18 watt tonestack

[geoff 1965]

Hello,
i found this layout and schematic for the 18 watt normal channel on a website with tonestacks but i can't match it to any in the forums downloads. is this the original marshall?

18watt-layout.gif

18watt-schem.gif

i would be interested in any feedback on this,the latest lite2b is a different configuration and does'nt have the resistor.
C1 =.01uf C2 = .005uf R1 = 100K

BN LITE2B LAYOUT.jpg

[Daviedawg]

The schematic for Ian's original Marshall 18 watt which is the basis for all the "original" 18 watts here, shows that the normal channel tone pot has a 100k resistor as the signal path between the vol and tone pots. The Trem channel does not have that resistor. It has a cap and another cap to ground.

The layout you show below the others is similar to the trem channel I think, but not the same.

So to answer your question no it is not for the 18 watt (not as we know it Jim). The Marshall design we know has one tone control with a resistor and one without. But in neither case does it work in the form shown in the layout you posted. But they both operate in a different manner. See download file 18 watt layout (original).

But I believe that there were variations. So anything is possible.

Dd

[geoff 1965]

18w Schematic.gif

this looks close Dd,it's Colin Macfarlanes 1966 18watt,the tone pot centre wiper goes to ground like the layout i posted.i was reading on a forum and some guy was saying he did'nt like the 18 watt tonestack because the volume & tone pots were too interactive and i wondered if he was referring to the very early marshall's like this one?

[Daviedawg]

Yes you're right Geoff. Just checked my file and the original normal channel pot goes direct to ground from the wiper. The trem channel goes through a cap.

Dd

[geoff 1965]

yeah so looking at both layouts you would think the latest lite2b with the tone wiper going to the volume wiper would be the most interactive?
has anyone tried the early tonestack in comparison to the later one?

[JMPGuitars]

yeah so looking at both layouts you would think the latest lite2b with the tone wiper going to the volume wiper would be the most interactive?
has anyone tried the early tonestack in comparison to the later one?

I'm certain it's all been tried. If you do enough digging through the site you might find the progression to get to where the lite 2b landed. Some people build their lite 2 amps with other tone stacks. I know some have used a 5E3 tone stack there with good results.

[geoff 1965]

BN LITE2B LAYOUT.jpg

just a further note on this lite2b tonestack,this is based on actual testing.some schematics say using a higher value cap across the vol/tone pots adds bass when in fact it's the opposite,22nf & 33nf cut bass and lower 4n7 & 2n2 added bass!

[Pressed_Rat]

BN LITE2B LAYOUT.jpg
just a further note on this lite2b tonestack,this is based on actual testing.some schematics say using a higher value cap across the vol/tone pots adds bass when in fact it's the opposite,22nf & 33nf cut bass and lower 4n7 & 2n2 added bass!

That is very similar if not identical to the vol/tone pots on a Marshall 20 watt 2061X. What I have found is the tone is indeed interactive with the volume. With the lead channel Vol on "1" out of "10" and the treble cranked, the amp is quite loud. Opening up the volume doesn't make the amp much louder, but brings up the bottom end.

[geoff 1965]

interesting!
so the "brown note lite2b" which i have used for the basis of my cage 18W is not the normal channel configuration,the tonestack is from the tremolo channel! there is quite a difference between the signal path of them,the trem comes from the plate through a .0047 then a 470K to ground then another .0047 to the vol/tone pots and the normal comes through a .01 and .0047 to the vol/tone pots but the tone wiper goes to ground. so at the moment i have .01 from the plate to the pots with no 470K to ground and no tone wiper to ground,might be time to do some experimenting.
does anyone know what the level of AC signal should be from the tonestack to the phase inverter?