The input stage of the EQP-1A features a transformer-coupled circuit, with a UTC-14A transformer providing a high-quality, low-noise interface for audio signals. The transformer is connected to a simple, passive circuit that provides a 1:1 gain ratio.
Before diving into the schematic, it’s worth taking a brief look at the history of the Pultec EQP-1A. The EQP-1A was designed in the 1960s by Eugene Pulte, the founder of Pultec, Inc. The unit was intended to be a program equalizer, capable of providing broad, gentle boosts and cuts to audio signals. The EQP-1A quickly gained popularity among audio engineers and producers, who appreciated its unique sound and flexibility. pultec eqp-1a schematic
The gain stage of the EQP-1A features a single tube (a 12AX7) that provides a high-gain, low-noise amplification of the audio signal. The tube is connected in a common cathode configuration, with a high-gain feedback loop that provides a stable, low-noise gain of approximately 40 dB. The input stage of the EQP-1A features a
