[ablaze]

I got this strange problem with my X-can. everytime I lightly tap the chasis of the amp, and especially the volume knob the tapping sound transmits all the way into my cans. in fact, lightly scratching or even lightly TOUCHING the volume knob with my fingernail is enough that I can hear it (amplified) thru my connected headphones!

Do other X-can users experience this (its a v2) or did I get a lemon?

(dang. typo in the title. mods, help me change it pls?

)

 

[ServinginEcuador]

Sounds like you got a set of microphonic tubes. I had the same problem with a pair of my Amperex 6922s a while back. Tuberolling them out got rid of the probelm.

Do you have a different set to roll in and see if the problem goes away?

 

[Sean H]

I'm pretty sure this sounds like one or both of the tubes have went microphonic. If you are not familiar with this it's very common. It usually happens with the pins becoming loose. There's nothing you can do really other than use some sort of tube damper which will only marginally help. This doesn't mean the tube(s) are worthless now, they can remain microphonic and work for hundreds or thousands of more hours. Some people have even found that in some cases microphonic tubes sound better after they went microphonic. I had a tube headphone amp (Wheatfield HA-1), in which several of my tubes for it were microphonic, and I had the same problem you described. Just don't tap on the amp!

Addendum:

Here's an interesting snippet from an article I found on Microphonics (kind of interesting, thought I'd post it):

Other types of defects (other than low emission) may develop with age or may be present after a short time of operation. Some of these are:-microphonic tubes, development of gas in the tube, burned out filaments, loose elements, and disarranged elements.

A microphonic tube is one that causes noises or howl in the speakers, due to mechanical vibration of the tube electrodes. All tubes are more or less microphonic, but some are worse than others. Certain stages of amplifiers are more susceptible to microphonic action than others and it is usually possible to arrange any set of tubes in an amplifier to eliminate a microphonic howl, but some tubes may be so highly susceptible to microphonic disturbance that they cannot be used any place in the amplifier and must be replaced.

 

[ablaze]

wow thanks guys. I learnt something new today

I didn't know tubes go 'microphonic'!
so its not a bad thing? guess I needn't bring it back and exchange it for a new set? (the amp's bought from a local dealer)

I've resorted to seating the amp on two fat pieces of foam, if not, even typing on my keyboard (which is just beside my amp) transmits "clanging" sounds to my cans!

*time to do a search on "microphonic tubes"

*

 

[Sean H]

I posted an interesting snippet from an article on Microphonics in my post above. Yep, microphonic tubes are frustrating. It's not necessarily a bad thing really. It's very very common, in fact all tubes are microphonic to some degree it's just the real bad ones are very noticeable.

If you were able to get right up to the tube and yell into it you'd likely hear it through your cans!

 

[ablaze]

Quote:

Originally posted by Sean H If you were able to get right up to the tube and yell into it you'd likely hear it through your cans!

lol!

thanks Sean. I did a search properly now (I didn't know what the hell to search for before) and found another X-can user with the same problem http://www4.head-fi.org/forums/showt...e+microphonics
reading it carefully now.

says to self: welcome to the world of tube amps

 

[ServinginEcuador]

ablaze,

I would return the tubes and get a new pair. It's not good to have a microphonic set of tubes in your amp. It's a novelty now, but impedes serious listening as you use them.

Next abalze big adventure: buying and tuberolling your X-Cans. Have you read either Joe's Tube Lore or Nick Dangerous' thread on goo dtubes for this amp yet?? Great stuff to be found in both of those sites.

 

[Magic Robert]

I have a B & O turntable with a tonearm that went microphonic on me a few years back. Not a problem with the dustcover down. But we could work out a trade, you could hook it up through your X-Can -- and have the most microphonic system of anyone.

Then all you would need is microphonic interconnects.

 

[ablaze]

Quote:

Originally posted by ServinginEcuador ablaze, I would return the tubes and get a new pair. It's not good to have a microphonic set of tubes in your amp. It's a novelty now, but impedes serious listening as you use them. Next abalze big adventure: buying and tuberolling your X-Cans. Have you read either Joe's Tube Lore or Nick Dangerous' thread on goo dtubes for this amp yet?? Great stuff to be found in both of those sites.

