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Old 6th March 2013, 05:53 PM   #1381
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I'm looking at doing the tone control / volume bypass as my first mod. I was wondering if I can implement it with a switch so as to be able to switch from full bypass back to original functionality.

I propose to do this that I would remove c30 and c31. Then go from the input before c30/31 through a pair of caps and into the common of a double pole double throw switch.

Then one side of the switch would land on the other pads where c30/31 had been, hence restoring the circuit to it's original state.

The other side of the switch would land on the right side pads of C20/21, thereby bypassing all of the volume and tone control stage.

The only way this works that I see is if I leave caps c20/21 in place. Will leaving that circuit complete and just landing on the right side of it with my switch work as a volume/tone defeat, or will this cause any problems?
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Old 11th March 2013, 06:49 PM   #1382
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Quote:
Originally Posted by Virpz View Post
If you want to correctly bypass and adjust the gain on your lepai then you need to connect directly to the RCA inputs instead of pads on R35 and R34 ( C31 and C 30 on pcb 120305 ) you should know that:

R8 and R10 and the Rin resistors while R9 and R11 are the Rfeed resistors. These are the resistors that adjust the gain. Look into the TA2020 datasheet to get the full explanation.

- For ipod and portable players with built in volume control use 22K for Rin and 39K for Rfeed

- If you want to play it safe with and set your lepai for general use you should use 22K for Rin and 22k for Rfeed.

- For signals coming from a pre-amplifier you can go for 56K for the Rin and 22K for the Rfeed

I will post an definitive mod list for the lepai in a few days . I just need the time to do it correctly with pictures and everything else.
I will also show how to make the "switch" button work as it should; bypassing tone controls for real.

[]'s

Would be so grateful if you could do this! I'm a noob and just learning. I got the 1/2 watt 22 ohm resistors will these work? They are so big I don't even know how to fit them there.
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Old 15th March 2013, 12:46 AM   #1383
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Default Lepai TA-2020A+ "Power on/off thump"

First just to be up front with everyone, Iím new to the world of DIY electronics. I did study electronic 20+ years ago, but I am a little rusty now. I just received a new Lepai LP-2020A+ amp. I am currently using a 12V 5A power supply to power it; So far Iím surprise of the "out of the box sound qualityĒ. I do have a very noticeable thump with the power on and off. I am already planning on replacing the large cap (3300uF) with a 5600uF version. While doing that mod I would like to address the thump. Will bypassing the tone and volume control reduce or eliminate the power on/off thump? Are there any other suggestions that may work for the thump?
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Old 15th March 2013, 01:57 AM   #1384
Bare is offline Bare  Canada
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Have Any of you people READ the Wiki?
What is in the Wiki is pretty well ALL that has proven to be worth the effort to do.. by a lot of people over quite some time
Wanna reinvent the wheel using Your superior skills/knowledge.. Fill yer boots trying :-).
These are Cheap/crappy circuits.. capable of passable to decent sounds IF modded with Intelligence and prior knowledge. NEVER forget these are ~$15 cheap a** 'amps' no more, no less. Are You.. expecting a Monet .. just lurking in there ??
The Lepai Tone controls are Junk..as they mess up the sound and even worse they are unreliable as Tone controls.. being barely functional.
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Old 15th March 2013, 07:55 PM   #1385
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Quote:
Originally Posted by Jeff Holbrook View Post
While doing that mod I would like to address the thump. Will bypassing the tone and volume control reduce or eliminate the power on/off thump? Are there any other suggestions that may work for the thump?
I found that bypassing the op-amps drastically reduced my turn on thump. I strongly suspect the volume op-amp to be the one causing (most of) it.
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Old 15th March 2013, 07:58 PM   #1386
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Quote:
Originally Posted by Bare View Post
Have Any of you people READ the Wiki?
What is in the Wiki is pretty well ALL that has proven to be worth the effort to do.. by a lot of people over quite some time
Wanna reinvent the wheel using Your superior skills/knowledge.. Fill yer boots trying :-).
These are Cheap/crappy circuits.. capable of passable to decent sounds IF modded with Intelligence and prior knowledge. NEVER forget these are ~$15 cheap a** 'amps' no more, no less. Are You.. expecting a Monet .. just lurking in there ??
The Lepai Tone controls are Junk..as they mess up the sound and even worse they are unreliable as Tone controls.. being barely functional.
You haven't had anything positive or helpful to add about these amps for some time. All you do is insult people. Why are you still posting?
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Old 15th March 2013, 08:12 PM   #1387
aj982 is offline aj982  United States
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Quote:
Originally Posted by Redshift187 View Post
I found that bypassing the op-amps drastically reduced my turn on thump. I strongly suspect the volume op-amp to be the one causing (most of) it.
I bypassed everything but kept my volume pot and I have no turn on thump at all.
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Old 15th March 2013, 08:12 PM   #1388
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That's exactly what I did too AJ.
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Old 15th March 2013, 08:18 PM   #1389
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I read the wiki yesterday after it was mentioned, and IMHO it does leave something to be desired.
Just sayin'
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Old 16th March 2013, 01:16 AM   #1390
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The wiki doesn't really address the A+ version at all. There's another thread here specific to that model that may be helpful too.
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