This is tough for me ,
yes , i have Alpine MRV-400 Amp that is full of BJT's but i have no power consumption , i only know that the max amount of power before the fuses in it blow is 40A ( which is about 576W ) .
And i guess a tranny that should output nearly 14.4v after bridge rectification .
Can anyone point me in the right direction ? ( It in the amp has a SMPS already . )
yes , i have Alpine MRV-400 Amp that is full of BJT's but i have no power consumption , i only know that the max amount of power before the fuses in it blow is 40A ( which is about 576W ) .
And i guess a tranny that should output nearly 14.4v after bridge rectification .
Can anyone point me in the right direction ? ( It in the amp has a SMPS already . )
I assume you are wanting to run a car amp off the mains and need a correctly sized transformer to do this?
Since 14.4V is around the max with the alternator running, and nominally the battery power is 12V I would say that it is safe to have something a bit lower than 14.4V, you probably don't want to go over it too much though.
10V secondaries will give you around 14.4V (or perhaps 13.8V after diode losses) however this would be under full load. if the transformer has 10% regulation it will be closer to 15.1V unloaded (allowing for .6v diode drop).
9V secondary might be safer, but it could be marginal as to whether you would get the required 12V... and you also need to consider mains voltage variations. It would probably be wise to check the absolute limits of the amps input power (possibly 16V max), and size for worst case of 10% over on mains , this would give around 16.38V allowing for 10% transformer regulation... as you will need a big VA transformer regulation will probably be closer to 6% which should be ok.
With regards to the power required, that is a bit tricky, you could just go with say a 600VA 10V transformer and hope it is enough. 40A fuses would tend to indicate that it won't be drawing that much current in reality. However where are the fuse(s) is it a single 40A before the smps or are they rail fuses after the voltage has been bumped up?
Tony.
Since 14.4V is around the max with the alternator running, and nominally the battery power is 12V I would say that it is safe to have something a bit lower than 14.4V, you probably don't want to go over it too much though.
10V secondaries will give you around 14.4V (or perhaps 13.8V after diode losses) however this would be under full load. if the transformer has 10% regulation it will be closer to 15.1V unloaded (allowing for .6v diode drop).
9V secondary might be safer, but it could be marginal as to whether you would get the required 12V... and you also need to consider mains voltage variations. It would probably be wise to check the absolute limits of the amps input power (possibly 16V max), and size for worst case of 10% over on mains , this would give around 16.38V allowing for 10% transformer regulation... as you will need a big VA transformer regulation will probably be closer to 6% which should be ok.
With regards to the power required, that is a bit tricky, you could just go with say a 600VA 10V transformer and hope it is enough. 40A fuses would tend to indicate that it won't be drawing that much current in reality. However where are the fuse(s) is it a single 40A before the smps or are they rail fuses after the voltage has been bumped up?
Tony.
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two things, first, fuses won't blow at 40A, so peak and short power could be a lot more, but you would probably clip the output way before that. Second thing is, amp is an audio amp, and consumtion is much lower then one would thing, because of creast factor of the music. also depends on amp, how much energy has stored inside, most car amplifiers not much, but still some
what you want, if going with mains power amp, probably the most simple thing is to get PC supply, load 5V with some load, like few fans or something, and use 12v rail for the amp
what you want, if going with mains power amp, probably the most simple thing is to get PC supply, load 5V with some load, like few fans or something, and use 12v rail for the amp
thank you for your input.
This amp is a mrv-400 a old one, but runs better at 14.4v
40A 2 20amp fuses .
Not sure where it is linked to as the fuses are on its exterior .
and also, i heard it runs hot, and at 14.4v it runs at 160W x 2 in bridge mode with 4 ohm. ( not 8 ohm but 4 )
I just need to feed it rectified and see how, i checked and its a SMPS inside .
This amp is a mrv-400 a old one, but runs better at 14.4v
40A 2 20amp fuses .
Not sure where it is linked to as the fuses are on its exterior .
and also, i heard it runs hot, and at 14.4v it runs at 160W x 2 in bridge mode with 4 ohm. ( not 8 ohm but 4 )
I just need to feed it rectified and see how, i checked and its a SMPS inside .
Dude, the SMPS is beyond just 12v .
