• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Help with this schematic? B+? B++?

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Hey, i'm pretty new to building amps and other DIY electronics. I feel silly bringing this question to a forum with seasoned enthusiasts, but i did a fair amount of searching online but didn't find anything that was sufficient to help me.
this is the schematic i am dealing with:
http://i263.photobucket.com/albums/ii151/cameramanlink/AllAmerican4GuitarAmp-1.gif

i don't understand what B+ and B++ are.
i found a site that explains B+
The Power Supply

but it doesn't make sense to me with the transformer shown in the schematic. and it doesn't state what the "++" one would be.

once again, sorry to clutter up the board with "noob" stuff, but could someone shed some light on this for me?

thanks for any help.
 
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They are different voltage rails. Look at the PSU section. B+ is after the rectifier. This is the main HT supply and can supply most current. B++ is fed from this via a resistor and another smoothing cap. It's a cleaner supply but able to supply less current.

B+ and B++ goes to the appropriate parts of the main circuit. Using the B++ rail which is "cleaner" to supply the first (low current) stages will result in less hum and noise.
 
IT just indicates different B+ voltage points. ON some other schematic they could have called it B+a and B+b, or B+1 and B+2. SOme other schematic could have not even used the term B+ at all. They might label those points simply X and Y, and maybe Z if there was a third position. This circuit is fairly simple, on a more complex amp they might have five or six different B+ voltages, and each would get some sort of unique identifier label. So the next one might have been B+++. Don't read anything into the sysmbol itself, it doesn;t imply more positiveness or something, they could have used any symbol they wanted to.
 
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The 3K3 in combination with the 47uf form a simple filter. Any noise on the main HT line (on the 220uf) is attenuated by these two components and appears less on the 47uf. The 3K3 value limits the current that can drawn however. You could add yet another R and C to the right of these and make a still cleaner rail and so on.
 
got it. thanks again.

one more thing: the schematic calls for two 12av6 tubes. i have one of them, and i could pick up a second fairly cheap, but i already have a 12BA6 and 12BE6. i read in another forum that one of these might be used to give the amp more gain. is this true? and can it be done safely, or should i just shell out a few dollars for the 12AV6?
 
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