1645

Overview

The Hammond Manufacturing 1645 is a shielded push-pull audio output transformer designed for tube amplifier circuits. It features a primary impedance of 5,000 center-tapped ohms with a 128 mA rating and secondary impedances of 4, 8, and 16 ohms. The unit supports ultra-linear operation via screen taps and delivers a frequency response from 30 Hz to 30 kHz at full rated power. With a 30 W power rating and above-chassis X-mounting, it utilizes insulated flexible leads for straightforward integration into triode, pentode, or tetrode output stages.

Feature Summary

• Designed specifically for push-pull tube output circuits including triode, ultra-linear pentode, and tetrode configurations
• Includes 40% screen taps on the primary winding to enable ultra-linear operation when desired
• Enclosed and shielded construction minimizes electromagnetic interference in sensitive audio applications
• Features redesigned secondaries to facilitate easy hookup of various secondary load impedances

Applications

• Push-pull triode connected audio output stages
• Ultra-linear pentode and tetrode amplifier designs
• High-fidelity tube amplifier reconstruction projects
• Audio signal processing equipment requiring isolated output transformation

Procurement Notes

Verify that the specific variant matches the required secondary voltage configuration, as some sources indicate a 70V tap option exists alongside standard low-impedance outputs. Confirm lead length requirements against chassis depth constraints. Ensure the application circuit supports the 5k CT primary impedance and 128 mA current rating. Cross-reference datasheet specifications for frequency response tolerances relative to your target bandwidth needs before finalizing procurement.

Selection Notes

Select this component when designing push-pull tube amplifiers requiring a 5,000 ohm primary impedance. It is suitable for applications needing integrated shielding and ultra-linear capability via screen taps. Consider the physical dimensions and X-mount style for chassis compatibility. Verify that the 30W power rating aligns with the tube pair's output capabilities. This model replaces older iterations in the 1608-1650 series with improved secondary connectivity.

Part Context

The 1645 belongs to the 1608A-1650A series of ultra-linear output transformers from Hammond Manufacturing. These components are engineered for audiophile-grade tube amplification, offering enclosed shielding and above-chassis mounting. The series provides standardized impedance matching for common vacuum tube output stages, ensuring consistent performance across various high-fidelity audio reconstruction and design projects.

Replacement Considerations

This unit serves as an updated version within the 1608-1650 series, featuring redesigned secondaries for easier connection. No direct cross-manufacturer substitutes are documented in public sources. When replacing, ensure the new transformer matches the 5k CT primary impedance and supports the desired ultra-linear tap configuration if utilized in the circuit design.