Lake Placid Blues
New member
Re: Really digging hot rodded Marshall tones... Soldano, SPlawn, others?
The Silver Jubilee is Marshall's take on this theme. I saw an interview with Steve Grindrod, Marshall's design engineer from the mid 70s until the 2000s. He said he used two LEDs instead of just plugging in an extra 12AX7 into the circuit and tweeking from there like almost everybody does, because they could not get decent 12AX7s that would work in a high gain circuit on consistent basis at the time. So he used his own LED clipper circuit he had been messing around with.
Elsewhere I learned some specific technical things pertaining to the LED clipper circuit used only in the Silver Jubilee. It is set up to cause an asymmetric clipping of the signal, or it clips only one side of the wave form. Asymmetric clipping promotes a lot of even order harmonics, even more than all tube.
However, the tone can be inconsistent from amp to amp because of the tolerances of the LEDs and also the bypass cap around the LED circuit. This is why some may sound buzz saw like and others very organic.
There are some unique aspects that stem from the use of LEDs. One is, that because the voltage must be brought low, the FX loop works really well with guitar level devices. Another factor from the voltage requirements is that the voltage must be built up again afterward. This is why the tone stack is plate follower instead of the usual cathode follower. The tone stack itself is much like that found on a Hiwatt instead of on a plexi. The volume on the Silver Jubilee is much more controlled than say a 2203. It doesn't start to get really loud until the master is up around 6 or 7 at which point your starting to get the power amp involved, so its not all preamp when the amp is really starting to sound good, but your able to have the amp sound good at more moderate volume if needed.
The Silver Jubilee is Marshall's take on this theme. I saw an interview with Steve Grindrod, Marshall's design engineer from the mid 70s until the 2000s. He said he used two LEDs instead of just plugging in an extra 12AX7 into the circuit and tweeking from there like almost everybody does, because they could not get decent 12AX7s that would work in a high gain circuit on consistent basis at the time. So he used his own LED clipper circuit he had been messing around with.
Elsewhere I learned some specific technical things pertaining to the LED clipper circuit used only in the Silver Jubilee. It is set up to cause an asymmetric clipping of the signal, or it clips only one side of the wave form. Asymmetric clipping promotes a lot of even order harmonics, even more than all tube.
However, the tone can be inconsistent from amp to amp because of the tolerances of the LEDs and also the bypass cap around the LED circuit. This is why some may sound buzz saw like and others very organic.
There are some unique aspects that stem from the use of LEDs. One is, that because the voltage must be brought low, the FX loop works really well with guitar level devices. Another factor from the voltage requirements is that the voltage must be built up again afterward. This is why the tone stack is plate follower instead of the usual cathode follower. The tone stack itself is much like that found on a Hiwatt instead of on a plexi. The volume on the Silver Jubilee is much more controlled than say a 2203. It doesn't start to get really loud until the master is up around 6 or 7 at which point your starting to get the power amp involved, so its not all preamp when the amp is really starting to sound good, but your able to have the amp sound good at more moderate volume if needed.
