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.

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.

I'm looking to buy an oscilloscope for working on solid state and tube audio projects(guitar and hifi related).  What MHZ minimum rating should I be looking for?  Any recommendations would be greatly appreciated.  Other considerations include single vs. dual trace.  Any brand or model recommendations?

What are your thoughts on these two products?

http://www.sparkfun.com/products/10244
http://www.seeedstudio.com/blog/2010/09/18/dso-quad-is-forming-make-a-wish/

I guess my max price range is around $200 U.S.  I've been looking at some on Ebay.  So many variables.  Some of the old ones seem to have really high starting bids.  Too bad oscilloscope prices aren't dropping like widescreen HDTV's.  I realize the above links are cheap 1 channel scopes with VERY limited MHZ ceilings but what actually does one need to analyze audio circuits for guitar amplifiers and home stereo equipment.

Thanks in advance.

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.

Quote from: polo16mi on March 11, 2011, 09:21:21 PM
I found Micron site at http://micronpower.com/products/selection_guide.php

Maybe you can find your model on that table and identify properly how much tension you can expect at terminals.

The picture posted looks like MD120-24-1 model.   Datasheet says that it has an adjustable output of 22-28 V

Here datasheet http://micronpower.com/pdf/MD120-spec.pdf

Hope help.

I bought this to power an lm3886t chipamp.  You are correct.  It is MD120-24-1.  I guess it isn't going to work because it's not a "bipolar"  power supply.  Is that the right terminology?

What do you mean by tension?

Am I correct in assuming the upper far left connector is ground?

Quote from: awdman on March 11, 2011, 09:02:25 PM
it looks to me that that is not a negative/postive power supply, just a positve rail.  hook your black to - and red to + and tell me if you get +24vdc.

Yes,  +24 vdc

I just picked up this Micron Dinergy power supply so I could start experimenting.  The secondary connectors are across the top as seen in the picture.  I'll label them as the following :  Ground plus1 plus2 minus1 minus2 (from left to right).

I hooked up the primary wire inputs(towards bottom of picture) to a standard US power cord as follows :  

L    connected to black
N    connected to white
GND  connected to green

I'm getting voltage readings I don't understand:

If I put black probe on ground and red probe on minus1 or minus2 I get -24 volts DC which is what I expected.

If I put black probe on ground and red probe on plus1 or plus2 I get 62 milivolts DC.  I was expecting +24 DC.

Any combination of minus to plus yields a + or - 24 volt reading.  Is the power supply functioning properly?

Any help greatly appreciated.