Elementary resistance question

[Guitarski]

Hi,

Although the Soldano Astroverb 16 was made for 16 Ohm, the manual says it's possible to connect it to 8 Ohm, but will that reduce the headroom and the dynamics? If so, would it be possible and advisable to add an 8 Ohm resistance?
I may have to hook the AV up with two 16 Ohm speakers, resulting in an 8 Ohm parallel wiring.

Thanks/regards
Guitarski

 

[IM4Tone]

Re: Elementary resistance question

Doubt you'll notice any change, except for a perceived increase in volume w/ two speakers. Adding an 8 ohm resistor in series will just waste 1/2 of the amps output and will sound like a cheap attenuator (not good).

 

[zzmoore]

Re: Elementary resistance question

Doubt you'll notice any change, except for a perceived increase in volume w/ two speakers. Adding an 8 ohm resistor in series will just waste 1/2 of the amps output and will sound like a cheap attenuator (not good).

All good advice above.....
Try the cab the way it is at 8 Ohms. Do not worry about any "loss". Just give it a try.
Can you disconnect one of the speakers in your cab.?
The amp you have is fairly low power. What are the speakers rated at.?
best

 

[GuitarStv]

Re: Elementary resistance question

The resistor won't work. Speakers don't operate like a regular resistor. They give different R values at different frequencies. If you take your probes and measure the resistance of an 8 ohm speaker you won't get 8 ohms.

BTW - If you connect a lower ohm speaker to an amp (that can handle it) you should pull MORE power out of it, not less.

 

[jeremy]

Re: Elementary resistance question

thats true in solid state amps but not really in tube amps. in ss amps there is usually one or two speaker jacks and they will have a minimum rating, tube amps either have a switch or different jacks for different impedance's. they use different taps off the output tranny.

the output tranny is between the tubes and speakers so changing the speaker load changes what the tubes see.

 

[GuitarStv]

Re: Elementary resistance question

thats true in solid state amps but not really in tube amps. in ss amps there is usually one or two speaker jacks and they will have a minimum rating, tube amps either have a switch or different jacks for different impedance's. they use different taps off the output tranny.

the output tranny is between the tubes and speakers so changing the speaker load changes what the tubes see.

Cool! I did not know that . . .

 

[Little Pigbacon]

Re: Elementary resistance question

What's more, while a solid-state amp acts essentially like a voltage source, an output tube acts more like a current source. The solid-state amp is usually modeled as a voltage source in series with a resistance (or a complex impedance). The tube is modeled as a current source in parallel with a complex impedance. These are called the output impedances, and they might be given as the DC resistance value, as the phasor magnitude, the phasor magnitude plus phase angle, or even as a branch combination of a resistance plus an inductance or capacitance.

The output transformer scales the output impedance of a tube amp, and often the different 4-ohm, 8-ohm, 16-ohm, etc. speaker output jacks are coming from different taps on the OT's secondary, so that the output transformer can scale different speaker loads optimally for the tubes.