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Chip Amps Amplifiers based on integrated circuits

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Old 2nd May 2008, 02:05 PM   #161
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Quote:
Originally posted by Greg Erskine
. . .In Australia there are 4 or 5 kit makers, Altronics, Jaycar, Dick Smith Electronics, etc. Most of their kit documentation appears as an article in Siliconchip magazine in the month of it's release. A lot of the kits are designed by Siliconchip magazine, some are sponsored projects by one of the kit makers and sometimes it is an independant third party.

When you buy the kit, you get a black and white photocopy of the Siliconchip article, you don't need to buy it, plus, depending on the kit supplier, you get a small booklet (~10 pages) on the basics. The kit suppliers don't give you online access to their project articles because its probably Siliconchip's copyright.

. . .BTW: PM your postal address and I'll dig up some examples. I don't have any chipamp articles unfortunately, but I do have a handful of discrete amp articles.
Hey Greg! This reminds me. I got a Dick Smith Electronics kit once, and the documention was overkill, but it was plentiful!

It was a discrete kit rather than a chip+ kit. Anyway, after that, I wasn't bluffed by "difficulty" ideas anymore. They had made it easy.
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Old 2nd May 2008, 03:20 PM   #162
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Valleyman -

Some real good points and tips as well.

Regards 'test' speakers. I have more drivers in this house than you can count. Am I correct to assume a tweeter is worthless for this purpose ? Reason I ask is I'd rather blow up my cheapest stuff 1st and I bought a boatload of Onkyo buyout tweets from P.E. just because they were 20 cents. I also own a bunch of little FR's that were given to me that would be 2nd. on my list. Next would be my NSB's but I like them things .

Thats funny isn't it? Deciding which of your collection you want to blow up 1st?

Might as well get extra chips right off the bat. Can anybody give me an idea what Digi Key is charging for shipping these here in the States?

Bluto
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Old 2nd May 2008, 03:21 PM   #163
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Yes, I'd encourage a beginner to start with a kit, or a diy on vero, or even a pre-built.

Pre-built? Is that okay? Yes. Just trust me when I say that the "hard part" is actually putting the amplifier into the enclosure, connecting up the pot, speaker terminals, rca jacks, heatsink, power cord, and optional source selector.

When choosing a kit, its pretty obvious that Audiosector is a good choice. Peter, the owner, has posted much helpful information at this thread.

If I have gathered the specific information correctly, the LM3875TF Audiosector kit's approved configuration for AC coupled (use any source) is:
source. . .potentiometer. . . 4.7uF (he said Blackgate N 50v). . . 15k input impedance resistor (instead of 22k).

I like his "stereo" layout quite well. Its extremely durable, quite elegant, and, like a magic genie, the engineer appears whenever you need help--just rub the side of the amplifier, or, actually, post a question at this forum.


I'm providing another option for if you're short on cash or just want to make your own on phenolic board. The design is complete and is just awaiting proofing. There's not any deliberation or agonizing on design. Its already done.
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Old 2nd May 2008, 04:09 PM   #164
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Quote:
Originally posted by Bluto
Gychang, Dan, Et Al -

I was cruising at other threads and noticed the subject of pre-amps had come up.

The poster posed a question regarding the use of a PC soundcard being used as a pre-amp. I had never considered this as an option. To my surprise a few said Yes. This leaves more options for a newbee builder and I'd simply never thought of the possibility so likely 'skipped' it several times and wouldn't have seen it not for the fact it was in a pre-amp section. 5.1? 7.1? I have read some threads regards gainclones not being so good with compressed material so maybe not such a great idea.
Sound cards and other trouble sources:
The majority of PC sound cards, notably quite a few that claim high end, do contain the very cheapest op amp chips.
Also
The majority use a digital gain control volume system, whereby the ouput gets lesser quality as the gain goes up. Now, that's not bad news for relaxing listening, but jamming out could be met with defeat.