Making a amp head with this, you wouldn't want a battery while touring trust me.
And on top of that, a 12v PSU rated 500W isn't exactly cheap and i need 14.4v for 160 x 2 .
Making a amp head with this, you wouldn't want a battery while touring trust me.
And on top of that, a 12v PSU rated 500W isn't exactly cheap and i need 14.4v for 160 x 2 .
Look, its Class AB and can amplify to 320W .
400VA maybe, but there are two rail 20A fuses.
Searched around without much luck, this is a old but good alpine amp, back when Alpine made proper amps, this was top of the line , no doubt.
Its full of BJT's by the way.
400VA maybe, but there are two rail 20A fuses.
Searched around without much luck, this is a old but good alpine amp, back when Alpine made proper amps, this was top of the line , no doubt.
Its full of BJT's by the way.
a fully charged battery is 12.8V, float charge is ~ 13.8 bulk charge is about 14.4V DC. So if you want to do it right, I would build or buy a smallish high quality battery charger (3 state w/ 10A current limit) along with a sealed lead acid battery sized 2x average amp hours of the longest listening session. If you don't need mobile and want to build an unregulated linear supply, I would target 13.4V as the fully loaded voltage at 25A or so.Then you need ~ 300 to 400 VA transformer, 2 HD rect diodes and a huge 40,000 uF cap.The short term peak music power of the inflated car audio amps power comes from the internal SMPS and the average power from the alternator is much less than the safety fuse ratings.
edit> buy a 400VA 11 - 0 -11 Vac transformer, two 50A diodes w/ heatsink, and a 40,000 uF 25 Vdc capacitor. make sure the secondary ac voltage is known under load.
edit> buy a 400VA 11 - 0 -11 Vac transformer, two 50A diodes w/ heatsink, and a 40,000 uF 25 Vdc capacitor. make sure the secondary ac voltage is known under load.
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Yes but its not typical in terms of performance.
Really o.o my 30w amp draws 50w at 3pm position.
Really o.o my 30w amp draws 50w at 3pm position.
320W output ... thats nominal .
Or should i use a 15v tranny and use a high forward voltage bridge recto?
What's a hd bridge recto o.o
40k uf hmm ... i could parallel smaller ones?
edit> buy a 400VA 11 - 0 -11 Vac transformer, two 50A diodes w/ heatsink, and a 40,000 uF 25 Vdc capacitor. make sure the secondary ac voltage is known under load.
No, you want to minimize the diode drops which is about 1.0-1.2 V depending on size, temp, and peak charging current. Yes you could parallel caps but only about 2 or 3 w/o careful wiring due to high ripple concerns.
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heavy duty rectifier diodes similar to this part http://download.siliconexpert.com/pdfs/2004/0616/semi_b/1/ixy/ds/l124.pdf $ 3.5 USD
calculate nominal Vo dc at 25A > 11.0 Vac x 1.4 - Vd where Vd = 0.9V so Vo ~ 14.4 Vdc
calculate nominal Vo dc at 25A > 11.0 Vac x 1.4 - Vd where Vd = 0.9V so Vo ~ 14.4 Vdc
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I will go look for them though, after getting hold of a tranny (1 positive 14.4 is enough )
Don't you think you should be taking into account mains fluctuations and transformer regulation? with 10% over on the mains and a 6% transformer regulation the unloaded voltage output by this will be around 17V... at least some Car equipment (not sure about amps) has 16V zenners wired across the power rails, it is a safety feature, blows the fuse (or the zenner) if the voltage spikes to over 16V to protect the equipment from over-voltage. That's why I suggested finding out the max input voltage of the amp and designing around that. Tony.
yes I thought about that, that's always an issue going with unregulated. The XFMR regulation and initial tolerance of the mains voltage should be taken care of for the most part with checking the transformer under full load in situ. ie not really mobile. Also using an oversized 400 VA toroid should bring the regulation closer to +2% at light load ie not zero load. The preferred solution is using a battery and an auxilary charger.
The OP's target of 14.4 V seems a little high, I would aim lower, like I said earlier s/b at 13.4 Vdc nominal.
The OP's target of 14.4 V seems a little high, I would aim lower, like I said earlier s/b at 13.4 Vdc nominal.
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