Lumpy's Tone Shop Class A Overdrive


Lumpy's Tone Shop

Formerly the "Jelly Roll", the Class A Overdrive is based on a late 1950's Supro that featured the unique 6973 power tube in a single ended setup. It was more common to see a 6V6 in the small single ended Supros.  This one appeared to replicate the 1624T in a single ended setup

The Class A Overdrive uses JFET (Junction Field Effect Transistor) gain stages based on the amps own tube gain stages. I chose JFETs for their warm, but clear character when overdriven and superb dynamics which you will find the Class A Overdrive to be full of. The tones range from fat jazzy clean tones to a crunchy classic rock sound with hints of a British timbre. Unlike some of my other pedals, the Class A Overdrive isn't geared towards any particular recorded or artist's tone. However you'll find sonic shades of Keef, Page, Townshend and many more.


The Class A Overdrive has three controls for volume, drive and tone.

  • The volume control sets the output level of the pedal.  Unity gain is around 10 o' clock depending on where the drive level is set and it only gets louder from there making it usable as a boost too.
  • The drive control is what would be the volume control on the actual amp. At it's minimum, the tone is clean. As you turn the dial up to about noon you get that clean but dirty sound, think Communication Breakdown. Turn the drive all the way up and you'll find a harmonic rich overdriven tone. The drive levels are accurate compared to the acutal amp. There are no over the top high gain tones. You have clean, low gain, and medium gain.
  • The tone control is a simple, but effective high cut filter.  Same type found on the amp and numerous other Supro/Valco amps for that matter.  Turn it down and you'll decrease the high end content, turn it up and it gets brighter.  You will find the tone and drive controls are quite interactive.

The Class A Overdrive can run on 18 volts as well.  As you increase the voltage, the headroom and output level increase.

Electronics and Hardware

The Class A Overdrive is still made on veroboard consisting of Philips/BC Components capacitors, Switchcraft jacks and features true bypass switching.

There are two enclosure options available. The 1590B sized enclosure with side mounted jacks or the 125B sized enclosure with top mounted jacks. The enclosures are powder coated in a color of your choice, the colors shown are Sonic Blue and Plum Crazy.

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Where to find one?

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