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Class D Switching Power Amplifiers and Power D/A conversion

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Old 25th January 2011, 10:20 PM   #731
210 is offline 210  Germany
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Seems that the new LP2020A+ is more sensitive
for disturbances from newest switching power supplies.
My old one (a few month old) don't produce hf noise
out of my speakers with a EcoFriendly-PSU (P0<0.3W),
but the new one does. With an older switching PSU
there's no noise.
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Old 28th January 2011, 02:54 AM   #732
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Hi Tvih,

Yes, it sure could very well be your Power supply that is making it sound "thin". The power supply is the KEY with these amps! I've tried many and this one is very good.

Switchmode Power Supply 11-14 volts ADJ 3.5 A power max - eBay (item 250756185604 end time Feb-11-11 06:36:36 PST)

I have many of these Tripath Amps, and have experimented with many power supplies and a bad power supply can make a great amp sound crappy.

I purchased one of these Lepai Amps around a year ago and played it a few times and put it away until about a month ago. I pulled it out and hooked it up to my Pioneer HPM 900's and hooked up my Trends TA-10.1 Amp Power supply that always sounded great. Well the Lepai shocked me with lot's of bass and very Liquid soundstage, even for Tripath amps, (yes, you have to fine toon the bass & treble) but you can get a nice sound there. You just can't turn it up too loud. It really did get me with with it's LIQUIDness and it's RESOLUTION in the backgroud, squeaks and stuff. It didn't do it as much with another power supply, 12v 5a one. I think it likes the Trends SMPS.
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Old 28th January 2011, 07:51 AM   #733
tvih is offline tvih  Finland
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I was looking at this power supply, it'd be 5A so at least it would have sufficient current. But of course the quality otherwise and thus effect on sound quality... who knows. The one you linked... well, it's price is the same as the amp itself was, not to mention it'd apparently require tweaking... something I'm not comfortable with, especially in the case of a PSU.
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Old 28th January 2011, 08:17 AM   #734
210 is offline 210  Germany
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Disturbance sounds like a 1kHz tone
that's maybe demodulated from the HF-noise of
this PSU : Minwa MW3R15GS (1500mA).
There's another switching PSU that
even emitts this sound out of the PSU itselfs
(this power supply produces sound without an amp!):
Minwa MWS9125GS (the best choice for a hammer bass).
I prefer so far: McVoice/MCPower/EDC 2000 (06-0126)
but it seems only available for 230V input.

I use TA-amps only for comparison purpose
(guess, there are The sound reference up to 1000$).
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Old 28th February 2011, 12:30 AM   #735
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Hi folks, I was wondering if any of you gurus can help me. Parts Express was sold out of these Lepai amps for a little while but they just got new stock last week and I got mine on Friday. I'm using it to run a subwoofer and some old planar speakers (from the Monsoon Planar Media 9 set) that are just lovely and only need a small amp. Anyway, mine works fine out of the box (thank goodness!) and it sounds pretty good, but I am having a couple issues. Oh, btw I haven't opened it up but on the outside it is the same as the newer ones that people have been getting with the tone/direct pass through button.

So, anyway, a few questions for you diy gurus (or anyone who wants to chip in their thoughts):

1) So the one real problem that I had is I was testing how it was driving my speakers and how loud it would go and I slowly turned the volume up to 2pm, and it suddenly went mute, then I turned it back down and the volume came on again. Is this normal, and is there anything I should worry about that I might have damaged? I only have the signal coming from my computer set to 75% so I didn't think I was really risking much to turn the volume only up to 2pm. It still seems to sound pretty good, but I didn't get a chance to listen to the amp for very long before that happened.

2) I'm pretty disappointed with the power levels this thing is putting out. If I even turn the volume up to 12pm I get noticeable distortion. I feel like for 20w rms this is not driving my speakers very hard, I had them jerry rigged to an old cambridge soundworks computer system that put out like 4w rms and I think that was just as loud as this.... So I guess what I am trying to ask is why I am getting the distortion, what is the limiting factor there that is preventing me from cranking up to higher volumes, and if there is something I can do to fix it?

3) Maybe I'm crazy, but the audio signal sounds richer and cleaner if I use the tone feature rather than the 'direct' pass through button. If I use the &quot;direct&quot; button the sound is sort of tinny and a bit flaccid by comparison. Does anyone know why this would be?

4) Do you think swapping out most of the capacitors on this board would help the sound quality much? It gives a nice, clean sound right now at low to medium volumes, but the sound could definitely be a little richer, it is a little thin. I'd probably use some gold nichicon capacitors or something like that. And would capacitor change help with the distortion at higher volumes?

Anyway, thanks a lot for any insight or tips! This thread is really cool and was helpful to me in picking out this amplifier which in most regards is exactly what I needed to get my beloved monsoon sattelites playing beautiful music again after the amplifier on the old sub circuit crapped out.
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Old 28th February 2011, 11:25 AM   #736
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Hi. Last week I bypassed the preamp/tone controls on my Lepai. Replaced it with simple ELNA electrolytic capacitors between the volume pot and R24 + R26. Really simple mod and yes it was a big improvement Next up is upgrading the pot

Regards /Bo

PS. Im including a schematic
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File Type: png lp2020sch.png (51.3 KB, 1066 views)
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Old 3rd March 2011, 07:03 PM   #737
mintos is offline mintos  United States
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Do you have a pic of the board? The chart hurts my eyes >_<
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Old 3rd March 2011, 08:29 PM   #738
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Quote:
Originally Posted by mintos View Post
Do you have a pic of the board? The chart hurts my eyes >_<
Mines screwed together so no pix but I have this. Lemme know if u can read it or not

Regards /Bo
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File Type: jpg lepai board.jpg (568.3 KB, 710 views)
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Old 3rd March 2011, 09:08 PM   #739
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Hey all? I know this is out of place but i need help with d/a conversion.
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Old 4th March 2011, 08:27 AM   #740
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Hi! Does anyone know which op-amp are used in the newest version which has two of them and a tone defeat switch? Does the tone defeat also bypass the op-amps?
Thanks.
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