Powerstage 700 to power 2 cabs with different impedance in both

[lesmick]

Ok, I have no idea if this is a dumb question, but I don't want to blow up my gear so I figured I'd ask.

Basically, I run a split signal into 2 different amp heads right now, one for guitar and one for bass.

I was hoping to scale down and run split left and right signals into the Powerstage 700 and then output into a guitar amp (left) and bass amp (right). My worry is, while I know that the Powerstage can support cabs from 4-16ohms, would there be an issue running left signal into a 16ohms cab and the right signal into an 8ohms cab?

Is that going to blow anything up, ya think?

 

[IMENATOR]

Do you mean using each channel of a stereo power amp as two independent mono power amps? One for a guitar cab the other for a bass cab? If that is your question I recommend you better call technical support at duncan. I had a similar question once about my ISP Stealth stereo power amp and I called the vendor to get my answer because this is very specific and you better get the answer from the vender in order to be sure you stay in warranty.

 

[jeremy]

id think you are ok. i believe that its a true stereo setup so should be fine with a mismatch, but again, doesnt hurt to call duncan to confirm

 

[GuitarDoc]

I'm not sure I even understand your question. You're running the Powerstage 700 into your two different AMPS? So how is adding a Powerstage 700 to your rig, "scaling down"? Plus, your amps are plugged into their respective cabinets so where is the concern about speaker impedence? Or did you mean that you are eliminating your amps and plugging the Powerstage into you speaker cabs (not your amps)?

 

[jeremy]

i believe he is talking about replacing his two amps with the powerstage

 

[Ewizard]

The short answer is the PS700 will be fine running one load on one side, and a different load on the other.

Class-D and other solid-state amps like these don't have a problem with impedance as long as it is at or above the minimum. Solid state amps output sections are not like tube amps, they simply convert X voltage into X load/resistance to arrive at X wattage. That is it. The side with the lowest impedance will have the most wattage/power, at the cost of more distortion. The side with the highest impedance will have less wattage/power, but less distortion.

 

[andreluckman]

I had the same question to SD support, and Jeff Collier from Customer and Technical Support aswered me this:


Thank you for reaching out, it is safe to use 2 different level cabs as long as the total load per channel is not lower than 4 ohms.

Just be aware that because the Level controls are ganged together, using 2 different impedance cabinets will result in volume differences that you would not be able to compensate for at the Level control.

 

[andreluckman]

The short answer is the PS700 will be fine running one load on one side, and a different load on the other.

Class-D and other solid-state amps like these don't have a problem with impedance as long as it is at or above the minimum. Solid state amps output sections are not like tube amps, they simply convert X voltage into X load/resistance to arrive at X wattage. That is it. The side with the lowest impedance will have the most wattage/power, at the cost of more distortion. The side with the highest impedance will have less wattage/power, but less distortion.

Mr. Wizard, just to confirm: 4 ohm cab = more power and distortion, 8 ohm cab = less power and distortion. Right?

 

[GuitarDoc]

Whether you get more or less distortion from a speaker is more a factor of what speaker you are using (power handling, SPR, signal to noise ratio) rather than its impedance.

 

[Ewizard]

Mr. Wizard, just to confirm: 4 ohm cab = more power and distortion, 8 ohm cab = less power and distortion. Right?

Correct.

Solid-state amps can be stated as being voltage amplifiers. I.E, the power rail, where the amplifier power is derived from, has a fixed high voltage source that is utilized to power a speaker's mechanical motion. As you reduce the impedance, you increase the flow of voltage out of the power rail through the speaker. As you can imagine, as the power rail becomes depleted of its voltage, it loses the potential to faithfully reproduce the incoming audio signal. This is distortion.

Conversely, with higher impedance loads, the wattage dissipated ( literally heat produced ) is reduced, thus reducing the stress on the power rail to maintain its fixed voltage. The output wattage is lower, but because the power rail can keep up with things, distortion is minimized.

And for extra credit:

Tube amps are the polar opposite of solid-state amps. Tube amps are current amplifiers, which use a transformer to convert the high voltage, low current from the tubes into low voltage with high current on the secondary side of the output transformer. This also allows optimization of the circuit so that despite the impedance of the load, as long as the matching tap ( output secondary tap ) is similar to the speaker's impedance, the output of the amplifier will have the same wattage. This simply means that as long as you use an 8-ohm speaker on the 8-ohm tap, a 4-ohm speaker on the 4-ohm tap, and a 16-ohm speaker on the 16-ohm tap, the wattage dissipated will be the same for all loads.

 

[IMENATOR]

Mr. Wizard, just to confirm: 4 ohm cab = more power and distortion, 8 ohm cab = less power and distortion. Right?

Yes, because you are sending less power, assuming you keep the level knob with no change. But in reality you will. Every SS power amp manual should include the amount of power at which it will start distorting.