20/20 16 ohm cab drawbacks?

[mr_mojo]

Hi,

I would simply like to know if there are any drawbacks associated with running two 16ohm speaker cconnections/cabs, from the 8 ohm 20/20 outputs. I'm aware the manual says it "can be done", but also says that it is better using two 16 ohm cabs with Y cables... And i'm wondering why its "better".

Most importantly however, I am specifically interested in this following setup:

2 speaker cables (one from each 8 ohm output) to each of the 16ohm stereo inputs on a 2x12 cab loaded with V30's.

Pros/Cons/better solution for my stereo FX to VC30's?

Thanks very much for your time!

 

[elvis]

The load impedance affects the bias of the power tubes. Bias is adjusted for nominal 8 Ohms. Using 4 or 16 Ohms will not cause damage, but changes the bias slightly. You may hear a minor change in tone vs. 8 Ohms, but the speaker cabinet itself causes as much as a change.

 

[mr_mojo]

Thanks for this helpful reply!

By a minor tone change what do you mean, is there a typical change associated with this? Am i right in assuming that the tubes will sound like they are being worked slightly harder to deal with the higher impedence?

 

[elvis]

Actually, the tubes are worked less hard because it's easier to drive a high impedance than a low impedance.

To illustrate, driving an 8 Ohm speaker to 8 Volts requires 1 Amp. Driving a 16 Ohm speaker to 8 Volts takes half an Amp.

It's a bit more complicated tho. The speaker load change will affect the load on the tube, which changes its output gain.

 

[mr_mojo]

useful information, thanks!

 

[user 17783]

if i'm running the 20:20 into 2 16 ohm speakers, how many watts will the 20:20 put out per side?

the speakers are celestion blues, and the amp's output should be lower into 16 ohms, which is good because the blues are rated at 15watts...

also, will tube life be decreased by running into 16ohms?

how about differences in the tone?

thanks in advance!