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Class D Switching Power Amplifiers and Power D/A conversion

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Old 19th June 2011, 12:35 PM   #1861
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Join Date: Apr 2006
Location: Reykjavík
Quote:
Originally Posted by Nahaz View Post
I notice that the sound become very distorted on lower volumes than expected.
I verified that its not the speaker/box by connecting it to my home hifi system and here I can play fine to ridiculus volume levels with far less distortion than with my lepai/battery setup.

Also Ive noticed that if I max out the volume knob on the lepai the bass is non existant pretty much. Even if the source volume is turned down (not playing at max). If I lower the lepai volume knob to about 75% the bass comes back. This in itself is not a major problem the volume is far too high even at 75% when the source is maxed. But maybe it can give a hint as to what might be the cause of the distortion?
Weird! Might be an out-of-phase issue. I can't really imagine how exactly, but it sounds like the potentiometer is physically malfunctioning and causing the bass to bleed off into ground or the channels to cancel each other out. It's strange at any rate.

I'd jumper the potentiometer and see what happens then. Use an iPod or something else that has a built-in volume control.

If that fixes it, then the potentiometer is to blame.

Also suggest you buy a prebuilt Amp6 or Amp9 and swap it in for the Lepai The Lepais don't exactly have a stellar reputation for quality.
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Old 19th June 2011, 12:53 PM   #1862
Nahaz is offline Nahaz  Sweden
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Pics:

I was not involved in selecting colors, logo or patterns, and I did not ask him to paint me inside the lid : ), He made that as a surprise.

Thomas (a friend and camp member) had full creative control and this is what he ended up painting.
Attached Images
File Type: jpg boom1.jpg (206.3 KB, 540 views)
File Type: jpg boom2.jpg (127.7 KB, 501 views)
File Type: jpg boom3.jpg (137.1 KB, 488 views)
File Type: jpg boom4.jpg (178.2 KB, 494 views)
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Old 19th June 2011, 12:57 PM   #1863
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I like it
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Old 19th June 2011, 01:19 PM   #1864
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I love it. Bring it to the Boominator meet up, please.
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Old 19th June 2011, 01:23 PM   #1865
Nahaz is offline Nahaz  Sweden
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It's sort of a "cartoonish" steam punk look to it I think. Unfortunately there is a lot of dust and crap in the clear coating which does not look very good. But after all it is a Roskilde boombox, it will be scratched and get dirty sooner or later.
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Old 19th June 2011, 01:25 PM   #1866
Nahaz is offline Nahaz  Sweden
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Ill be there:

Tuesday, June 28, 2011 at 3:00pm
Agora G
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Old 19th June 2011, 02:03 PM   #1867
ThokN is offline ThokN  Denmark
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Quote:
Originally Posted by Nahaz View Post
Hello again, I finally got the boominator back after the paintjob.
So yesterday we had the first field test at a party.

I notice that the sound become very distorted on lower volumes than expected.
I verified that its not the speaker/box by connecting it to my home hifi system and here I can play fine to ridiculus volume levels with far less distortion than with my lepai/battery setup.

Also Ive noticed that if I max out the volume knob on the lepai the bass is non existant pretty much. Even if the source volume is turned down (not playing at max). If I lower the lepai volume knob to about 75% the bass comes back. This in itself is not a major problem the volume is far too high even at 75% when the source is maxed. But maybe it can give a hint as to what might be the cause of the distortion?

Measured voltage on the batteries today is 12.1V

I will continue testing with Trends audio amp with external pre amp (the trends audio can not reach the volumes where I have distortion issues with the lepai without a pre amp).
I will also test using regular power supply (not battery) to rule out power as the root cause of this problem.

But meanwhile it would be great if anyone had tips on what might be the problem.
I actually experienced the same thing, but with a small homebuild boombox with the SP-60/4's. I thought it was because of wrongly dimensioned enclosure, but now you have made me think twice... Is the amp really not capable of playing at 100 volume without distorting? That would be bad Anyway, I think I will try to change the input caps to 0.47uF as recommended by Saturnus (I think..or V-Bro, don't remember), and hopefully that will remove some of the distortion.

Anyway, if it can help you, we tried to cut off the frequencies below 125Hz on the MP3-player, which helped, but didn't remove it completely.

I hope it was just the wrong dimensions, since I'm building a small box myself which I have used a lot more time on, but I will first have the speakers tomorrow and test Wednesday or Thursday to see if correct dimensions solves the problem. I can post the results here if you are interested.


BTW...What an awesome paintjob
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Old 19th June 2011, 04:34 PM   #1868
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So... I'm gonna ask, like many others, about the wirering

I have bought a 6W solar panel Rated 0.4A @ 14.5V.

Can i connect this directly to my battery, without a charge regulator?

I will be using 2 Yoasa 7,2Ah batterys, don't know if i should parralel them?
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Old 19th June 2011, 05:06 PM   #1869
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Originally Posted by joak0068 View Post
So... I'm gonna ask, like many others, about the wirering

I have bought a 6W solar panel Rated 0.4A @ 14.5V.

Can i connect this directly to my battery, without a charge regulator?

I will be using 2 Yoasa 7,2Ah batterys, don't know if i should parralel them?
Yes.

You should parallel the two batteries to form a 14,4 Ah 12v battery (acting as one big battery)
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Old 19th June 2011, 07:26 PM   #1870
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Quote:
Originally Posted by Kostecki View Post
Our boombox is as close to being finished as it can be. It's assembled, painted and everything, but yesterday when we had assembled everything we discovered a tiny little crack on the raised part of the "kantophæng" (don't know the english word) on one of our bass units.

It looks like this: http://dl.dropbox.com/u/170632/crack.png

Are there an easy fix for this?
I'm sorry for "double-posting" but i can't just let my question drown since i really need some clarity on this
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