Maybe its me but I always thought the AC Booster sounded a bit too "wooly" in the low end and it lacked enough mids to make it really "sing". Right now I have 4 clipping diodes (2 pairs of 4148 diodes) in mine and a OPA2134PA opamp and I think it is an improvement over the stock sound but the low end still seems a bit "muddy".
Anybody have any suggestions on mods to clear up the wooly low end and also improve the mids? I was thinking about swapping the electrolytics in the signal path with metal film caps and maybe lowering their values a notch.
Hi guys, I have to say that I degooped my AC and RC boosters and my pcbs are not like the one Rota has published, but the AC and the RC PCBs are just the same thing with some different components. I will leave three picture here of both units. Mi IC was sanded to, but I can perfectly read the transistors. I will post the exact kind tomorrow, and if you need any values let me know and I´ll post them.
Roa - The pics you posted are of the latter-day layouts by Xotic - the pics/layout-version earlier in this thread are of the older type - there are at least three, with the first two layout/versions being single board, most similar to the first one in this thread.
It's the same circuit, just a diff layout/configuration to take advantage of the small/board-mounted pots, et al.
A little OT - one of my fave RC Booster tweaks is to add yet another pair of diodes to the FB loop - small but noticable diff @ stage volume.
Vref setup I would build it different. A NPN EF transistor buffer can "turn on" more than the 10K can pull down and you have the VBE drop that is a good fraction of the 9VDC supply. I would offset Vref 1 more to +9 in other words flip the resistors Vref 2 would still be about 1/2 and Vref 1 would be at the two resistor node but closer to 9Vdc.
How stable is the input buffer bias with a 2SC1815 and a 1meg R3? If I wanted a 1meg R3 I would use a higher hfe transistor in that section or make R3 a 470K and R1 a 10meg.
Is R2 as 10K in the circuit just to add noise?
The output buffer goes to Vref 2? If both go to Vref2 as drawn I would get rid of C10 and R16 and wire the base to the volume wiper but you could have wiper noise when adjusting the circuit.
Look at the 3 tran the input buffer is offset more to +9
Thanks for the link. Now the vref makes sense MAYBE they copied it from the BOSS FET input for a 2sc1518. Changed a couple resistors and caps in the tone section and added clipping diodes.
The stock boss circuit looks very good, well thought out IMO.