Pultec EQP1A Equalizer

  
Inside:
Repository
This is about as close as you can get to a real vintage Pultec EQP-1a. Built from the original Pulse Techniques Pultec schematic with the layout designed around modern replacement parts (filter caps and trannys); and utilizing best practices regarding lead dress and component placement. Parts cost is around $1265 USD. I now offer a complete Pultec
Pultec EQP1A Equalizer - schematic

EQP-1a Kit for $1645 that includes upgraded filter section capacitors, a new master layout and 500 high-resolution assembly photos. The Pultec`s original Triad HS-56, HS-29 and Peerless S-217-D transformers would have been great, but sourcing them all is very difficult, primarily because of the rarity of the Peerless S-217-D output tranny. As the Peerless is so exotic, I didn`t really care about sourcing the input and interstage trannys because without the S-217-D, the point seemed moot. On the plus side, modern EQP-1a equivalents from Sowter have a much smaller footprint which facilitates a 2u rack chassis if desired - and the quality is artisan. For those inclined, the original Chicago PCC-55 power tranny does appear on eBay with some frequency and modest pricing. For the inductor, I chose Cinemag`s Pultec replacement CML-150T. Build notes: I separated the EQP-1a`s amplifier section from the Pultec passive filter circuit by way of two separate turret boards. The amp section is on the rear panel. This provided a nice way to route the filament wires in the upper corner of the rear of the chassis to keep things quiet as well as keeping the HT stuff away from the passive. One particularly interesting thing is that the 6x4 rectifier runs off the same 6. 3V filament as the 12ax7 and 12au7 tubes, and the power transformer rectifier 5V winding only powers the lamp. I ended up moving the interstage and input transformers to the...



Leave Comment

characters left:

New Circuits

.