Chassis / transformer vibration

[julesd68]

Once my phono stage is fully warmed up I'm noticing a small amount of hum from the transformer when the music is not playing. It's not intrusive but I'd still like to deal with it if poss ...

I've noticed that when I press down on the chassis it nearly disappears completely. So obviously the chassis is vibrating "in tune" to the transformer. Needed to be built more solidly I expect.

What's the best way to deal with this? I could put a weight on top of the chassis but would there be another way to deal with the vibration?

I remember seeing some pics of weights on various units somewhere on AOS but can't remember where - had a look in the Gallery but can't find them - anyone remember?

[Riislingen]

First off:

1. Open the chassis and make sure the transformer is tightened down properly.
2. Pick up a sheet of Dynamat Extreme from Fleabay and bolster the inside of the chassis with it - stops ringing too.
3. Ultimately get a sheet of sorbothane and add that underneath the transformer before tightening. Is it a totoid or a traditional transformer ?

I´ve done all of the above on my pre-amp - quiet as the grave. Cheap too:cool:

[walpurgis]

Check the transformer isn't loose, that can cause vibration.

If the gap between the case and the top of the transformer is not too big, use a decent blob of silicone sealant between the transformer and case. This works rather well. Silicone is fireproof and adheres well. Just don't block any air vents.

My DAC needs the treatment, it's a bit mechanically noisy at the moment.

[julesd68]

Thanks chaps - most helpful!

Well that's the second time I've had the lid off today - I just hate doing that! :doh:

Nevermind, I hope it is worth it - the two transformer fixing bolts that I had clear access to I was able to tighten significantly. So will fire it up tomorrow and see how she goes ...

CJ customer services were very prompt in answering my emails. They also suggested possibly trying neoprene O rings under the transformer feet as Sorbothane might "run" when it gets warm.

Hopefully fixing those bolts has sorted it. The hum isn't a big deal but when the stage is perfect in every other way it just bugs me a bit ...

[Riislingen]

Fantastic, hopefully it´s solved with tightening the bolts.

I wouldn´t worry about Sorbothane, it´s much better at absorbing vibration than
Neopren, typical span of operation is well into 70 degrees celsius. If we are talking a P10 phonostage, it wont get into that territory.

[julesd68]

Thanx dude! I'm actually trying out a Conrad Johnson EV-1 at the moment! Sorry - should have made that clear ...

The (traditional) transformer is bolted to the back wall of the case, so there is a small gap underneath it where I could probably slip some Sorbothane - as long as you promise me it won't turn into soup!! :eek:

As you say, hopefully just tightening the bolts has done it ...

[Riislingen]

I had sorbothane over/under two transformers in my tubed pre. 8 bottles in that and no issue. I wouldn't rest the transformer on it, if you want to use it - unscrew it, put between bolting surface and transformer, tighten up.


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[Riislingen]

Nice pre btw :)


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