PA-Amp

DaKurt · February 17, 2004, 06:37:39 AM

Is it possible to build a PA-amplifier, in a little BB box? It would be cool, then I would buy some 200Watt pieces for 30â,¬ and build this amplifier, because the amp costs very much.

Are there any schematics for that things?

DaKurt · February 17, 2004, 06:42:31 AM

And would that then work also with passiv speakers or just active?

Marcos - Munky · February 17, 2004, 10:26:44 AM

I have a schematic for a 260w RMS amp and others. E-mail me if you want them. But you need to build them in rack style I think, for heat reason.

Mark Hammer · February 17, 2004, 10:55:55 AM

One way of building compact PA systems is to use smaller local amps for each driver, and some sort of distribution system able to send out line level signal over long cables. The same sort of thing that is used for the little "powered monitors" you see. You can probably help things out, I would imagine by having one substantial amp for a single centrally located subwoofer, and use the distributed local-amp arrangement for stuff above 500hz, which 5" speakers will handle admirably.

DaKurt · February 17, 2004, 12:11:53 PM

so I mailed you, I hope you send it to me

And I didn't think of a big PA just 2 little speakers to have something to sing over

Marcos - Munky · February 17, 2004, 12:30:48 PM

I sent the files for you. You don't told about that is just two speakers to sing over. I think 50w RMS will do the job for this. Check the LM3886 datasheet, it's a simple 64w amp IC.

smoguzbenjamin · February 17, 2004, 01:32:18 PM

LM3886 = Fast, fun, simple 50W SS amp madness!

petemoore · February 17, 2004, 01:52:18 PM

Doesn't take much at all watt-wise for your EQ to work [even if it's preset] and make your voice, guitar or other input source sound sparky.
You can hear all the information contained in the tones at a very low volume [IMO], depending on background noise level.
I just like LOUD guitar 'cause it works bettere and is More Fun to play that way sometimes...
Somebody Tell that DrUMmer to turn down....HE's the one setting the minimum legible volume in here...

smoguzbenjamin · February 17, 2004, 02:06:52 PM

I like drummers that play lud it gives you an excuse to crank your amp above what everyone would normally agree with :mrgreen: By the time you've cranked your amp they won't be able to tell you 'turn it down' because you can't hear them

DaKurt · February 17, 2004, 02:08:33 PM

so, do I just need a LM3886, a fitting circuit (caps, res...) and then I can connect the output to the 200W boxes?

smoguzbenjamin · February 17, 2004, 02:10:32 PM

You could connect a 1W amplifier to a 200W speaker if you wanted to

Yup, that's all you need!

DaKurt · February 17, 2004, 02:12:33 PM

but then the speakers have just 1 watt?

Do I also need a transformator to make an amp?

smoguzbenjamin · February 17, 2004, 02:14:31 PM

SS circuitry won't need an ouput tranformer because of the nice output impedance SS circuitry has. A speaker will be rated at a maximum wattage RMS and then will run on whatever you feed it. Wheter it's 1W or 100W the speaker will do what it's given.

The Tone God · February 17, 2004, 02:29:02 PM

Depending on your output amp you MAY not need a output transfomer. You will need an power transformer and depending on how much wattage you want the more the heavier and bigger the transformer will need to be.

You also have to look at heat dissapation of the both the power amp and other power supply components. Getting things into a small space is one thing, getting them to run properly in the space is another.

Be aware that you will probably have to play with line AC. If you not careful or have much experience you may want to rethink this. Just your standard warning.

I don't think your going to get 50W-200W into a 1590BB and have it run long term without failure.

Just my opinion.

Andrew

DaKurt · February 17, 2004, 02:31:53 PM

yepp, if I do it, I'll put it in a bigger box...are there already any schematics for such amps? And how much does a transformator cost?

smoguzbenjamin · February 17, 2004, 02:32:41 PM

True, you might wanna put it in something more the size of a DD.

DaKurt · February 17, 2004, 02:33:53 PM

@smoguzbenjamin: Do you have ICQ or some chat-programs like that? It would be cool, if I could ask you there, when I have some problems :oops:

Mark Hammer · February 17, 2004, 02:46:23 PM

If you adopt the powered monitor approach, it is a simple matter to make a bunch of identical power modules in Hammond chassis. The aluminum chassis is especially strong, easily machined, and doubles as a heatsink.

Think in terms of cumulative rather than focussed power. So, for instance, eight boxes with a pair of 4-1/2" full-range drivers, each powered by its own 15-watt amp is actually a fair amount of power and air movement. Supplement that with a single 10" subwoofer and its own 60W amp, and that's pretty damn loud. Not Wembley Stadium loud, obviously, but thoroughly capable of pissing off a pub owner.

If you do it modularly, you can make the setup as big or little as the circumstance requires, and keep adding more boxes and power as time and money permit.

In many instances, bands have to deafen people at the front just to make sure people at the back can hear. Why not just stick speakers back there?

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PA-Amp