[moredes]

Hello,

I'm just getting into headphones and HA's. My toys have arrived and I have some really dumb questions that I can't find answers for with 'search' or Google...

1) Is it bad to remove the headphone jack with the amp turned on? Can I plug in headphones after the amplifier has been turned on?

2) What's the proper method for removing tubes? Muscle it straight up or rock it and pull? (I barely know enough to know not to twist the tube, but what if one of them is in there good and tight?)

3) It seems obvious that tube amps ain't "Plug and Play", so I'm sure I can't swap tubes while the amp is on... but how long should I wait to pull a tube after I've turned the amp off?

4) Do tube dampers work?

5) If an amp hums, can you hear 'hum' when the source isn't playing? (I hear something like *very* light pink noise when listening to some of my SACD's, but nothing when the source isn't playing. It's like the background hiss that the Dolby process used to remove.)

Thank you, All... do the questions ever get any dumber?

 

[warrior05]

Not dumb questions at all. We all start somewhere and it certainly is better to be cautious. Some of your questions however, lead to debatable answers so you won't get any absolutes. But I will start things off for you:

1) No problem in switching headphones while the amp is on. I highly recommend though that you turn the volume all the way down. You can get a sharp pop as the signal end of the plug contacts the ground upon insertion. If you've got your amp cranked, there is potential of damaging a driver in the headphone.

2) On stubborn tubes I use a gentle rocking motion while pulling up. You don't want to bend the pins.

3) This is where some debates might pop up. Me? I waited till the tubes were cool enough to the touch before switching them. Some have yanked them out wearing a glove right after switching off. I just prefer to let them rest a bit first.

4) I'll leave this to others. I used them but I honestly can't say if they made a perceptible difference.

5) I'll also leave this to those more experienced (I'm mostly an SS guy). When I had my Darkvoice, I didn't always hear a tube hum but when I put on my headphones I could hear it then. I don't know if it always is a 1 to 1 relationship though. See? Not so dumb. Of course I'm not the sharpest tool either.

 

[Asr]

Quote:

Originally Posted by moredes /img/forum/go_quote.gif 3) It seems obvious that tube amps ain't "Plug and Play", so I'm sure I can't swap tubes while the amp is on... but how long should I wait to pull a tube after I've turned the amp off?

I would personally wait until a tube is cool enough to the touch before attempting to pull it out, but I thought I would let you (and other Head-Fiers) know that I've personally witnessed Mikhail @ Singlepower (who builds tube amps day in day out) remove tubes instantly after turning off an amp!

 

[Jahvetti]

Maybe he knows what he is doing, but my Supra plays as nothing had happened for ~20 seconds after switching it off.

 

[Uncle Erik]

Quote:

Originally Posted by Jahvetti /img/forum/go_quote.gif Maybe he knows what he is doing, but my Supra plays as nothing had happened for ~20 seconds after switching it off.

That would be the big caps in the power supply. When you cut power, current stops flowing into the caps. However, the caps still aren't discharged, so they keep the circuit powered up.

This is a good thing. If you have a music transient that needs lots of power, the circuit can pull that from the caps instead of straining the iron and clipping.

 

[Jahvetti]

Exactly so, but would you pull the tubes when the sound is still pouring out?

 

[Happy Camper]

I also pull after draining the circuit but while still warm. I do this by leaving the volume level alone and turning the power off. Once no more sound is heard, I turn the volume down all the way and pull the tube(s). I rock the tube out of the socket by the base. The base may be hot so use glove or tube puller. Don't sit a hot tube on a cool surface.

 

[Happy Camper]

Quote:

Originally Posted by Jahvetti /img/forum/go_quote.gif Exactly so, but would you pull the tubes when the sound is still pouring out?

If current is flowing and you break the pin contact, it would arc and start corroding the pin/socket. For maintenance purposes, I'd let the circuit drain completely before pulling. IMO

 

[jilgiljongiljing]

Also take a look at "The New & Improved™ Tube FAQ for Newbies!" Sticky Thread on this forum, it has a lot of other useful information as well.

 

[larry.said]

There is always residual current flowing in the circuit due to the RC filters set up in the power supply. The tubes will not be powered to their fullest potential but transient currents are still present. The RC constant is relatively small but just to be safe, I would wait 10s before pulling anything out.

 

[breakfastchef]

4) Tube dampers are generally indicated if you are having microphonic problems.

5) You need to identify the source of the hum. Disconnect all inputs to the amp. Is there any hum? How about after you turn up the voume knob? If the amp is dead quiet, your hum problem is coming from external sources. Another thing to do is make sure all your periphersls are plugged into the same outlet/outlet strip to insure you are not getting ground loop hum/noise.

 

[moredes]

I'm wondering--what do they do?

I don't hear any hum when I disconnect my input sources, nor when they're connected and the volume is adjusted on the HA louder than I normally listen.

Do dampers lessen the effects of vibration from music? Or, without hum, are they not necessary?

Thank you.

 

[breakfastchef]

Sounds like you have a hum problem, and no, tube dampers would not be indicated. Hum is an electrical problem; microphonics is primarily a physical anomaly. Do not get them confused.

If you hear no hum from the headphone amp with just your headphones attached, you are picking up noise (electrical, ground loop, etc.) from something else you are connecting to your amp. Process of elimination through a series of plugging and unplugging of interconnects might help you flush out the 'hummer'. Again, also make sure anything hooked to your amp is connected to the same outlet/s as your amp to rule out a possible ground loop issue.

Turn on your amp and plug in your headphones. Turn the volume up a little and lightly tap a driver tube with you fingernail. Chanes are you will here that physical impact on your headphones. That is microphonics. Something internal or external to a tube can cause unwanted vibrations leading to microphonic artifacts. A tube dampener, as I understand, prevents or lessens this vibration so the resulting noise does not interfere with your listening pleasure.