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Old 6th September 2012, 11:20 AM   #71
back is offline back  Greece
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Quote:
Originally Posted by AndrewT View Post
500W lme49810 !!!!!
What voltages are you planning to run at?
i have a pair cristi`s smps1000a at 75volt.

i could use them and if i like them i will add linear supply 85volt for the

input stage.

have you heard them?
 
Old 6th September 2012, 01:13 PM   #72
AndrewT is offline AndrewT  Scotland
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500W into 8r0 is equivalent to >89Vpk. You can't get 89Vpk from a 75Vdc, nor from an 85Vdc supply.

500W into 4r0 is equivalent to >63Vpk.
You should be able to get that from a 75Vdc supply. You will be able to easily achieve that with an 85Vdc supply.
But this will only happen if the current demand can be met, without significant drop in the supply voltage.
For 63Vpk into a resistor test load, the PSU must be able to deliver >15Apk to the load.
For effective performance into a reactive speaker the minimum current delivery must be at least 30Apk into a 4ohms load and preferably >45Apk. Again without significant drop in supply voltage.

Can either supply deliver those levels of current to the load?
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Old 6th September 2012, 02:59 PM   #73
Cristi is offline Cristi  Europe
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For a Class AB amplifier such as LME49810 based one, there is no advantage at all to supply the power stage with more than +-70 to +-75V while willing to achieve 500W on 4R. any extra voltage will only increase the amplifier losses, reducing the efficiency. The power supply has regulated output voltage and if the maximum current is exceeded the smps will simply shut down for a brief period (2 sec.) and restart again if the overcurrent condition was removed. will not drop the voltage or sag like a classic mainstransformer+rectifier bridge+caps power supply.
while doing the math I found the RMS current for 500W 4R ~11.2 and peak current ~16R. even in the worse case scenario where the speaker impedance drop to half, the peak current will be ~22.3A, slightly less than the values calculated earlier.
The power supply which @Back wants to use can deliver approx. 6.5A at +-75 V and a peak of 8A. You might want to say that is far less than required, that's true, if we use the amp for playing sine or square waves, but for music with crest factor of 1/8 to max. 1/3 I would say that it might be enough. For this application (LME49810 Amp + A1000SMPS) some extra 8200-10000uF caps should be added on each rail.
The smps will provide the average power, then the large caps will provide the energy reserve for peaks. In this way we might get it work much more cheaper than using a power supply capable to deliver 45A at +-75V (6750W) for a 500W class AB amplifier.
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Old 6th September 2012, 03:00 PM   #74
back is offline back  Greece
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the supplies are 1100watt continues with adjustable voltage 75-95volt and i will use

one per channel.

no voltage drop, they are regulated.

here is the datasheet with current capabilty vs voltage but i think your calculations

are too stiff.

suppose that the psu is capable to deliver that current.

that would be translated to at least 1500watt peaks.

you think the module will be able to survive that?

the load will be about 3ohms so it`s even worse.

p.s.have you heard them?
 
Old 6th September 2012, 03:09 PM   #75
back is offline back  Greece
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Quote:
Originally Posted by Cristi View Post
For a Class AB amplifier such as LME49810 based one, there is no advantage at all to supply the power stage with more than +-70 to +-75V while willing to achieve 500W on 4R. any extra voltage will only increase the amplifier losses, reducing the efficiency. The power supply has regulated output voltage and if the maximum current is exceeded the smps will simply shut down for a brief period (2 sec.) and restart again if the overcurrent condition was removed. will not drop the voltage or sag like a classic mainstransformer+rectifier bridge+caps power supply.
while doing the math I found the RMS current for 500W 4R ~11.2 and peak current ~16R. even in the worse case scenario where the speaker impedance drop to half, the peak current will be ~22.3A, slightly less than the values calculated earlier.
The power supply which @Back wants to use can deliver approx. 6.5A at +-75 V and a peak of 8A. You might want to say that is far less than required, that's true, if we use the amp for playing sine or square waves, but for music with crest factor of 1/8 to max. 1/3 I would say that it might be enough. For this application (LME49810 Amp + A1000SMPS) some extra 8200-10000uF caps should be added on each rail.
The smps will provide the average power, then the large caps will provide the energy reserve for peaks. In this way we might get it work much more cheaper than using a power supply capable to deliver 45A at +-75V (6750W) for a 500W class AB amplifier.

cristi those power supplies powering hypex ucd2k`s (ok they are more efificient but still) where able to

easily to drive the speakers to their limit.

i believe the power is enough but my question have to do with how they

sound.

ps.i believe i could change a resistor to make them go lower than 75 volts

since the load is small?

minimum is 3 ohm at 180hz i measured it.

Last edited by back; 6th September 2012 at 03:14 PM.
 
Old 8th September 2012, 11:18 AM   #76
back is offline back  Greece
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cristi can you tell me which resistor i need to change?

even 5 volt is enough.

75 volt is now the minimum.

70 volt would be ok.
 
Old 11th September 2012, 08:33 AM   #77
Cristi is offline Cristi  Europe
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On the last boards version, R43, the resistor in series with the potentiometer which allow voltage adjustment. for lower voltage need to reduce the value of this resistor proportionally with the value which you want to obtain. Do not use larger value and never start the power supply without this resistor as the control loop will be open, and the output voltage will jump to extreme values, over +-100V and can possibly damage components, especially the capacitors.
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Old 11th September 2012, 06:27 PM   #78
back is offline back  Greece
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ok thanks cristi.
 
Old 15th February 2013, 06:26 PM   #79
meltman is offline meltman  United States
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Cristi,
I'd like to build a two-channel 500W-LME4981 amplifier.

Is the SMPS2000R sufficient or would the SMPS3K6QR be a better choice? I notice the 3k6 has dual output voltages. Would this be a better match for the separate driver and power stage capable LME4981?

Any other thoughts and considerations?
 
Old 19th February 2013, 08:40 AM   #80
Cristi is offline Cristi  Europe
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SMPS2000R can be used to supply two LME49810-500W modules, it has regulated output voltage so the higher voltage rails for driver and input stage is not absolutely required like when a linear supply or unregulated output smps is used. the output voltage of SMPS2000R can be adjusted to about 80-82V (+-84v version) to be able to deliver the rated output power. If the full power is not always required, and slightly lower power dissipation is the goal, the +-72V version is suitable as well with the output voltage set to +-75V. In any case the amplifier modules must be installed with the heatsink outside the housing for better cooling or a cooling fan should be used for better cooling.
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