In the early years of The Groundhogs, Cruickshank's bandmate Tony McPhee personally built amplifier cabinets for him, as stated by McPhee in this March 1, 2011 WFMU interview and on page 171 of London, Reign Over Me: How England's Capital Built Classic Rock by Stephen Tow.

WFMU's Beware of the Blog, "Split: A Conversation with Tony McPhee" by Alex Goldstein (March 1, 2011)

"Thank Christ For The Bomb" is one of my favorite albums. How did that record come together? Did you record it live in the studio? Is there a good amount of improvisation within the Groundhogs?

Following on from the last question when I heard "Oh, Well" by Fleetwood Mac I knew we had to record in the same studio because that was an incredible recording. In fact there was a Karlson Speaker cabinet which Martin Birch, who was the engineer there, told me was used by John McVie, that name again... This was/is an incestuous business! I used to make speaker cabinets for Pete Cruickshank at the time, in fact he used one on the album which is why I was so interested in the Karlson enclosure (too difficult for me to build at the time).

London, Reign Over Me: How England's Capital Built Classic Rock (2020) by Stephen Tow, Chapter 6, pg. 171

In 1966, the Groundhogs would morph into the psychedelic Herbal Mixture in 1966, but that fizzled out after a couple of years; they eventually re-formed the Groundhogs as a power trio by 1969. By that time, the blues boom was in full force. What distinguished this generation of blues from the earlier R&B boom? One word: “Heavier,” McPhee exclaimed. The evolving equipment, including the Marshall Super 100 head featuring 100-watt power, had something to do with it as well. “With the invention of the fuzz box used on the Stones’ ‘Satisfaction,’ [plus the Taste’s] Rory Gallagher had used a treble boost for ages, so changing or modifying the guitar sound was necessary even in the ’60s,” McPhee wrote me. “Heavier sounds was the next step, so amps and speakers had to get louder and bigger. I made or modified my own amps and made my own speaker cabinets. I made [bassist] Pete Cruickshank’s cabinets also.”