why a 22k presence pot?

[12AX7]

My amp as i have said is a take off on a 2204. But the power section is pure 2204 aside from slight PSU differences. (cap values) So any idea why they use a 22k presence pot when mine is 5k and gives me the full range? What i mean is from full brightness when i turn it down, at about 10 or 11:00 on down to full counterclockwise there is not perceivable change. What  might account for a 2204's presence running the full range from max brightness to min brightness all within the last say 10% of it's rotation? I'm using the same config as the 2204 with a 100k NFB resistor off the 4 ohm tap.

[navdave]

Using a 4.7k shunt resistor and a 25k pot gives you a much
wider sweep of the presence control and stability than using a 5k
pot by itself. As long as your using a long tail pair.

[12AX7]

Like i was saying, it's power section is like a 2204 except the 5k pot. So it does have that 4.7k resistor,  assuming you're talking about the one thats in parallel to the presence pot and cap.

[The_Gaz]

I'm not sure I understand the question, but there are two Marshall presence arrangements. One replaces the tail resistor with a 5k pot, and the other puts a 25k pot in series the presence cap in parallel with the tail resistor to vary the amount of NFB in the selected frequencies.

The former has a better taper, while the latter prevents DC on the pot and a scratchy sound when turned. I prefer to split the difference with the later arrangement, but with a 5kL or 10kL pot in place of the 25K.

Using a 4.7k shunt resistor and a 25k pot gives you a much
wider sweep of the presence control and stability than using a 5k
pot by itself. As long as your using a long tail pair.

Can you please explain why the later Marshall method gives more stability?

I have to disagree about the wider range thing, because n practice with most circuits a 25k pot does just about nothing for most of its rotation.

[jojokeo]

Can you please explain why the later Marshall method gives more stability?

I have to disagree about the wider range thing, because n practice with most circuits a 25k pot does just about nothing for most of its rotation.

I believe what was meant is that "stability" = better/finer control w/ the 25k pot and it's not the range in what you hear but rather the pot's control range that's created by the divider ratio w/ the higher value.