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Old 4th November 2012, 06:21 PM   #1291
Bare is offline Bare  Canada
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Join Date: Dec 2001
Location: vancouver
No thump on My YJ . A click tho as the relay operates.
Replacing the YJ's "wima' input caps with Decent ones helps increase detail accuracy.
Dunno.. Lepai can sound V good but I had to wipe off the ..entire... tone circuit crap to get there. As well as replace inductors output caps anf Input caps.
Not many OEM bits left at all :-)
YJ seems to improve further by judicious parts upgrades as well.
IMO there is NO need for a preamp... Tried it, No improvement/advantage whatsoever for me.
But then My tube pre is a decade long project and it IS "transparent'.
One can cap roll to tame percieved tizzyness.
I've found that a simple resistance reading on a input cap will give indication.
Higher resistance ones will be less bright.
Dunno if that's an accurate correlation but it's works for me.
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Old 4th November 2012, 10:53 PM   #1292
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Quote:
Originally Posted by Bare View Post
No thump on My YJ . A click tho as the relay operates.
This is the one I have - no relay.
Is yours different?

YJ TA2020 amp
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Old 4th November 2012, 11:21 PM   #1293
Bare is offline Bare  Canada
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Sorry .. confused,
No on off sounds. on yj... well almost none.. very slight ones. Seems to be input cap dependent ;-)
My Lepai has the relay widget.. it clicks audibly.
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Old 8th November 2012, 03:58 AM   #1294
joeoz is offline joeoz  Australia
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Default Older model vs. newer model Lepai?

Hello,

I have an older model Lepai (without tone defeat button, and through-hole PCB) as well as the newer model. I performed quite a few of the mods on the older version and that really made a huge difference. The biggest improvement was the mod to bypass the tone controls.

Since the newer model has lots of SMD components, I haven't done any mods to it. It sounds OK, but to me, the older version (modded) sounds better.

On the newer model, I wonder if the tone defeat button actually bypasses the exact same part of the circuit and achieves the exact same result as the bypass mod that applies to the older version?

Anyone compared the older and newer versions side-by-side?

I think the older models are hard to find now on eBay as they are no longer in production. I believe some sellers on AliExpress still have them.

Cheers,
Joe
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Old 9th November 2012, 02:11 AM   #1295
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The newer LP-2020A+'s have a second op-amp used for the volume control (the pot is used in the feedback loop to set the gain, instead of being used as a straight up attenuator. The tone controls are bypassed with the tone/direct button, but the op-amp in the volume control is not.
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Old 9th November 2012, 02:58 AM   #1296
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I have experimented a lot with the Lepai 2020s, have 1 of the old model and 2 newer ones. To me these sound very good, especially driving headphones (either with transducer leads isolated, or with the negative outputs bridged by two 5.6 Ohm power resistors, connected to the common terminal of a standard headphone jack (this setup works for the Lepai, but not for other T-amps). I find that a good substitute for the Lepai as a power amplifier is the TPA3122 (TI) based through hole kit from Sure Electronics or Parts Express. At the moment this sells for $15, but does not include a power supply, though a couple of compatible 24VDC supplies are available from various sources. The TI chip design is single ended and will drive headphones without trouble (but not phones and speakers simultaneously). Into loudspeakers, this little amp board has tremendous headroom (much more than the Lepai), and its gain can be adjusted (4 settings) so that it will match pretty much any computer audio output or MP3 Player/smartphone. The Lepai's sound very good into high efficiency speakers, and have the Tripath characteristic (described in reports of multiple TA2020 and TA2024 based amps) of making some speakers that sound mediocre with class AB drive sound much, and sometimes much MUCH, better.

Driven by a 30VDC or so power supply, this board will put out about 15 clean watts per channel into 4 ohm speaker loads. about 10W into 8 ohms, but I have driven 8 Ohm medium sensitivity speakers to room filling volume with these. The design of these boards is over simplified, and some have been marginally stable, needing repeated on-off cycles to achieve stable operation. Once they 'catch', they remain stable. I liked the TPA3123 board, also, from Sure (about 25 WPC into 4 Ohms) but this was not cost effective and was withdrawn. In passing, I have not tried out the new STM based class D boards, which reviewers have panned somewhat for sound quality, even when properly output filtered. Apparently the Tripath and TI class D amps, as well as the more finicky high powered IR chip (which demands a 50+VDC bipolar supply, unlike the other chips, which makes the power supply twice as expensive as the board(!) and also means that you have 100+ VDC potential difference in your rig, which makes it a potentially dangerous design for novices). I am intrigued by the TI TAS5630 design, and wish TI would bring out a lower power version (250 WPC into 4 Ohms sounds like an invitation to set your speakers on fire if you accidentally turn the volume too high, let alone eardrum damage). I have heard that if you drive the 5630 with less that 50VDC the sound quality deteriorates.

Last edited by stujonesmd; 9th November 2012 at 03:01 AM.
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Old 10th November 2012, 08:23 PM   #1297
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Default Older Lepai

I purchased one of the older models on Ebay for a project a few years back but never really ended up using it. I moved recently and figured it would make a good way to bring sound to the kitchen. Unfortunately when I actually tried to use it I found that the left channel had no sound and the right had a loud buzz coming out of it. I read through this thread and started doing some of the mods (replaced inductor with toroids, replaced tone caps w/ mkt, removed the fault diode, replaced the op-amp with a n5332, replaced the volume pot with a log pot and grounded it, and changed out a few resistors) hoping that I would fix the problem as I went along. Right now I'm guessing that there's a bad ceramic cap somewhere or the TA2020 went and cooked itself.

I've still got a few things left on the mod list as well such as replacing input and power filter caps, and adding the overshoot diodes. I might also add the pop suppressor circuit as well assuming I can actually get this thing to work.

Anyway, does anyone have any suggestions on the channel issue? Or has anyone had a similar problem and traced out the issue?

Thanks a ton,

-Nate


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Old 10th November 2012, 08:26 PM   #1298
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Oh yeah, the issue happens regardless of wether or not I have any input source or not. Thanks again!

-Nate
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Old 11th November 2012, 12:54 AM   #1299
Bare is offline Bare  Canada
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On one of my Lepais, there is no output on one channel.. it's because the Chip is damaged (tripped over/pulled out a speaker wire while in use)
IMO the entire Lepai tone Garbage circuit needs deleting !
It's the Ta chip which holds the goodness.
NOT the Mickey Mouse Lepai board implementation.
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Old 11th November 2012, 01:15 AM   #1300
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So the fix would be to replace the TA2020 chip huh? I figured that might be the case. As for the tone circuit I figured I'd play around with it for a while before bypassing it completely.
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