Fender Deluxe 5E3 question

[MarkXXX]

This regards the tone stack.Would someone check my facts on the basic operation of the tone circuit.I understand that the two volume controls,that are for the instrument and normal channels, operate to control volume by "loading",in an adjustable way, the plate outputs of the first preamp tube.In other words the volume controls do not work as voltage dividers.The "output" therefore to the grid of the next preamp tube,the 12AX7, is the tone potentiometer itself.Unlike many amps where the volume pot is the "output" for the signal going to next tube.

This would be a big help to know if I have it right.I do know what loading means in the usual sense like a voltmeter can "load" a circuit during testing changing the voltages dropped from what they would otherwise be.

If there are any other unusual things about this tone circuit?

[fyl]

Check the thread here: http://music-electronics-forum.com/t8568/

[MarkXXX]

Check the thread here: http://music-electronics-forum.com/t8568/

Thanks for the thread.I first need answers to my basic questions above,that would help me understand correctly the information that's in that thread.That thread assumes a little more knowledge than I have at the moment on this topic. Mark

[martin manning]

You are correct that the 5E3 volume controls do not work like the usual voltage divider type. In this case, the output of the first stage is taken to ground, as opposed to the input of the second stage, as the volume control is turned down.

Either way the signal being fed to the second stage will be reduced, but here the AC load on the first stage is also reduced, which will alter its operation and tone quality, as in its distortion and frequency response. Ultimately this arrangement will prevent the first stage from generating any signal voltage at all, when the AC load is reduced to zero and the signal is shunted to ground.

The AC load on the first stage is primarily determined by the parallel combination of the tube's plate resistance in parallel with the plate load resistor, and the volume control resistance to ground (as if the 0.1u coupling cap were shorted). The tone control and the other stage's volume control are also involved, but at low volume settings the volume control will dominate. In the usual arrangement, the volume control's contribution is its entire element resistance, and the AC load remains more or less constant.

The tone control alternately bypasses high frequencies around the volume control of the bright input stage, or bleeds high frequencies from both inputs to ground. So, it makes both inputs "more bright" at the same time. With the bright input volume all the way up, only the treble bleed function is active (for both inputs) since the bright cap and the top of the tone control are shorted.

MPM

[MarkXXX]

Thanks Martin for the detailed explanation on your part.I'll go to work on that information and I should be able to understand it.

[MarkXXX]

just one more thing

regarding both bright and normal channels, which resistance(s) function as the "grid resistor" to the next preamp tube, the 12AX7?
In another thread, it was stated that both volume control pots ALSO function as a summing mode.What are they saying and does this have anything to do with the input signals into the next preamp tube, the 12AX7?

thanks, I hope somebody knows these answers.

[tubeswell]

regarding both bright and normal channels, which resistance(s) function as the "grid resistor" to the next preamp tube, the 12AX7?
In another thread, it was stated that both volume control pots ALSO function as a summing mode.What are they saying and does this have anything to do with the input signals into the next preamp tube, the 12AX7?

thanks, I hope somebody knows these answers.

Re: the grid leak resistance for the 1st half of v2, you have 2 x 1M in parallel, which is a 500k grid leak. (Is this what you are asking?)

[MarkXXX]

Yes, thanks.