Tube failure or ear fatigue?

[Boogie]

2 years ago, the Super Dallas was experiencing what I would describe as power tube filament microphonics...when playing at gig volume, one could hear a metallic, vibrational ringing after big chords. We were in the middle of lots of gigs and I didn't have time to properly debug the situation so I bought a pair of regular JJs and replaced the sweet =C= EL34s (no longer readily available). There's a slight tonal difference but it boils down to mostly nuance differential. As a policy, I now place the head on the floor and not on the cab to isolate it from the heavy bass and hopefully the environmental microphonics.

Fast forward to last weekend. Practicing with the prog Rock/fusion (or whatever-the-hell you call our brand of craziness) guys, I noticed a change. The =C=s went back in 3 weeks ago to see if I noticed a difference. Since then, I've maintained the same controlled feedback and infinite sustain kookiness that I've enjoyed for a while with these guys. But after a couple of hours into practice, I couldn't find that "sweet spot" for the harmonics nor sustain. Normally, I'd chalk it up to a heat issue and maybe change the power tubes, but here was one other factor. Unlike my science and math background dictates, I modified a second variable: I changed the string gauge on the Cu24 from 11s to 9s. Ugh.

So, what do you suspect is the cause for guitar response resulting in less liveliness? Heat-related power tube "sag", resonance change with string gauge change, or did my ears just fatigue and only perceive a difference?

 

[11top]

So, what do you suspect is the cause for guitar response resulting in less liveliness? Heat-related power tube "sag", resonance change with string gauge change, or did my ears just fatigue and only perceive a difference?

Drugs.

 

[rugerpc]

Drugs.

Not really clear here...

Should he do drugs or stay away from them?

(I'm voting strings - easy enough to test.)

 

[László]

As Mark Twain famously said, "Ya ain't never gonna change two variables at once in a guitar rig and figure out which one caused the tone change."

Not really clear here...

Should he do drugs or stay away from them?

Hahahaha!

Do them. Then he won't have to change strings or tubes, and won't care about ear fatigue.

 

[László]

As a policy, I now place the head on the floor and not on the cab to isolate it from the heavy bass and hopefully the environmental microphonics.

I have recently experienced a rather odd thing, now that you mention this.

A while back I posted about tube rattle with the Winged Cs, and my HXDA 30 head when sitting on its original 1x12 cab. The thing is, this never happened when my 50 Watt HXDA head sat on my 2x12 Mesa cab in the past, or on my 2x12 PRS Grissom cab.

Anyway, just before my surgery I replaced the 1x12 with a PRS Big Mouth 2x12, and just for ease of getting to everything while my arm heals, sat the head on top, thinking I'd live with the rattle until I'm able to manhandle the gear again, once the doc says lifting is OK.

But as with the 2x12 Grissom cab, there's no rattle at all, regardless of volume!

What I've noticed simply by striking a chord and putting my hand on the cab is that there's quite a bit less vibration I can feel on the cab than there was when I sat my hand on the vibrating 1x12. Also, the 2x12s feel more stable on the carpet in the studio - the combination sits on the carpeted floor with no wobble if I try to move it, where the 1x12 with its lighter weight and a heavier head on top wobbled easily on the carpeted floor.

I'm experiencing no environmental microphonics or tube rattle now with the head sitting on the cab, regardless of volume.

I think it was that the 1x12 with its smaller dimensions and closed back, vibrated quite a bit, and because it was light, with the head on top, probably wobbled back and forth a bit on the carpeted floor due to the movement of the speaker inside the cab and the padding under the carpet being pretty soft. Not only the vibration, but also the wobbling probably caused the power tubes to rattle their filaments. The heavier 2x12s don't have this issue, and as a result, there's no tube rattle.

 

[veinbuster]

I might be missing something: could you find the sweet spot for the first two hours and then couldn't?
or could you not find the sweet spot during the two hours?
former - ear fatigue is what I would blame
later - try 11s again

 

[László]

Just do what I did - have a few surgeries and forget about it for a while.

When you come back, presto! Everything sounds great.

 

[elvis]

The sweet spot is at my house. Sorry, I'm not giving it back.

 

[Rider1260]

If you were going OK for 2 hours I would just say you were getting tired and not playing the same thats what happens to me.
your not getting any younger

 

[László]

your not getting any younger

Hey! I'm getting younger!

Had the heart vessels replaced, got some nerve damage fixed...I'm like an old car that's being restored.

 

[Boogie]

Here's another tidbit...

The week before, I took a different guitar *gasp!*...get this...an Ibanez JS1200 that belongs to my son. He let me convert it back to bone stock (unblock the trem and replace the 11s with 9s) and try it with this project. It worked beautifully! Sustain, feedback, all there. It sounded insanely good!

So, what do you think?

Oh, and there's no doubt I was getting tired, but with the ease of coaxing that feedback, I could probably do it in my sleep.

 

[vchizzle]

So you started out the day with 9's on the guitar and everything was "normal" for the first couple hours, then the troubles began?

 

[László]

The week before, I took a different guitar *gasp!*...get this...an Ibanez JS1200 that belongs to my son. He let me convert it back to bone stock (unblock the trem and replace the 11s with 9s) and try it with this project. It worked beautifully! Sustain, feedback, all there. It sounded insanely good!

So, what do you think?

Definitely time to ditch that terrible DGT and steal your son's Ibanez?

 

[Boogie]

So you started out the day with 9's on the guitar and everything was "normal" for the first couple hours, then the troubles began?

Basically, yes. I'm not really blaming the string change, though. It's just another variable in the equation.

Definitely time to ditch that terrible DGT and steal your son's Ibanez?

The thought crossed my mind...








...NOT!

I listened to what you guys said and decided to swap back in the JJs EL34s.

Last night's gig yielded no surprises. The DGT was the primary guitar with the One for drop D Stuff, with no appreciable tonal shift or other changes. We were fighting sound level issues all night (hard wood floors, walls, and ceilings and not enough people to deaden the room) but pedal tweaks solved most of my problems. In all, I wasn't upset or disappointed and others thought I sounded pretty good. It was a good night (a local venue owner even approached us to be our management company )!

The real litmus test will have to wait until next week since I have to do end-of-the-month accounting tasks and practice had to be cancelled. I'll report back after the next tests.

Thanks guys!

 

[vchizzle]

It seems by your description that it is entirely possible the tubes have enough wear on them that after they're runnin' hot for a few hours, things seem to go south. You wouldn't figure it would take that long, but who knows? Tubes are weird like that.

 

[Boogie]

The PRS Heat management system (aka, the small fan) does a pretty good job. But, it's limited. I came to the same conclusion and will comment next week.

 

[László]

I've got a pair of NOS Siemens EL34s waiting for when the Winged Cs eventually need to be replaced, but they're sounding better than ever at a year old, so I don't want to mess around on the theory that it ain't broke, I ain't fixin' it.

 

[Boogie]

I've got a pair of NOS Siemens EL34s waiting for when the Winged Cs eventually need to be replaced, but they're sounding better than ever at a year old, so I don't want to mess around on the theory that it ain't broke, I ain't fixin' it.

Smart move. In a studio environment, I could imagine those tubes lasting a long time.

 

[László]

Smart move. In a studio environment, I could imagine those tubes lasting a long time.

I think you're right.

The Siemens are supposed to be the real deal as well, so I'm looking forward to using them when the Winged Cs finally need replacement.

 

[G-Man]

Ever try tube dampeners? Some people think it is snake oil and some swear by them.