Peavey Valve King 8 question

[Electron Tornado]

I picked up the chassis for a Peavey Valve King 8. Here is the schematic, which looks fairly similar to a VOX AC4: http://www.tremolo.pl/Firmowe/PEAVEY/ValveKing%20Royal%208.pdf

Here's a question:  What does R17 just before the volume control do? One mega-ohms seems like quite a bit of resistance in line with the signal.

[thermionix]

I reckon it's there to cut a little high end and volume.  The amp would work without it, but might get a little harsh.

[Electron Tornado]

I reckon it's there to cut a little high end and volume.  The amp would work without it, but might get a little harsh.

I'm thinking of getting rid of the stock tone control, and as much of that resistor as I need to, and try something like the tone control from a Traynor DH15H:  http://traynoramps.com/downloads/servman/sm_dh15h.pdf

[Electron Tornado]

Looking at the two schematics, it looks like I can remove the stock tone control and R17 from the Peavey and add the tone controls from the Traynor.

Here is a question: how do I determine whether a circuit (like a filter...like a tone control circuit) will create too much signal loss for the next gain stage to adequately amplify. OR, put another way, if I want to put a circuit in between gain stages, how much amplification will be needed to bring the signal level up to some desired level?   

I'm thinking I'll be fine with the EL84 since the Traynor uses a pair of 12AU7s for a 2 Watt power setting.

[GibsonGM]

You can simulate each tone stack/control with LT Spice etc., and note how much signal loss there is, to make a basic comparison of how each needs to be driven or recovered.   

Keep an eye on your source impedance (the Z of the stage driving it), probably a good idea to try to make that close to what you would really be using, or at least 'similar' (low or high).   

Note that if tone control taken from amp "A" was driven by Z impedance in that amp, and you change the impedance driving it in your amp "B", the control may need component adjustment to 'sound the same'.    Not a big deal but worth keeping in mind...

[Electron Tornado]

You can simulate each tone stack/control with LT Spice etc., and note how much signal loss there is, to make a basic comparison of how each needs to be driven or recovered.   

Keep an eye on your source impedance (the Z of the stage driving it), probably a good idea to try to make that close to what you would really be using, or at least 'similar' (low or high).   

Note that if tone control taken from amp "A" was driven by Z impedance in that amp, and you change the impedance driving it in your amp "B", the control may need component adjustment to 'sound the same'.    Not a big deal but worth keeping in mind...

The two 12AX7 stages in both amps are very similar, so I think impedance shouldn't be an issue. I should find a copy of LT Spice and learn how to use it as well.