resonance/micro phonic sound when tapping on the unit

[xcoolhandx]

I bought this unit with the speedball upgrade already pre-build

I don't know what to make out of it ...I recently noticed resonance coming through my right channel (there is some in the left but not as much),for example when the unit is ON and I have nothing playing any tapping on the base or aluminium plate-most pressent when tapping next to headphone jack will travel through right channel ,it's more of a micro phonic sound ...what gives
I've tried  changing tubes ,headphones and it's not going away ,I was about to swap some caps but this have to be addressed first ,any help ?
I tried power tube on my Darkvoice336SE and it's silent ,tried 3 different tubes with the same results

[fullheadofnothing]

So don't tap on it.

[Grainger49]

Microphonics are a tube related problem.  The longest thread in the Crack Folder is Tube Rolling.

I suggest you read some of the thread and purchase a pair of new tubes and see how it goes.

[Paul Birkeland]

Microphonics are a tube related problem.

Microphony is not a problem, it's an attribute. 

[xcoolhandx]

@ fullheadofnothing,I'm just given the example ,what lead me to it was "pulling to one side" ->left channel always seems to be stronger

@Grainger49, I'm not sure if I used the right description as "microphonic" or resonance but anyway you want to call it -it shouldn't be there -I'm not tapping on the tube for crying out loud ,I have plenty of new tubes so pointing me to a tube rolling thread won't solve the problem

[vetmed]

Does it make any difference where on the base you tap? Of necessity the tube sockets are bolted to the chassis so it should come as no surprise that there is noise. If this was a power amp connected to a speaker then the sound the speaker makes could cause resonance, the only way that could happen in a headphone amp is if one of the tubes was wearing the phones Seriously if the loudness varies by where you tap, then possibly something needs tightened. And we also need to understand what this "resonance" is to be able to help you. Good luck

[Grainger49]

Microphonics are a tube related problem.

Microphony is not a problem, it's an attribute. 

So you are saying that all 12AU7s and all 6080s are microphonic?

This is not a problem I have had with the 12AU7s in my FP 2.

[xcoolhandx]

Does it make any difference where on the base you tap? Of necessity the tube sockets are bolted to the chassis so it should come as no surprise that there is noise. If this was a power amp connected to a speaker then the sound the speaker makes could cause resonance, the only way that could happen in a headphone amp is if one of the tubes was wearing the phones Seriously if the loudness varies by where you tap, then possibly something needs tightened. And we also need to understand what this "resonance" is to be able to help you. Good luck

worthless post ..why bother posting bro?
P.S. I can tap anywhere on DV336SE -tube included and you won't here a thing  .."good luck" to you

[JamieMcC]

Well that looks like a very clean build it takes a little bit extra time and trouble to do so.

I can only suggest twisting your rca input cables together and see if that helps. I had some microphonics  when I touched the volume knob I would get a hum take my finger off and it went, twisting the rca input cables cured this. Its a easy enough thing to try you never know.

 

[xcoolhandx]

thanks Jamie ,finally someone that actually trying to help ,yeah Crack seems to be very vulnerable to anything and everything ,just noticed very similar thread here with dead end as well
http://bottlehead.com/smf/index.php/topic,5806.0.html

right channel is barely audible

[John EH]

If that were mine I'd run through the ohm and voltage tests.  Then while it was upside and playing I'd do the old chopstick test and push around on things gently with particular attention to the rca connectors, volume pot, and tube sockets.  Problem might reveal itself.

Also don't discount craziness like input cables and sources.

[xcoolhandx]

If that were mine I'd run through the ohm and voltage tests.  Then while it was upside and playing I'd do the old chopstick test and push around on things gently with particular attention to the rca connectors, volume pot, and tube sockets.  Problem might reveal itself.

Also don't discount craziness like input cables and sources.

I have Fluke MM and will do what you suggested ,I want to get to the bottom of this
Thanks

[JamieMcC]

I have had a few noise issues with my Crack in the past and all of them have been due to outside influences such as routing of connecting cables, power supply extension leads, even a electric radiator in a different part of the house that was tripping in and out on a thermostat causing a intermittent hum on the Crack (that one was a real puzzle) and was very  frustrating at the time.  I am sure the resident gurus here will be able to offer some better ideas than myself to help chase down the cause. 

[vetmed]

FWIW mine is dead silent. You buy this already assembled by someone else and you seem to think that this is a problem related to design rather than the obvious solution. Maybe you should be talking to the "bro" that sold it to you, rather than coming here and dissing an extremely successful design. Have a nice life

[Grainger49]

thanks Jamie ,finally someone that actually trying to help    .  .  .  .   

I think my post was an attempt to help....