quick tube question

jjl5590 · #1 03-22-2010, 01:39 PM

hi guys,

i just got a quick couple of questions about amps with a tube preamp:

#1 is it possible to blow the tube if you set the input gain too high?

#2 do you have to let the tubes warm up if they are just in the preamp?

cheers for any help given

Calaverasgrande · #2 03-22-2010, 01:50 PM

#1 with in reason no. though I have head stories of some 60's band, Cream? that would run the speaker out of one amp to the input of another. It would sound brilliant for about 30 minutes than blow up. So as long as you arent exceeding a volt or so I am sure you are fine. People have been using clean boost pedals on amps for decades.
#2 I am not 100% on this but from what I understand, even with preamp tubes it shortens the life somewhat to play on them while they warm up. Though I don't think it takes more than 30 sec for them to get warmed up enough.
Some guys I know like to leave there amps plugged in for an hour or two before the show so that they are fully ready to go.

JimmyM · #3 03-22-2010, 02:14 PM

1. it can but it won't happen overnight, and in some amps it may never happen because they don't run the gain hot enough to cause it. plus preamp tubes are cheap enough to where you really shouldn't care that much, especially if there's only one.

2. tubes take about 30 seconds to warm up enough to use, and after about 10-15 minutes they're about as warmed up as they'll ever get.

jjl5590 · #4 03-22-2010, 02:17 PM

ok cheers for the answers, got another quick q I just thought of:

is it ok to run an amp with tube preamp with no load?

Cheers

JimmyM · #5 03-22-2010, 02:20 PM

sure, as long as the power amp is solid state. if it's tubes, you can't since it has an output transformer and they will cause amp failure if used without a speaker load.

Krügmeister · #6 03-22-2010, 02:26 PM

Doesn't Mesa/Boogie have a safety thing that will allow you to run it without a load or something or other?

Bassmec · #7 03-22-2010, 03:04 PM

Well yes i suppose there is the standby switch, also it will turn its self off automatically under no load conditions as the output transformer insulation burns away and the carbon formed by the burning insulation tracks more and more ht current away till the ht fuse blows or the transformer goes open circuit.
Then all you have to do is order a new transformer and some tubes
and a fuse to switch it back on.
Sorry its only the transistor product line thats almost totally idiot proofed.