However, it should go fine on the updated circuit that I posted, with gain 35, a groundlift resistor, a dc blocker cap, and a cap compensator resistor. Success with modern use is exactly what the design is for. Its 2008 now and CD availability has been falling for some time, so we might as well have a 2008 amplifier design with success on a variety of source devices.

I can't do anything about codec (software) gain; but you can. Discontinue use of Windows Media player in favor of something with the ReplayGain feature. Foobar2000 is scott free and has that feature for all music files. Coolplayer does it manually, with a control, but it can't play wma. Also, check out converting to .WAV (cd) with good quality software on its slowest setting (High Quality), which isn't the default option. Convert to .WAV before making audio CDs (good backups in case of a computer crash). See other discussions about hifi codecs. After all, its your music, and you may as well hear it.


Next topic:
Surround sound, software enhancement, software equalizations, and EAX, CMSS, hall effects, etc. . . the whole gang shreds up and disposes of the natural ambients that are individualized per each individual recording, and then this bit of tomfoolery goes on to replace the natural ambients with a fake. The technology has a great use, but home playback isn't it. In the home, the presentation of every recording coming from the same site, can cause listening fatigue (due to the fakery of one boring "location" all the time).
The natural on-site recorded ambients are part of your music purchase, so please don't waste it.

See this discussion on non-fake surround sound. http://www.linkwitzlab.com/surround_system.htm
It works with a standard stereo hifi running the main two channels, while the surround effects are substituting for room reflections without shredding up the details. This approach, as I understand it, is "replacing your room without replacing parts of your music" or so it seems.


An option to this computerized mess is a hifi USB DAC, which is an adaptor that circumvents the junk on the sound card. You'll still need good playback software, though.
This dandy little device contains a preamplifier, which, hopefully, allows enough headroom so that your "CD era" audio equipment can do a good job on internet music purchases.
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Old 2nd May 2008, 04:12 PM   #165
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Baited breath.

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Old 2nd May 2008, 04:18 PM   #166
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Default RE: Post # 164

Dan -

This is great stuff! Thank you.

I now have a very good guideline to study from when I'm ready for this step.

Bluto
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Old 2nd May 2008, 05:05 PM   #167
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Quote:
Originally posted by Bluto
Baited breath.
Bluto
Although the new design is so simple that it should work for quite the variety of applications, I'm waiting on more thorough testing.

My reservation (and additional testing) comes from the polite "non comment" of post #131, where Peter liked the 15k input impedance, but made no comment on other resistor settings.
The possible meanings are:
1). Didn't like the design
2). Doesn't go with the Audiosector kit
3). Would do something differently
4). Wasn't as interesting as the 15k deal

Possibilities 2 and 4 are a sure thing, leaving no information whatsoever about possibilities 1 and 3.
Last time, it was #3, so more "exploration" and testing is indicated.

In the mean time, it would be great to figure out how to get the chipamps into the amplifier enclosure as easily as possible.
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Old 2nd May 2008, 06:32 PM   #168
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Enclosure:

I've just got 3 things here on the enclosure.

1. It would be nice if hot air went up. So, its good to provide a means for air to enter underneath the heatsink. Its good for hot air to exit the top (or top of the back panel) of the enclosure.
Air in, air out. Otherwise hot air doesn't go up.

2. The heatsink represents an opportunity to, A) ground it (chassis neutral), and then B) use it for a sheild. While I've never personally had any trouble with an EI core (square) transformer, the established means to be absolutely sure, is to face the "fin side" of the heatsink "towards" the transformer. Sheilds up, captain!

3. The front and rear panel should probably be thin enough so that your potentiometer dial, power switch, rca jacks, ect. . . can mount to it.

Any other enclosure ideas?
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Old 2nd May 2008, 08:25 PM   #169
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Dan,

What do you think about the Squeezebox?

regards
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Old 2nd May 2008, 08:49 PM   #170
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Default Handling the chip

I know that some transistors, mosfet for example, are very easily damaged by static, so lots of precausions have to be taken while handling them.

Is it the same with LM3886 or LM3857?

Thanks

Antonio
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