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Tube Amp - Output Power Fuse Protection

The question is why do some manufactures of tube amps ,not have protection for the output stage of the amplifiers?
I have been auditioning some tube integrated amps that did not have any kind of fuse protection for the output stage of the amplifier.

I was in front of one amp when an EL34 tube flashed and knocked out the left channel. It blew out an output resistor , which has to be replaced to restore the amp. A simple fuse in the plate circuit would have protected the amp and with a new fuse , restored service. Instead , one would have to take the amp to a local repair shop , or have it shipped if not local.

Is this a common practice of manufactures to not have protection? Is it worth purchasing an amp that does not offer protection?

As we all know , it can be fun not to use protection , but sooner , or later it will cost you! One way or the other!
timo62

Showing 1 response by xti16

xti16
1,525 posts
 
First you would want to get the most out of the circuit. By adding a fuse in line with the resistor the fuse would have to blow before the you damage or burn the resistor. That would limit the output power to less than the design without the fuse. Tough call. I personally would take a little less power to save a repair. But OTOH I know how to solder.

That said I do have an integrated that protects against frying the resistor. For whatever it's worth it's an Octave. Back when I had a V70SE I did lose some tubes with flash over and dead shorts. These tubes were also bought used. Never know what you are going to get. I later upgraded to the V110 and not had any failures for over a year (but a good chance I weeded out the bad tubes).
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