1760L Hammond PP Übertrager Bassman 125A13A 022871 60W

Hammond 1760L – 60 W output transformer with 4.2 kΩ and 4/8/16 Ω taps

The Hammond 1760L is a paper-wound push-pull output transformer providing 4.2 kΩ plate-to-plate with secondary taps for 4, 8 and 16 Ω. Hammond lists it for compatible Bassman, Hot Rod DeVille and Concert II versions.

The documented principal references are 125A13A and 022871. Compared with the fixed-4-Ω 1750L, the 1760L adds two further loudspeaker taps.

Suitable applications

• Fender Bassman amplifiers using reference 125A13A or 022871
• Documented Blackface and Silverface Bassman chassis
• Hot Rod DeVille amplifiers with a matching equipment and transformer version
• Concert II amplifiers with a corresponding output stage and mechanical layout
• Push-pull stages using two 6L6GC, 6L6 or 5881 valves
• New amplifiers requiring 4.2 kΩ with a 4, 8 or 16 Ω total load

Technical data

Product type

Push-pull guitar- and bass-amplifier output transformer

Model

Hammond 1760L

Documented amplifier families

Bassman, Hot Rod DeVille and Concert II

Documented principal references

125A13A and 022871

Documented chassis families

Including 5F6, 5F6A, AA864, AA165, AB165 and AA270

Primary impedance

4.2 kΩ plate-to-plate with centre tap

Secondary impedances

4, 8 and 16 Ω

Transformer power rating

60 W on the current product page; the component drawing carries a 50/60 W marking

Amplifier topology

Push pull

Typical output-valve complement

Two 6L6, 6L6GC or 5881 valves in total at a suitable operating point

Winding type

Paper winding

Primary inductance

Approx. 5.72 H at 1 kHz, 1 V and open secondary

Brown-to-red primary DC resistance

Approx. 46.48 Ω

Red-to-blue primary DC resistance

Approx. 51.04 Ω

Total brown-to-blue primary DC resistance

Approximately 97.52 Ω

Secondary DC resistance at 4 Ω

Approx. 0.238 Ω between green and black

Secondary DC resistance at 8 Ω

Approx. 0.405 Ω between green and yellow

Secondary DC resistance at 16 Ω

Approx. 0.578 Ω between green and white

Secondary inductance at 4 Ω

Approx. 9.31 mH at 1 kHz and 1 V

Secondary inductance at 8 Ω

Approx. 18.15 mH at 1 kHz and 1 V

Secondary inductance at 16 Ω

Approx. 34.23 mH at 1 kHz and 1 V

Primary leakage inductance

Approx. 3.506 mH at 1 kHz, 1 V and short-circuited secondary

Frequency response

70 Hz to 15 kHz, 0/-1 dB referenced to 1 kHz

Distortion

Less than 2% at 70 Hz under the documented test conditions

Dielectric test

2,828 V DC

Temperature range

-40 to +105 °C

Lead length

At least approximately 229 mm or 9 inches

Dimensions

Approx. 103.2 × 80.0 × 88.9 mm

Mounting dimensions

Approx. 88.9 × 63.0 mm

Mounting slots

Approx. 4.6 × 7.6 mm

Hammond shipping weight

Approx. 1.81 kg

Lead connections

Blue

First primary connection to one output-valve plate

Red

Primary centre tap to B+

Brown

Second primary connection to the opposite output-valve plate

Green

Secondary common or loudspeaker ground

Black

4 Ω loudspeaker tap

Yellow

8 Ω loudspeaker tap

White

16 Ω loudspeaker tap

Selecting the loudspeaker tap

The selected secondary connection must match the total impedance of all connected loudspeakers. Insulate every unused lead separately.

An incorrect tap changes the primary load reflected to the output valves and can significantly affect output, distortion, plate current and valve dissipation.

Comparison with the Hammond 1750L

The Hammond 1750L has a fixed 4 Ω output with the same nominal 4.2 kΩ and 60 W ratings. The Hammond 1760L adds 8 and 16 Ω taps.

Interchangeability still requires matching mounting, lead routing, reference and feedback phase.

Comparison with the Hammond 1750M

The Hammond 1750M provides 2, 4 and 8 Ω taps. The 1760L instead provides 4, 8 and 16 Ω and is documented with paper winding and Bassman references 125A13A and 022871.

Safety notes

Lethal plate and signal voltages are present on the primary. Install the transformer with complete touch protection and adequate mechanical support.

Questions about selection and use

Which output transformer suits a Bassman or Hot Rod DeVille using 125A13A or 022871?

Hammond 1760L is intended for these documented Fender applications and provides 4.2 kΩ plate-to-plate, 4/8/16 Ω taps, paper winding and a 60 W rating.

Which 60 W output transformer suits two 6L6GC valves requiring 4.2 kΩ and several speaker impedances?

Hammond 1760L is a suitable starting point for a correctly designed two-6L6GC or 5881 output stage requiring 4.2 kΩ plate-to-plate and a total load of 4, 8 or 16 Ω.

Can the Hammond 1760L be used in a compatible Concert II output stage?

Yes, the Hammond 1760L can be used in a Hammond-documented Concert II version when the primary load, reference, mounting, loudspeaker load and feedback phase correspond.

Is the Hammond 1760L a suitable alternative to the Hammond 1750L?

Yes, the Hammond 1760L can replace the 1750L in a compatible circuit and adds 8 and 16 Ω taps to the fixed 4 Ω output of the 1750L.