Because the band was used to playing small hops and school dances, many of the members found themselves ill-equipped with the amplifiers that they were currently using.

Bassist Norm Sundholm discovered that his bass amp was not nearly powerful enough to play larger concert halls.

By 1965, the demand for Sundholm's amplifiers had increased to the point where the family garage could no longer be used as the manufacturing facility.

Throughout the original Sunn Amplifier line they employed Dynaco designed and built transformers (up to the 120 watt MK VI transformer set) and Hafler based power amp designs until Sunn stopped producing the original line of tube amplifiers in favor of the solid-state Concert and Coliseum models.

[citation needed] The stated intent was to both revitalize the Sunn amplifier lines and to produce some Fender-branded models as well, which included the Standard Series (Princeton Chorus and Ultra/Ultimate Chorus, both solid-state) and M-80 Series, and are identified as USA-made amplifiers with an "LO"-prefix serial number.