1750U Hammond 100W Übertrager JCM800 JMP 1,7k Marshall AÜ

Hammond 1750U – 100 W Marshall output transformer with 1.7 kΩ

The Hammond 1750U is a bobbin-wound push-pull output transformer for documented 100 W Marshall JMP and JCM800 output stages. It provides 1.7 kΩ plate-to-plate with 4, 8 and 16 Ω secondary taps.

Hammond lists P-TM0100 as the comparison reference. Its low primary impedance is intended for a parallel push-pull output stage using four output valves in total.

Suitable applications

• Marshall JMP amplifiers with a compatible 100 W output stage
• Marshall JCM800 amplifiers in a corresponding 100 W chassis version
• Replacement applications around comparison reference P-TM0100
• Parallel push-pull stages using four EL34 or 6CA7 valves in total
• Total loudspeaker loads of 4, 8 or 16 Ω
• New amplifiers requiring approximately 1.7 kΩ in the 100 W transformer class

Technical data

Product type

Push-pull guitar-amplifier output transformer

Model

Hammond 1750U

Documented amplifier families

Marshall JMP and JCM800

Hammond comparison reference

P-TM0100

Primary impedance

1.7 kΩ plate-to-plate with centre tap

Secondary impedances

4, 8 and 16 Ω

Transformer power rating

100 W

Typical output-valve complement

Four EL34 or 6CA7 valves in total

Output-stage topology

Parallel push pull with two valves in each half

Winding type

Bobbin winding

Primary inductance

Approx. 8.85 H at 1 kHz, 1 V and open secondary

Blue-to-white primary DC resistance

Approx. 15.36 Ω

White-to-red primary DC resistance

Approx. 16.56 Ω

Total blue-to-red primary DC resistance

Approximately 31.92 Ω

Violet-to-green secondary DC resistance

Approx. 0.320 Ω across the complete 16 Ω winding

Secondary inductance at 4 Ω

Approx. 22.59 mH

Secondary inductance at 8 Ω

Approx. 47.54 mH

Secondary inductance at 16 Ω

Approx. 88.86 mH

Primary leakage inductance

Approx. 7.97 mH at 1 kHz, 1 V and short-circuited secondary

Frequency response

50 Hz to 12 kHz, 0/-1 dB referenced to 1 kHz

Distortion

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

Dielectric test

2,160 V RMS

Temperature range

-40 to +105 °C

Lead length

At least approximately 279 mm or 11 inches

Dimensions

Approx. 95.2 × 100.0 × 116.8 mm maximum

Mounting dimensions

Approx. 83.3 × 71.5 mm

Mounting slots

Approx. 5.2 × 9.5 mm

Hammond shipping weight

Approx. 3.63 kg

Manufacturing note

Made in Canada according to the current component drawing

Lead connections

Blue

First primary connection to the first plate group

White

Primary centre tap to B+

Red

Second primary connection to the opposite plate group

Violet

Secondary common or loudspeaker ground

Orange

4 Ω loudspeaker tap

Yellow

8 Ω loudspeaker tap

Green

16 Ω loudspeaker tap

Four output valves and current sharing

The 1.7 kΩ primary load applies to the complete parallel push-pull stage. It must not be interpreted as the load of one individual EL34.

Verify all four quiescent currents. Individual control-grid and screen-grid stoppers together with a sufficiently capable bias and power-supply section support stable operation.

Comparison with the Hammond 1750N and 1750Q

Hammond 1750U

1.7 kΩ, 100 W and four output valves for JMP or JCM800 applications

Hammond 1750N

3.2 kΩ, 50 W and typically two EL34 valves for JMP or JCM800 applications

Hammond 1750Q

7.371 kΩ for the substantially different JTM45 or P-TM450 application

Safety notes

High and immediately lethal voltages may be present on the primary. The heavy transformer requires mechanically secure installation with complete touch protection.

Questions about selection and use

Which output transformer suits a 100 W Marshall JMP or JCM800 using P-TM0100?

Hammond 1750U is intended for these documented Marshall applications and provides 1.7 kΩ plate-to-plate, 4/8/16 Ω taps, bobbin winding and a 100 W rating.

Which 100 W output transformer suits four EL34 valves requiring approximately 1.7 kΩ plate-to-plate?

Hammond 1750U is a suitable starting point for a correctly designed four-EL34 parallel push-pull stage requiring 1.7 kΩ plate-to-plate and a total loudspeaker load of 4, 8 or 16 Ω.

Can the Hammond 1750U be configured for 4, 8 or 16 Ω?

Yes, the Hammond 1750U has dedicated secondary taps for 4, 8 and 16 Ω. Use only the tap corresponding to the actual total loudspeaker impedance.

Is the Hammond 1750U suitable for a newly built 100 W EL34 amplifier?

Yes, the Hammond 1750U can be used in a new amplifier when the 1.7 kΩ load, four output valves, supply voltages, quiescent currents, driver capability and feedback circuit suit the design.