Tube Amp Precautions??

Do not roll tubes until about one hour after powering off. Do not open them up.
Enjoy!!!

Tube amps generally operates at a much higher voltage (100-200V, sometimes even up to 500V or higher) than SS amps, so don't pry on the innards when it is live! Wait for a while after power off before touching the circuit, those caps might still be charged.

When you hear a crackling noise chances are one of your tubes just failed and you will see it burning inside with blue light. Don't panic, just turn it off, let it cool then replace the failed valve.

Sizzling is too late. That means your headphones are fried.

Which amp?

 

If it is a style that requires manual biasing, recommend getting a plastic screwdriver to turn the bias pots.  I dropped my metal screwdriver, once and blew out one of the output tubes.

With this amp, you will not need to set the bias.  

 

All tubes are biased -- as I understand it -- to put them into their linear operating zone.

With some amps, especially when putting in new tubes, you make

sure the bias is the same across all of the output tubes so they

are working in the same part of their operating curve.  Sorry, not

much of an expert in this... but this is my understanding.

 

It looks like the v8p has a ECC88 tube input stage and solid state

output stage.  Seems like it will be very nice.  The EC88 are going

to last a very long and it's easy to find replacements when needed.

Nice to hear that it works well with the HE-500.

 

Is the sizzling noise constant? Is it in both channels?

 

Depending on the circuit, you have to take more (or sometimes

less) care in matching individual tubes or taking care to get ones

with low noise.  So you might want to get replacements directly from MF;

they would know.

 

But these tubes are not exotic and it would not be expensive to try out

different types to see if it makes an audible difference.

 

I could see replacing after 3 years... although the actual life of the tube

might well be something like 10,000 hours of operating time.  But if you're 

getting a sizzling noise, then that's certainly enough reason to replace.

That sounds like your input tube has gone microphonic, and will need to be replaced. Good NOS ECC88s are not too expensive, though

As a precaution though, it's not generally a good idea to tap tubes to see if they are microphonic. If you tap it too hard, you might end up damaging a perfectly good tube! Also, never keep tubes in a drawer. The sudden impact on closing can cause perfectly good tubes to go microphonic. A box is much better.

A microphonic tube, might well pick up the vibration from the case tap or perhaps

even just plugging and unplugging the headphones.  

 

When the tube is operating normally, I assume that it sounds fine.  True?

 

If you're getting elevated background noise during 'normal' operation, then I'd

definitely replace.