Norman86 wrote:
im just going to chip in with:
Shaun has the AFD, with attenuation straight from Marshall, so im pretty sure he knows whats going on in that department.
Shaun, what kind does the AFD use again? And how are the tubes biased in that amp?
Hi Norman,
All of the amps I have currently have some form of power/volume reducing trickery in them, and each is different.
The AFD100 has a Power Scaling system built in that Marshall developed themselves, based on other commercially available systems. The Power knob has a special pot with 16 trigger points along its rotation, allowing 16 different power settings between 0.1w and 100w. At each of these trigger points, the amp adjusts its bias to the optimal range for the plate voltage being delivered to the power tubes. This system is incredibly effective, even at the lowest wattage settings and truly allows the amp to be equally at home in the bedroom being played late at night at whisper volumes, or delivering its sonic roar from the stage in a stadium.
My Trainwreck Express clone has a VVR designed specifically for fixed bias amps. This VVR works similarly to the AFD100 Power Scaling system, except that it is totally variable, without fixed points around the controls rotation. Again, the bias is adjusted dynamically to be optimal for the voltage being supplied to the power tubes. Again, this system is very effective and the amp sounds great, down to relatively low volume levels. It doesn't go down to the low power levels that the AFD's system allows though.
My JMP's use PPIMV's. Initially I used the Lar Mar PPIMV design which works well to control volume down to "reasonable" levels. At bedroom levels it wasn't the greatest. Anything above about 1/3 on this MV control though sounds decent. A while ago I decided to try a different PPIMV design, as was demonstrated in that video I posted, and I haven't looked back. It sounds great and has all its character and tone on tap even at low volumes.
Of course, having recently moved house where my nearest neighbours are quite far away, and having a dedicated guitar jam room/man cave away from the main house, I no longer need any of this technology! ?
