Inside the Big Lol GP2 Guitar preamp

Overal specs

The Big Lol GP2 guitar preamp is a versatile, 2 independent  channels guitar preamp, inspired by the input stages of guitar amps from various brands such as Carlsbro or Music Man and revisited by Big Lol. The main characteristics are :
  2 channels : The clean channel produces a sound range that varies from crystal to a crunch sound. The drive channel sound varies from overdriven to cataclysm. 
Each channel has its own input gain and volume controls
  12AX7 / ECC83 tube distorsion (drive channel)
  Versatile connections : 1 input per channel so that both channels can be  used simultaneously (a friend plays the bass on the clean channel when he comes to visit me) or, the standard configuration, one single guitar is connected to both channels that can be switched or mixed. 
  One three band (bass, trebble and parametric medium) equaliser per channel plus bright pre-emphasis circuitry.
  On FX loop per channel including dry/wet control
  Exclusive BLS (Big Lol Switching) system : FX insertion, crunch mode and channel selection can be controlled from both the preamp panel or a footswitch or any electronic circuit that has open collector outputs. On top of this, 2 channel switching mode are provided : either clean drive or clean / drive / clean + drive. Play the guitar with your teeth while your hands take care of the bass line !
  Second exclusive design : the Big Lol Output Filter ( BLOF ) shapes the sound at the output of the drive channel and offers a wide range of tones. Good news, it can be controlled from the preamp, a pedal (eg volume pedal) or any LF signal generator. Try it, it's a must hear.
  Master volume and 32 ohms phones output rated at a power that would blow up your hears. 
  Low noise design ... as long as you keep your hands off the guitar
To summarise, the BIG SOUND for VALUE

Block diagram

Take a look at the Big Lol GP2 guitar preamp block diagram below..
Click on the picture for more details on a block
Both channels have the same structure, that is : 

Input stage (gain and  Z adaptation) 
Bass  / trebble equalisation 
Parametric medium equaliser 
Overdrive and lowpass filtering 
Channel volume 
FX loop 

Then come the channel selector, the line output buffer (master volume) and  the phones output stage. A TTL logic module - part of the BLS system contols the various switches.
 Main frame | Introduction | Clean channel | Drive channel | Channel selector
Logic module | Power supplies | Wiring | Notes & Symbols | Schematics | Demos | FAQ
Big Lol