LP-2020A+ mod thread - diyAudio
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Old 12th November 2012, 02:13 AM   #1
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Default LP-2020A+ mod thread

I think it might be better to avoid confusion to create a new thread for the A+ model of the LP-2020, as the input section is very different from previous versions.

To start with, I reverse engineered the input circuit, and present it here. To follow are the mods I've done so far. In the second photo I have already begun my mods, so don't be alarmed that C20/C21 are empty.

Notice that there is a mistake in the left (lower) channel, C41 is connected to the wrong place. Compare with C40.
Attached Images
File Type: jpg lp-2020a+.jpg (58.7 KB, 2842 views)
File Type: jpg Input section 1 - Copy.jpg (303.6 KB, 2716 views)
File Type: jpg Input section 2 - Copy.jpg (320.9 KB, 2493 views)
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Last edited by Redshift187; 12th November 2012 at 02:23 AM.
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Old 12th November 2012, 02:30 AM   #2
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Location: San Antonio
Thank you.
The most noticeable difference with my A+ blue board is the change to a toroid inductor on the DC input. I'm building a dedicated linear regulated supply for mine, so I may just remove and jumper that location.
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Old 12th November 2012, 02:34 AM   #3
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The red board came with a toroid for the power input inductor.

The first mod I did was to replace C20 & C21 with film caps. Because I didn't mind low end roll off at a higher frequency, I used a 100nF to start with, then made it even smaller to roll off more low end. I also replaced the volume op-amp with a OPA2132. Much improved sound just from those two changes.
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Old 12th November 2012, 04:18 PM   #4
Bare is offline Bare  Canada
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Interesting.
thanks.. for the schematic and posting the info.

On my first Lepai I replaced Every single cap, added wire/wound torroid inductors and 2.2 uf Film inputs.
Left tone stuff alone.. although I find the tone controls as poor / ineffective.
Sounds fairly good.. Much improved over the original.

Second one I took my Iron and wiped off :-).. ALL.. the SMD Tone 'stuff'. Replaced All the remaining caps with Japanese name brand ones, fresh torroids, and film 2.2 uf inputs
This one sounds Good, noticeably better that the first one.
Tone circuit assembly seriously gets in the way, best deleted entirely is my observation.
A YJ version ta 2020, bought on a whim, it was $20 shipped, fitted with fresh supply caps and film 2.2uf's but otherwise stock.. so far, is at least the audible equal of my tone stack removed and parts upgraded Lepai, arguably better, not fully sure yet.
Currently assembling MY diy Ta2020 board .. fiddly work.
Just to reference a genuine Tripath circuit version sound.

Other unspoken aspect: Cost.
I have spent at least triple the purchase price in Modding these Lepais into usefulness.
Decent parts are not free. Likely a few more $ to go before I'm finished fooling about.
Frankly , in hindsight of course :-), there are better Amps for same or less coin than I have spent. Just a bit of a heads up kids.
In fairness I've had fun doing this.. but there is an 'entertainment fee' associated.
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Old 12th November 2012, 04:43 PM   #5
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I've only spent $65 total on the amp, replacing all through hole capacitors and inductors and shipping. I can't imagine something better for the price. I certainly couldn't make something better for that.
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Old 12th November 2012, 11:54 PM   #6
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My second mod was to remove the volume op-amp and almost all of the components around the op-amps, and wire the volume pot as a regular attenuator.

I removed R42 and R43 (to the right of the tone/direct switch, behind the treble pot) to disconnect the tone circuit from the switch, then wired the pot to the "tone" side of the switch. Now "tone" = on, "direct" = mute. I did it this way because in order to use the "direct" side of the switch, I would have had to remove the resistors under the switch, which were too hard to get to. I grounded the one end of the volume pot to the through-hole where the ground strap for the pot is connected.

This mod also improved clarity, and gave me more useful volume control range.
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File Type: jpg Volume.jpg (436.0 KB, 2305 views)
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Old 13th November 2012, 12:00 AM   #7
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My third mod was to replace all through-hole caps with Panasonic FR (low ESR long life) or Wima ployester, and the output inductors with Wurth 10uH 4.7A shielded inductors.
This mod made less difference than the input mods, but was still noticeable.

