic reset will occur in the event of an over-current condition.
 
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