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Specification:
Item Type: Audio Transformer
Impedance Ratio: 1300 : 8
Power Phase Number: Single Phase
Proof Way: Open
Cooling Method: Oil-Immersed Air-Cooled
Frequency Characteristics: Medium Frequency
Winding Form: Self Coupling
Iron Core Form: Amorphous Alloy
Iron Core Shape: EI Type
Structure: Vertical
Package List:
10 x Audio Transformer
Donald M. Dodge
Reviewed in the United States on January 13, 2023
Needed for a Ham Radio headset to change the impedance .
Monica
Reviewed in the United States on April 3, 2022
It was junk.
Rock Dubois
Reviewed in the United States on July 2, 2021
I connected the 8 ohms side to the 8 ohms amplifier output (absolutely zero output on the high impedance side. I tried with two and getting the same results.
Alan Yates
Reviewed in the United States on March 23, 2021
These are absolutely not 1300:8 Ohm transformers. I've bought several lots of these from different sellers and they all measure about the same: The transformer winding ratio is closer to 5.1:1 than 12.75:1.The primary is about 86 ohms DC resistance and 257 mH at 1 kHz. The secondary is 9.8 mH with a 2.6 ohm DC resistance. The primary inductance with the secondary shorted is about 1.88 mH and the secondary inductance with the primary shorted is about 75 uH. This means the coupling coefficient is about 0.996. The in-phase inductance of both windings is 358 mH and anti-phase it becomes about 174 mH, meaning the mutual inductance is about 45.8 mH. The mutual inductance measurement along with the coupling coefficient is consistent with a turns ratio of about 5:1 which I confirmed with open circuit voltage measurements using a few volt 1 kHz sine wave.A secondary load impedance of 8 ohms would reflect about 200 ohms to the primary, not 1300. The primary winding's impedance magnitude is also only about 1600 ohms at 1 kHz (the secondary is around 62 ohms) so it seems to be designed for fairly low impedances as one would typically want the reactance magnitudes to be at least 5 or so times the load impedances.All that said, they are a 5:1 transformer that is still useful, just not as the typical collector/drain/plate load matching application of larger ratios. They might be more useful as an interstage or with a lower impedance to get more power out with a largish standing current in a class-A amplifier. The lack of a center-tap definitely makes them less generally useful, they can certainly be used as a choke or rewound but disassembling them to rewind is difficult. They definitely roll off quickly at lower frequencies when you try to use them with higher impedance loads, I suspect they were actually designed for a non-audio application or audio but at lower impedances than the traditional 1K:8R transformer of old. With a pair of modern 32 ohm earphones in series that 64 ohms would be reflected as about 1.6 K which is reasonable for a simple class-A amplifier delivering perhaps 20 mW with a 9V supply, but the lower frequencies would be seeing a lot more of the losses than with higher impedance windings.
Dan K.
Reviewed in the United States on November 23, 2021
Although these transformers are made for driving speakers, I am using them as isolation devices. In my design, I am effectively using them backwards with the input on the 8-ohm side and the output on the 1000 ohm side. This provided not only the isolation I needed but also a step up in amplitude.
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