Hello
I'm not an electrical engineer so please bear with me.
I'm refurbishing an old receiver amp (HK930) and would like to add some modern functionality 'under the hood'. I want to add a Raspberry Pi 4 and an Allo Boss v1.2 DAC preferably internally as there is space in the chassis to do so. The problem is supplying power to both. The RPi4 needs 5vdc 3A and ideally the DAC would get 5vdc 1.2A from a linear supply.
There is are unswitched & switched mains sockets on the back of the receiver for other parts of a separates system albeit one with the wrong plug for me in the UK. Unswitched would be ideal as I'd leave the RPi and DAC powered at all times and just have the receiver powered on/off from it's own power button.
My current thinking is to get a cheap off-the-shelf adaptor to take 230vac to 7-8vdc 5A and then filter it (LCRC?). It would then feed two separate power supplies in parallel. One SMPS to 5V 3A and one a linear regulator to 5V 1.2A.
Is this a valid approach? My main concern is having as little power as possible that needs to be dissipated by the linear regulator to limit heat output. Is there a better way of doing it or a good reason I shouldn't do as I've described?
Any help, advice, links or thoughts are greatly appreciated. Thank you in advance.
I'm not an electrical engineer so please bear with me.
I'm refurbishing an old receiver amp (HK930) and would like to add some modern functionality 'under the hood'. I want to add a Raspberry Pi 4 and an Allo Boss v1.2 DAC preferably internally as there is space in the chassis to do so. The problem is supplying power to both. The RPi4 needs 5vdc 3A and ideally the DAC would get 5vdc 1.2A from a linear supply.
There is are unswitched & switched mains sockets on the back of the receiver for other parts of a separates system albeit one with the wrong plug for me in the UK. Unswitched would be ideal as I'd leave the RPi and DAC powered at all times and just have the receiver powered on/off from it's own power button.
My current thinking is to get a cheap off-the-shelf adaptor to take 230vac to 7-8vdc 5A and then filter it (LCRC?). It would then feed two separate power supplies in parallel. One SMPS to 5V 3A and one a linear regulator to 5V 1.2A.
Is this a valid approach? My main concern is having as little power as possible that needs to be dissipated by the linear regulator to limit heat output. Is there a better way of doing it or a good reason I shouldn't do as I've described?
Any help, advice, links or thoughts are greatly appreciated. Thank you in advance.
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There is nothing wrong with your line of thought, however, the 5V linear regulator would need a minimum of about 8V at it's input.
Why not get a toroidal transformer 0-6 0-6 dual secondaries at 5A - ie 60VA.
Rectify and smooth both secondaries separately and regulate both to 5V.
Why not get a toroidal transformer 0-6 0-6 dual secondaries at 5A - ie 60VA.
Rectify and smooth both secondaries separately and regulate both to 5V.
Dual secondaries from a transformer would work nicely and help keep the power supplies separate; the RPi is going to introduce noise I'm sure.
Thank you, I'd not considered that.
Thank you, I'd not considered that.
There are ultra-low dropout linear regulators, 6V in 5V out ought to be possible, but you'll need to identify a suitable part and be careful to use the recommended caps with it.
Great advice everyone. After some thought and costing things I think an off-the-shelf 9V 5A SMPS as an input would work well.
I've put together this circuit diagram to work off based off of 2x LT1085 . What do you think? Would it benefit from adding inductors on each branch before it gets to the 10uF / LT1805?
Thanks
I've put together this circuit diagram to work off based off of 2x LT1085 . What do you think? Would it benefit from adding inductors on each branch before it gets to the 10uF / LT1805?
Thanks
