2. amps-preamps
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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
erik_squires
15,710 posts
 

The only place I know where this happens is in tube amps with transformer outputs.

The idea is to keep the power output the same, so the 4 Ohm tap has less voltage, more current, same power as the 8 Ohm.

 

gs5556
1,211 posts
 

Each tap is a secondary winding on the output transformer. The primary voltage is transferred to each of the 8-ohm and 4-ohm secondary windings equally. The impedance is set by the turns ratio of wires between the primary and the 4 ohm tap, and the primary and the 8 ohm tap. The relationship is the square root of the impedance so to get an 4 ohm impedance, you wind 1.44 times as much wire to the 4-ohm tap (square root of 2) as you do for the 8-ohm tap. This will set both the voltages the impedances the speakers the speaker sees when connected. 

 

rodman99999
5,988 posts
 

      YEP (GS beat me to it)!

       Here are two references, that may illustrate/shed more light on the subject:

                                   and (under ’Output Tranny Types’, parameters):

                      https://education.lenardaudio.com/en/14_valve_amps_5.html

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