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Class D Switching Power Amplifiers and Power D/A conversion

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Old 1st December 2006, 11:50 PM   #61
Pano is offline Pano  United States
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Front panel.

Yes, it came that dirty and scuffed up. But looks aren't everything, you know.
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File Type: jpg lepai03.jpg (13.1 KB, 2240 views)
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Old 2nd December 2006, 03:35 AM   #62
Fin is offline Fin
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Thanks for the pics Michael

I haven't had time to open mine yet...so it's good to know what to expect.

Yes - the facia of the case has a strange finish to it. Mine looked perfect when it arrived - until I started to handle it. It seems to oxidise easily after human contact. A good reason to rebox it or paint it a whacky colour.

Is the board actually sagging under the weight of the inductors - or is it just squeezed into the case a bit too tight and flexing so it can fit?
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Old 2nd December 2006, 04:39 AM   #63
zBuff is offline zBuff  New Zealand
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You're right about the quality.

I just got mine, ran into some problems straight off the bat. Powered it up, and I started getting smoke (and music mind you) out of the amp. Quickly turned it off.

Upon later inspection after dismantling it I found that the capacitor closest to the chip had it's plastic insulation broken so it was shorting directly with the chip. So I unsoldered the breached cap, put in another one of the same value (100uf, 16v). Powered it up again, all seems sweet. Sounds pretty good too, ableit a bit of hum, but that might be because I've got it out of it's case at the moment.

Also noticed that the poweron switch cables were not inserted all the way into the board so, it might have been shorting there aswell.

I did talked to Eric(the seller) he offered to replace it and play for the shipping aswell, so that was good of him.

The 2 caps on the bottom right hand corner of the board right above the volume pot. I take it they're input caps, on the board it's marked 3.3uf but the value of the caps is 10uf. The amp does have a bit of a turnon sound. Candidates for immediate replacement perhaps? I do them first, and bump up the 2200uf reserve capacitor first.

What is that other little chip? it's not an opamp is it?

My board is saggy too, it's not from the weight of the components, the amp is very light. It 'could' be from the way it is held in the case.
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Old 2nd December 2006, 05:10 AM   #64
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Hi zBuff

Sorry to hear you had dramas with something that I have recommended - but good new that you have solved the problem and that Eric is looking after you.

The info you provided is very useful....I'll be changing some caps soon......

What are your plans for the amp....rebox....other mods?
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Old 2nd December 2006, 07:22 AM   #65
zBuff is offline zBuff  New Zealand
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Hey no problem. Would have been nice if Eric tested them before shipping, but he has been very good about the whole thing.

I'm probably just going to stick with the cap mods for a starter, once I have a closer look at the circuit at some stage (though I'm only a beginner at electronics), I'll see if I can bypass the treble and bass controls. Once I'm done there I'll probably replace the volume pot with one of those little green Jaycar ones, they've served me well in the past on my chipamps.

A recase is definitely in the works once I've got my more exotic larger caps in from overseas and I've decided what sort of connectors I'm using (building a whole system, and I've decided not to use standard consumer connectors, might go pro, either XLRs or something similar)

The thing I like about this board is that it's all thru hole components, it should be easier to mod, especially for clumsy people like me I've been to frightened to do some of the mods to my Sonic Impact Tamp
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Old 2nd December 2006, 07:32 AM   #66
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Quote:
Originally posted by zBuff
I'll probably replace the volume pot with one of those little green Jaycar ones, they've served me well in the past on my chipamps.

The thing I like about this board is that it's all thru hole components, it should be easier to mod, especially for clumsy people like me I've been to frightened to do some of the mods to my Sonic Impact Tamp
Any chance you can give us the catalogue number or link to the Jaycar volume pot.....I'm really interested in something that is good and not too expensive.

Indeed - the thru hole construction suits me too. I'll definitely be doing more to this one than the SI.

What do you think of the sound compared to the SI?
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Old 2nd December 2006, 07:55 AM   #67
zBuff is offline zBuff  New Zealand
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CAT. NO. RP8756
10K 9MM SQUARE POTENTIOMETER LOG DOUBLE GANG (A)

CAT. NO. RP8760
50K 9MM SQUARE POTENTIOMETER LOG DOUBLE GANG (A)

There are linear pots too in those values if you're after them instead.
$5.50 AUD a piece.


The sound compared to a stock SI ? there's more bass, things are clearer, and more microdetails, but the SI amp is warmer and smoother. That was my initial impressions, can't do an A/B test as I don't have my SI t-amp on my at the moment.
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Old 3rd December 2006, 11:19 AM   #68
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I like the BOSS -pot on the front panel. What is it for? :-)

The 8pin chip might be an opamp since it is so close to the input RCAs and most of the cheap D-class amps were meant to be driven by low-output iPods and the like.
Just a suggestion of course.
Is this amp already available through international resellers or still only from Hongkong?
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Old 6th December 2006, 05:25 AM   #69
Fin is offline Fin
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Quote:
Originally posted by DocLorren
I like the BOSS -pot on the front panel. What is it for? :-)
That is only to be used when listening to Bruce Springstien
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Old 12th December 2006, 01:04 PM   #70
zBuff is offline zBuff  New Zealand
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I've been using the Lepai Tamp for a while, then I thought, gee I never did test for DC on the speaker output. So out comes the multmeter, 10mv on the right and 150mv on the left, quite a difference, is 150mv OK? Now the big shocker is when I turn the power switch off on the Tamp, the right channel is ok goes up to a spike of about 300mv, but the left channel spikes up 2.5v and then drops down to 1.5v after a little while, woah doggie, that's not good is it? I assume there must be a short somewhere on the amp but I'm not sure where. I'm wondering whether that shorted cap that was smoking on my amp when I first got it had something to do with it(I did replace the cap)?

Anyone got any ideas? or should I send it back to Eric?
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