General question; Combo as opposed to head?

[cellardweller]

What are the advantages/disadvantages?

I had heard that the vibration of the tubes in combo amps significantly reduced tube life-expectancy....

So beyond the convenience aspect of having one unit to move, what advantage do combo's present??? :?

 

[rickc007]

What are the advantages/disadvantages?

I had heard that the vibration of the tubes in combo amps significantly reduced tube life-expectancy....

So beyond the convenience aspect of having one unit to move, what advantage do combo's present??? :?

Probably convenience and cost, the combo is usually only
50 to 100 bucks more than a head
but Mesa cabs will set you back at least 3 to 4 hundred bucks
for a 1x12

Heads are cool, but the 5:25 was only 50 bucks more in combo
lots of great tones come out of that 10 inch speaker
and you can easily plug in an external

 

[cellardweller]

Can anyone comment/address the truth of reduced life expectancy of tubes due to vibrations???

The vibrations would be significant if you cranked a 50-100 watt combo!

 

[rickc007]

Can anyone comment/address the truth of reduced life expectancy of tubes due to vibrations???

The vibrations would be significant if you cranked a 50-100 watt combo!

Yes, I have heard this numerous times.

I spoke with one the larger more notable online tube stores
about this who knows Mesa really well, asked his opinion
on an ACE 2x12....he highly recommended against a high
watt 2x12 combo due to rattles and failures

below is a link to a post from John Suhr, of Suhr guitars
who mentions even a head on top of the cabinet can cause tube
rattles

http://www.thegearpage.net/board/showthread.php?t=246302

Johns post is near the bottom

 

[rickc007]

below is another comment he made further down on the thread

"Very true. Combo's are horrible for tubes, also terrible to record. Some power tubes work just fine but can have a mechanical vibration that mics pick up. I'm always resisting making combo's"

"There is interaction between the power tubes and the speaker if they are really close, good or bad is anyones guess"

"Yeh and engineers curse about it all the time and combo owners change tubes twice as much. Clapton had me drive into LA one day cause his tweed had a rattle, it was a power tube, really nothing wrong with it but the speaker rattled the tube, took 5 replacements to find one with no rattle for the engineers mic.

As for old recordings.... who cared? there were rattle buzzes everywhere."



John posts a lot on another forum, is quite informative and very knowledgable

 

[cellardweller]

Kewl!

thanks for the reply and ANOTHER forum for me to haunt!!! :lol:

 

[Russ]

When tubes were invented they were never considered to be sharing the same space as a speaker(s). They really shouldn't be in a guitar combo amp but because people like the all in one package they end up in there and the tubes end up getting blasted sonically. I too agree that the same principle applies to a head on a cab but the effect is lessened considerably. Ideally you would want your tube amp behind a closed back cabinet. This would allow the brunt of the sound waves to be projected away from the amp and the resonant frequencies from the speaker cabinet to be transferred to the ground/floor first thus greatly reducing the amount of vibration your tubes would be subjected to. If you really want to minimize the damage you could put your amp in a shockmount road case and place it somewhere out of the line of fire. Many pros do this.

 

[Platypus]

I've had countless combo amps both open and closed back and never noticed a premature death of a power tube due to vibrations.. sounds like a lot of FUD to me without any backing evidence to suggest it's true in the slightest other than anectdotal evidence.

I'd like to hear from more people on the issue however, not doubting Mr. Suhr but you think if there was a substantial problem they would have engineered a better solution.

Abstract : Nine tubes of each of four subminiature types (Type 5718, Type 5719, Type 5840, and Type 5899) were subjected to shock excitation at a fundamental frequency of 23 cycles per second with an amplitude of 0.11 inches. Various parameters and leakages were measured as well as microphonic noise. There is no evidence that any tube was seriously affected by this treatment and, on the average, the tubes were essentially unchanged by the 22,000 hours of vibration which they experienced. (Author)

http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0657158

Good enough for military missle guidance systems.. good enough for a tube amplifier I'd say.

 

[rickc007]

Abstract : Nine tubes of each of four subminiature types (Type 5718, Type 5719, Type 5840, and Type 5899) were subjected to shock excitation at a fundamental frequency of 23 cycles per second with an amplitude of 0.11 inches. Various parameters and leakages were measured as well as microphonic noise. There is no evidence that any tube was seriously affected by this treatment and, on the average, the tubes were essentially unchanged by the 22,000 hours of vibration which they experienced. (Author)

http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0657158

Good enough for military missle guidance systems.. good enough for a tube amplifier I'd say.

not sure what a "shock excitation at a fundamental frequency of 23 cycles per second with an amplitude of 0.11" really does

if it doesn't generate mucho harmonics, it's prob not the best test
most amps prob don't even produce frequencies that low, humans sure can't hear that low

 

[Platypus]

I'd really love to hear from some folks with credible backing evidence on this one, I'm not doubting the rumor and I've heard it for years but never seen it myself. Hopefully some gurus respond to this thread, might be worth making a seperate thread?

 

[recto-robbie]

they not only use them in guidance systems but also in tanks of the past.
There may be a loss of some life in a tube due to rattle, but I personally wouldnt make a purchase entirely on life expectancy of a tube in a combo...Besides many of the most famous recordings were done using combo amps. So until tubes start going bad in a month or two, I will keep playing combos and enjoying the year or more I get out their tubes

 

[cellardweller]

Good enough for military missle guidance systems.. good enough for a tube amplifier I'd say.

Well....
Except as we all should know, the military can afford to change tubes much more frequently than I can!










*EDIT*~What exactly is "FUD"? :lol:

 

[ashjn]

I spoke with someone at Bogner a while ago about this and he said yes there is rattle but it is not significant unless you are playing at really high volumes

 

[Rocco Stiletto]

With the Stiletto Ace and Roadster Combos, the speaker is completely sealed off. The tubes would probably last longer than in a traditional openback combo. I'm not too worried about it.

 

[Russ]

For the typical home/small gig/studio guitarist there is nothing wrong with a combo. Even with big touring acts there is really nothing wrong with a combo. Just expect to change tubes more often.

 

[Russ]

So beyond the convenience aspect of having one unit to move, what advantage do combo's present??? :?

Combo's can give you a more airy feeling than a sealed cabinet. They tend to be less punchy and actually fill a room better because you get your sound going everywhere instead of beaming out of the front of a sealed cab.

 

[tommyhawk13]

Combo's can give you a more airy feeling than a sealed cabinet. They tend to be less punchy and actually fill a room better because you get your sound going everywhere instead of beaming out of the front of a sealed cab.

Isn't that the thinking behind the Halfback cabs? At least that's what the Boogie catalogs used to say.

To me, it's just a packaging issue.
Sure, there are vibrations, and even the heat from the tubes means the combo can't be sealed.
If you need to take your rig to practice twice a week in the back seat of a Honda, then go for the combo.
If you still need a small package, but can't stand the open back, get a small head and a sealed 1 x 12.
And of course either one of those can be used with bigger cabs.

 

[Platypus]

Good enough for military missle guidance systems.. good enough for a tube amplifier I'd say.

Well....
Except as we all should know, the military can afford to change tubes much more frequently than I can!










*EDIT*~What exactly is "FUD"? :lol:

"Fear, Uncertainty, Doubt"

microsoft is notorious for it

 

[Russ]

Microsoft just releases products too soon before all the bugs are worked out. My guess is that it is to pay for the time already invested in the software and to fund the Service Packs which should be part of the complete retail package anyway.