Hammond 124B 10K to 90K CT Nickel-Core Interstage Tube Driver
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Create Free Business AccountKey Features
- 49% nickel laminations for greater fidelity than the grain-oriented steel 124A
- 10K ohm primary to 90K ohm centre-tapped secondary, 5 W audio rating
- Frequency response 150 Hz - 15 kHz (+1/-3 dB) @ 1 kHz reference
- Primary inductance 65.38 H and leakage inductance 37.4 mH at 150 Hz
- 500 V RMS dielectric strength, temperature range up to 105 degC
- Open style with minimum 6" leads out and 0.19 in (5 mm) mounting holes
- For push-pull or phase inverter drivers; not for single ended use
- RoHS and REACH compliant
The 124B is a 5 watt tube driver interstage transformer for push-pull and phase inverter tube driver circuits. It is aimed at amplifier builders, restorers and OEM engineers who need a general purpose or replacement interstage part with a 10K ohm primary and a 90K ohm centre-tapped secondary.
What sets the 124B apart from the 124A is its core: it uses 49% nickel laminations for greater fidelity, where the 124A uses grain-oriented steel. The drawing lists typical DC resistance of 405 ohms ±20% on the primary (RED-BLUE) and 1525 ohms ±20% on the secondary (GRN1-GRN2), with the ordering table giving 403 ohms and 1500 ohms. Dielectric strength is 500 V RMS and the temperature range is up to 105 degC.
Measured at 150 Hz and 2.0 V, primary inductance is 65.38 H with an impedance of 71.46 kOhms, and leakage inductance is 37.4 mH. Frequency response is 150 Hz to 15 kHz (+1/-3 dB) referenced to 1 kHz.
The unit is an open style transformer with flying leads (the drawing states a minimum of 6 inches) and a 0.19 in (5 mm) mounting hole. Outline dimensions are A 2.38 in (60 mm), B 1.35 in (34 mm), C 1.43 in (36 mm) and D 2.00 in (51 mm). The drawing lists a weight of 5.9 oz; shipping weight is 1.2 lbs (0.54 kg).
Note that the 124B has no air gap for DC bias current, so it is not recommended for single ended applications. It is RoHS and REACH compliant.
Ideal For
- Push-pull tube amplifier interstage driver
- Phase inverter tube driver circuits
- Replacement interstage transformer in valve audio equipment
- High-fidelity tube audio builds needing nickel-core interstage
Overview
| Style | Open style |
| Series | 124 Series Tube Driver - Interstage |
| Description | Transformer, tube driver, interstage, 5 watts, for push-pull circuits |
| Part Number | 124B |
| Circuit Type | Push-pull or phase inverter tube driver circuits |
| Primary Leads | Minimum 5" long |
| Single-Ended Use | Not for single ended applications; no gap for DC bias current present in SE mode |
| Short Description | AUDIO TX |
| Frequency Response (Series) | Minimum 150 Hz - 15 kHz (+1/-3 dB) @ 1 kHz |
Dimensions
| A | 2.38 in (60 mm) |
| B | 1.35 in (34 mm) |
| C | 1.43 in (36 mm) |
| D | 2.00 in (51 mm) |
| Weight (Drawing) | 5.9 oz |
| G - Mounting Hole | 0.19 in (5 mm) |
Electrical
| Audio Watts | 5 |
| Lead Colours | Primary RED, BLU; Secondary GRN1, BLK (C.T.), GRN2 |
| Output Power | 5W |
| Primary Impedance | 10K ohms |
| Frequency Response | 150 Hz - 15 kHz (+1/-3 dB) @ 1 kHz reference |
| Dielectric Strength | 500 V RMS |
| Secondary Impedance | 90K ohms C.T. |
| DCR RED-BLUE (Typical) | 405 ohms ±20% |
| DCR GRN1-GRN2 (Typical) | 1525 ohms ±20% |
| Primary Inductance RED-BLUE | 65.38 H @ 150 Hz, 2.0 V OC |
| Primary DC Resistance (Table) | 403 ohms |
| Leakage Inductance PRI RED-BLUE | 37.4 mH @ 150 Hz, 2.0 V SC |
| Secondary DC Resistance (Table) | 1500 ohms |
| Primary Impedance RED-BLUE (Measured) | 71.46 kOhms @ 150 Hz, 2.0 V OC |
Identifiers
| UPC | 623980241968 |
| UNSPSC | 39121301 |
Packaging & Shipping
| Shipping Weight | 1.2 lbs (0.54 kg) |
Construction & Finish
| Leads | Minimum 6" leads out (drawing) |
| Style | Open style |
| Laminations | 49% Nickel |
Environmental & Protection
| Temperature Range | Up to 105 degC |
Compliance & Certifications
| RoHS Compliant | Yes |
| REACH Compliant | Yes |
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Frequently Asked Questions
What is the difference between the 124B and the 124A?▾
The 124B is the same as the 124A except that it uses 49% nickel laminations for greater fidelity; the 124A uses grain-oriented steel.
Can the 124B be used in a single ended amplifier?▾
No. The unit has no gap for DC bias current present in SE mode and is not recommended for single ended applications. It is designed for push-pull or phase inverter tube driver circuits.
What are the impedances of the 124B?▾
The primary is 10K ohms and the secondary is 90K ohms centre tapped, with a 5 W audio rating.
What frequency response does it have?▾
150 Hz to 15 kHz (+1/-3 dB) referenced to 1 kHz.
How is it mounted and how long are the leads?▾
It is an open style transformer with 0.19 in (5 mm) mounting holes; the drawing specifies a minimum of 6 inches of lead out.
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