Depends on the DC voltage available.
If you have 12 volts use pins 4 and 5. Leave pin 3 o/c. (It will automatically 'reference' about half heater voltage so not floating.)
If you have 6 volts, use pin 3 and join pins 4 and 5 together for the other connection.
Just the same for AC of course.
Alan
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If your DC heater source already has a DC path to ground, something other than a capacitor somewhere in the entire heater circuit is connected to ground, then do NOT connect the heater tap to ground. Doing so could upset something like a regulator, or cause unwanted current flow somewhere. It's hard to tell what could happen without knowing how your DC is made, and how the transformer winding is connected.
If the entire heater circuit does not have any connection to ground, then one should be made. It makes no difference where if the heaters are fed pure DC as long as the HK ratings of all connected tubes are observed.
If the entire heater circuit does not have any connection to ground, then one should be made. It makes no difference where if the heaters are fed pure DC as long as the HK ratings of all connected tubes are observed.
Triodes have two 6Volt heaters, one for each triode. They can be wired in series for 12 V power but most often they are wired in parallel for 6.3VAC If you are using DC heater power to reduce the hum coupling into the audio, you probably want to use a 12VDC because capacitors for 12V are more efferent.
It is a good idea to ground the heater power, but not at the tubes since there are (usually) several. If the 6.3VAC buss has a Center tap on the power transformer, then use that , otherwise it should be grounded with a pair of capacitors, one from each side. Those caps should be about 0.1uF and only need to be 25V(AC). You may also want a couple resistors to bleed any DC, and those could be about 1K to 10K.
In any case, very few tube amps bother with this. Have fun playing with it.
It is a good idea to ground the heater power, but not at the tubes since there are (usually) several. If the 6.3VAC buss has a Center tap on the power transformer, then use that , otherwise it should be grounded with a pair of capacitors, one from each side. Those caps should be about 0.1uF and only need to be 25V(AC). You may also want a couple resistors to bleed any DC, and those could be about 1K to 10K.
In any case, very few tube amps bother with this. Have fun playing with it.
> Triodes have two 6Volt heaters, one for each triode.
Not "all" triodes. Nor "all" twin-triodes.
And 12B4 is a single triode.
You are correct that this tube (and many (but not all) with a heater tap) can be run as two heaters series or parallel at two different voltages. In this case (like 12AX7) it can be wired for 6V or for 12V.
Decide how you want to wire the heater (usually based on available heater supply). Don't go grounding heater taps recklessly.
Not "all" triodes. Nor "all" twin-triodes.
And 12B4 is a single triode.
You are correct that this tube (and many (but not all) with a heater tap) can be run as two heaters series or parallel at two different voltages. In this case (like 12AX7) it can be wired for 6V or for 12V.
Decide how you want to wire the heater (usually based on available heater supply). Don't go grounding heater taps recklessly.
Since the transformer CT is already grounded, do not add any other ground. Doing so could short out some of the rectification or filtering, and would cause an unwanted current path with AC current flowing in it. Not what you want for minimal hum.
AFTER the amp is up an running, if there is objectionable hum, you may try disconnecting the CT from ground and grounding the negative side of the heater supply. In theory it won't make a difference, but theory does not always predict minimal hum.
AFTER the amp is up an running, if there is objectionable hum, you may try disconnecting the CT from ground and grounding the negative side of the heater supply. In theory it won't make a difference, but theory does not always predict minimal hum.
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