Putting the distortion back!

Homemade Valve Overdrive for Hammond T-202

Homemade Valve Overdrive for Hammond T-202

The classic Hammond Organs of the 60’s all had valve amplifiers, as did the Leslie speakers they usually played through. Played loud, you got a bit of overdrive resulting in a gentle warm distortion. The clean sound of the later Hammonds can be great (like Tony Banks with Genesis) but sometimes you just need that dirty sound! I found an easy to make valve overdrive on instructables aimed at guitar distortion and with a little help modified it to be more suitable for my organ – here’s what it sounds like!

 

How to do it

Spot the valve

Spot the valve

To construct the homemade valve overdrive I used the instructions for Valve Caster 2 and also referenced Matsumin’s Valve Caster which has a clearer schematic. The differences between the two made me brave enough to experiment with the resistor values to lower the amount of distortion and gain which is better for keyboards than the heavy distortion wanted by some guitarists. I also got some good advice from my friends Andy Williams and Chris Gandy so special thanks to them. If you want specific detail, or more information message me – I’ll be glad to help.

To put the homemade valve overdrive in circuit to work with the Hammond’s inbuilt speakers I had to break into the signal chain – pin 8 on the amplifier board is where I broke in – feel free to contact me if you want help doing the same thing!

Rats Nest

Rats Nest

Rats Nest

I built the homemade valve overdrive without any circuit boards – a so called “rats nest” its a bit messy but it works!

Inside the Pre-amp

Inside the Pre-amp