Hi it's my first time building a am. I'm a bit stuck on the power supply I was looking at using a 2x 18v 160va toridal but after some reading realised I need a split rail power supply as I'm using 2 lm3886 to build a stereo amp do o have to buy 2 centre taped transformers or can I use 1 to feed 2 split rail power boards.? Thanks.
One power board with a bridge rectifier and decoupling of a positive rail and a negative rail is sufficient. LM3886 deserves a minimum of 10000uF for each rail. Look for a power board with two large electrolytic capacitors (of same size) and then check it is for a transformer with a center-tap and has got both a "+" and "-" output.
One example of such a board with three capacitors per rail. The use of the bridge rectifier in the schematic shown below is absolutely wrong but I guess the board is made right (it is correct seen from the below side of the PCB):
Dual Power Rectifier Filter Fever Capacitor Filter Positive And Negative Power Amplifier Board Audio Rectifier Power Supply -in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
Dual Power Rectifier Filter Fever Capacitor Filter Positive And Negative Power Amplifier Board Audio Rectifier Power Supply -in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
Here's some good reading about PSUs, if you have time there's lots of other interesting articles too.
Linear Power Supply Design
Power Supply Wiring Guidelines
A wide variety of cases, looks good and reasonably priced
Modushop by Hi-Fi 2000 | Contenitori per Elettronica | Electronic Enclosures | Hi Fi Chassis
Note here Power Supply Wiring Guidelines in fig 1 a centre tapped transformer is used whilst in fig 2 a transformer with separate secondaries is shown. There are cases here The diyAudio Store - DIY amplifier kits, chassis, and parts
Do you mean the transformer is a 30-0-30 VAC type or do you mean the DC rails produced by this transformer are around -/+30 volts. There is a big difference.
If the former then you are looking at DC rails of -/+42 volts, if the transformer voltage is higher than 30 volts at light loading then the DC voltage will be higher still. That is right on the upper limits of the LM3886's spec and would not be something I would recommend.
The -/+30 volts DC option would be perfect.
If the former then you are looking at DC rails of -/+42 volts, if the transformer voltage is higher than 30 volts at light loading then the DC voltage will be higher still. That is right on the upper limits of the LM3886's spec and would not be something I would recommend.
The -/+30 volts DC option would be perfect.
I have done the same as you and cannibalized old amplifiers for use in new constructions. Mooly is (of course) right, you end up with around 2x42Vdc.
An LM3886 can handle max. +/-42V so you are close. It would be a pity to waste a good transformer so what can be done?
* Either, use the transformer for a regulated power supply eventually based on a buffered LM317/337 design.
* Or, double or even triple the rectifier diodes, before the buffer capacitors in order to get a moderate reduction of the rectified voltage.
If you can do a small test: Connect the transformer to a rectifier bridge and to two buffer capacitors. Draw 100mA from each buffer capacitor and measure the two buffer capacitor voltages. Then, we can better tell you what to do.
Eventually, use the rectifier and the buffer capacitors from the Pioneer for this test.
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Two options if you really need to use that transformer.
Either you regulate down the output, a zener+a big darlington would do the trick. But you'll need some heatsinking.
Or you use a smaller transformer as bucking transformer, to reduce the voltage produced by the one you found. See Bucking Xfmrs
Either you regulate down the output, a zener+a big darlington would do the trick. But you'll need some heatsinking.
Or you use a smaller transformer as bucking transformer, to reduce the voltage produced by the one you found. See Bucking Xfmrs
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