I am rather a newbie in the world of amplification, and I want a first project so I can get into it without worry that my result won't work. So I decided to build a stereo amplifier with the alesis modules at ApexJr. It comes with no power supply, but they recommend the Signal BL1733A they sell and some 10,000uf capacitors. I have a few questions:
How many capacitors should I use?
Would this psu be capable of owering more than one module?
What power fuse would be suitable for this arrangement?
Thanks.
How many capacitors should I use?
Would this psu be capable of owering more than one module?
What power fuse would be suitable for this arrangement?
Thanks.
I suggest you use their recommendations. I would guess they mean 10,000 uF per supply, but higher won't hurt, just cost more money.
The rule of thumb I've seen is Transformer VA = 2 * DC watts required. This will keep the transformer from getting too hot. You therefore need to know the efficiency of the amps, or what DC power they draw.
If you don't have enough info from them, post all the information you do have (power, speaker impedance, specs, etc.) and we'll try to sort it all out.
The rule of thumb I've seen is Transformer VA = 2 * DC watts required. This will keep the transformer from getting too hot. You therefore need to know the efficiency of the amps, or what DC power they draw.
If you don't have enough info from them, post all the information you do have (power, speaker impedance, specs, etc.) and we'll try to sort it all out.
Amp module contains one LM 3886T 68W amp and a LM 2876T 40W amp along with op-amps
LM 3886 uses +-34V
LM 2876 uses +-20V
op-amps use +-12/15V
Transformer secondary is 48VCT 7A and 28VCT 3A, I can get the op-amp voltage with a LM7815 voltage regulator.
There is a schematic here for the module:
http://www.apexjr.com/images/alesis_amp.pdf
That is about all the info available from the website (http://www.apexjr.com/alesis.htm)
Remember, my understanding of this is fairly basic. I plan to examine a number of powersupply schematics before I do anything, and hopefully find a similar schematic so that I don't make any mistakes. Thanks in advance.
LM 3886 uses +-34V
LM 2876 uses +-20V
op-amps use +-12/15V
Transformer secondary is 48VCT 7A and 28VCT 3A, I can get the op-amp voltage with a LM7815 voltage regulator.
There is a schematic here for the module:
http://www.apexjr.com/images/alesis_amp.pdf
That is about all the info available from the website (http://www.apexjr.com/alesis.htm)
Remember, my understanding of this is fairly basic. I plan to examine a number of powersupply schematics before I do anything, and hopefully find a similar schematic so that I don't make any mistakes. Thanks in advance.
Ignite,
These modules are for biamping - separate amps for woofer and tweeter (you knew that, right?).
First off, I suggest you visit the National semiconductor site www.national.com and download the datasheets for those two devices. They're full of interesting graphs like how much power is dissipated in the chip at various power levels into various loads (this will let you calculate the total power).
Another site to look at that includes some basic articles on power supply design and other stuff is at www.sound.au.com. There is also an LM3886 project there (might actually be another chip in the same family, like the LM3875). Check out the power supply he recommends. There is a very comprehensive article there on biamping as well. The power requirements for woofer vs. tweeter depend on the crossover frequency.
It sounds like the transformers you mentioned would be enough for stereo, but you need to do a bit of research.
Do a search here on LM3875, LM3876, LM3886 and you should get lots of hits on power supplies for these chips. You need to scale them for your system. One person (might be 'downhere', can't remember exactly) went through quite a few iterations with transformers and such.
The opamps require a +/- supply so you would actually use both a 7815 and 7915 to get them from the higher voltage supply.
These modules are for biamping - separate amps for woofer and tweeter (you knew that, right?).
First off, I suggest you visit the National semiconductor site www.national.com and download the datasheets for those two devices. They're full of interesting graphs like how much power is dissipated in the chip at various power levels into various loads (this will let you calculate the total power).
Another site to look at that includes some basic articles on power supply design and other stuff is at www.sound.au.com. There is also an LM3886 project there (might actually be another chip in the same family, like the LM3875). Check out the power supply he recommends. There is a very comprehensive article there on biamping as well. The power requirements for woofer vs. tweeter depend on the crossover frequency.
It sounds like the transformers you mentioned would be enough for stereo, but you need to do a bit of research.
Do a search here on LM3875, LM3876, LM3886 and you should get lots of hits on power supplies for these chips. You need to scale them for your system. One person (might be 'downhere', can't remember exactly) went through quite a few iterations with transformers and such.
The opamps require a +/- supply so you would actually use both a 7815 and 7915 to get them from the higher voltage supply.
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