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Amplifier circuitry-4 ohm vs 8 ohm

Obviously there are different wires leading into the four or eight Ohm taps on the back of an amplifier from the one amplifier.  The single amplifier at some point splits the signal going into either one of these Ports.  What differences are there in the circuitry?

Maybe this will help me better understand the difference between these two taps. I believe 4 ohms is a wider more open path for voltage to flow. So when you're speaker attempts to go lower, which requires more power, the 4 ohm more easily allows this to happen with a better outcome. Or maybe I got this wrong.

 

 

 

emergingsoul
emergingsoul OP
1,125 posts
 

What does light loading of tubes mean? Is this concept specific to a certain type of amplifier or is it a universal concept.

 

tubeguy76
153 posts
 

Rogue Audio has told me in the past to try either 4 or 8 ohm and use whichever sounds best. 

trivema's avatar
trivema
84 posts
 

Hmmm, I have two pair of Vienna Acoustics that are 6 ohm speakers and a simple EL34 amp with 8 ohm and 4 ohm taps. Thanks to the excellent posts above I am much better informed but more confused!  VA support told me to run off the 4 ohm tap, but the best advice seems to be try both and see which sounds better! 
 

Thanks for the science and advice. : )

emergingsoul OP
1,125 posts
 

The manufactures/distributors of these very very expensive products should be better positioned to answer these types of questions.

while above points help to clarify it, there’s still seems to be great confusion about relationship of voltage and its influence to amplifiers and speaker drivers.

It seems clear very few people understand these complex areas, and the communication of this understanding is very challenging. Kudos to those above who have been helpful.

 

atmasphere's avatar
atmasphere
11,793 posts
 

Implied, but so far not stated specifically, is that the output tubes of an amplifier need to see a high load of several thousand ohms (the exact value depends on the tube and amp design.)  If you run an output tube straight into a speaker, whether 4 or 8 ohms, it looks like a dead short to the tube -- not good. 

And, straight from the tube, one is talking an output of up to hundreds of volts. Also not good for the speaker, which wants a lower voltage, but more amperage. 

We've been flying in the face of this for nearly 50 years making Output TransformerLess (OTL) amplifiers with a direct coupled output.

Somewhere along the way I realized that the distortion of the amplifier is also the 'sonic signature' that almost any amplifier has. So that meant if you could build a solid state amplifier with the same distortion spectra/signature, it would sound the same also. That proved out to be true.

So there are now solid state amps that allow you to leave the tube world behind without missing them for anything.

 

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