What should i use for ground??

I am building the typical application circuit of a TDA2006 audio amp. I am connecting Vs+ and Vs- to the battery pack (or supply wall wart), but i dont know where or what to connect ground to. I have limited space, about 4x4x1 inches, i just need to connect things to a ground... any help is appreciated :)

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So, to summarize, you can split the battery pack to make the amp work with a split supply, if you do, at the expense of the splitting, you make the amp work to lower frequency, and you need fewer bits.

If you stick with a single supply, off a wallwart or suchlike, then you need to use the single supply circuit from the app note.
ChrisH52 years ago

can I just use a nut & bott. With the ground wire?

framistan6 years ago
Some amplifiers utilize a DUAL power source. That means a PLUS voltage for ONE... and a MINUS voltage for the other. Both go to a common GROUND point as pictured by astroboy97. If your chip calls for a V+, and a V-, AND a ground, then it is a DUAL supply. if your chip calls for just a V+, and a ground, then it is only a SINGLE voltage supply.
astroboy907 (author)  framistan6 years ago
so the modified battery pack would mimic a dual power supply?
astroboy907 (author)  steveastrouk6 years ago
So a perfect dual source supply would supply positive voltage (in this case 9v), negative voltage, and ground, so +9v, -9v, and +-0v (ground)?
last question- does this change battery life at all?

also will probably adapt it to 8aa, to get a better input

ok i was wrong, this is the last question- how would i do this with a wall wart or similar outputting 12v?
If you only have a single supply, the you have a couple of options

1) use an inverting DC DC converter chip to provide a negative rail
2) use a 6V regulator (see LM7806) to create a virtual com (you'd say ground)

the first solution has a potential problem in that most inverting dc dc converter chips introduce switching noise, and they're not all that cheap in general.

the second requires that you isolate the input side from whatever you're hooking it to (or more precisely "from"). This can be accomplished using differential input configuration for the amplifier. the 7806 isn't all that expensive, although they're not quite as easy to get as say a 7805, but they're out there. A cheat is to use a 7805, with the com lead tied thru a 1N4001 diode back to 0V, which boost it to ~5.7V, then use an offset adjustment at the amp to clean things up. However, you're down to a ~6V bipolar supply, which isn't all that ideal for something that really wants a 12-15V bipolar supply.

The speaker is then referenced to the 6V, as are any ancillary components that would normally go to "ground"

Now, if you happened to have a +24V wallwart, you could use a 7812 to create the common return (your "ground)

The one danger with this method is that if anything can provide a return path to the original power source and the speaker "negative" lead gets shorted to it, it will be shorting half the power supply voltage...that could spell trouble for the power supply

Much easier in the long run to either use a true single supply amp suitable for audio or use a bipolar supply, at least for the "novice" (no offense intended)
astroboy907 (author)  seandogue6 years ago
k. it looks like i will be trying the single supply circuit again. at least this time i have all the parts and will not have to improvise for a 22k resistor with pots :)

well a novice is what i am so no offense taken :)
1.) Exactly.
2.) No

And for your FINAL question.
3.) You're back to single supply, unless you add extra parts in a non-trivial way
astroboy907 (author)  astroboy9076 years ago
could i use v+ and v- on the wall wart, would i just leave the ground on the battery pack?
It would not only "mimic" one it IS one.
Make sure you use the single supply version of the circuit, and have a nice fat output capacitor. Ground is then Vs-, supply is Vs+.
astroboy907 (author)  steveastrouk6 years ago
i tried that, got absolutely nothing out of it.... how would i do it with the typical use circuit? use 2 supplys?
Yes, If you ran it on 6 AA batteries, the middle of two groups of three would be "ground", the +ve end would be your +ve supply, and the -ve end your negative supply.

The TDA2006 does not use a split power supply. The ground is the negative pole.
No it isn't, it works split rail or single supply. See datasheet and application circuits.
Yea, I went and looked at more diagrams. I've always used it with a single supply.
I tend to use it split rail, and you can get to lower output frequencies.
astroboy907 (author)  astroboy9076 years ago
or is it like a mains plug, a V+, V-, and ground?
astroboy907 (author)  steveastrouk6 years ago
cue very poorly made image:

like that? would i connect all grounds to there? (speaker gnd, 100nf cap gnd, and input gnd?)
Thanks for your quick replys :)
astroboy907 (author)  astroboy9076 years ago
hmmm. didnt upload....
That's right, you now have a split rail supply.
That diagram is wrong. The V- is the ground not the middle of your battery chain.
astroboy907 (author) 6 years ago
but i guess thats wrong, as AC is non-polar :)
If you're dealing with AC, the connections are Hot, Neutral, and Safety Ground. Safety ground gets connected ONLY to the case, to ensure that if the circuit shorts to case it blows the breaker before it fries you.