Hammond 125C 8 W Universal Push-Pull Tube Output Transformer
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Create Free Business AccountKey Features
- 8 W push-pull output with 1,200 to 25,000 ohm CT primary range
- Secondary solder lugs 1-6 match 1.5 to 15 ohm speakers
- 45 mA max DC bias per side; 5.60 H primary inductance
- Temperature range -40 to 105C; 1500 Vrms dielectric strength
- Typ. 1.0 dB response from 100 Hz to 15 kHz
- Open style, 2.81 x 1.50 x 1.69 in, 0.5 lbs
- RoHS and REACH compliant, made in Canada
The 125C is an 8 watt universal push-pull "classic" tube output transformer, built for general purpose or replacement use (not Hi-Fi) in push-pull tube output circuits. Amplifier techs and hobby builders can use it to replace an unknown or hard-to-find output transformer, because its tapped secondary covers a wide span of impedances.
The secondary is brought out to solder lugs numbered 1 to 6. Connecting a speaker between different lug pairs produces a total primary impedance, blue wire to brown wire, between 1,200 and 25,000 ohms for voice coils of 1.5 to 15 ohms. An 8 ohm speaker on lugs 3&5 reflects 17,600 ohms; the same speaker on lugs 1&6 reflects 3,000 ohms.
Ratings for the 125C are 8 audio watts and a maximum of 45 mA DC bias per side, with a primary inductance of 5.60 H in the ordering table. Typical drawing values are 285 ohms primary DCR (blue - brown), 4.40 H primary inductance and 25.5 kOhm primary impedance at 1 kHz, 1 V. Dielectric strength is 1500 Vrms and the temperature range is -40 to 105C. Typical response is 1.0 dB from 100 Hz to 15 kHz, and the label is marked 100Hz - 30kHz.
The 125C is an open style unit with primary leads at least 5 inches long (BLU plate, RED B+, BRN plate). It measures A 2.81 in (71 mm), B 1.50 in (38 mm), C 1.69 in (43 mm) and D 2.38 in (60 mm), with 0.19 in (5 mm) mounting holes, and weighs 0.5 lbs (0.23 kg). It is made in Canada and RoHS and REACH compliant; for single ended designs, see the 125SE Series.
Ideal For
- Replacement output transformer for push-pull tube amplifiers
- Push-pull tube output stages up to 8 W
- Matching tube outputs to 1.5-15 ohm speakers
Overview
| Series | 125A-125E Series Universal Push-Pull Tube Output |
| Application | General purpose or replacement use (not Hi-Fi) in push-pull tube output circuits |
| Description | Audio transformer, universal push-pull tube output, 8 watts |
| Part Number | 125C |
| Short Description | AUDIO TX OUTPUT SE OR PP |
| Single-Ended Alternative | For single ended use, see the 125SE Series |
Dimensions
| A (Overall) | 2.81 in (71 mm) |
| B (Overall) | 1.50 in (38 mm) |
| C (Overall) | 1.69 in (43 mm) |
| D (Overall) | 2.38 in (60 mm) |
| Weight (Table) | 0.5 lbs |
| G - Mounting Hole | 0.19 in (5 mm) |
Electrical
| Audio Watts | 8 |
