Output transformer question

woody · 18th November 2011, 10:47 AM

I have a small amp using the 6c45pi. The output transformer has 4 and 8 ohm taps but I am considering hooking a 32 ohm speaker to it. Assuming
I am getting 1w into 8 ohms what should my output be into 32 ohms.

payitforwardeddie · 18th November 2011, 09:16 PM

1w into 8 ohms needs 2.8volts. 2.8 v into 32 ohms gives 1/4 watt.
Power = volts x amps
Power = volts squared divided by resistance
Power = amps squared times resistance

Gilgy · 19th November 2011, 12:57 AM

Quote:

Originally Posted by woody

The output transformer has 4 and 8 ohm taps but I am considering hooking a 32 ohm speaker to it

Why?

aardvarkash10 · 19th November 2011, 02:20 AM

Quote:

Originally Posted by payitforwardeddie

1w into 8 ohms needs 2.8volts. 2.8 v into 32 ohms gives 1/4 watt.
Power = volts x amps
Power = volts squared divided by resistance
Power = amps squared times resistance

disregarding the shift in the operating point of the output tube due to the change in the reflected impedance...

DF96 · 19th November 2011, 01:10 PM

Yes, it all depends on the output impedance (which is the triode anode impedance transformed by the transformer). Without knowing this you can't do an exact calculation. However, some reduction in output power is likely.

18th November 2011, 10:47 AM	#1
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	Output transformer question I have a small amp using the 6c45pi. The output transformer has 4 and 8 ohm taps but I am considering hooking a 32 ohm speaker to it. Assuming I am getting 1w into 8 ohms what should my output be into 32 ohms.

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18th November 2011, 09:16 PM	#2
payitforwardeddie diyAudio Member Join Date: Feb 2011 Location: South Wales, UK	1w into 8 ohms needs 2.8volts. 2.8 v into 32 ohms gives 1/4 watt. Power = volts x amps Power = volts squared divided by resistance Power = amps squared times resistance

19th November 2011, 01:10 PM	#5
DF96 diyAudio Member Join Date: May 2007	Yes, it all depends on the output impedance (which is the triode anode impedance transformed by the transformer). Without knowing this you can't do an exact calculation. However, some reduction in output power is likely.

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