flash front end?

[browndog1978]

Hi guys...my first post here

anyway, I am thinking of building my own front end with flash and actionscript for a jukebox I plan to build.
Anyone foresee any problems I may encounter?
Has anyone done this before?

[richms]

Sounds like a good idea rather then developing it in a programming language since there are already loads of ways to make a nice visual presentation in it.

I dont know if you would want to play the audio in flash however. I havent done much in flash to know how well you can communicate with other software on the computer, but visually its sure to be a winner.

[browndog1978]

I have been running a few experiments with flash over the past few day. I can get a flash file to load up in full screen mode when the computer boots no problems. Now Im just thinking about how I can send the mp3 file names to flash. I could use an xml file, but this would have to be updated every time I added new music. Or I was thinking I could have PHP running on the computer and have the php generate the xml from looking at folder and file names.
As you can probably tell, Im a web developer.

The biggest problem I am having today is deciding on the speakers and amp. I already have some car audio gear laying around (4 speakers and a sub) so was going to buy a cheap 5 channel can amp to power them. But I have been looking at the price of power supplies to run the amp and it turns out that a supply that puts out the power I would need is quite expensive. So I am still a little unsure about that.

[richms]

Ignore the wattage and current capabilities of the amp, those will never be hit in real world use.

Just get a good PC power supply and use the 12v from it, if you overload it, then it will shut down and you know thats all your gonna get.

If you want the crossovers and stuff then a car amp cant be beat for value since the only other ones you will get are pro audio ones for PA and nightclubs with the corresponding cost or else audiophool grade ones.

If you get 2 smaller car amps you can run on separate power supplies, but by the time your doing something that needs that you would have serious cooling issues in your cabinet to worry about.

[Freeplay]

I set my Jukebox up with a lowend Pent 4.
For sound..... I went from a cheap $20 2 channel sound card, to a secondhand amp.
The amp I picked up from a garage sale for $30 (Aus).

For speakers, I got some cheap party speakers off eBay.
That way the whole system is mains powered. (240v)
The sound is more than ample to upset the neighbours.

This is the link to the build post from a couple of years ago.

http://forum.arcadecontrols.com/index.php?topic=43453.0

[browndog1978]

I am quite set on using car stereo speakers now as I already have good quality ones sitting around doing nothing.
I have also been working out the sort of pwer supply I would need with the help of
http://www.electronics2000.co.uk/calc/calcpow.htm

It seems the fuses on most car amps are way over what the amp will usually draw from the supply.
Ive worked out that I can get a  total of 400watts RMS running with a power supply capable of 29amps at 13.8 volts and that these power supplies can be had on ebay for about $70. So thats what I plan to use. And luckily the cash converters down the road is having a 20% off sale this month so I can source amps there.

Ive also been researching Adobe AIR. It allows you to develop desktop applications in flash/ flex or javascript. So I am thinking that I will use it when I develop my front end in flash. This will allow me to use databases to sort the music and have some good search capabilities.

[browndog1978]

I have just decided, instead of going out and buying cheap amps, I will just use the amps I have. So the amps I will be using are an MTX RT202 and an MTX RT 404.   HAHA    this juke will pump.

[richms]

Oh hell yeah, once it became common knowledge that the numbers printed on the amps was complete BS, people "In the know" would tell you that you just had to compare the size of the fuse on the amps to see which is more powerfull, so thats when they started to stick 3 30 amp blade fuses in the ends of amps instead of the single 40 amp it really needed and other games like that.

However, the calculation on the amps rated power is flawed in 2 ways, one is that the amps are not 100% efficiant, the 400w 'RMS" is half real the peak the amp will have, which is 800, which will in theory need twice the power.

The second is that musics power is way below the peak, so you have really only got an average of 80 watts unless you listen to test tones all day on it.

So the power draw will go up and down, but the average out of the amp will be about 80 watts when you are running it as hard as you should without going into distortion land. The amp will be 40-50% efficiant, so thats 160 watts with more occasionally. Luckily thats why they put capacitors in the amp to average it out somewhat.

look at the power supply in your average 5x100 watt home theater reciever, you wont be needing anything bigger then that in reality.

[browndog1978]

So richms
with the 2 amp specs outlined below do you think a power supply with 29amps at 13.8 volts (400 watts) with be adequite to run them both?

RT202
RMS Power measured at 14.4 Volts DC:
150 Watts bridged into a 4 Ohm load with < 1% THD

RT404
RMS Power measured at 14.4 Volts DC:
37.5 Watts x 4 into a 4 Ohm load with < 1% THD

[richms]

It depends on how hard you push them really, Easiest way to know for sure is to grab a car battery and an ammeter and see what it actually takes. I know that the 12" sub in a mates car when pushed to the point that the sub is distorting (its not a particually good one) is only taking about 15 amps - the one for the front components takes about the same when its blending well with the sub. If we play something like a cd with test tones at 70Hz on it then the draw of the sub will go up to 40 amps since the gain can go up more then on music, but at those power levels the amp shuts down after 2 minutes - when you think about it, it has the same surface area as a george forman grill and about half the power going into it so its gonna get pretty damn hot.

There is no way of knowing how much power you can put into the speakers in your cabinet before they start to bottom out or the room starts to make it distort to know what it will consume.

I would hook it up and put a 30 amp slow blow fuse on the power supply to be sure, if you can blow it without being stupid then you need a bigger one, chances are you wont.

[browndog1978]

Thanks for the info.
If I just make sure the gain setting on the amp is not too high, will it help?

Also,
I want to have a volume control on the back of the cabinet. Can I put an inline volume control (same as on earphones) between the computer line out and the amps to achieve this?

[richms]

Yeah, set the gains to as loud as you want it to go with the other control turned up thats not distorting or causing other problems. The only other concern is the startup surge which most amplifiers have under control IME.

Inline volume controls for headphones tend to be made for a low impedance load, so may not adjust much when put into an amplifier, and the shielding on them is non existent since they are driving speakers not something that will get noise and amplify it.

There are schematics on here and other places on how to get a 10K log potentiometer and hook it up for a volume, just do that, but also tie the shields to the metal cans on the pot too to reduce noise, which is often overlooked.