Hello all...
A while back I hired Jacob Kokura to construct a PCB layout of a slightly modified version of the distortion channel from the Randall RG100ES. The slight modification is the addition of the "Voicing" section that was available in the Randall Century. (The RG100 and the Century 200 are the sound of Pantera). The schematic used was created by mensur and posted on another forum.
I've assembled one PCB and have signal passing and the unit mostly working. The lows and mids aren't reacting as they should and something seems wonky, but overall it's working. I could've wired something incorrectly or swapped values somewhere on the board.
Mensur's schematic
http://dl.dropbox.com/u/8772719/DIY/Men ... 0schem.jpg
Jacob's layout
http://dl.dropbox.com/u/8772719/DIY/JKMensurRandall.pdf
I figured since there are a lot of folks chasing the Dimebag/Crowbar/Down sound that this would be a cool project. I've been busy lately so if anyone would like to pick up where we left off...be my guest.
Randall RG100/Century - Semi verified
I took a stab at building this one dead bug style and actually it sounded nice. I surprised that the gain quality was good (no trim pots for biasing - different JFETs), I used:
(4) J201 JFETs
(2) TOSHIBA 1S1588 Silicon Epitaxial Planar Diodes for clipping
I just have one knob: Gain
Instead of a Master volume, a I have a voltage divider with 9.2k ohms one way, and 680 ohms the other, simulating the volume knob turned way down. Mids scooped out on the amp. I added a capacitor for smoothing on the power rails.
No tone stack at all. No end resistor either. No zener diodes.
Cacmcorder recorded audio *behind* the amp which is a partially openback. Volume on as low as the amp will go, making it a volume that can be talked over (you'll notice at the end I am actually talking over it - it's not loud)
That's it.
(4) J201 JFETs
(2) TOSHIBA 1S1588 Silicon Epitaxial Planar Diodes for clipping
I just have one knob: Gain
Instead of a Master volume, a I have a voltage divider with 9.2k ohms one way, and 680 ohms the other, simulating the volume knob turned way down. Mids scooped out on the amp. I added a capacitor for smoothing on the power rails.
No tone stack at all. No end resistor either. No zener diodes.
Cacmcorder recorded audio *behind* the amp which is a partially openback. Volume on as low as the amp will go, making it a volume that can be talked over (you'll notice at the end I am actually talking over it - it's not loud)
That's it.
Anyone happen to have the schematic from the OP?
I've got the original RG100 schem but would like to see how voicing section was added in. I've searched around but can't find the Randall Century schem to pinch the values/design from.
TIA.
I've got the original RG100 schem but would like to see how voicing section was added in. I've searched around but can't find the Randall Century schem to pinch the values/design from.
TIA.