ROG Thunderbird with a dual supply?

[sajy_ho]

Hi guys, I'm trying to build a combo SS amp for my nephew and I'm thinking of a TDA2040 as the power amp with the Thunderbird as the preamp: http://www.runoffgroove.com/thunderbird.html

I'm planning to use a 12V-0-12V transformer(+- 16V DC)for the power amp, and use 12V + and - regulators for the preamp, so what changes should I apply to the original schematics so it can be powered using a 12V dual supply?
I'm a total newbie to opamp circuits, so any help will be appreciated...

Thanks
Sajad

[slacker]

All you need to do to run it on a dual supply is get rid of all the stuff relating to the LT1054 and vref, the whole lower section of the schematic. Connect +12 volts to pin 8 of the opamps and connect pin 4 of the opamps to -12 Volts instead of ground. Then connect all the points that are connected to vref to ground instead.
There's some caps and resistors that probably aren't needed if you run it on a dual supply but it will work fine with them left in.

[sajy_ho]

All you need to do to run it on a dual supply is get rid of all the stuff relating to the LT1054 and vref, the whole lower section of the schematic. Connect +12 volts to pin 8 of the opamps and connect pin 4 of the opamps to -12 Volts instead of ground. Then connect all the points that are connected to vref to ground instead.
There's some caps and resistors that probably aren't needed if you run it on a dual supply but it will work fine with them left in.

Thank you Ian, so how about the points that are already connected to ground, other than IC's negative supply? Should I connect them to -12V too? I mean like clipping diodes, etc..

[GibsonGM]

All you need to do to run it on a dual supply is get rid of all the stuff relating to the LT1054 and vref, the whole lower section of the schematic. Connect +12 volts to pin 8 of the opamps and connect pin 4 of the opamps to -12 Volts instead of ground. Then connect all the points that are connected to vref to ground instead.
There's some caps and resistors that probably aren't needed if you run it on a dual supply but it will work fine with them left in.

Thank you Ian, so how about the points that are already connected to ground, other than IC's negative supply? Should I connect them to -12V too? I mean like clipping diodes, etc..

It's easy to misinterpret what's up with a dual supply...you have PLUS 12, and MINUS 12....they are both voltages with certain magnitudes of their own...minus 12 isn't ground.  The point exactly 1/2way between them is!    That is zero.  That's where grounded things go in your schematic.

If you give it some thought, you'll see why this is - you are removing Vref, which was a bias point set to raise the incoming signal halfway between the power supply poles so it could go plus AND minus.  You arbitrarily set "minus" as ground in those circuits, but it doesn't HAVE to be.  It is just a COMMON (some circuits call ground common).

With a dual supply, you don't need to do this....the signal can "do its thing" with no help, going plus AND minus....so the zero crossing would be your new ground.    Your dual power supply must account for this, no?

[sajy_ho]

It's easy to misinterpret what's up with a dual supply...you have PLUS 12, and MINUS 12....they are both voltages with certain magnitudes of their own...minus 12 isn't ground.  The point exactly 1/2way between them is!    That is zero.  That's where grounded things go in your schematic.

If you give it some thought, you'll see why this is - you are removing Vref, which was a bias point set to raise the incoming signal halfway between the power supply poles so it could go plus AND minus.  You arbitrarily set "minus" as ground in those circuits, but it doesn't HAVE to be.  It is just a COMMON (some circuits call ground common).

With a dual supply, you don't need to do this....the signal can "do its thing" with no help, going plus AND minus....so the zero crossing would be your new ground.    Your dual power supply must account for this, no?

Oh! Now I get your point; so you're saying the 'Vref' is just there as only an artificial center bias point for Opamps and the signal ground is completely a different thing...
So as Slacker said all I need to do is just to replace all the 'Vref' with ground and connect the opamps' negative supply (pin 4) to -12V, right?
How about the extera parts that can be ommited with a dual supply?

[anotherjim]

Everything on the lower part of the scheme goes. But you will need to put bypass caps back in. 2 of everything because of the extra power rail.
As it's likely to be hardwired to supply, you don't need a protection diode, unless you don't trust yourself

I would feed + & - supplies via 100R with main bypass caps of 100uF with 100nF ceramic across them.
Tantalum caps were probably specified because they're supposed to be better than Alu electro's for suppressing hf noise from the switching regulator chip & you can use any type now it's gone.

If you can keep the op-amps placed close to the power input, you may well get by with just the power input caps -  but it's better to put a little more power bypass at the furthest part of the circuit from the input, say 10uF. Properly by the book, there should also be 100nF ceramics on each op-amp power pin to ground. Messy, since you need 2 of them per amp, but if you don't you may get HF instability. ROG have shown x3 1uF tantalum caps, these intended for each opamp pin8. You now need 6 of them if you want to copy the designers intention, but I think the 100nF ceramics are perfectly adequate.

You really might get away without regulating the pre-amp supplies, since it's all op-amp based & they are good at rejecting supply ripple, but I'd stick with regulating it if it isn't a production cost concern.

[sajy_ho]

Everything on the lower part of the scheme goes. But you will need to put bypass caps back in. 2 of everything because of the extra power rail.
As it's likely to be hardwired to supply, you don't need a protection diode, unless you don't trust yourself

I would feed + & - supplies via 100R with main bypass caps of 100uF with 100nF ceramic across them.
Tantalum caps were probably specified because they're supposed to be better than Alu electro's for suppressing hf noise from the switching regulator chip & you can use any type now it's gone.

If you can keep the op-amps placed close to the power input, you may well get by with just the power input caps -  but it's better to put a little more power bypass at the furthest part of the circuit from the input, say 10uF. Properly by the book, there should also be 100nF ceramics on each op-amp power pin to ground. Messy, since you need 2 of them per amp, but if you don't you may get HF instability. ROG have shown x3 1uF tantalum caps, these intended for each opamp pin8. You now need 6 of them if you want to copy the designers intention, but I think the 100nF ceramics are perfectly adequate.

You really might get away without regulating the pre-amp supplies, since it's all op-amp based & they are good at rejecting supply ripple, but I'd stick with regulating it if it isn't a production cost concern.

.
Thank you so much, so I guess I got all of the answers I needed and I'm ready to design the PCB.

Thank you all guys for all your help ...

[GibsonGM]

Come back and tell us how it sounds when you get it done!! 

[sajy_ho]

Come back and tell us how it sounds when you get it done!! 

Sure I will
Thanks