valve amps must be connected to speaker cab b4 powering up?

[Dave_the_bass]

[quote name='Grissle' timestamp='1405954525' post='2506882']
If the amp only has valves in the preamp however you can generally treat it like any other SS amp. Anyway I'm not aware of any amps with non-valve power sections that require a speaker load?
[/quote]

Ashdown mag amps employ a switched jack speaker output. No jack in any speaker socket presents a dead short (or 0 ohm impedance load) across the output transistors. They'll get very hot and melty very quickly!

[gsgbass]

This little dude always has a main speaker out plugged in before anything starts up.

[IMG]http://i.imgur.com/3gOn1V9.jpg[/IMG]

[Guest monsterthompson]

[quote name='Billy Apple' timestamp='1405852604' post='2505725']
A valve amp must be connected to a load or you risk damage to the power section of the amp. The load is usually the speaker, but you can get dummy loads for DI'ing in a studio or to work on the amp. Always remember to have to right selection of [u][b]ohmage[/b][/u] on the head for the speaker
[/quote]

[Guest monsterthompson]

[url="http://www.mesaboogie.com/Product_Info/Bass_Amps/prodigy/bassProdigy.html#gpm1_2"]http://www.mesaboogi...igy.html#gpm1_2[/url]

Mesa will let you run the valve Prodigy without a load IF you flip the right switch. I believe my Buster also has similar technology, though the manual still suggests keeping a speaker connected (on the off chance somebody bumps the switch by mistake). The M6 and Walkabout (solid state power sections) have instruction manuals saying to never run them without a load. Mesa Hollywood employees and techs will tell you the same. I've run my WA without a load for recording silently, and it worked fine. I know others state the same.

I'd say it is always wise to have a load connected. However, there are exceptions to that rule.

Edited September 4, 2014 by monsterthompson

[Bill Fitzmaurice]

[quote name='mart3442' timestamp='1406894967' post='2515679']
I'll tell that to my friend with the fried amp......
[/quote]His amp may be fried, but it had nothing to do with the lack of the speaker. When in standby mode there is no current flowing to the tube plates. That's why no sound comes from the amp when in standby. If there's no current there's no potential for damage. He might as well have claimed that he blew the engine in his car by pressing the gas pedal to the floor...whilst the ignition was off.

Edited September 4, 2014 by Bill Fitzmaurice