| Label Marking | PRI: BLU - RED - BRN 1200 - 25000 OHM CT; 100Hz - 30kHz; 8 WATTS |
| Secondary DCR 1-2 | 137 mΩ |
| Secondary DCR 1-3 | 299 mΩ |
| Secondary DCR 1-4 | 470 mΩ |
| Secondary DCR 1-5 | 670 mΩ |
| Secondary DCR 1-6 | 890 mΩ |
| Dielectric Strength | 1500 Vrms |
| Primary Connections | BLU (plate), RED (B+ centre tap), BRN (plate) |
| Output Power (Typical) | 8 Watts |
| Max. DC Bias Per Side | 45 mA |
| Primary Impedance Range | 1,200 to 25,000 ohms |
| Secondary Impedance 1-2 | 1.76 Ω @ 1.0 kHz, 1.0 V OC |
| Secondary Impedance 1-3 | 10.75 Ω @ 1.0 kHz, 1.0 V OC |
| Secondary Impedance 1-4 | 29.3 Ω @ 1.0 kHz, 1.0 V OC |
| Secondary Impedance 1-5 | 66.2 Ω @ 1.0 kHz, 1.0 V OC |
| Secondary Impedance 1-6 | 121.5 Ω @ 1.0 kHz, 1.0 V OC |
| Secondary Inductance 1-2 | 0.24 mH @ 1.0 kHz, 1.0 V OC |
| Secondary Inductance 1-3 | 1.29 mH @ 1.0 kHz, 1.0 V OC |
| Secondary Inductance 1-4 | 3.33 mH @ 1.0 kHz, 1.0 V OC |
| Secondary Inductance 1-5 | 7.27 mH @ 1.0 kHz, 1.0 V OC |
| Secondary Inductance 1-6 | 13.24 mH @ 1.0 kHz, 1.0 V OC |
| Input Impedance (Typical) | 1200 - 25000 Ω |
| Primary DCR, Blue - Brown | 285 Ω |
| Secondary Impedance Range | 1.5 to 15 ohms |
| Output Impedance (Typical) | 1.5 - 15 Ω |
| Primary Inductance (Table) | 5.60 H |
| Frequency Response (Series) | 150 Hz - 15 kHz at full rated power (+/- 1 dB max, ref. 1 kHz) |
| Frequency Response (Typical) | Typ. 1.0 dB from 100 Hz to 15 kHz |
| Primary Impedance Blue - Brown | 25.5 kΩ @ 1.0 kHz, 1.0 V OC |
| Primary Inductance Blue - Brown | 4.40 Hy @ 1.0 kHz, 1.0 V OC |
Identifiers
| UPC | 623980188805 |
| UNSPSC | 39121301 |
Hook-Up Data
| Speaker On Secondary Lugs 1&2 - Resulting Primary Impedance (BLU To BRN) | 1.5 Ω speaker: 27000 Ω |
| Speaker On Secondary Lugs 1&3 - Resulting Primary Impedance (BLU To BRN) | 1.5 Ω speaker: 5400 Ω; 2 Ω speaker: 7200 Ω; 3.2 Ω speaker: 11500 Ω; 4 Ω speaker: 15000 Ω; 6 Ω speaker: 21600 Ω |
| Speaker On Secondary Lugs 1&4 - Resulting Primary Impedance (BLU To BRN) | 1.5 Ω speaker: 2150 Ω; 2 Ω speaker: 2900 Ω; 3.2 Ω speaker: 4600 Ω; 4 Ω speaker: 5800 Ω; 6 Ω speaker: 8700 Ω; 8 Ω speaker: 11600 Ω; 12 Ω speaker: 17400 Ω; 15 Ω speaker: 21500 Ω |
| Speaker On Secondary Lugs 1&5 - Resulting Primary Impedance (BLU To BRN) | 2 Ω speaker: 1400 Ω; 3.2 Ω speaker: 2200 Ω; 4 Ω speaker: 2800 Ω; 6 Ω speaker: 4200 Ω; 8 Ω speaker: 5600 Ω; 12 Ω speaker: 8400 Ω; 15 Ω speaker: 10200 Ω |
| Speaker On Secondary Lugs 1&6 - Resulting Primary Impedance (BLU To BRN) | 3.2 Ω speaker: 1200 Ω; 4 Ω speaker: 1500 Ω; 6 Ω speaker: 2300 Ω; 8 Ω speaker: 3000 Ω; 12 Ω speaker: 4500 Ω; 15 Ω speaker: 5600 Ω |
| Speaker On Secondary Lugs 2&3 - Resulting Primary Impedance (BLU To BRN) | 1.5 Ω speaker: 18000 Ω; 2 Ω speaker: 24000 Ω |
