hi everyone im a beginner to this stuff i just want some help regarding transformer yesterday i found some transformer in our stock room with a rating 220vac primary and 13vac secondary @ 5 ampere i hook up a rectifier diode and did make a fullwave now i make a test in output to make it DC it reads 20vdc is this normal?can i used it to power up my car audio amplifier?because im planning to make a subwoofer with a car amplifier which only need 12vdc to power up.follow up question what should be the rated dc output with a 13vac secondary output?
thanks for the response
so you mean to say i can't hook this up in my car audio amplifier because the max voltage is 15.5vdc right?i got lightning audio LA-600m model i just want to make sure that my amp will not be damage when i connect this transformer to my amp.
The rectified voltage will be too high,also,the current rating is a bit low.
Something like a 9-10Vac 10Amp(or more) transformer would be suitable for running a car amplifier.
Edit: That amp claims to be 600W,you're gonna need a hefty transformer for that.
Do you have any old microwave ovens around? You could possibly rewind the transformer from one and get enough power to run your amp.
Something like a 9-10Vac 10Amp(or more) transformer would be suitable for running a car amplifier.
Edit: That amp claims to be 600W,you're gonna need a hefty transformer for that.
Do you have any old microwave ovens around? You could possibly rewind the transformer from one and get enough power to run your amp.
No, no, no !!!!
The level of competence of this Member has already been shown. Do not suggest he/she wind their own mains transformer.
600W of total maximum output power normally requires a transformer rated from 600VA to 1200VA.
A 10Vac transformer meeting this specification would have a current rating from 60Aac to 120Aac.
Car Audio is silly. Don't make it any sillier.
Quite, for both posts Andrew.
The safer way for the OP to do it would be to use a car battery, and recharge the battery as required from a correctly rated (commercial) SLA charger. And even then using lead-acid batteries indoors is probably a bad idea - esp. at high discharge rates.
ETA: I always figure car amp ratings are for teh birds. It'll be something like ' 600w = 2 channels added, which each are PMPO into 1ohm' or about 600/8, 75w into each channel if generous. It still requires n internal SMPS, but probably limits PSU draw to somthing like 8-10A. Even so, even large car batteries (i.e non traction-rated lead-acids) will droop a lot under such loads. A big lump like the spare 90Ah unit I use (for testing some low-noise toys) will only last about an hour and a half under such a load. That's because SLA amp-hour ratings are non-linear, and usu. based on a notional '20hour' rate, Ie how much current it will supply when new to draw-down to 10.8v after 20rs... And unless it's a traction /'leisure' ie marine-use battery, such gross charge/discharge use will soon kill it. Car batteries are for 'float' use only!
The safer way for the OP to do it would be to use a car battery, and recharge the battery as required from a correctly rated (commercial) SLA charger. And even then using lead-acid batteries indoors is probably a bad idea - esp. at high discharge rates.
ETA: I always figure car amp ratings are for teh birds. It'll be something like ' 600w = 2 channels added, which each are PMPO into 1ohm' or about 600/8, 75w into each channel if generous. It still requires n internal SMPS, but probably limits PSU draw to somthing like 8-10A. Even so, even large car batteries (i.e non traction-rated lead-acids) will droop a lot under such loads. A big lump like the spare 90Ah unit I use (for testing some low-noise toys) will only last about an hour and a half under such a load. That's because SLA amp-hour ratings are non-linear, and usu. based on a notional '20hour' rate, Ie how much current it will supply when new to draw-down to 10.8v after 20rs... And unless it's a traction /'leisure' ie marine-use battery, such gross charge/discharge use will soon kill it. Car batteries are for 'float' use only!
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Some car audio amplifiers only contain a pair of output transistors/channel, so if you are in for a mod then it'll be better to add another pair on the unused space inside the amplifier casing, as I did with my Boss 4x250W amp (true rating btw). This will make the amp stand better against more demanding cases.
thanks
hi everyone i did find some 12vdc 3a transformer that's manufactured ready i did hookup the amp and it works fine the only problem is that the transformer got heats up easily its because it drops current when a low freq was draw from amp.now i'm still afraid to used this 13vac 5a transformer to hook my amp. i just need some advice if its 100% safe to used this transformer hoping for the best advice. thanks
hi everyone i did find some 12vdc 3a transformer that's manufactured ready i did hookup the amp and it works fine the only problem is that the transformer got heats up easily its because it drops current when a low freq was draw from amp.now i'm still afraid to used this 13vac 5a transformer to hook my amp. i just need some advice if its 100% safe to used this transformer hoping for the best advice. thanks
No, it's not safe. I wouldn't even recommend using the 12V transformer you hooked up, since 12Vac * SQRT(2) = 16.9Vdc, which exceeds the maximum input voltage of your amp. Realistically, it will only provide something like 12Vac * 1.3 = 15.6Vdc under load, but then you're still pushing the envelope. What's probably saving your amp right now is the fact that your little 36VA transformer is probably struggling to cope with the power demands of the amplifier, causing the voltage to drop. Possibly the transformer runs hot as well, especially if you play the amp.
Pay heed to the advise others have given already in this thread. You'll need more power even if those 600W printed on the amp is a gross exaggeration; if it is capable of doing about 75W rms as Martin suggested, you'd still need a transformer that's about 6-10 times the size of the transformer you're using now. And any transformer that supplies more than about 11Vac (>15.5Vdc rectified; maybe about 14.3Vdc effectively under load) is a no-go, as you risk blowing up the amp with a too high input voltage.
Pay heed to the advise others have given already in this thread. You'll need more power even if those 600W printed on the amp is a gross exaggeration; if it is capable of doing about 75W rms as Martin suggested, you'd still need a transformer that's about 6-10 times the size of the transformer you're using now. And any transformer that supplies more than about 11Vac (>15.5Vdc rectified; maybe about 14.3Vdc effectively under load) is a no-go, as you risk blowing up the amp with a too high input voltage.
thanks mastodon i better change my transformer if thats so. what would you recommend (transformer Vac and amp)if i want to use those 75W rms full power?
You could try to find a transformer that will output about 10 Vac @ 20A minimum (200VA) for 75Wrms per channel and a bridge rectifier that will stand such currents (so including an adequate heat sink). And it might be a good idea to filter the power as well, so you'll need some big elcos. Mind you, we're working at this hypothetical 75W per channel, but it's possible that this amp is capable of much more. That would require an even beefier power supply though, so you're venturing into the realms of really expensive and infeasible parts.
Or you could do as Andrew says and just build something else. Because this car amplifier just isn't going to be a very practical solution, all considered.
Or you could do as Andrew says and just build something else. Because this car amplifier just isn't going to be a very practical solution, all considered.
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