New Roadster owner: a couple of questions

[Gontur]

Just bought a used Roadster. First of all: it sounds gorgeous. I tried factory settings and I was blown away. Cleans are really clean, there's a ton of headroom in there. Channels 3 and 4 are just brutal. I'm very satisfied. A couple of questions:

1) I noticed that some tubes don't glow. From left to right: 6L6 glowing - 6L6 glowing - 6L6 NOT glowing - 6L6 glowing - rectifier NOT glowing - rectifier NOT glowing. Why?
2) Not all power tubes are Mesa labeled. From left to right: JJ labeled tube, JJ labeled tube, Mesa labeled tube, Mesa Labeled tube - may this cause problems?
3) To me the amp seems very quite, no humming or noise whatsoever BUT when I dont play there is a very little crackling sound coming from the speakers - when output knob is all the way down this little little sound disappear. Suggestions?

 

[RPercival]

First thing I do when I buy any used amp more than a few years old is new power tubes. If they're mismatched and some look dead, slap a new set in it. Can't hurt and will (almost) guantanee to eliminate that as an issue. I have a Road King and all tubes are lit no matter what tubes are selected.

Thetubestore.com, Dougstubes.com, and Eurotubes.com have all done me well. Tubedepot has made an enemy of me so I tell people to steer clear.

 

[screamingdaisy]

Glow comes from oxygen in the bottle. Ideally, none should glow (is a vacuum tube), but the fact that they do isn't a big deal. Some are sealed better than others.

Mismatched tubes are fine, but the way yours are mismatched is wrong. The tubes are paired:

A B B A (inner and outer)

And not:

A A B B (left and right).

My guess is in the past one of the tubes went bad and a former owner replaced the one "pair" of tubes without understanding how tube pairs works.

 

[knotts]

2) Not all power tubes are Mesa labeled. From left to right: JJ labeled tube, JJ labeled tube, Mesa labeled tube, Mesa Labeled tube - may this cause problems?

From my understanding of this seems to be incorrect. The two outside 6L6's should be paired and the two inside tubes should be paired. It should either be Mesa, JJ, JJ, Mesa, or JJ, Mesa, Mesa, JJ. I don't think it will harm the amp. Can anyone else confirm my understanding?

 

[domct203]

2) Not all power tubes are Mesa labeled. From left to right: JJ labeled tube, JJ labeled tube, Mesa labeled tube, Mesa Labeled tube - may this cause problems?

From my understanding of this seems to be incorrect. The two outside 6L6's should be paired and the two inside tubes should be paired. It should either be Mesa, JJ, JJ, Mesa, or JJ, Mesa, Mesa, JJ. I don't think it will harm the amp. Can anyone else confirm my understanding?

screamingdaisy already confirmed this, one post above yours.

Dom

 

[knotts]

2) Not all power tubes are Mesa labeled. From left to right: JJ labeled tube, JJ labeled tube, Mesa labeled tube, Mesa Labeled tube - may this cause problems?

From my understanding of this seems to be incorrect. The two outside 6L6's should be paired and the two inside tubes should be paired. It should either be Mesa, JJ, JJ, Mesa, or JJ, Mesa, Mesa, JJ. I don't think it will harm the amp. Can anyone else confirm my understanding?

screamingdaisy already confirmed this, one post above yours.

Dom

Very strange. There were no other posts when I submitted my post. I'm not sure if there was a lag in the posting or if I didn't refresh my browser before my response. Either way, I'm just glad I got it right.

 

[Gontur]

Today I submitted my amp to an extensive test. So far everything seems OK. Sound and tone are beautiful, no hum or hiss, no volume drops etc.
There's only one issue: when fx loop is not hard bypassed I hear a crackling noise coming from the speakers. This occours even if channels fx loop switch are off. I tried without any cable plugged into the amp and the outcome is always the same: fx loop hard bypassed NO crackling - fx loop engaged crackling from speakers.

It's a very subtle sound.. very similar to the noise that you can hear when a defective cable is plugged into guitar or amp.

Maybe it's time to change the preamp valve dedicated to fx loop?

 

[domct203]

Today I submitted my amp to an extensive test. So far everything seems OK. Sound and tone are beautiful, no hum or hiss, no volume drops etc.
There's only one issue: when fx loop is not hard bypassed I hear a crackling noise coming from the speakers. This occours even if channels fx loop switch are off. I tried without any cable plugged into the amp and the outcome is always the same: fx loop hard bypassed NO crackling - fx loop engaged crackling from speakers.

It's a very subtle sound.. very similar to the noise that you can hear when a defective cable is plugged into guitar or amp.

Maybe it's time to change the preamp valve dedicated to fx loop?

Absolutely, that sounds like a classic noisy tube.

Even when the loop is off, the dry signal still flows through the FX circuit. Hard bypass will completely remove that FX circuit (and any noises from it).

Dom

 

[bandit2013]

Make sure you have matched pairs of power tubes as described in previous posts.

As far as glow, are you referring to the blue hue or the heater glow. All of the tubes 6L6 and rectifier tubes should have the orange heater glow to them. Note that the rectifier tubes will be dim relative to the power tubes as the heater filaments are not as visible. Heaters are usually bright to some extent, but if you see one tube that is extremely dim compared to the others of the same type (6L6 tubes), chances are the glass envelope has a leak or crack and will essentially be a dead tube.

Power tubes do not need to emit the blue hue in order to work, however there should be a blue aura around the cathode (center part of the tube) which may be difficult to see but under dark room conditions will be noticeable (depends on the tube and if the plates have holes, some tubes do not have holes in the plates). Most tubes I have used will have the blue hue at various intensities. I have also had tubes that had the blue glow that suddenly stopped glowing and then began glowing again. I did not notice much of a difference in tone at moderate volume levels but at lower volume levels the gain character changed from grinding lows to brittle unsavory tone. This was due to a fault in the tube that was actually shutting off momentarily.

If all sounds great, crunch to clean, your tubes should be fine. However, I would replace the power tubes with new ones. I found the Mesa 6L6GC STR 440 or the Ruby 6L6GC-MSTR sound the best and provide that rectifier tone. I have used other tubes but they have a bit different character to them and the frequency response is a bit different. The Tung Sol 7581 actually sounded good but were old and used up tubes. Good luck and enjoy your new Roadster.

 

[Gontur]

Head brought to a qualified tech.
Crackling noise issue resolved: something went wrong in the fx loop circuitry - tech replaced a resistor and now everything it's OK.
No matching tubes: tech said that this mix is unusual, but after some testing he suggested not to swap/change tubes.

One more thing: many people complain about tone suckin' fx loop. To be honest, at gig volumes, I cant hear ANY difference between fx loop hardbypassed/fx loop engaged. This beast sounds amazing.