Pultec founders Gene Shenk and Ollie Summerland unveiled the first passive program EQ in 1951. Black tyxn knob are used for the Boost/Atten Pultec knobs. The On/Off knob is a small pointer knob we have in our collection too. The Triad HS 56 input trafo and the Triad HS-54 for the output are very rare and hard to get. Most people like to use Edcor XS1100 instead to replace those or for building similar passive circuit designs, for example the g-pultec or other highend diy equalizer.
knob Diameter: 61 knob materal：Phenolic with brass knob Shaft type:6.35mm or 6.0mm Set-Screw