Building a Sound-Sytem with parts lying around. Some questions about it. - Page 1
Forum section: electronics / projects

author: Sebastian S.
author_rank: Newbie
timestamp: October 08, 2014, 09:50:16 am
content: Hey everyone,Thanks to Daves' youtube channel I have already learned a lot. And scince I'm sick right now some ideas crossed my mind and I was thinking how to get it done.So what's my plan. I want to use a 400W car-amp, a subwoofer and some speakers lying around and make my own Sound-System for home-use. I know how to cable everything up and the idea is to use a phone or my PC with a 3.5mm to chinch adapter for audio input. I already know that if I use the full power of the amp I'll need at least 33 amps to have a stable power supply. But as this will be way to loud the current should never get this high. And I would build in a 1F cap in the main power rail.So for power supply I need to have 12V DC and my wall socket delivers 230V AC. So I thought a normal ATX-Power-supply would do the trick. And lucky me there is one lying around. An Enermax ELT500AWT whith max. 500W output.It claims to have a 384W output with 32A on both positive 12v rails.I also need a remote signal in which wiring I would put in a little switch so I could deactivate the whole system when needed.And now I'm stuck on a few questions.1. Will this work at all or should I discard that idea right away?2. What do I need to do to use both positive 12V rails at the same time?3. Is it okay to use one of the positive 12V rails for the remote signal?4. The wiring of the PSU seems a bit thin for that high power output. I'd use a 10mm² copper-wire with a max. lenght of 1m. Or can I use the normal Wires from the PSU?5. Do you think I missed something in my thoughts? If so please let me know. I won't power nor wire this up until I'm fully sure everything seems okay.Thanks for reading and thanks for your help.Sebastian S.

author: simingx
author_rank: Contributor
timestamp: October 08, 2014, 03:29:56 pm
content: you could try it with some speakers you don't really care about... take note that car amps usually need 5V levels for their "line" signal input as opposed to 0.7V for consumer equipment.i believe the "remote on" can be accomplished with the "PS-ON" signal on the ATX plug, connect it to ground and the psu will switch on.car amps aren't usually fantastic in terms of thd+n... that "400W" might be at 10% THD and 13.8Vjust parallel all the yellow wires for 12V and parallel all the blacks for ground... good luck!

author: Lightages
author_rank: Unknown
timestamp: October 08, 2014, 04:32:16 pm
content: Buy a wheel chair battery and use this as the power supply. Keep it connected to the charger all the time. This will let you get full power from the amp and it will be less expensive in the long run.

author: Sebastian S.
author_rank: Newbie
timestamp: October 08, 2014, 07:41:50 pm
content: Like I said i won't need the full power and I have everything I need for this little experiment lying around at home so I want have to pay a cent on anything this far. If I wanted I could get a normal 12V car-battery (free) for this but I thought the PSU has more stable Voltages even if I connect a charger to the battery.

author: simingx
author_rank: Contributor
timestamp: October 09, 2014, 03:46:05 am
content: Quote from: Sebastian S. on October 08, 2014, 07:41:50 pmWell if you already have everything lying around what's stopping you from doing it?

author: david77
author_rank: Frequent Contributor
timestamp: October 09, 2014, 04:26:37 am
content: It will work, but as has been mentioned it's not the most brilliant setup. Power wise it won't be a problem. You can not possibly run anything close to 400W in a normal domestic environment. Most peoples ears'll start bleeding at 80-100W not to mention the neighbours would hate you.A friend of mine had a setup like this for his subwoofer, that worked well. THD isn't much of a problem there I suspect.

author: Sebastian S.
author_rank: Newbie
timestamp: October 09, 2014, 02:29:35 pm
content: After some further research I found out that PSUs are activated by the mainboard so I had to build in a switch which allowes me to turn the PSU on and off. I only opened this topic because security was bothering me. I didn't want to blow anything up or something like this.As This works now, the Subwoofer only consumes 230W which will also never be used scince I will only bother my neighbours so I can connect a few speakers to it. I won't be able to build a 5.1 sorround-system but I have some things in mind such as switchable audio-input, connecting a car-radio, my TV, PC etc.Thanks for all your input. It really helped me out!