I'm going to build a "boombox" for my brothers doughter, using two LM3886, two fullrange elements, and a volumepot in the same box.
I'll be using a pair of RCA inlets, and a 3,5mm jack for her mp3 player.
This won't need a whole lot of power, my question is, is a 150VA 2x15V~ a big enough transformer?
I'll be using a pair of RCA inlets, and a 3,5mm jack for her mp3 player.
This won't need a whole lot of power, my question is, is a 150VA 2x15V~ a big enough transformer?
Hi,
150VA can support upto 100W of output.
15Vac will give about 20 to 22Vdc.
This results in about 15W to 20W into 8ohms or about 25W to 35W into 4ohms.
Seems like plenty of noise for an MP3 player.
It will sound a lot louder than those advertised as 1000W of pmpo power.
Have a look at that other thread on hum in a two channel chipamp. He has a solution that works.
150VA can support upto 100W of output.
15Vac will give about 20 to 22Vdc.
This results in about 15W to 20W into 8ohms or about 25W to 35W into 4ohms.
Seems like plenty of noise for an MP3 player.
It will sound a lot louder than those advertised as 1000W of pmpo power.
Have a look at that other thread on hum in a two channel chipamp. He has a solution that works.
If it's a stereo kit, just hook the secondarys with a dot in the datasheet to the underlined AC on the psu card, and the others to the not underlined AC on PSU, just remember to keep them paired.
One pair of secondarys goes to underlined AC1 and AC1, the other pari goes to underlined AC2 and AC2.
Did I make any sence?
One pair of secondarys goes to underlined AC1 and AC1, the other pari goes to underlined AC2 and AC2.
Did I make any sence?
Re: Sorry, I want advice on the power requirements
You might just be able to stretch to 4channels out of it. But hum reduction on multi channel from one trafo seems to be a problem with the PCBs as supplied.
Do not go any higher with 8ohm speakers.
If you allow for max mains voltage and max transformer regulation and minimum quiescent current in the chipamp you will have a lot more than +-35Vdc in the worst case (fortunately not too often).
If you have 4 to 8 ohm speakers then 25Vac is already too high.
yes, that will support three channels @ 60W into 8ohms.ppcblaster said:
You might just be able to stretch to 4channels out of it. But hum reduction on multi channel from one trafo seems to be a problem with the PCBs as supplied.
Do not go any higher with 8ohm speakers.
If you allow for max mains voltage and max transformer regulation and minimum quiescent current in the chipamp you will have a lot more than +-35Vdc in the worst case (fortunately not too often).
If you have 4 to 8 ohm speakers then 25Vac is already too high.
Hi Ppc,
how far do you want me to go back?
25Vac gives about 34 to 37Vdc.
This results in about 60W into 8ohms.
2 channels is 60+60=120W and a 120 to 180VA transformer can meet this demand.
Your selection has a capacity of about 50% to 100% more than that, indicating that 3 or 4 channels could be powered from this transformer (if you had that need).
If one were building a 5.1 system, the simultaneous demand from all the channels rarely matches the sum of the channels and if the sub were run from a separate transformer (or separate windings off the same transformer) then the 5channels may/will run successfully from a smaller transformer than normally recommended.
hum.
mayday and a few others are finding a problem silencing stereo and multi-channel chipamps. There are solutions, but they seem to vary from build to build. Be prepared for experimentation - bolted ground connections are a lot easier than soldered!
how far do you want me to go back?
25Vac gives about 34 to 37Vdc.
This results in about 60W into 8ohms.
2 channels is 60+60=120W and a 120 to 180VA transformer can meet this demand.
Your selection has a capacity of about 50% to 100% more than that, indicating that 3 or 4 channels could be powered from this transformer (if you had that need).
If one were building a 5.1 system, the simultaneous demand from all the channels rarely matches the sum of the channels and if the sub were run from a separate transformer (or separate windings off the same transformer) then the 5channels may/will run successfully from a smaller transformer than normally recommended.
hum.
mayday and a few others are finding a problem silencing stereo and multi-channel chipamps. There are solutions, but they seem to vary from build to build. Be prepared for experimentation - bolted ground connections are a lot easier than soldered!
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