| Speaker On Secondary Lugs 2&4 - Resulting Primary Impedance (BLU To BRN) | 1.5 Ω speaker: 4200 Ω; 2 Ω speaker: 5600 Ω; 3.2 Ω speaker: 9000 Ω; 4 Ω speaker: 11200 Ω; 6 Ω speaker: 16800 Ω; 8 Ω speaker: 22500 Ω |
| Speaker On Secondary Lugs 2&5 - Resulting Primary Impedance (BLU To BRN) | 1.5 Ω speaker: 1550 Ω; 2 Ω speaker: 2050 Ω; 3.2 Ω speaker: 3300 Ω; 4 Ω speaker: 4100 Ω; 6 Ω speaker: 6150 Ω; 8 Ω speaker: 8200 Ω; 12 Ω speaker: 12300 Ω; 15 Ω speaker: 15500 Ω |
| Speaker On Secondary Lugs 2&6 - Resulting Primary Impedance (BLU To BRN) | 3.2 Ω speaker: 1700 Ω; 4 Ω speaker: 2100 Ω; 6 Ω speaker: 3150 Ω; 8 Ω speaker: 4200 Ω; 12 Ω speaker: 6300 Ω; 15 Ω speaker: 8000 Ω |
| Speaker On Secondary Lugs 3&4 - Resulting Primary Impedance (BLU To BRN) | 1.5 Ω speaker: 16500 Ω; 2 Ω speaker: 22000 Ω |
| Speaker On Secondary Lugs 3&5 - Resulting Primary Impedance (BLU To BRN) | 1.5 Ω speaker: 3300 Ω; 2 Ω speaker: 4400 Ω; 3.2 Ω speaker: 7000 Ω; 4 Ω speaker: 8800 Ω; 6 Ω speaker: 13200 Ω; 8 Ω speaker: 17600 Ω; 12 Ω speaker: 26400 Ω |
| Speaker On Secondary Lugs 3&6 - Resulting Primary Impedance (BLU To BRN) | 1.5 Ω speaker: 1300 Ω; 2 Ω speaker: 1700 Ω; 3.2 Ω speaker: 2700 Ω; 4 Ω speaker: 3400 Ω; 6 Ω speaker: 5100 Ω; 8 Ω speaker: 6800 Ω; 12 Ω speaker: 10200 Ω; 15 Ω speaker: 12800 Ω |
| Speaker On Secondary Lugs 4&5 - Resulting Primary Impedance (BLU To BRN) | 1.5 Ω speaker: 10000 Ω; 2 Ω speaker: 13500 Ω; 3.2 Ω speaker: 21600 Ω; 4 Ω speaker: 27000 Ω |
| Speaker On Secondary Lugs 4&6 - Resulting Primary Impedance (BLU To BRN) | 1.5 Ω speaker: 2400 Ω; 2 Ω speaker: 3200 Ω; 3.2 Ω speaker: 5100 Ω; 4 Ω speaker: 6400 Ω; 6 Ω speaker: 9600 Ω; 8 Ω speaker: 12800 Ω; 12 Ω speaker: 19200 Ω; 15 Ω speaker: 24000 Ω |
| Speaker On Secondary Lugs 5&6 - Resulting Primary Impedance (BLU To BRN) | 1.5 Ω speaker: 8500 Ω; 2 Ω speaker: 11000 Ω; 3.2 Ω speaker: 18000 Ω; 4 Ω speaker: 22000 Ω |
Packaging & Shipping
| Shipping Weight | 0.5 lbs (0.23 kg) |
Construction & Finish
| Style | Open style |
| Primary Leads | Minimum 5" long |
| Country Of Origin | Made in Canada |
| Secondary Connections | Solder lugs 1-6 |
Environmental & Protection
| Temperature Range | -40 To 105C |
Compliance & Certifications
| RoHS Compliant | Yes |
| REACH Compliant | Yes |
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Frequently Asked Questions
What output power is the 125C rated for?▾
8 audio watts.
How much DC bias current per side can it handle?▾
A maximum of 45 mA per side.
How do I choose the primary impedance?▾
Connect the speaker across the secondary lug pair listed in the hook-up table; results range from 1,200 to 25,000 ohms blue to brown for 1.5 to 15 ohm speakers.
What is the operating temperature range?▾
The drawing lists -40 to 105C.
What are the 125C dimensions?▾
A 2.81 in (71 mm), B 1.50 in (38 mm), C 1.69 in (43 mm), D 2.38 in (60 mm), with 0.19 in (5 mm) mounting holes.
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