[holland]

Use the jack I linked above.  Your switchcraft 3.5mm jacks tie the 1 pin to the screw barrel.  Your case is at input and output ground level.
 
The -12 is actually 0, according to the wallwart.  The +12 is 24V according to the wallwart.  The TLE2426 splits it into half, creating -12V, VG (what is used as the 0 point for the opamp circuit) and +12V.  The opamp circuit uses the VG as the ground point, so it is elevated 12V above what the wallwart thinks is 0V.  It's just a bunch of reference points, and how you tie them together is what matters.  This is what makes it important to isolate.  You'll learn more as you do more.  Some of the isolation carries over to dealing with wall electricity (120V), where the case is "earth" and you need to isolate IG/OG/etc. and use things like ground busses or star ground.
 
If you fried your TLE2426, you'd smell it and you would no longer see -12V, 0V, 12V, but something else or nothing at all.

 

[Avro_Arrow]

I had this long, convoluted conversation with someone else about this...
 
Your wall wort is supplying 0 volts and +24 volts.
The TLE splits this into 0 volts, +12 volts and +24 volts.
Because everything is relative, if we use the +12 volts as our
ground reference, we effectively have -12 volts, ground and +12 volts.
The problem is that the output TRS jack and the power jack sometimes get
shorted together by a metal case. We have to pay close attention
to keeping the output TRS jack isolated from the power jack and maybe
even from the input TRS jack (or RCA) depending on design.

 

[nikongod]

It looks like the BUF-634 is buffering the ground channel. This is a nice touch, particularly in a CHA-47 type design.
 
If this is the case, the BUF634 will protect the TLE2426 from the destruction that the sorts of problems you are facing normally brings around.
 
It does sound like most of your problems come from conflicting ground references shorting against each other. I would solve them (isolated jacks AND floating power supply) The fact that nothing in the amp has gone smoky is just the BUF634's protection circuitry. Once you get the ground issues sorted out Id bet that the BUF634 will start to run reasonably cool.
 
As a temporary fix/test:
Disconnect the power input from the case. Fire up the amp. This will tell you if that is causing your problems quickly. If things get better get an isolated power input jack. 
 
The floating power supply is also advisable, particularly if you will be plugging this amp into things that have rigidly fixed ground references (most things that are plugged into the wall, actually) 

 

[holland]

If there is a buffer between the TLE2426 ground, then the output jack must be isolated (ala M3 picture).  Keep the input jack grounding the case, IMO.
 
Use this 3.5mm jack
 
 
in addition to the power jack I linked before.

 

[Mullet]

I'm using this layout that I found in another thread. Not sure of its origins but here it is...
 
Just out of curiosity, how does it compare to Ben Feist's A47? http://benfeist.com/a47/
 
If I were to guess, I'd say that the L and R channels are from the same opamp and the 2nd opamp is used to gain more current. Whereas Ben Feist's version has a separate opamp for each channel. Which layout is better?
 

 
More to come about the grounding solutions... and what everything means. Just need to get out of work and to the gym first.

 

[nikongod]

I personally prefer the layout you used and used the same on my old CHA-47 build. 
 
both channels in both opamps allows you to remove the second opamp to improve battery life in portable apps, and offers some flexibility in the inevitable opamp rolling. 

 

[holland]

I like the one you used as well.  Symettric, less jumpers/connections all over the place.

 

[Mullet]

 

holland -- Yes, the cleaner look and smaller footprint was why I chose it as well. Plus I wanted to do all of this in an Altoids tin. Thanks for the jack suggestions. I'm about to put in another order at mouser. Hrmmm this might be time to put in my parts order for a Gamma 2 I'm fixing to build.
 
Ok so now all of this is starting to make sense. Because the power supply and output jacks are grounded to different voltages they are shorting out. Thus we have to isolate these points so they don't conflict with each other. Other than getting new jacks is there a way to ground the dc jack that I'm currently using to the tin properly? I'm assuming it could be done, but isolation is preferred and it's at a reasonable cost. I'm thinking of going with two of the 3.5mm jacks that holland recommended just for aesthetic posterity.
 
Nikongod -- what is a floating power supply? I'm currently using this... http://bit.ly/hvcG4I 
 
I'll be sure to post my results. Thanks.

 

[Fred_fred2004]

This is my A47 in an Altoids tin I used a discrete rail splitter (korean guy whos name I can't spell)
 


 
I still have the layout if its any help, you'll just have to make a board
 
cheers
FRED

 

[holland]

Quote:

 

Other than getting new jacks is there a way to ground the dc jack that I'm currently using to the tin properly? I'm assuming it could be done, but isolation is preferred and it's at a reasonable cost. I'm thinking of going with two of the 3.5mm jacks that holland recommended just for aesthetic posterity.
 

 
No.  The DC jack is 0V and 24V.  The 0V of the DC jack corresponds to -12V in your amp.  Using the tin as 0V would make input ground (which sits at 12V) to short out to 0V, and you get trouble.  The DC jack must be isolated.
 
You *need* output ground isolated.  It is buffered via the buf634 and electrically is not the same point as the output of the rail splitter.
 
You can try using electrical tape as a patch.  Plug the dc jack into the amp before plugging it into the wall.  If your dc adapter is regulated you could blow some caps in the adapter on the discharge into the case, which is the sparks you are seeing.

 

[nikongod]

 
Quote:

Nikongod -- what is a floating power supply? I'm currently using this... http://bit.ly/hvcG4I 
 

It means that the power supply ground is not tied to ground at the wall.
 
Since that wallwart does not have a ground pin, and does not indicate any connections in the datasheet, I'd ASSUME that its a good contender but its always best to check with a multimeter. Unplug everything, and check if there is DCr from the output connections to the wall connections. If they all read as open your probably OK.

 

[Mullet]

Fred your layout looks slick. What is that orange thing you're using to separate the battery and pcb? Also, I know this is probably been addressed elsewhere in other threads, but what do you use to punch holes in your tins? I'm currently using a $5 single hole punch that I bought at Staples. It works perfectly for the switchcraft 3.5mm jacks I've been using. Then I use a circular file to make the hole where my Alps RK097 and power jack goes. The only tough part I have is making a hole for my lcd because it's smaller. I usually whip out a drill but have been having a hard time with it. I probably need a small piece of wood inside the tin to ensure a smooth hole when drilling. Do you drill your holes or use a hole punch? I might go down to Staples tomorrow and see if they have smaller hole punches.
 
Eventually, I'll graduate from Altoid tins and move up to making my own out of wood, metal, etc when I move to the burbs and have more room for more tools. Aside from that prefabbed cases are what I have to rely on. 

 

[Fred_fred2004]

The orange thing is a piece of folded cardboard

 
I use a single hole paper punch for the holes, and ream out to size, I find that if I use 5mm LEDS the hole puch is the right size for the led holder and it just snaps in.
 
I never use a drill on an altoids type tin they are just too thin, sometimes I use a stepped drill which give more control
 
cheers
FRED

 

[Mullet]

Fred - do you have part #s for what you'd use for LED, resistor, and LED housing from preferably Digi-Key (I'm buying some parts for a Gamma-2 in the near future). If not Mouser is fine.

 

[Fred_fred2004]

Sorry I have no idea about the part numbers, but if you PM your address I'll drop a couple of sets in the mail
 
cheers
FRED