I am building an amplifier project which requires -50 and +50 VDC supply. I intend to use it in my van so need to run it from 12 to 15 VDC source. Boost converters I see are mostly non-isolated....
isolated ones are prohibitively expensive for my project. I need around 15A.
Isolated boost are several hundred dollars where as non isolated are 20 dollars online. Weird question maybe..Is there a way to isolate a pair of non isolated boost converters..? So I can get my plus and minus voltages..or any other way I can get my supply voltage...I can run an inverter then a centre tapped transformer then a rectifier but is there a better way ? I would prefer to build something rather that just buy an inverter

 

Either way, you will need an inverter.
Using a 12VDC to 120VAC inverter looks like the easiest solution.

 

Dual isolated batteries is one simple way to use non isolated converters but then you need a way to recharge the isolated batteries from van power.

 

You can use non-isolated converters if one of them is designed to output +50V and one to output -50V.
Unfortunately it may be difficult to find an over-the-counter one that can output the -50V.

You do realize that drawing 15A from two 50V supplies will require over 125A from your 12V source?

 

You do realize that drawing 15A from two 50V supplies will require over 125A from your 12V source?

sorry my mistake, I made an error in my calculation.
7.5A peak in total when amplifier operating at full power..
nominal draw would be around 2 - 3 Amps continuous

 

nominal draw would be around 2 - 3 Amps continuous

Okay.
That will draw a minimum of 17A-25A from your 12V battery.

 

I believe 12v based (car) amplifiers typically do it with a switching power supply that uses a center tap transformer. For an example, see if you can find the schematic for Phoenix Gold MS-250 or MS-275 amplifier (or probably any other car amplifier). I've got the MS-250 myself and the high side of the transformer gives +/-40V, so 80Vpp. That would be a good starting point.

 

The Mackie subwoofer SWA1501 uses a 100VDC supply with a high power virtual ground, creating the isolated +/- 50V supply. You could use that idea with a 12V to 120V inverter to get what you need. The schematic for the thing is available on their website. E

 

I have an amplifier that claims 200 watts per channel out with 12 volts at 20 amps supply current. The whole package was less than $200, so the transformer for the inverter supply can't be terribly expensive. There are lots of published designs and circuits for such supplies. Check the "schematicsforfree" website, under "power", and under "automotive" for circuits.
AND, an inverter is simpler to get working than a switching power supply.