Great thread! Ive been watching the internet for years on the topics of load boxes and attenuators, but only just found this.
My stuff is on the Marshall Forum:
Background Passive attenuators are wired between the amp output and the speakers. Their function is to absorb most of the output power of the amp, feeding a smaller amount to the speaker itself. This allows the amp output stage to run at higher power, letting the glorious tone of a good valve...
marshallforum.com
(huge thread, but post#1 has the key info)
It focusses mainly on attenuators rather than load boxes, but it was heavily inspired by the Aiken design and particularly
@James Freeman 's TGP thread. My lightbulb-moment was to find how extend that thinking to accurately scale down the signal to the speaker, while keeping tone intact.
I also needed cab impedance info, and Mike Lind on TGP has some great files, including a G12M 1960 cab.
I have previously made some graphs available showing the impedance curve of some well-known and not so well known devices. I thought it would be easier to have them in the same thread so here they are. Brake Lite is the latest addition even though it is not technically a reactive one. Load...
www.thegearpage.net
For the attenuators, we found that the bass resonance circuit wasnt too important, since theres a real cab involved which can do it itself. But we have an option for one anyway. Its more important when its a load box
On this thread, what type of caps are you using? The big film caps are best, but big and expensive? Some designs use bipolar electrolytic, but I worry about ripple current ratings.
