I found this forum in my search for information about the Randall RG100ES. I appreciate all the information available, and have learned a lot. Finally, after fruitless interenet searching, I have decided to tentatively ask my first question.
As most RG100 users are aware the treble pull pot on this amp increases sustain, but results in noticeable volume drop. Reportedly, to combat customer complaints about this 'feature' Randall sold a product called a XP-3 Block Booster. This was to be connected between the signal out and speaker jack. These are fairly rare items to find for sale, and scouring the internet has only turned up external pictures of the unit. I cannot find any interior shots, schematics, layouts, or even a thorough explanation of what this box does. Any of the knowledgeable people here have this type of information, or guideance on how to clone one?
Just thinking aloud.
The "standard" distortion clips 2 back to back Zeners, to around 4 or 5 Vpp .
The distortion boost parallels with them a couple regular diodes, for 700mVpp , so distortion is increased 6X ... and signal level drops to 1/6 :( .
Unfortunately every gain stage is already running at max gain, there´s no "hidden reserve" to tap to compensate for that loss.
Only guessing here but unless you somewhat add an (active) 6x gain block into the path, (best would be just after the clipping diodes) , the *only* other stage where we have *some* extra gain is in the power stage itself, by lowering negative feedback by the same amount.
Not the best solution, it brings other problems with it, but I can´s imagine other solution.
*Or* you might add a clean boost, set to some 6X gain, in the effects loop.
*Or* plain use a distortion pedal in the loop.
Using a boost with these amps is the best way to get a great sound out of them. Any overdrive set with the level cranked and drive low in front of the amp will give you a much tighter, punchier sound than that treble pull feature does...which overly compresses the signal and muddies things up IMO.