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Old 29th June 2012, 06:45 AM   #21
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I have a small 150w power invertor that I can gut to make a +/- supply and fit all 3 amps inside. It's fairly simple with a regulated PWM push-pull step-up convertor then a H-bridge after that with another PWM IC driving it to make "AC". The two stages may be easy to seperate. Looks like only a shutdown signal from the second PWM going back to the first. Could be promising to make a bipolar supply with.
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Old 29th June 2012, 06:52 AM   #22
MarianB is offline MarianB  Romania
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It would be best to sepparate the two PWM and take the output voltage from the first one's circuit, but even that way you would still need much power from the battery wich i don't think it can cope by it's self with the demands so only with the engine started you could use the device.
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Old 29th June 2012, 08:02 AM   #23
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I think the battery is rated 9-10ah and a 1000cc twin is NOT easy to push start. lol

Right about the inverter. I'd ditch the second PWM and AC stage. I'd place the amps in that area. I'm not sure if the secondary has a center tap or not. If not, I could probably use a transformer from a PC power supply. I've seen a few of those with a CT primary (120v) and CT secondary (12v). If I could find a car amplifier small enough I'd use it but all the little ones I could find use ICs running off the 12v supply. If that's the case then I'd rather make my own.
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Old 29th June 2012, 08:16 AM   #24
MarianB is offline MarianB  Romania
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There is a big difference between jumpstarting an engine and powering an amplifier, the engine requires much more power than the amplifier granted, but that is only for a few seconds, after that the alternator takes the bulk of the charge/load, on the othe hand the amplifier requires less power but continuosly as long as you listen to music on it, so the battery even if it is rated at let say 10A/h it can give more than that ( much more ) for a short time without discharging much, but it cannot sustain an important load continuosly too much time, and an 150W converter would require at least 13A constant from the battery, now you understand why the battery would discharge quikly.

It is not such a big problem if the converters transformer does not have a center tap on it's output, you can simply reconstruct the secondary coil to your specs, just make sure you respect the turn ratio and other specs on that converter ( if any ).
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Old 29th June 2012, 08:20 AM   #25
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The tda7560 looks like a nice chip. http://www.st.com/internet/com/TECHN...CD00001962.pdf

Can I parallel the outputs of any of these ICs even if they're internally BTL?
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Old 29th June 2012, 08:31 AM   #26
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Quote:
Originally Posted by MarianB View Post
There is a big difference between jumpstarting an engine and powering an amplifier, the engine requires much more power than the amplifier granted, but that is only for a few seconds, after that the alternator takes the bulk of the charge/load, on the othe hand the amplifier requires less power but continuosly as long as you listen to music on it, so the battery even if it is rated at let say 10A/h it can give more than that ( much more ) for a short time without discharging much, but it cannot sustain an important load continuosly too much time, and an 150W converter would require at least 13A constant from the battery, now you understand why the battery would discharge quikly.

It is not such a big problem if the converters transformer does not have a center tap on it's output, you can simply reconstruct the secondary coil to your specs, just make sure you respect the turn ratio and other specs on that converter ( if any ).
I understand batteries. I've built many electric vehicles.
The inverter draws 250ma without a load. It's input is proportionate to it's output so if I'm drawing 120w (120v@1a) it's drawing 120w (12v@10a) minus the efficiency of the inverter of course. I don't expect the amplifiers to be operating at peak output 100% of the time either. The battery in the bike is SLA and they seem to handle constant draws. I use one on my test bench often. No doubt it can push current if it needs to. Ask my how many jumpers I have melted. lol One of these days I'll put a fuse on it.
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Old 29th June 2012, 08:37 AM   #27
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I think you have e deciding issue, too much options do more harm than good sometimes.

What you need toi understand is that you cannot espect a high power audio sistem on a motorcycle no matter what the solution choosen is, on the other hand 20W for a good woofer is often more than enough, the same for the other 2 speakers so you have to make up your mind on what you can do with, an simple IC amplifier at 12V ( BTL or otherwise ) and that way you can run the amplifier even with the engine off but not too much time, or you use an converter to get more power but it is more complicated and you can only run the amp at high volume with the engine started, the choice is yours
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Old 29th June 2012, 09:30 AM   #28
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I'm still left searching for a 4ch single ended IC to make a 2.1 system by bridging ch3 and 4. -or- Use two ICs. A 2ch BTL? for the fronts and a single channel for the sub. In the ICs I've been fiddling with so far it seems that 12v is plenty to provide the power I need into 4ohm speakers.

Is any way better then the other? My thought was a 4ch would use less components but I can't find a "high power" 4ch IC other then the TDA1554Q http://skory.gylcomp.hu/alkatresz/tda1554q_cnv_2.pdf I'm sure there are higher then 11w versions of it. I've been digging on mouser but their selection guide is a mess.
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Old 29th June 2012, 09:41 AM   #29
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You still don't get it:

-In Class AB ( or B ) on 12V power supply no matter what IC you use, you cannot get on single ended amplifier more than 10W on 4 Ohm load ( that 11 figure is forced with verry high THD ), it is not fisicaly possible.
-On a BTL config at same 12V power supply, same class same load you can only get about 20W maximum no matter what IC is used.
-The only way to troubleshoot this limitation is class H like TDA1562, but i think that is forcing the issue.

So bottom line is, you have a given voltage rail wich the output devices cannot exeed so no matter what the IC pdf says, it is not possible to get more.
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Old 29th June 2012, 09:48 AM   #30
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I thought you can get up to ~20w or so into 4ohm. 12v into 4ohm is 3a *12 = 36w -IF- it could swing rail to rail which it can't but only 10w? I know they can do better then that. Maybe 10w into 8ohm. Or is this where the whole SE vs. BTL comes into play? I have been thinking SE could swing rail to rail but that's probably my mistake.

No one here has said until now that 10w is the limit with a 12v supply. OK... So... It there a 3ch BTL (20w x3) IC?

Last edited by lazzer408; 29th June 2012 at 09:51 AM.
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