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Chip Amps Amplifiers based on integrated circuits

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Old 9th November 2007, 08:55 PM   #21
dnsey is offline dnsey  United Kingdom
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Quote:
hen another one or two to run some monitors at my church.
If your neck of the woods is like the UK, that's a whole other ballgame!

For use in a 'public' environment, your homebuilt gear will have to pass the same PAT (or equivalent) and construction requirements as commercially built stuff - quite rightly, as you're free to electrocute yourself, but other people are a different matter! Seriously, there's more to this than meets the eye, and perfectly safe gear can fail,the test as it doesn't meet the strict specifications involved.
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Old 9th November 2007, 09:25 PM   #22
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Quote:
Originally posted by seth556
can I just buy a 24vdc 10amp (or however many amps) psu and use that?
VERY expensive.

Like I said before, build for the right reasons, not to save money. Really, the only way to save money building your own is by replicating an amp (that you NEED) that is outrageously priced for less. Some of the higher end products. Unfortunately, not many (if any) of these use chip amps.
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Old 9th November 2007, 09:29 PM   #23
seth556 is offline seth556  United States
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Another guy and I are the only people that mess with the sound stuff at church and the only time we would be using the monitors is when I'm there (and I am the one to run it), so that doesn't seem like a big problem.

Nuuk - That's the site I've been reading on.
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Old 9th November 2007, 10:38 PM   #24
dnsey is offline dnsey  United Kingdom
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That's not the point - I don't want to pour cold water on your idea at all, but you need to understand the implications of designing and building gear for use in public places. It doesn't matter who's using it, accidents can still happen, and you'd be amazed at the misuse that can occur, even when the 'public' aren't supposed to touch!
Are you aware of your country's regulations regarding insulation dielectric strength, live terminal isolation and access restriction, strain resistance for line cords, etc?
Will your monitor amps withstand someone tripping over with a glass of water in their hand, which ends up tipping over them, for example?
If an accident should happen, not only would you be implicated, but your church's public liability insurance would probably be invalid.
For many years, I built and used PA equipment in a wide variety of contexts, but would be very hesitant to do so nowwithout very careful risk analysis.
As a related example, I heard of a group who, when using stage pyrotechnics at an outdoor event, carefully roped off the stage area to keep the public at an appropriate distance. A cyclist rode into the ropes and fell off, and successfully sued!
It's a minefield out there.
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Old 9th November 2007, 10:48 PM   #25
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Originally posted by theAnonymous1
Does anyone know the voltage rating of the toroid in the Accurion amp?

They have these in stock at my local store and for $15 I might pick some up just for the transformer.

BTW, if you really want to be stingy you don't even need a PCB.
28-0-28 and around 200va.
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Old 9th November 2007, 11:03 PM   #26
gootee is offline gootee  United States
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If you do decide to make your own PCB(s), this is one of the easiest, cheapest, quickest ways to do it well, at home:

http://www.fullnet.com/~tomg/gooteepc.htm

But, since it is your first time, you might find it better to use either a ready-made "prototype" PCB, which has pre-arranged patterns of holes and copper traces (search for "prototype pcb" at, for example, mouser.com), or, use something like a "perfboard", which has a closely-spaced array of holes but no copper. It's usually nice to have something to at least hold your parts in place.

You should also download and study the following:

http://www.national.com/ds.cgi/LM/LM1875.pdf

and probably also the ones for other chipamps, such as LM3875, LM3886, et al, which can be found by searching at http://www.national.com .

IMO, you should also do some searches for information about "star grounding" layouts.

This might also provide some insights that you will need, especially regarding power supply voltages and power levels:

http://www.national.com/an/AN/AN-1192.pdf

If you do decide to make a PCB, and want to do the layout yourself, OR, if you end up with "hum" or "interference" problems, study application notes such as AN-202 at analog.com, and AN-643 at national.com, among many others that can be found on the various IC manufacturers' websites.

P.S. I just read about the safety concerns, for equipment you might build for use in your church. Please take them very seriously. That's a whole different ballgame.

- Tom Gootee
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Old 9th November 2007, 11:15 PM   #27
seth556 is offline seth556  United States
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Ok, so I'm guessing it's not a good idea to use anything diy for my church. I guess I'll just get some t-amps.

dnsey - The monitors are going to be out of the way completely. The one for the choir will be by the piano where you can't possibly walk and then two on the stage in the corner.

If I did buy a 24v psu how many amps does it need to be? I can get a ~5amp for pretty cheap. Although I'll probably end building my own.
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Old 9th November 2007, 11:46 PM   #28
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Quote:
Originally posted by seth556

If I did buy a 24v psu how many amps does it need to be? I can get a ~5amp for pretty cheap. Although I'll probably end building my own.
Hi,
The supply must be split - that's +/-V. Chipamps won't work on single supplies.
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Old 9th November 2007, 11:50 PM   #29
seth556 is offline seth556  United States
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Ok, that makes since now. I see how it can be very expensive to go that way.
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Old 10th November 2007, 03:57 AM   #30
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Quote:
Originally posted by seth556
[B]Ok, so I'm guessing it's not a good idea to use anything diy for my church. I guess I'll just get some t-amps.

dnsey - The monitors are going to be out of the way completely. The one for the choir will be by the piano where you can't possibly walk and then two on the stage in the corner.
T-Amps are probably out of the question for Pro Audio use just as much as DIY amps, albeit for different reasons.

You need to spend cold hard cash here, don't skimp on this stuff! If you can't pay for decent pro-grade amps for that type of setting, don't bother buying anything until you can.
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