Chuck D. Bones
Circuit Wizard
I bought a RAT 2 from Musician's Friend for $88. These days, RATs contain an OP-07 and are made in China. Just peeking in thru the battery door, the build quality looks ok. No premium parts. Cheap Chinese metal film resistors (the ones Tayda sells are much better). Aluminum electrolytic caps. The single-sided board is not nearly as nice as the ones Robert sells here. The stomp switch is smooth and not too loud. It has an LED indicator, something the older RATs lacked. It also has the industry standard 5.5mm center negative power jack. The heavy gauge steel chassis weighs a ton.
This is the output from the OP-07 with the distortion knob dimed:
Clipping is asymmetric and contains a lot of even-order harmonics.
The scope photo shows the slew rate:
The slew is much faster than the LM308 and is very asymmetric.
It actually sounds pretty good. At low DISTORTION settings, where the opamp runs clean, it sounds like a vintage RAT. With the DISTORTION turned up, the tone is "hotter" with a lot more harmonics. Not unpleasant, but not the perfect RAT tone either. I'll keep it this way for a while, but eventually I'll swap out the opamp and aluminum caps and dial-in the tone.
This is the output from the OP-07 with the distortion knob dimed:
Clipping is asymmetric and contains a lot of even-order harmonics.
The scope photo shows the slew rate:
The slew is much faster than the LM308 and is very asymmetric.
It actually sounds pretty good. At low DISTORTION settings, where the opamp runs clean, it sounds like a vintage RAT. With the DISTORTION turned up, the tone is "hotter" with a lot more harmonics. Not unpleasant, but not the perfect RAT tone either. I'll keep it this way for a while, but eventually I'll swap out the opamp and aluminum caps and dial-in the tone.
Last edited:
