Ah, that's simple enough then. I wasn't sure if the 8 ohm primary output needed something plugged into it as well. Thanks!
Oh, on a side note, just clarifying, am I correct in believing that if you run a 16ohm cab into a 8ohm output, it doesn't do damage, you just don't receive full power? Please correct me if this is wrong, I'd hate to do damage.
That's correct for
transistor amps,
not tube amps. For a tube amp to function optimally (and safely) you want a
matched load; 8 ohm load to the 8 ohm tap, 4 ohm load to the 4 ohm tap, etc.
Once again, the search function is your friend. This was from Jan. of this year;
Speaker impedance isn't an exacting science, not nearly as cut and dry as the ohm rating of a resistor for example, which is generally a <5% variance from the marked rating.
Speaker impedance ratings are "nominal"; for example an 8 ohm driver can fluctuate from just a couple of ohms to 100+ in actual use depending on frequency, power, cabinet, etc.
But, there is a reason that tube amps have output transformers, and a reason they are tapped off at specific impedances. The output transformer is used to match the load (speaker) impedance to the output stage impedance (tubes) for optimal performance.
A 2.67 ohm load on your amp probably won't cause any damage, your tech is right about tube amps being pretty flexible, but the mismatched load can hinder the amp from working up to it's design specification.
Which can be good or bad depending on what you are trying to accomplish. When I was a kid my goal was to be as loud as I could get, and using my basic high school electronics class skills I would hook up as many speakers as I could to whatever amp I could get my hands on with little regard for sound quality. I understood impedance, but took extensive liberties in pursuit of "loud".
Eventually I figured out that for me anyway, quality was a more desired attribute than quantity.
IMO it's easy to get loud, not so easy to sound good doing it.
HOWEVER; That post was addressing a "too
low" impedance situation. The situation you described is a “too high” impedance example, and IMO a load that’s too high in impedance is potentially more destructive than too low impedance.
Running a tube amp with
no load plugged into the speaker jacks can cause very expensive damage. While the phrase “no load plugged into the speaker jacks” may sound like zero ohms, it’s in fact just the opposite, it’s about a bazillion ohms, If you short the jack; connect the ring directly to the sleeve,
that’s close to zero ohms.
With that in mind, here’s yet another post from earlier this year that I found in a couple of seconds using the search function.
Should have mentioned this but you NEVER want to have your head set to a higher load than the speakers because you risk blowing hte output transformer. ie. an 8 ohm head going into a 4 ohm cab
Its OK the other way around, say a 8 ohm head going into a 16 ohm cab, you will just lose a little bit of volume because you're not using the amp efficiently but it won't hurt it.
I think you have that backwards. What you posted seems as if you are trying to apply SS amp wisdom to a tube amp, and they are different animals indeed.
Additionally, many people knowledgeable about tube amps say that running a tube amp at a higher impedance than the load is better then running it at less. That is, it's better to run a 4 ohm load at the 8 ohm setting than vice versa, which is decidedly not the case with transistor amps.
Tube amps are pretty rugged and will generally tolerate a mismatch pretty well. Speaker ratings are “nominal”, which in kind of like an average, and an 8 ohm cabinet can actually show an amp anywhere from <3 to >50 ohms depending on frequency, power, etc..
But IMO, as Isaac points out, a lesser load is preferable to a higher load.
Leo Fender’s amp designs had a jack that shorted out when there was no speaker plugged in as a protection device.
That is; without a plug in the jack it was a dead short; an 8 ohm tap going into a +/- ZERO ohm load – to keep from damaging the amp. If Mr. Fender felt “higher was better” as you posted, he would have left the jack open when there was no plug as a safety measure.
As is mentioned in the above posts, tube amps are pretty rugged, and will take pretty much abuse before they give up their magic smoke. I think it usually takes an extreme impedance mismatch at fairly high output levels to cause permanent
damage, however your amps
performance can be easily compromised by mismatching loads.
