Single 12v and +-12v needed, What options?

[karmik]

Well you gave me a very nice news sir The dc/dc converter is not cheap (7 euros for one) but overall i believe it will be a cheaper solution.

42 milliamperes on each rail should be enough to drive an OPA2134 right?

[Mooly]

It will run several OPA2134 (10ma per package worst case) so no problems there.

[Andy5112405]

Originally Posted by karmik

That's what i thought!

Ok so, i worked a bit on the schematic and i think much of the incomprehension came from my poor skills rather than actual problems, i apologize for that.

To draw this schematic i copied information from:

• LM338 Datasheet for the single rail +12v part
• Rod Elliot's Project 43 - Ultra Simple Split DC Supply For the dual rail part of the schematic.
• I added bypass caps everywhere was suggested to but not shown in the schematic, that would be Ceramic Discs 0.1uF: C3 and C4 on the LM338 Regulator, and C8 and C9 on the supply pin of the opamp

So here is it, what did i get wrong this time?

Thanks for your feedback!

Just don't connect Virtual 0V to 0V because they are different DC potentials.

[Mooly]

Originally Posted by Andy5112405

Just don't connect Virtual 0V to 0V because they are different DC potentials.

Its not that easy as both are used as reference points for the audio... they have to be connected. Can't think of an easy way to explain it

[discrete]

Originally Posted by karmik

That's what i thought!


So here is it, what did i get wrong this time?

Thanks for your feedback!

As said before, it will work if you AC couple the pre-amp and power amp.
(Just fix the small error: R1/R2 junction should tie to the +IN, not -IN, of the opmps).

But if your brick can do +12V, the DC-DC convertor solution of Mooly is much more elegant.

[Minion]

If you can get a 12v AC transformer you can use a Voltage doubler and regulators to get your +/- 12v DC then use a seperate rectifier and regulator for your 12v DC for the power amp ......
The Preamp won"t use very much current so a voltage doubler would be suitable and there isn"t a problem with it sucking more from one rail .....


Cheers

[karmik]

I'll fix the schematic as soon as possible, but i think i'll go with Mooly's solution. Would it be a good idea to regulate the 2 rails after the dc/dc converter as well? or would that be overkill?

Best regards,

GC

[Mooly]

Originally Posted by karmik

I'll fix the schematic as soon as possible, but i think i'll go with Mooly's solution. Would it be a good idea to regulate the 2 rails after the dc/dc converter as well? or would that be overkill?

Best regards,

GC

You have many options... you could go with a 15/0/15 convertor and use 78and 79L12 regs. The 3 volts is sufficient headroom for these to work well.

You could just use a simple R/C filter feeding the opamp rails.

Or just use it "as is" with suitable caps on each rail.

Or again with a 15 volt reg you could use a resistor/zener/cap arrangement which in many cases for low currents is a very good option... this "shunt" arrangement is the one I use in my integrated amp.