Which Cut control should I use?

[leaveitalone84]

Hey all,

While I cut down on a lot of the brightness in my build with some NOS tubes there is still a little too much. I dont want to change speakers because I like their interaction and tone. I also dont want to tweak with the tone stack because I like how the amp sounds....

So which Cut schematic should I use? The AC-15 seems popular but should I use those values? What are the values in the Komets? I just need a little bit taken off the top. Not too much. I've done a search through the archives here and didn't find a lot of info.

Thanks all!

[Firestorm]

Have you tried playing with the value of the snubber cap (fizz cap) across the plates of the PI? A lot of hi end adjustment is possible there.

[gearhead]

Try the one used for the Rocket; .047 uF and 250k pot. I haven't, but know of at least one board member (whom I hold in very high esteem) who has, with great results.

FS - the snubber cap; the 50 pF? I've always wondered what that one was for.

[leaveitalone84]

Gearhead is that a Log of Audio pot?

I haven't played around with the fizz cap yet. Since I have the extra hole in my chassis for another pot, I figured id rather have the ability to tweak for different guitars, tubes, cabs, and rooms.

For instance my Les Paul is too bright, but my Dot is slighty dark.

[Firestorm]

FS - the snubber cap; the 50 pF? I've always wondered what that one was for.

GH -- I'll reply here in case anyone else is interested. This is an OLD trick used in tweed Fenders (but it predates them) to stabilize an amp by cutting high frequencies in the output stage. Because the outputs of the PI are out of phase, a small value cap (47pF-50pF) connected between them forms a high-pass filter that allows high frequencies to pass from side to side, allowing them to phase cancel. I didn't work it out, but 47pF will operate on VERY high frequencies (the ones that create dog-hearing oscillations). Use 100pF, 150pF, 250pF and so on and you can reduce high end at any point you want. I forget if the cut will be 3dB down or 6dB, but it won't kill them all; just attenuate them by 3 or 6dB per octave. This is not adjustable, obviously, (although it is essentially the same idea behind the Vox high-cut circuit, which is placed a little later in the circuit.)

[ODwan]

Standard Vox Cut circuit is 250kAudio pot and 4n7 cap in series across the gridleak resistors of the powertubes. It's also used in the Komet. I used it on my Express and Liverpool clones and it's great! Slightly alters the tone even when dialed out. Use 1Meg pot or make it switchable to minimize this effect.
You can also play with cap values!
Timo

[leaveitalone84]

Standard Vox Cut circuit is 250kAudio pot and 4n7 cap in series across the gridleak resistors of the powertubes. It's also used in the Komet. I used it on my Express and Liverpool clones and it's great! Slightly alters the tone even when dialed out. Use 1Meg pot or make it switchable to minimize this effect.
You can also play with cap values!
Timo

Just what I wanted to hear! Maybe I'll try a no load pot so when I dime the sucker it'll be pretty transparent.