I just ordered a couple of these so I can run 4Ω speakers on amps that were originally designed with 8Ω speakers. Those amps required a plate load of about 2.5kΩ. This transformer fits the bill.

Transformers don't have inherent impedances, they transform impedances from primary to secondary, and back, according to the square of the turns ratio. In this case, since this one is specified as 5kΩ:8Ω, the impedance ratio is 625, and the turns ratio therefore 25.

With the output connected to a 4Ω speaker the primary impedance is 2.5kΩ.

This sees to be a common plate load for radio tube amps using 50L6 or similar output tubes, like the Kay 503A.

This output transformer got here fast, was inexpensive and works great in a 6V6 amp.

working great thanks

I have installed two of these replacement transformers over the years (and at least one P-T291) and I am convinced this transformer will give your single ended tube radio or amp the best possible performance at the lowest cost. If it is single ended (and not a small AA5 from the miniature tube era), this is the output transformer you need. PERIOD. Don't waste time fretting about impedance matching, DC resistance readings, or the fact that the original speaker is 4 ohm or 3.2 ohms. And don't spend more money than you have to. It's very simple: If you need a new output transformer for a singled ended radio or amp, buy this unit. Your audio will rock! If your radio or amp is a push-pull dual output, buy a P-T291. (But don't use a P-T291 on a single ended unit, even though you can. In my experience, the P-T31 has noticeably better audio on single ended units.)

Great when they work. Poor quality control.

Great little single-ended output transformer for low power applications. I've used it in 2 radio projects -- with an 8 ohm speaker for restoration of a 1928 Sparton with an RCA Type 50 output tube, and with a 4 ohm speaker in a 6CU5-based output stage for AES's 2-tube regenerative radio kit. Superb value.

If you need a single ended output transformer for anything up to and including a 6L6 , this is the best buy you'll find. It works very well . I think the frequency response rating may be a bit conservative , it sounds fairly impressive to me. I just put one of these in a 1952 Philco Golden Grid Instrument amplifier (6L6G) and it worked really well . It's a good purchase for antique work , but probably not for audiophiles .

Perfect audio transformer for single ended tube radios. Very good price.

I recently built a single ended amp based off the 5 watt Fender Champ schematic. I have been building these fore a couple of years now, so I have a pretty good idea as to what they are supposed to sound like. At any event I have used a small variety of single ended transformers from another company and I have to say I have been quite happy with them so far. I stumbled upon the 8 watt single ended transformer at Antique Electronics while purchasing resistors, capacitors and a bunch of other tube amp parts. I was a little leery at first simply because the price was fairly low, so I purchased two of them. My amps still sound like a Black Face Champ. As long as these last and continue to perform well I am sure I will be buying more of them.