For the time being I also reduced the 10r resistor on the output zobel to 6r8 to push the frequency up closer to the output filter frequency. Once I get the proper 220nF capacitor I'll put back the 10r.
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File Type: jpg Input section 3.jpg (238.8 KB, 2122 views)
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Old 22nd November 2012, 03:04 AM   #8
Fynn is offline Fynn  Germany
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I recently bought this amp on ebay. (LP-2020A+)
Currently i have a PC-PSU hooked up to it, (12V, plenty of A).
Now i saw that you can get more power out of it(or lower distortion at the same power output), if you raise the voltage.
I was planning on hooking up a 14V PSU. (Relatively cheap and good availability)
The auction stated that the operating voltage is "DC10~14.4V3A" and it shuts down at >14.4V DC.

I was planning on modding it anyways, so I bought some replacement caps, pots and 4x40V 1A schottkys. (Datasheet says they are needed for >13.5V input)

Question is, will it even run on 14V?
I read plenty of reviews where it said, that it won't work with DC >13.5V
Are there multiple versions of that amp with different input ratings or do the schottkys do the trick?

Also: It is stated in the datasheet specifically, that the additional diodes should be connected to VDD1/VDD2 directly.
But VDD1,VDD2,VDDA&VDD is the same thing in parallel...
Is it because the circuit is shorter if it is directly connected to the correct pins and does it matter?
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Old 22nd November 2012, 06:49 PM   #9
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Quote:
Originally Posted by Fynn View Post
I recently bought this amp on ebay. (LP-2020A+)
Currently i have a PC-PSU hooked up to it, (12V, plenty of A).
Now i saw that you can get more power out of it(or lower distortion at the same power output), if you raise the voltage.
I was planning on hooking up a 14V PSU. (Relatively cheap and good availability)
The auction stated that the operating voltage is "DC10~14.4V3A" and it shuts down at >14.4V DC.

I was planning on modding it anyways, so I bought some replacement caps, pots and 4x40V 1A schottkys. (Datasheet says they are needed for >13.5V input)

Question is, will it even run on 14V?
I read plenty of reviews where it said, that it won't work with DC >13.5V
Are there multiple versions of that amp with different input ratings or do the schottkys do the trick?

Also: It is stated in the datasheet specifically, that the additional diodes should be connected to VDD1/VDD2 directly.
But VDD1,VDD2,VDDA&VDD is the same thing in parallel...
Is it because the circuit is shorter if it is directly connected to the correct pins and does it matter?
Yes,

It will run on 14.4v. I got this installed on my bike. I had an issue with my regulator going to 14.8v at high RPMs and shuts off. I've been running on 14.4v everyday for about 6 months. Just recently, I did a mod and added a regulator in place of the inductor input power to keep it steady at 12v 5A. It still gets loud enough to hear on the open road.
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Old 22nd November 2012, 06:54 PM   #10
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Join Date: Nov 2012
Quote:
Originally Posted by Fynn View Post
I recently bought this amp on ebay. (LP-2020A+)
Currently i have a PC-PSU hooked up to it, (12V, plenty of A).
Now i saw that you can get more power out of it(or lower distortion at the same power output), if you raise the voltage.
I was planning on hooking up a 14V PSU. (Relatively cheap and good availability)
The auction stated that the operating voltage is "DC10~14.4V3A" and it shuts down at >14.4V DC.

I was planning on modding it anyways, so I bought some replacement caps, pots and 4x40V 1A schottkys. (Datasheet says they are needed for >13.5V input)

Question is, will it even run on 14V?
I read plenty of reviews where it said, that it won't work with DC >13.5V
Are there multiple versions of that amp with different input ratings or do the schottkys do the trick?

Also: It is stated in the datasheet specifically, that the additional diodes should be connected to VDD1/VDD2 directly.
But VDD1,VDD2,VDDA&VDD is the same thing in parallel...
Is it because the circuit is shorter if it is directly connected to the correct pins and does it matter?
It will run on 14.4v. I got this installed on my bike. I had an issue with my regulator going to 14.8v at high RPMs and shuts off. I've been running on 14.4v everyday for about 6 months. Just recently, I did a mod and added a regulator in place of the inductor input power to keep it steady at 12v 5A. It still gets loud enough to hear on the open road.
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