Switchable Superlead/Superbass

[sixpakldp]

Anyone know of a schematic that would allow you to switch between Superbass and Superlead? My amp is wired up as a Neil Special, which I have come back to after trying all the Marshall flavors. I have an extra hole from when I had a split/shared cathode switch that I need to use up. Was thinking it would be cool to have Superbass, Superlead and 2203 in one amp. I already have two out of three and like Meatloaf says, that ain't bad. But just curious if anyone else has considered this. Most go the other direction, more gain with the AFD addition. But I'm thinking the other direction.

[neikeel]

I've looked at this problem and not come to conclusion. Have two versions on the go now but am short of time.

The SB has shared cathode and 56k/250pF tone stack, all 0.022uF couplers up front but 0.1uF PI output couplers.

To do the switch properly would involve a new V0 with split cathode and a switchable tone stack (+/- cathode bypass cap on V2a), switching pi couplers would be tricky so a compromise value of 0.047uF or similar does work (I've tried it!).

You could compromise with the tone stack (47k/330 or 390pF)?

At present I have modded a 71 SB to have V1 a stock SB and V0 as a switchable 1959/2203 but keeping SB tone stack and PI. I have not finished it yet but have a back up plan to just use V1b with 25uF/1k5 cathode in SB mode and use V1a as switchable third gain stage before V2.

If you beat me to it let me know how you get on. Mine has to be finished by Christmas as it is part of my son's Christmas present (an orange hot-rodded 71 SB )

[sixpakldp]

You will beat me to it probably. I forgot about the 0.1 PI couplers. That would be an issue. On the pre amp side I was thinking it might me more than one switch. I've done a split/shared switch, the tone stack switch from the VH style mods could be simplified and then there are only a few more pieces to put together.

[coldengray]

I had a 1987 clone with switchable split/shared cathode and lead/bass tone stack, it worked great. If I recall it needed to be two switches to keep from oscillating. Mine had lead spec PI couplers but I like the idea of splitting the difference and going with .047 in there, great idea Neil!

[Doug H]

do .1 output caps really make much difference with a SL front end? I can usually hear a good difference with any of the cathode switches I've setup on V1.

[neikeel]

do .1 output caps really make much difference with a SL front end? I can usually hear a good difference with any of the cathode switches I've setup on V1.

I think it depends on how you play. My experimentation was mainly with a 50w and the 0.1s slow down the amp response making it feel a bit woolly under your picking hand if you are playing at moderate volume/gain settings, maxed out volumes and only playing big power chords the differnce is not as marked.

[sixpakldp]

I notice the change to 0.1 in the amount of attack on the bridge pickup (reduced on the larger caps) and the neck pickup gets flabby on the bottom and changes from a hollow woody sound to a more solid and wooly tone.

[ezietsman]

I did a 68 Plexi with switchable tonestack. One 3pdt switch that switches split -> shared cathode on V1 AND 33k -> 56k AND 500pf -> 250pF. Works like a charm. I used a slightly modified turretboard layout to fit in the extra components.

[herbvis]

I would say anything is possible with a little creative touch. Theres gotta be a way to safetly and correctly add caps in parrallel with a switch so you can get your tonestack value and pi couplings how you want them.

[Doug H]

I've implemented what would be better described as a superlead/bassman switch. I switch the mixer network between 470k/470k/500pf and 270k/270k...sort of. It's one of the more versatile mods I've ever tried.

[sixpakldp]

Check this out:

http://www.vintageguitar.com/wp-content ... 20_011.jpg

If you look real close you can see what appears to be .1 coupling caps with some smaller value (.022?) over top in the preamp section. These amps have a switch to modify bass response for single coil vs. humbucker. Guess there's a way in the preamp section.

[neikeel]

Sorry to be slow back

I did this for my son's Christmas present.

If I can wrestle it off him I will take some pics.

I went with stock SB power amp but used NOS Winged C 6550s with 120k grid leak Rs and 47k/8ohm NFB.

V1 cathode 1k5/22uF with Hi and lo inputs

V0 (added tube) is 0.68uF/2k7 into 8k2 via 0.022uF couplers.

470k/1800pF peaker combination into a gain pot (in lo input jack)

use channel 1 spot as pre-pimv and channel 2 pot as volume for normal channel

you can ABY across both channels pretty well.

I''ll post some pics at w/e

[white noise]

Sorry to be slow back

I did this for my son's Christmas present.

If I can wrestle it off him I will take some pics.

I went with stock SB power amp but used NOS Winged C 6550s with 120k grid leak Rs and 47k/8ohm NFB.

V1 cathode 1k5/22uF with Hi and lo inputs

V0 (added tube) is 0.68uF/2k7 into 8k2 via 0.022uF couplers.

470k/1800pF peaker combination into a gain pot (in lo input jack)

use channel 1 spot as pre-pimv and channel 2 pot as volume for normal channel

you can ABY across both channels pretty well.

I''ll post some pics at w/e

Very nice Neil!
A picture would be cool to see.