transformer recommendations for powering an lm3886 amp + tone circuits?

[Cornholio]

I want to build an LM3886 guitar amp with a couple of tone circuits integrated into the head.  Most likely the tone circuits will be an:

Thor  http://www.runoffgroove.com/thor.html and a
professor tweed  http://www.runoffgroove.com/professor.html

Can I power all three (amp, Thor, professor tweed) with the same bipolar toroidal transformer or will I need a separate power supply to power the tone circuits as opposed to the power amp?

I'd like the power output as close to max for the LM3886 chip driving an 8 ohm speaker but I don't want it "sitting on the edge" of blowing it.  Any specific transformer recommendations would be greatly appreciated.

Thanks in advance.

[bry melvin]

my best suggestion for this project if you are not experienced would be to hunt junk amp that has useable voltages. And even some parts or circuits you can borrow or copy. Example the schematic I attached is a Fender Frontman 25 DSP

I just saw a lot of 5 of them on ebay for about 25 bucks yesterday

Note this amp was designed for 3876  some of them (later ones) and the frontman 25Rs actually had 3886s in them

[Cornholio]

So in that circuit :

  P8 = +27V DC
  P9 = ?
P10 = -27V DC

with P8 and P9 driving the power amp chip

  P3 = +11.5 DC
  P2 = +11.5 DC

These eventually powering the DSP, foot switch, and other incidentals

Is that right so far?

What does the VAC represent in the upper left hand corner of the attached picture?

Thanks in advance.

[bry melvin]

p 8 p9 p10 are AC from transformer with p9 the center tap. not DC till the diodes following in the schematic.

P2 and 3 are also AC from the second set of secodaries from the transformer.

The p 8 9 10 secondary set provide 2 voltages After the rectifier diodes  and filter capacitors you then have the +-27 and after dropping resistors and zeners you have +-12

P2 P3 windings go to a single sided power supply  rectifier dioes filters an provide 11.5 VDC to a 5 volt regulator for the DSP etc.

If you are using a stomp box low current preamp design you probably can get away with using the 11.5 VDC for the stomp box design preamp, You don't need the 5 volt portion of the circuit

and then use the other set seconaries circuit only as far as the +-27 Volt for your chip amp lm3886 power amp.

you won't need the 12 volt part of the circuit.


take a look at the power supply rectification guide on hammond transformers site.


with diode rectification  your 27 Volts comes from X (ac voltage) times 1.414 - approxiamtely a volt for the diode

Hammond explains it better than I do

so that transformer is approxiamtely 18 0 18 or 36VCT on one winding and approximately 9 volts on the other

[Cornholio]

OK,
 So the -+12V DC is powering what in the schematic?  I've attached a fragment of the schematic that show the region I can't figure out.  What function does this area of the schematic perform?  The direction of the arrows has me confused.  At first I thought it indicated the direction of electron flow but everything is exiting in this portion of the schematic  It looks like it takes +-12V DC and exits at the arrow on the bottom.  What is the significance of the arrows being solid vs. wireframe?  What does that arrow pointing down mean?  Where does it go?

Sorry for all the stupid questions.

Thanks for your help,  I really appreciate it.

[phatt]

Nothing is exiting anywhere.

The arrows are just pointers to the power rails.
The bottom arrow is Circuit Common.

That particular drawing is just to show the DC supply setup for the onboard chips.

You may want to learn more about how to read schematics before you venture into Amp building.
Phil.