DSL401 - Is this an empty tube socket?

[eddy126]

Hi folks! apologies for the multiple threads. I just took the back off the dsl401 and noticed what looks to be an empty tube socket to the right - the long silver thing. Can someone tell me what that is and/or if I'm missing anything?

 

[Dogs of Doom]

no, that's an interference sleeve...

It's a spring-loaded twist & release mount. So, if you take a firm grip of it, w/ 2 fingers, push down on it (less than 1/8" or 2mm's) & twist it ½ turn or so & release the pressure, it should unlock & spring up. Then you can remove it, simply by lifting it up.

I see the point of the tube in there...

 

[eddy126]

Ah, okay. thank you! Is there a reason why that's the only one mounted like that? Apologies for the dumb questions - just trying to learn a bit as I haven't see that on my other tube amps.

 

[Dogs of Doom]

no prob... yes, it's because that tube is the 1st in the circuit. It needs to be as clean as it can get (from noise & interference), because all other gain stages amplify what that tube produces.

So, if you have noise/interference at that stage, the noise/interference will be amplified along as part of the signal. The further you go down the signal path, the less each stage is amplified later on.

Some amp's have all pre-amp tubes covered, especially high gain amp's. Marshall didn't feel that the DSL needed it. Keeps costs down & not really needed, as long as your tubes are in good shape...

 

[eddy126]

Understood. thank you so much for the explanation. I really appreciate it!