1760C Hammond SE Übertrager Champ Bronco 125A35A 022905 5W

Hammond 1760C – 5 W SE output transformer with 5/8 kΩ and three speaker taps

The Hammond 1760C is a single-ended output transformer for classic small valve guitar amplifiers. A primary tap provides approximately 5 or 8 kΩ, while the secondary offers 3.2, 8 and 16 Ω connections.

Hammond documents the 1760C for Bronco, Champ, Vibro Champ, Harvard and corresponding early Princeton circuits together with references 125A35A, 022905 and 125A3A.

Suitable applications

• Fender Champ 5C1, 5E1, 5F1 and related versions
• Fender Vibro Champ AA764 and compatible chassis versions
• Fender Bronco AB764
• Harvard and early Princeton applications using a suitable output stage
• Single-ended 6V6 stages requiring approximately 5 or 8 kΩ
• New amplifiers using 3.2, 8 or 16 Ω loudspeakers

Technical data

Product type

Single-ended guitar-amplifier output transformer

Model

Hammond 1760C

Documented amplifier families

Bronco, Champ, Princeton, Vibro Champ and Harvard

Documented references

125A35A, 022905 and 125A3A

Primary impedances

Approx. 5 or 8 kΩ plate load

Secondary impedances

3.2, 8 and 16 Ω

Transformer power rating

5 W

Amplifier topology

Single ended

Typical output-valve complement

One 6V6 or compatible valve at a suitable operating point

Maximum primary DC

40 mA; a transformer limit rather than a universal target for every circuit

Winding type

Bobbin winding

Primary inductance at 5 kΩ

Approx. 16.2 H between red and brown at 1 kHz and 1 V

Primary inductance at 8 kΩ

Approx. 23 H between red and blue at 1 kHz and 1 V

Primary DC resistance at 5 kΩ

Approx. 272.08 Ω between red and brown

Primary DC resistance at 8 kΩ

Approx. 359.90 Ω between red and blue

Secondary DC resistance at 3.2 Ω

Approx. 0.278 Ω between black and yellow

Secondary DC resistance at 8 Ω

Approx. 0.624 Ω between black and green

Secondary DC resistance at 16 Ω

Approx. 1.491 Ω between black and white

Leakage inductance at 5 kΩ

Approx. 583 mH at 1 kHz with the secondary short-circuited

Leakage inductance at 8 kΩ

Approx. 719.5 mH at 1 kHz with the secondary short-circuited

Frequency response

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

Distortion

Less than 1% at 70 Hz under the documented test conditions

Dielectric test

1,750 V RMS

Temperature range

-40 to +105 °C

Lead length

At least approximately 229 mm or 9 inches

Dimensions

Approx. 71.5 × 39.6 × 42.7 mm

Mounting centres

Approx. 60.3 mm

Mounting-hole diameter

Approx. 4.7 mm

Hammond shipping weight

Approx. 0.25 kg

Primary and secondary connections

Red

Common primary connection, normally connected to B+

Brown

5 kΩ primary tap to the valve plate

Blue

8 kΩ primary connection to the valve plate

Black

Secondary common or loudspeaker ground

Yellow

3.2 Ω loudspeaker tap

Green

8 Ω loudspeaker tap

White

16 Ω loudspeaker tap

Selecting the primary load

The 5 kΩ connection tends towards greater plate current and output-valve loading. The 8 kΩ connection requires greater voltage swing and can support a more conservative operating point.

Select the connection from plate voltage, quiescent current, valve type and intended output. The 6V6 designation alone does not determine whether 5 or 8 kΩ is correct.

Comparison with the 1750C and 1760CP

Hammond 1750C

Bobbin winding with a fixed 3.2 Ω output

Hammond 1760C

Bobbin winding with 3.2, 8 and 16 Ω taps

Hammond 1760CP

Paper winding with 4 and 8 Ω secondary connections

Safety notes

Lethal plate voltage is present on the primary. Insulate the unused primary tap separately and install the transformer with complete touch protection.

Questions about selection and use

Which output transformer suits a Champ, Vibro Champ or Bronco using 125A35A or 022905?

Hammond 1760C is intended for these documented applications and provides 5 or 8 kΩ plate loads, 3.2/8/16 Ω taps, a 5 W rating and up to 40 mA primary DC.

Which SE output transformer provides 5 or 8 kΩ for one 6V6 with several loudspeaker impedances?

Hammond 1760C combines two primary loads with 3.2, 8 and 16 Ω secondary connections and is a suitable starting point for a correctly designed 6V6 single-ended output stage.

Can the Hammond 1760C operate with an 8 or 16 Ω loudspeaker?

Yes, the Hammond 1760C has dedicated 8 and 16 Ω taps. The selected 5 or 8 kΩ primary connection must also suit the output-valve operating point.

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

Yes, the Hammond 1760C can be used in a compatible 1750C application when the primary load, mounting and winding phase correspond; it additionally provides 8 and 16 Ω secondary taps.