8ohm output transformer with a 4ohm load

nightanole · 16th February 2010, 01:44 AM

I know if you run too high of a impedance load on a tube amp the plates could fry just like if you had no speaker attached. But what happens when you pop a 4ohm speaker on a 8ohm tap? Is it perfectly safe as long as you dont go above the normal wattage of the amp? I dont know what happens when the tubes see 2.5k instead of 5k.

Aka if its a 10 watt amp at 8ohms, dont go for 20watts at 4ohm , keep the volume at half...

Joshua_G · 16th February 2010, 06:19 AM

In such a case you will get much higher distortion, since distortion increases as the tube's load impedance decreases.
Also, it seems to me that you'll get less output power, since the operating point of the tube will not be suitable for the new load impedance.

Ian444 · 16th February 2010, 07:06 AM

What happens if you put 4 ohm resistors in series with the 4 ohm speakers, besides halving the output power to the speakers, all else should be OK as far as the amp is concerned? Yes? No? Halving the power is only -3dB. Sure its not the "right thing" to do but if you're stuck...

Ian.

sacpul · 16th February 2010, 10:33 AM

It is better to use 2 inseries 4 ohms speakers instead of 4ohms resistor. It will be better from my experience. Btw the 4ohms resistor needs to by high wattage coz it will blow

rotaspec · 16th February 2010, 07:09 PM

Quote:

Originally Posted by Ian444

What happens if you put 4 ohm resistors in series with the 4 ohm speakers, besides halving the output power to the speakers, all else should be OK as far as the amp is concerned? Yes? No? Halving the power is only -3dB. Sure its not the "right thing" to do but if you're stuck...

Ian.

Halving the damping factor too.....

16th February 2010, 01:44 AM	#1
nightanole diyAudio Member Join Date: Feb 2009	8ohm output transformer with a 4ohm load I know if you run too high of a impedance load on a tube amp the plates could fry just like if you had no speaker attached. But what happens when you pop a 4ohm speaker on a 8ohm tap? Is it perfectly safe as long as you dont go above the normal wattage of the amp? I dont know what happens when the tubes see 2.5k instead of 5k. Aka if its a 10 watt amp at 8ohms, dont go for 20watts at 4ohm , keep the volume at half...

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16th February 2010, 06:19 AM	#2
Joshua_G diyAudio Member Join Date: Nov 2008 Location: Israel	In such a case you will get much higher distortion, since distortion increases as the tube's load impedance decreases. Also, it seems to me that you'll get less output power, since the operating point of the tube will not be suitable for the new load impedance.

16th February 2010, 07:06 AM	#3
Ian444 diyAudio Member Join Date: Nov 2008 Location: Brisbane QLD	What happens if you put 4 ohm resistors in series with the 4 ohm speakers, besides halving the output power to the speakers, all else should be OK as far as the amp is concerned? Yes? No? Halving the power is only -3dB. Sure its not the "right thing" to do but if you're stuck... Ian.

16th February 2010, 10:33 AM	#4
sacpul diyAudio Member Join Date: Jul 2009	It is better to use 2 inseries 4 ohms speakers instead of 4ohms resistor. It will be better from my experience. Btw the 4ohms resistor needs to by high wattage coz it will blow