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Old 7th March 2013, 12:54 AM   #81
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What up Dudes:

Just got my Lepai 2 days ago.. I only had some lm4562s opamps on hand. So that was my only mod so far.

The sound is MUCH cleaner... so much so... that I'm wondering if I should bypass the opamps at all since the Tone-defeat button seems to bypass the tone controls.. I think my opamps are fine.

I am an expert on ghetto replacement of SMDs with total crap equipment

Does anyone know if I could use REGULAR polarized capacitors for C20 and C21, because I don't have any bi-polars on hand..


Picture of my board attached, It seems they went even more cheapo on components

Look at the dinky inductors this time around...

And they went for a ghetto dual power relay
--- Not sure if this portion greatly affects sound... maybe some experts could chime in...
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Old 7th March 2013, 06:26 AM   #82
aj982 is offline aj982  United States
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I've been messing around with these as well. I found out the hard way that C20 & C21 can not be polarized. I made this mistake on my first mod attempt. Since then, I have learned a great deal about these things. I didn't kill my amp but it took me 3 days to figure out why it sounded like crap.

Now I have 2 lp2020a+ amps. One of them came like yours but with a single relay and the other came witg better components; they both look like salvaged parts. They will both be modded; one with all tone controls wiped, audio grade caps and ferrite core inductors all around. The other will have only upgraded caps. I'll post pics when I finish. Still waiting for parts.
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Old 7th March 2013, 12:45 PM   #83
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Hey aj982, sup

Thanks for the information on the polar caps.. I will have to find some nichi-es to replace them.. kinda hard..

You see those transistors in the Power Path?

I hate "muting" transistors in the signal path,

This irrational hatred also translates to transistors in general, because cheap ones always seem to introduce a great deal of "sssssssss--- noise"

Do you have any idea how to bypass these transistors...


Also are the opamps only necessary for tone and volume?
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Old 7th March 2013, 01:04 PM   #84
danzz is offline danzz  Spain
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Hi tp4tissue

Yes the opamps are necessary for tone control and volume, If you bypass you Will loose the volume and tone control.

I did the exactly same mod upgraded the opamps for 4562s, as I didnt want to loose the tone control, also modded the output inductors with coils and the output caps with same value but from wima... And also changed the input cap for a 4700uf from Panasonic. With this modes I use it to drive a país of Overnight sensations and Im very happy with it...
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Old 7th March 2013, 01:22 PM   #85
xrk971 is online now xrk971  United States
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Quote:
Originally Posted by cogitech View Post
Hey xrk!

I'm going to cobble together something similar, except I plan to build an ultra-low budget hybrid integrated (tube pre and 2020 power).

I already own a 2020 and I have ordered a $21 "YJ" single 6N3 pre-amp kit, some switches and other small parts, an $8 power supply, etc. About $33 in total. Going to bypass the volume control on the 2020 (already bypassed the tone and opamp) to turn it into a straight power amp and then wire the pre-amp directly to the 2020. Stick it all in a homemade chassis and maybe even integrate a USB DAC.

I don't expect it to challenge an expensive amp, but it'll be fun as hell to build!
Is this project complete and now appears as that amp with the two open windows where the vu meters used to be in the photo of your Castles and amp in front of the window with mountain view?

Click the image to open in full size.

Last edited by xrk971; 7th March 2013 at 01:25 PM.
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Old 7th March 2013, 01:23 PM   #86
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Quote:
Originally Posted by danzz View Post
Hi tp4tissue

Yes the opamps are necessary for tone control and volume, If you bypass you Will loose the volume and tone control.

I did the exactly same mod upgraded the opamps for 4562s, as I didnt want to loose the tone control, also modded the output inductors with coils and the output caps with same value but from wima... And also changed the input cap for a 4700uf from Panasonic. With this modes I use it to drive a país of Overnight sensations and Im very happy with it...
hello hello hello

Question... is there a difference between "high pulse" and "general purpose" wima capacitors

I am thinking of replacing the 6 output for .22uf Wima

---as a post suggested .22uf would give better bass.. I am using 6ohm speakers

and

the two "input" C20, 21 for 2.2uf Wima

__until such a time when 2.2uf nichicon es comes back instock at mouser
__unless you guys know of another trusted place with 2.2uf nichi-es
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Old 7th March 2013, 07:09 PM   #87
aj982 is offline aj982  United States
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I saw a post that showed how to disable all tone controls and enable the volume control. This bypassed all opamps. I don't know how to bypass the transistors but I don't think they are an issue with this amp. I haven't heard of anyone bypassing those or needing to.

