Hello
I have built my first own amp and have a some questions.
The amp consists of:
2 L25D boards
1000W DC12V power supply adjusted to ±60V (1000W DC12V Switching Boost Power Supply Board Adjustable Output Voltage | eBay)
TC-780i stereo line level amp (used as pre-amp)
All is powered by a 12V lead acid battery.
I have managed to assemble everything, and once started it works great, but I have a peculiar issue with the power supply.
When I first tested everything I used thin test leads with alligator clips to connect the power supply to the 12V battery. It started as expected when "control" was connected to +12V.
So I went ahead and soldered two 10 mm2 cables to +12V and GND on the board, to be able to handle a larger current. Now when connecting "control" to +12V the power supply will not start. When I measure the output, it goes directly to around 8V, stops and then slowly goes back to 0.
I have a workaround by first connecting a thin test lead between the battery and the board, then connect "control" to +12V (now the power supply starts up) and finally I connect the 10 mm2 cable. At this point I can remove the test lead and it is still running fine. Anyone have any idea what could be causing this, and how it can be resolved?
The system is meant to be mobile so portable mp3 players and cell phones will mostly be used as audio sources. That's why I'm using a active pre-amp, to compensate for the low line level output of most of these devices. I am aware that the pre-amp I'm using has a larger output impedance (2kΩ) than recommended for the L25D. Will this impact the performance of the amp a lot, and if so in in which way?
Finally, recommended voltage for the L25Ds is ±72V, but my power supply can only deliver ±60V. This is still within the specification, but would there be much difference with ±72V instead?
I have built my first own amp and have a some questions.
The amp consists of:
2 L25D boards
1000W DC12V power supply adjusted to ±60V (1000W DC12V Switching Boost Power Supply Board Adjustable Output Voltage | eBay)
TC-780i stereo line level amp (used as pre-amp)
All is powered by a 12V lead acid battery.
I have managed to assemble everything, and once started it works great, but I have a peculiar issue with the power supply.
When I first tested everything I used thin test leads with alligator clips to connect the power supply to the 12V battery. It started as expected when "control" was connected to +12V.
So I went ahead and soldered two 10 mm2 cables to +12V and GND on the board, to be able to handle a larger current. Now when connecting "control" to +12V the power supply will not start. When I measure the output, it goes directly to around 8V, stops and then slowly goes back to 0.
I have a workaround by first connecting a thin test lead between the battery and the board, then connect "control" to +12V (now the power supply starts up) and finally I connect the 10 mm2 cable. At this point I can remove the test lead and it is still running fine. Anyone have any idea what could be causing this, and how it can be resolved?
The system is meant to be mobile so portable mp3 players and cell phones will mostly be used as audio sources. That's why I'm using a active pre-amp, to compensate for the low line level output of most of these devices. I am aware that the pre-amp I'm using has a larger output impedance (2kΩ) than recommended for the L25D. Will this impact the performance of the amp a lot, and if so in in which way?
Finally, recommended voltage for the L25Ds is ±72V, but my power supply can only deliver ±60V. This is still within the specification, but would there be much difference with ±72V instead?
Looks like the internal resistance of your battery is to high to handle the inrush current of the SMPS . The battery voltage is to low at this high current to start the SMPS . ( The thin wire works because of the much lower inrush current due to it's higher resistance )check the max current of the battey , try with a bigger battery .
You can try a BIG ( 1F ? ) capacitor in parallel with your battery . or a softstart circuit .
The L25D will work fine on dual 60V rails , the only difference is a lower output power around 185 Watts at 8 ohms .
Cheers ,
Rens
You can try a BIG ( 1F ? ) capacitor in parallel with your battery . or a softstart circuit .
The L25D will work fine on dual 60V rails , the only difference is a lower output power around 185 Watts at 8 ohms .
Cheers ,
Rens
You'll need a large deep-cycle battery. It's probably cheaper and lighter to just get a small gasoline generator and use an amp that runs from line voltage.
Or, maybe you're over-estimating how much power you need. 10 watts RMS into an efficient speaker is plenty loud. Inside a car, that's enough for bass you can feel.
Or, maybe you're over-estimating how much power you need. 10 watts RMS into an efficient speaker is plenty loud. Inside a car, that's enough for bass you can feel.
Thank you for your replies!
The battery I'm using is a 45 Ah car battery. It's a cheap one however, but still shouldn't it be able to keep the voltage up even at quite a lot of inrush current? I have tried with a smaller 4.5 Ah lead-acid battery as well. It has the same problem, but I need less "thin wire" to get it started. For me (being the novice that I am in this field) it seems that the SMPS fails to start when connected to a source that can deliver a lot of current.
I have tried with a capacitor in parallel, but it was just 11mF, so perhaps it was too small. I will investigate how I can build a proper softstart circuit. I did experiment with a simple Potentiometer in series with the battery (knowing it would probably be fried) to test the theory. It was also semi-successful, by slowly lowering the resistance of the pot, the SMPS would finally power on, but just for a second before the pot, as expected, burned up.
Yes, I did realize that I should have bought a deep-cycle battery instead of a car battery. But I guess this will have to do now until it fails, then I can get a better suited power source. I want to avoid gasoline generators though, this thing will partly be used in an inflatable boat 😉.
When I started this project I probably overestimated my power need quite a bit. It will be used in an open field however, and my previous 2x15W T-amp did not deliver enough. Now I know this was probably mostly because of quite low sensitivity (90 dB/mW) speakers which were not suited for outdoor use. So I am also planning to build new speakers to use with this amp. But I guess it does not hurt to have an amp that can deliver a lot of peak effect when needed, even if it's running on quite low RMS.
The battery I'm using is a 45 Ah car battery. It's a cheap one however, but still shouldn't it be able to keep the voltage up even at quite a lot of inrush current? I have tried with a smaller 4.5 Ah lead-acid battery as well. It has the same problem, but I need less "thin wire" to get it started. For me (being the novice that I am in this field) it seems that the SMPS fails to start when connected to a source that can deliver a lot of current.
I have tried with a capacitor in parallel, but it was just 11mF, so perhaps it was too small. I will investigate how I can build a proper softstart circuit. I did experiment with a simple Potentiometer in series with the battery (knowing it would probably be fried) to test the theory. It was also semi-successful, by slowly lowering the resistance of the pot, the SMPS would finally power on, but just for a second before the pot, as expected, burned up.
Yes, I did realize that I should have bought a deep-cycle battery instead of a car battery. But I guess this will have to do now until it fails, then I can get a better suited power source. I want to avoid gasoline generators though, this thing will partly be used in an inflatable boat 😉.
When I started this project I probably overestimated my power need quite a bit. It will be used in an open field however, and my previous 2x15W T-amp did not deliver enough. Now I know this was probably mostly because of quite low sensitivity (90 dB/mW) speakers which were not suited for outdoor use. So I am also planning to build new speakers to use with this amp. But I guess it does not hurt to have an amp that can deliver a lot of peak effect when needed, even if it's running on quite low RMS.
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