Re: Two amps, one set of speakers ...

Karl Uppiano spake thus:

"jakdedert" <jakdedert@xxxxxxxxxxxxx> wrote in message news:rhSdg.49437$QU3.23858@xxxxxxxxxxxxxxxxxxxxxxxxx

Karl Uppiano wrote:

"Pooh Bear" <rabbitsfriendsandrelations@xxxxxxxxxxx> wrote in message news:4476830B.22479521@xxxxxxxxxxxxxx

Karl Uppiano wrote:

"Pooh Bear" <rabbitsfriendsandrelations@xxxxxxxxxxx> wrote in message
news:447679EC.14732CA2@xxxxxxxxxxxxxx

Karl Uppiano wrote:

I cannot recall a single failure that was attributable to
unloaded operation.

These were tube amps.

In which case that's relatively unusual. There can be circuitry
to detect the issue though and prevent it becoming a problem.

That's only because OTL amplifiers behave entirely
differently. If a solid state amp has an output tranny it
would hate unloaded outputs too.

Hint. An unloaded transformer is simply a huge inductor.

An unloaded transformer still has feedback windings that tell
the amplifier what the output is doing.

Not *always* by any means and even so, one that I know
certainly does have this feedback was nevertherless instantly
trashed when someone accidentally disconnected the speaker.

Ok, what is the failure mode then? Because frankly, I'm just not seeing it.

Listen, you've gotten some pretty good advice already. Either take it or not. If you don't I think you'll get to see some pretty sparks, or even get to watch the smoke get let out of your tube amp.

If you do, you won't. Take your choice. IMO, it's like the agnostic who said that he didn't know if God existed, but he wasn't taking any chances....

Perhaps you've confused me for the original poster. I am an engineer trying to understand what mysterious mechanism would cause this problem, coupled with many examples in my real life experience of it not happening -- in harsh industrial settings, no less.

My calculations show that the phase shift in the transformer never exceeds 90 degrees due to impedance changes, and that the overvolt situation for the ends of a center-tapped primary only approaches 2 x B+. True, I might be missing something.

If this is a known phenomenon, then there should be articles and white papers about this at the Audio Engineering Society. If anyone knows of any such authoritative and scientific analyses, please point me to them.

So far, my money's on you: your real-world empirical experience trumps the usual Usenet speculation. (Although I do wonder about that other poster who experienced real-world arcing in the output tubes of his guitar amp when the speaker got disconnected ...)


--
I hope that in a few years it [Wikipedia] will be so bloated that it
will simply disintegrate, because I can't stand the thought that this
thing might someday actually be used as a serious reference source.
Because in its current form, it's not to be taken seriously at all.

- Horst Prillinger (see
http://homepage.univie.ac.at/horst.prillinger/blog/archives/2004/06/000623.html)
.