Quote:
Originally Posted by tp4tissue View Post
Hey aj982, sup

Thanks for the information on the polar caps.. I will have to find some nichi-es to replace them.. kinda hard..

You see those transistors in the Power Path?

I hate "muting" transistors in the signal path,

This irrational hatred also translates to transistors in general, because cheap ones always seem to introduce a great deal of "sssssssss--- noise"

Do you have any idea how to bypass these transistors...


Also are the opamps only necessary for tone and volume?
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Old 7th March 2013, 08:11 PM   #88
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Quote:
Originally Posted by xrk971 View Post
Is this project complete and now appears as that amp with the two open windows where the vu meters used to be in the photo of your Castles and amp in front of the window with mountain view?
Hi XRK,

No, the 2020 + tube pre-amp project is still in the works and is intended for my bedroom setup. In fact, I just received a few of the parts I need for that project and I am very much looking forward to it.

What you see in that photo is my Shuguang I-25 tube amp and one of my dual EL70 microTowers. The windows in the amp are there so one can enjoy the tube glow better. Some vu meters would be cool, though. Perhaps another project there for me... The only modification I have made to the I-25 is to add a supplementary, higher amperage filament transformer so I can run 12BH7 tubes in the 12AU7 sockets. The 12BH7s draw 2x the amperage, and sound a great deal better doing so. Oh, I also strapped a heat sink to the power transformer and modified the rear cage to fit over it. I do plan to put new coupling caps in the I-25 as well...

Last edited by cogitech; 7th March 2013 at 08:15 PM.
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Old 7th March 2013, 08:25 PM   #89
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Quote:
Originally Posted by tp4tissue View Post

I am thinking of replacing the 6 output for .22uf Wima

---as a post suggested .22uf would give better bass.. I am using 6ohm speakers
I chose to do the same, based on the details in the TA2020 whitepaper. In there they specify all .22uF for 8 ohm loads and a combination of .47uF and .22uF for 4 ohm loads. My 2020B has all ******* .47s, and my speakers are 8 ohms. Not ideal, in the least.

Quote:
and

the two "input" C20, 21 for 2.2uf Wima

__until such a time when 2.2uf nichicon es comes back instock at mouser
__unless you guys know of another trusted place with 2.2uf nichi-es
I got some NOS 2.2uF Roederstein Gold bipolars off ebay for the input coupling. They sound great. Anything is better than the stock crap.
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Old 8th March 2013, 02:45 AM   #90
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Quote:
Originally Posted by cogitech View Post
I chose to do the same, based on the details in the TA2020 whitepaper. In there they specify all .22uF for 8 ohm loads and a combination of .47uF and .22uF for 4 ohm loads. My 2020B has all ******* .47s, and my speakers are 8 ohms. Not ideal, in the least.



I got some NOS 2.2uF Roederstein Gold bipolars off ebay for the input coupling. They sound great. Anything is better than the stock crap.
Yea, my situation is even less ideal than urs according to the paper, as I have 6ohm speakars , since the datasheet doesn't detail what equation they're going by with the output caps.


I also chose to replace the 2x .01uf bipolar ceramic Cap in the output circuit with Wimas, LOL they were only 81 cents each, so i figured, F... it

I didn't even see them until I saw the datasheet... I honestly don't trust the SMDs they put in there.. because I have some "hissssss" goin' on, I'd like to put as much good high freq noise filtering in there as possible...

You can see the 0.01uf speced caps on the data sheet.. they are right above the inductors on the lepai board

Picture with cap circled below'

Another question... if I bypass the opamps//tone//volume

----- DO I need to remove all of those components? because I feel like if I did not, they would be erroneously grounding something in the signal path?

----- This leads to the issue, it is quite tricky to remove those things, confusing traces...
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Last edited by tp4tissue; 8th March 2013 at 02:58 AM.
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