I have a 48v supply to run a 48v amplifier however I have a pll in which case takes 12 to 15v. Now I want to hook this 12 to 15v pll to this 48v supply. Could anyone suggest the best 48v drop to 12 or 15v converter?


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Any way you choose to do this is wrong! If you use a resistive dropper and a zener regulator (for example), you'll be generating a huge amount of heat!

If you try a switched-mode dropper, you'll never be able to get rid of the switching noise completely.

You really need to put a second power supply in the box! When I was building 48V rigs, I used to use a toroid with a 18 - 0 - 18 secondary. I used the 36V, rectified and smoothed - unregulated - which gave around 49V on load. I used to wind an extra secondary on to the toroid, which gave about 11V, which was rectified and smoothed for about 15.5V DC, then went through an LM317 variable regulator for 13.5V for the exciter. It was a complete PITA to wind an extra secondary, but it was a relatively cheap solution.

What about low noise buck converters ?

Albert H wrote:Any way you choose to do this is wrong! If you use a resistive dropper and a zener regulator (for example), you'll be generating a huge amount of heat!

If you try a switched-mode dropper, you'll never be able to get rid of the switching noise completely.

You really need to put a second power supply in the box! When I was building 48V rigs, I used to use a toroid with a 18 - 0 - 18 secondary. I used the 36V, rectified and smoothed - unregulated - which gave around 49V on load. I used to wind an extra secondary on to the toroid, which gave about 11V, which was rectified and smoothed for about 15.5V DC, then went through an LM317 variable regulator for 13.5V for the exciter. It was a complete PITA to wind an extra secondary, but it was a relatively cheap solution.

I be as well to hook it up to my 48volt telephone line lol just joking. I was thinking of two separate supply's so I'll take your idea 48v supply for amp. 13.8v supply for the driver.

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rigmo wrote:http://www.n4ga.com/50v-to-14v-regulator/

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Two power supplies in the same box is the best solution, that’s how I’ve done it. Dropping 48v to low voltages is ok for very low current requirements eg bias networks etc... but really uneconomical for anything requiring more then that - the heat is too much to get rid of for such a large voltage drop. A buck converter will appear to work and is efficient with much less wasted energy and heat, however you then end up with the switching interference which causes spurs and other unwanted products.

This 1 works good 10amp

Tec1 87.5fm London wrote:This 1 works good 10amp

Seems ideal, I'm on to one of these nice find tec.

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You'll have spurs and whistles from that switching PSU. You'll make yourself very unpopular when your rig is "mostly" on the right frequency!

Albert H wrote:You'll have spurs and whistles from that switching PSU. You'll make yourself very unpopular when your rig is "mostly" on the right frequency!

Hmm I never thought about the switch mode on 48v power supply your right there about spurs. I'll have to look at a toroidal power supply build I reckon.

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If you've already got a 48 VDC power supply (I'm assuming it's one of those shiny silver switch-mode types) it makes no sense to go down the route and ballache of winding what will feel like a few thousand turns onto a toroid as you'd be replacing the PSU you've already got at great expense and additional weight.

You could buy a 12 V mains power supply like your 48 V one and if you get noise problems, buy a different one. Even one of those wall-warts can be made to work if you cut it open and solder the mains directly to the PCB inside the black plastic housing. I've done it before, it's an extremely cheap way of doing it. You could do it for about a fiver. It's extremely hit-and-miss but it can work.
If you buy an unregulated one it can be a very cheap source of a 12 V transformer, rectifier etc. as opposed to being switch-mode. Like this:

https://www.ebay.co.uk/itm/Unregulated- ... 2967536382

Failing that, build a small linear power supply for your 12 V (or whatever) rail - a small transformer (doesn't need to be toroidal), bridge rectifier and some smoothing followed by a 7812 or LM317.

nrgkits.nz wrote: ↑Tue May 19, 2020 1:27 pm Two power supplies in the same box is the best solution, that’s how I’ve done it. Dropping 48v to low voltages is ok for very low current requirements eg bias networks etc... but really uneconomical for anything requiring more then that - the heat is too much to get rid of for such a large voltage drop. A buck converter will appear to work and is efficient with much less wasted energy and heat, however you then end up with the switching interference which causes spurs and other unwanted products.

IS not the best but easier if we do not know how to solve the noise interference.. .
two PSU take a lot of space in the box !
RF Interference, fan noise etc can be solved with filter LC RC ... decoupling capacitors... shielded wire.
3A is more then enough to drive all fans exciter RDS stereo...

thewisepranker wrote:If you've already got a 48 VDC power supply (I'm assuming it's one of those shiny silver switch-mode types) it makes no sense to go down the route and ballache of winding what will feel like a few thousand turns onto a toroid as you'd be replacing the PSU you've already got at great expense and additional weight.

You could buy a 12 V mains power supply like your 48 V one and if you get noise problems, buy a different one. Even one of those wall-warts can be made to work if you cut it open and solder the mains directly to the PCB inside the black plastic housing. I've done it before, it's an extremely cheap way of doing it. You could do it for about a fiver. It's extremely hit-and-miss but it can work.
If you buy an unregulated one it can be a very cheap source of a 12 V transformer, rectifier etc. as opposed to being switch-mode. Like this:

https://www.ebay.co.uk/itm/Unregulated- ... 2967536382

Failing that, build a small linear power supply for your 12 V (or whatever) rail - a small transformer (doesn't need to be toroidal), bridge rectifier and some smoothing followed by a 7812 or LM317.

I've just used two psu supply's 48v supply and 12volt supply. But ran into an issue. I cranked up the Watts to around 120watts then it shut down. So then i thought amp failure. But no it was psu, so then I shielded the psu from the rest of circuit seems to be running OK. I reckon it caused this problem due to it been to near each other so shielding it seemed to work. So thanks for all your time and efforts much appreciated.

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