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Would you please help me to think how to choose an approximate transformer with the least losses for my application? No exact transformer available at market.

Is it best, say, taking a 2600/8 ohms or a 600/4 ohms transformer?

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  • \$\begingroup\$ What is the VA rating ? Same? What does 2kW come from? amp rating into 600 R? \$\endgroup\$ – Sunnyskyguy EE75 Jun 20 '18 at 1:32
  • \$\begingroup\$ To match source Rs to load R talke sqrt(Rs/R) as your ideal turns or voltage ratio or slightly more for better dampening but lower power. \$\endgroup\$ – Sunnyskyguy EE75 Jun 20 '18 at 1:45
  • \$\begingroup\$ VA rating is the same. Would there be a way of doing this matching without transformer - maybe with another amplifier? \$\endgroup\$ – Martin Horst Jun 20 '18 at 10:49
  • \$\begingroup\$ Do you have a link to amp specs \$\endgroup\$ – Sunnyskyguy EE75 Jun 20 '18 at 12:32
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    \$\begingroup\$ That is NOT a 2000W amplifier - or even a 1W amplifier. Think again. \$\endgroup\$ – Brian Drummond Jun 20 '18 at 13:16
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Whatever made you think this can drive speakers , was incorrect. This tiny tube circuit can only buffer 47k Ohm phonograph signals to a pre-amp and add some hum.

This IS NOT A POWER AMPLIFIER or PREAMP. enter image description here

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  • \$\begingroup\$ thanks for checking it, Tony, much appreciated. DX specs were wrong then, as well as the device usefulness. Okay, so I need an amplifier to use between this device and the speakers, right? Should the amplifiers input/output impedances be matched as well? Is there no need of use of a transformer? \$\endgroup\$ – Martin Horst Jun 20 '18 at 20:04
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A bit strange application but your 2 kW @ 600 ohm amplifier needs to put out (P=U^2/Z) 1095 Vrms to supply 2 kW and your speaker needs 14.1 Vrms to produce 25 W.

As such, you can wind a 1095:14.1 transformer with at least 25 VA rating for the given frequency (audio frequency may heat up the core more than 50/60 Hz, hence margin for given frequency) to match your amplifier to your load. Please keep in mind that 1095 Vrms is more than most magnet wires are made for, so you may need to provide additional isolation.

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  • \$\begingroup\$ This is the guy (dx.com/pt/p/…) whose output I want to connect to passive speakers rated 8 ohms (on their label, it is also stated Power Handling Capacity 25 W and Power (Music) 50 W. Is a transformer the only solution for such a matching? thank you so much! \$\endgroup\$ – Martin Horst Jun 20 '18 at 10:52
  • \$\begingroup\$ No, but it's the most apparent. If you would have enough current capacility on your tube amp (you don't), you could have just connected it as is and played at very low volume. \$\endgroup\$ – winny Jun 20 '18 at 11:21

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