The Headcase Stax thread

[Deadneddz]

There seems to be a very very slight noise coming from the right channel on my O2. Its nothing like the squeal from dust getting into a Lambda or HE60 both of which I have had experience with. It kind of sounds like if you were to push a lens brush(or your own short hair) against the leather pads and the bristles would pop out. But the sound is extremely quiet and they come in small series of crackles and static. I checked the connections to the amp and its not the connectors. Wiggling the right channel cable doesn't make the sounds appear, so i'm hopeful that it is not cable failure. My set is barely used and in 9/10 condition. Plus I just got a SRE-725. Anyone have any experience with these kind of small noises?

[deepak]

If you're using a tube amp is it tube microphonics by any chance?

[Deadneddz]

Hmm maybe, it is a different SRM-T1 than the one I recently parted with. And its been coming up since i've been using this one I have right now. I don't have any experience with tube microphonics, so I couldn't really say if I thought it was or wasn't. All I know is that the sound is so slight that i'm confusing it for my hair settling against the leather pads once I have the phones in a "set" position on my head. But this sound is only coming from the right channel, so i'm not imagining it. This is definately not worthy of dismantling the black plate and cleaning the driver for particles, but i'm just curious if anyone has heard something similar.

[Dusty Chalk]

Swap the left and right channel tubes.

[spritzer]

You can certainly hear a whole range of amp related effects through the phones so start with swapping the tubes.

[Les_Garten]

I hear this on tube amps when they are cold and warming up. Were the tubes cold by chance?

[spritzer]

All Stax tube amps (post 1980's) have a 30 second delay so you will never hear any sound with cold tubes.

[Les_Garten]

All Stax tube amps (post 1980's) have a 30 second delay so you will never hear any sound with cold tubes.

I'm talking about for some time after till they get real hot and quit expanding. Mainly tubes that may be more prone to microphincs. I've heard little tinks for 10 minutes or so.

[spritzer]

That should never be an issue with the 6CG7's in this role.

[Deadneddz]

Ok, being the impatient bastard that I am, I switched the tubes to the opposite channels, and biased the amp. Stopped the music with the O2 on my head and that sound is gone completely. I don't hear it anymore in any channel. Strange, but so far it seems like the tubes were the culprit.

[spritzer]

Was the bias far off? DC on the stators could certainly cause some audible issues..

[Deadneddz]

Suprisingly no. Even after I switched the tubes most channels were within +/- .5V from zero or less. One channel was fluctuating around +1.6V but thats about it. Very strange, i'm still listening to my O2 right now and when I press pause it does not emit that sound anymore.

[spritzer]

Very strange indeed. One plausible solution would have been oxidation on the tube pins which was scraped off once you reinserted the tubes. A stretch though...

[Tachikoma]

Ugh, my SRM-X Pro has developed a channel imbalance, and there aren't any convenient balance knobs anywhere on the amp (I've checked inside). Should I panic?

[n_maher]

Are you sure that the main volume knob isn't a balance control? I can't find large enough pics to tell but most of the stax amps I've encountered are built that way.

[spritzer]

The small ones usually don't have a split volume know but some do have a built in balance control. What we could use are detailed pics of the circuit to see if you can take some measurements to see what's going on.

[Beefy]

So what might cause a Stax Lambda driver to make a occasional 'scratchy' sound, even after being disconnected from an amp? I'm pretty sure it isn't cable microphonics or anything like that, because it is only happening on one side......

[cetoole]

I presume the scratchy sound stops after you short the pins out? If it doesnt, then I have no clue what could be going on, but the drivers do hold bias for a good while.

[Beefy]

Yeah, it seems to decrease as the bias drops.

[mypasswordis]

Not sure about a scratchy sound but if it's buzzing then it's some dust that has lodged in somewhere it isn't supposed to.

[spritzer]

Clearly bias related but what exactly is going on is hard to say. Could be that the phones have arced and there is some residue on the diaphragm causing it to act up. No way to open up the drivers to check though.

[Beefy]

Clearly bias related but what exactly is going on is hard to say. Could be that the phones have arced and there is some residue on the diaphragm causing it to act up. No way to open up the drivers to check though.

I'll have a bit of a play around, listen some more on the SRD7-SB as well as the Exstata, and see what happens......

[spritzer]

I'd open up the housings and see if the drivers are not coming apart. That can happen with some of the older phones. They should be firmly glued shut. Also look for any gaps in the mylar dustcover on the front or the one on the back.

[manaox2]

I'd open up the housings and see if the drivers are not coming apart. That can happen with some of the older phones. They should be firmly glued shut. Also look for any gaps in the mylar dustcover on the front or the one on the back.

I might wish to give my lambda a check up. Is there any way to reglue or close the gaps safely if so?

[spritzer]

It is possible to reseal the drivers but it's far from easy. You need to strip them down and get rid of all the old glue residue and then assemble them again with polyurethane glue.