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Did I blow my tube amp?

So here's the story: I recently received my tube amp and replaced the power tubes. So naturally, I wanted to bias them to make sure they work properly. I've never done any biasing before and checked some youtube videos on biasing. One of the youtube video had a Manley Stingray connected to power, no input signal, and NO speakers connected. I did the same. After the biasing is done, I connected the speakers and input signal, but for some reason so sound came out.

So the question is: did I blow my output transformer? Simply by not connecting the speakers while biasing or just having the amp on for a short while? From what I have read, it should be ok to have no speakers connected as long as there's no input signal.

I had another tube amp before this, and turned it on one time without speakers connected and it worked flawlessly after.

Could you guys shed some knowledge or personal experience on this topic?
vu001

Showing 1 response by bombaywalla

bombaywalla's avatar
bombaywalla
1,958 posts
 
Vu001,
it's a bad idea to turn on a tube amp without a speaker load since tube amps always have a power output transformer where the primary winding is connected to the output tubes & the secondary winding is connected to the speaker binding posts & expecting a speaker to be connected. If not connected to a speaker, there is a high probability that the tuned circuit connected to the secondary of the output transformer can start oscillating & destroy itself.

Additionally, this cut & Pasted from David Berning's website:
Audio-output transformer-coupled amplifiers should not be operated without a load connected because the inductance of the transformer's primary can cause the plate voltage to reach a sufficiently high voltage to break down insulating materials, resulting in amplifier failure and even fire. Some amplifiers are even unstable without a load.
I used to own a Jolida & AES Six Pac tube amps & even tho' Cary said it did not matter whether or not there was a speaker connected I always made sure that a speaker load was present during biasing.
Some info for you to read:

http://www.hometheater.com/content/amplifier-damage
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