Looking for tube amp terminology

I've been studying a few tube pre circuits, collecting parts for a point to point build, reading a lot of threads and what not, and I keep running into some terminology that I kind of get but can't seem to find a really straight forward definition for.  For example...

Floating heaters
-I think this has to do with applying DC voltage to the heaters for the purpose of reducing hum.  I don't understand what this physically would be in a build.

referenced to ground
-I guess I have a hard time understanding what "reference" means in this context.  Does it mean connected?

potential
-like dc potential, another word i often use in conversation but am confused by in this context.

thanks!

If the heaters are floating just means neither connection is grounded.....same for say an output transformer......someone may come along and explain better than I can......

Potential .....possible voltage ......again someone will prob explain better than me, but I hope to have helped a little........

Floating heaters

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As Gary described, you lift it away from ground, eg. have one end of the filament at 100V and the other at 106.3V. It's now floating away from ground and less noise will be induced as a result.

referenced to ground

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This needs context, but it's often a term to decribe how a component is connected in some way to ground so that the potential developed is generated with respect to ground. That's not a great explanation. An example might make it more clear.

potential

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Voltage between to nodes. Eg. the potential between two nodes fed from a common source which sit at say, -4V and +8V would be 12V.

substitute said:

I've been studying a few tube pre circuits, collecting parts for a point to point build, reading a lot of threads and what not, and I keep running into some terminology that I kind of get but can't seem to find a really straight forward definition for.  For example...

Floating heaters
-I think this has to do with applying DC voltage to the heaters for the purpose of reducing hum.  I don't understand what this physically would be in a build.

referenced to ground
-I guess I have a hard time understanding what "reference" means in this context.  Does it mean connected?

potential
-like dc potential, another word i often use in conversation but am confused by in this context.

thanks!

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What it looks like in a build?

Take a look at the Pultec EQP schematic -

http://www.recproaudio.com/diy_pro_audio/diy_files/eqp_1a/eqp-1a_schem.jpg

Note the heater CT is at +60 VDC.  The heaters themselves are not DC but AC.  So floating doesn't mean the heaters are converted to DC. In this case it means they are elevated to a certain DC potential (voltage) with respect(referenced) to some other potential (voltage).  This usually means ground. So, into the 2nd question, referenced to ground means just what it says - any voltage that is measured with respect to ground(zero potential).  To clarify further, plate voltages are generally given in terms of being referenced to ground. They could be given as referenced to the cathode, that is, measured between plate and cathode.

So reference(d) does not mean connected - think of it as an arbitrary  'zero' point in which to measure a value between two points

Just think of potential as voltage. That's just what it is - a potential to do the work of delivering current.       

So, just to clarify a bit further (for my sake, maybe not the OP) in the pultec example, if the heaters are 6.3V, if you measured voltage at each end of the winding wrt ground, you'd have about 63.15 and 56.85?  3.15V either side of 60V, but still 6.3V wrt each other...  And this helps hum because there is no direct connection to ground?

mitsos said:

So, just to clarify a bit further (for my sake, maybe not the OP) in the pultec example, if the heaters are 6.3V, if you measured voltage at each end of the winding wrt ground, you'd have about 63.15 and 56.85?  3.15V either side of 60V, but still 6.3V wrt each other...  And this helps hum because there is no direct connection to ground?

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In the Pultec the heater winding is centre tapped & it is this point that is connected to +60v.  The signal on either end of the winding with respect to ground has both an a.c & a d.c component.  One superimposed on the other.

If the meter is set to read d.c volts, it wouldn't see the a.c component & should read around +60v d.c.  

If the meter was set to a.c it wouldn't see the d.c component & therefore read 3.15v a.c on either side.

In my understanding the heater is sometimes set at a voltage above 0v because the valve may be operating so it's cathode is quite a high voltage.  This would mean that you could have quite a voltage between the heater & the cathode which is often tubular & immediately around the heater.  This difference can make the valve unhappy & noisy or prone to hum.  A prime example is the regulator circuit in a Fairchild 670. where there is an EL34 and a 6084 valve.  They are both run from a separate heater winding that is set at 120v d.c

awesome guys, that's all very very helpful.