Lead /Bass switch (1968 Super Bass)

bill bokey

Well-Known Member
Joined
Jul 23, 2011
Messages
261
Reaction score
323
I just installed (at buyer's request) a Lead / Bass switch on a 1968 Super Bass I recently sold.
As I did not want to drill any extra hole in the chassis I used the largest switch I have ever seen (6PDT!!!) :

xskYm4R.jpg


It's located in the extra preamp tube socket hole :

itzin1J.jpg



Here's a video I might today, plugged into a 1967 VOX AC100 2x15, loaded with Celestion G15V-100 Fullbacks (sorry it's too long and badly played)



Bass positon (stock) :
- shared cathode V1
- 22nF V1b coupling cap
- no bright cap
- unbypassed V2a cathode resistor
- 56k / 250pF tone stack
- 27k NFB

Lead position :
- split cathode V1 (2k7 / 680nF V1b)
- 2.2 nF V1b coupling cap
- 4n7 bright cap on volume 1
- 680nF V2a cathode capacitor
- 33k / 500pF tone stack
- 47k NFB

Ony NOS components were used and NO extra hole was drilled in the chassis. The amp can very easily be reverted to original.
 

junk notes

Well-Known Member
Joined
Dec 10, 2018
Messages
4,019
Reaction score
5,524
Very nice, sounds great. Good use of the preamp tube socket hole as long as there are no noise issues. I have a dual voltage switch on one of my amps, and that hex-switch dwarfs that. :shock:
 

EndGame00

Well-Known Member
Joined
Mar 4, 2013
Messages
5,328
Reaction score
3,561
Location
Bay Area, CA
My 25-watt Fargen Plexi also has a lead/bass rotary switch and it exactly does the same as yours....
 

Hopislove

New Member
Joined
May 28, 2022
Messages
1
Reaction score
0
I just installed (at buyer's request) a Lead / Bass switch on a 1968 Super Bass I recently sold.
As I did not want to drill any extra hole in the chassis I used the largest switch I have ever seen (6PDT!!!) :

xskYm4R.jpg


It's located in the extra preamp tube socket hole :

itzin1J.jpg



Here's a video I might today, plugged into a 1967 VOX AC100 2x15, loaded with Celestion G15V-100 Fullbacks (sorry it's too long and badly played)



Bass positon (stock) :
- shared cathode V1
- 22nF V1b coupling cap
- no bright cap
- unbypassed V2a cathode resistor
- 56k / 250pF tone stack
- 27k NFB

Lead position :
- split cathode V1 (2k7 / 680nF V1b)
- 2.2 nF V1b coupling cap
- 4n7 bright cap on volume 1
- 680nF V2a cathode capacitor
- 33k / 500pF tone stack
- 47k NFB

Ony NOS components were used and NO extra hole was drilled in the chassis. The amp can very easily be reverted to original.

Hey awesome mod here!

Do you think the switch would physically fit in the polarity switch of old export Marshall amps? I'm planning to build my Metro/ValveStorm and I'd like to have the switch more accessible.

Thanks!
 

bill bokey

Well-Known Member
Joined
Jul 23, 2011
Messages
261
Reaction score
323
Hey awesome mod here!

Do you think the switch would physically fit in the polarity switch of old export Marshall amps? I'm planning to build my Metro/ValveStorm and I'd like to have the switch more accessible.

Thanks!

I doubt it very much, see how big it is (next to a vintage Arrow DPDT switch)

ewFQG5h.jpg


Npk22N8.jpg
 


Top