I've decided to just wait it out. I've got a 1 year warranty from my local distributor, so I think I'll just hang on to the X-can at least a couple more months more. I'm hesitant to open up the amp to tube-roll (does that void the warranty?)..but its in my plans for the future thats for sure

Robert: lol..most microphonic setup in head-fi. that'll be a real funny competition

 

[ServinginEcuador]

You can keep them, just don't touch the amp or volume control too much or it will drive you nuts.

 

[ablaze]

yeah I know

btw, Doug, you keep saying "them"..the tubes are the stock tubes that came with my X-can. I didn't buy them separately yknow.

 

[Sean H]

I think Doug is saying that they are warranted right along with the amp itself (unless there is a separate warranty for the tubes- which is common). However, a lot of manufacturers and tube dealers don't accept microphonic tubes as being warranted for replacement because, again, all tubes are microphonic to some degree and it's hard for manufacturers to find that fine line that would warrant replacement and so some in the end won't replace tubes that have gone more noticeably microphonic. If your amp is still under warranty it's worth checking into to see if you could get new ones though. I mean why not if they will send you out a free pair. Replacing them is a piece of cake, and fun!

I believe just about any manufacturer of tube gear accepts the fact that owners will roll tubes for better sound and of course will need to roll tubes when the stock tubes go bad. So rolling the tubes in your amp will not void the warranty (obviously you should ask - I'd email Musical Fidelity directly). I've heard the Xcan can sound dramatically better with NOS tubes, definitely keep that in mind. I'm hearing it drastically improves the sound of these amps.

 

[Rameish]

Ablaze,

You should be able to exchange the tubes as they normally carry a 30 to 90 day warrenty. Tubes that are microphonic tend to get more so with age.

Also,

If you're tuberolling do get properly tested ones (Kevin Deal of Upscale Audio) has some nice but expensive stuff. He tests them completely.

Another option is to get RAM tubes (they are normally current production stuff but grade their tubes) Obviously don't get the standard grade.

A third place to try would be

Watford Valves in the UK. They have an unfriendly website but offer good tested NOS stuff.

Happy Hunting but don't end up with hundreds of tubes like me - well it's down to about 150 now.

 

[ablaze]

Thanks guys,
will probably check out the warranty issue. the tubes are stock as I said, and I only bothered to check with the shop about the amp's 1 year warranty. I didn't ask if the tubes were warrantied separately.

btw, Rameish, I managed to get it at a 5% discount of the list price

 

[PinkFloyd]

Hi ablaze,

The valves (tubes) are most certainly covered by the Musical Fidelity warranty as I checked this with MF when I first got my X-Can V2.

One of my valves was making a noise and MF told me to return it to them and they would sort out a better pair. In fact the technician told me, and I quote "your amplifier will be returned to you sounding better than when you bought it as we will match a pair of valves and put your amp through tests, unfortunately we cannot take this time at the production stage so there will always be a few that pass through less than satisfactory"

I was very pleased with Musical Fidelities response but couldn't be bothered sending the amp back to them and decided to replace the valves with a set of Mullard E88CC's.

Certainly "don't" live with microphonic valves ablaze. Get back to your dealer and have them replaced with a set that are of merchantible quality.

I personally wasn't too concerned about my 2 year warranty as, if anything were to go wrong it would probably be the valves packing in.

If you're interested in replacing the valves please feel free to visit my X-Can V2 tweaks page at: http://freespace.virgin.net/rock.grotto/index2.htm Nick dangerous also has a great valve changing tutorial at http://www.nickdangerous.com/ although I'd think twice about using the JJ electronics valves in the V2, I tried 2 different matched pairs and they sounded pretty underwhelming.

Hope this has been helpful. If you are bothered about the "warranty" then get that amp back to your dealer ASAP and have those valves replaced.

Pinkie.