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What's likely to happen when an 845 tube fails?

I've been running tube gear as far back as I can remember and other than a CJ mono amp blowing a 6550 and requiring factory service many years ago, I've never had any serious issues. Sure, tubes age and you eventually replace them or on a rare occasion, a tube blows, maybe you replace a fuse, then you're back up and running, but that's been it.

Atma-Sphere MA-1 monos and MP-1 pre currently hold pride of place and I'm also very fond of a Cary SLI-80 F1 all triode that I run in another system. But... I've been itching to try a pair of deHavilland Aries 845-G SET monos and am wondering how much grief those big, high voltage 845's might cause me?

In the case of "catastrophic failure", is it likely to do serious damage to the amp? Worse yet, how 'bout my speakers? Any comments from those having personal experience with 845's or 211's would be appreciated.

Regards!
128x128rfogel8
marakanetz's avatar
marakanetz
5,473 posts
 
It depends on amp's circuit design more than on type of tube being used. Most of SETs are using primitive amature DIY design, but tubes in SETs last quite a long time before anything serious can happen. There are ways to prevent bad tube to blow:
1. Turn off tube amp when you're not listening to it. It takes only 5m to get tubes to the normal operation.
2. Eyeball the tubes having a normal glow when you play the music. One tube that will glow too bright or too dim might not be normal.
3. If you hear microphony, inspect tubes.
4. Have extra set of tubes. It helps you to check if problem goes away after you swap for the fresh one.
ths364
181 posts
 
No experience with the 845's, but generally catastrophic failures are pretty rare in tube amps. Yes, the tube may fail but the minimal number of parts in these amps means that there aren't a lot of things to go wrong. Output transformer isolates the speaker from DC so you're pretty safe there. Output transformers do NOT like open circuits when signals are present so make certain that speaker leads are hooked up properly before engaging the source. Enjoy!
rfogel8's avatar
rfogel8 OP
192 posts
 
Thanks for your responses. I agree that the amp's circuit is very important and that's why I'm considering the deHavilland.

I never leave tube gear on and unattended for very long and always keep plenty of spares around "just in case." I also have a Hickok tester and keep pretty good tabs on my tubes.

I was hoping for a few more responses from those who've lived with the 845 for a while, wondering how reliable they are and what I can expect if one fails.

Again, thanks to the two who responded!
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