1750W Hammond 100W Übertrager Fender TwinRev. 125A29A 022889

Hammond 1750W – 100 W Fender output transformer with a fixed 4 Ω output

The Hammond 1750W is a paper-wound push-pull output transformer providing 2 kΩ plate-to-plate, a fixed 4 Ω secondary and a 100 W transformer rating.

Hammond documents it for several large Fender amplifier families and references 125A29A, 022689, 022889, 022899 and 037612. The fixed 4 Ω output makes the total impedance of a multiple-speaker system particularly important.

Suitable applications

• Fender Twin Reverb amplifiers with a matching reference and 4 Ω total load
• Twin Reverb 65 Reissue amplifiers with a corresponding equipment version
• Bassman 100, Quad Reverb 100, Showman and Super Six Reverb 100
• Replacement applications for 125A29A, 022689, 022889, 022899 or 037612
• Parallel push-pull stages using four 6L6 or 6L6GC valves in total
• New amplifiers requiring approximately 2 kΩ and a fixed 4 Ω output

Technical data

Product type

Push-pull guitar-amplifier output transformer

Model

Hammond 1750W

Documented amplifier families

Bassman 100, Quad Reverb 100, Showman, Super Six Reverb 100, Twin Reverb and Twin Reverb 65 Reissue

Documented Fender references

125A29A, 022689, 022889, 022899 and 037612

Primary impedance

2 kΩ plate-to-plate with centre tap

Secondary impedance

4 Ω

Transformer power rating

100 W; not automatically identical to the rated output of the complete amplifier

Typical output-valve complement

Four 6L6, 6L6GC or compatible power valves in total

Output-stage topology

Parallel push pull with two valves in each half

Winding type

Paper winding

Primary inductance

Approx. 2.50 H at 1 kHz, 1 V and open secondary

Brown-to-blue primary DC resistance

Approx. 22.8 Ω

Black-to-white secondary DC resistance

Approx. 0.410 Ω

Primary leakage inductance

Approx. 1.31 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 1% at 70 Hz under the documented test conditions

Dielectric test

2,000 V RMS

Temperature range

-40 to +105 °C

Lead length

At least approximately 229 mm or 9 inches

Dimensions

Approx. 103.2 × 87.6 × 88.9 mm

Mounting dimensions

Approx. 88.9 × 63.5 mm, with further chassis dimensions shown in the manufacturer drawing

Mounting slots

Approx. 4.7 × 7.6 mm

Hammond shipping weight

Approx. 1.81 kg

Manufacturing note

Made in Canada according to the current component drawing

Lead connections

Blue

First primary connection to the first plate group

Red

Primary centre tap to B+

Brown

Second primary connection to the opposite plate group

Black

Secondary common or loudspeaker ground

White

4 Ω loudspeaker connection

Fixed 4 Ω design and multiple speakers

The nominal 2 kΩ plate-to-plate load is obtained with a total loudspeaker impedance of 4 Ω. Calculate the complete load where multiple loudspeakers use series, parallel or series-parallel wiring.

Two nominal 8 Ω speakers connected in parallel ideally provide 4 Ω. Four 16 Ω speakers connected fully in parallel also provide 4 Ω.

An 8 Ω total load on the fixed 4 Ω output would ideally reflect approximately 4 kΩ plate-to-plate and is not a normal substitute for the correct secondary tap.

Comparison with the Hammond 1760W and 1750WA

Hammond 1750W

Paper winding with a fixed 4 Ω output

Hammond 1760W

Paper winding with 4, 8 and 16 Ω secondary taps

Hammond 1750WA

Bobbin winding with 2, 4 and 8 Ω secondary taps

Safety notes

Lethal voltage and substantial signal levels are present on the primary. Install the transformer with complete touch protection on a sufficiently rigid chassis.

Questions about selection and use

Which output transformer suits a Twin Reverb using 125A29A or 022889?

Hammond 1750W is intended for these documented Fender references and provides 2 kΩ plate-to-plate, a fixed 4 Ω output, paper winding and a 100 W transformer rating.

Which 100 W output transformer suits four 6L6 valves with 2 kΩ plate-to-plate and 4 Ω?

Hammond 1750W is a suitable starting point for a correctly designed four-6L6 parallel push-pull stage requiring 2 kΩ plate-to-plate and a total loudspeaker load of 4 Ω.

Can the Hammond 1750W operate with a multiple-speaker load totalling 4 Ω?

Yes, the Hammond 1750W can operate with a correctly connected total load of 4 Ω. Verify the impedance of every individual loudspeaker and the complete wiring arrangement first.

Is the Hammond 1750W also suitable for references 022689, 022899 and 037612?

Yes, Hammond additionally lists the 1750W for 022689, 022899 and 037612. The chassis version, mounting, 4 Ω total load and lead routing must still correspond before installation.