Coke Bottles

[MesaENGR412]

Has anyone tried the 5U4 "Coke Bottle" Rectifier tubes in 3 channel Dual and Triple Rectos? I was just wondering what the sound characteristics of those were compared to both the 5U4GB's and the GZ34's. I just got to thinking and most of the old 2 channel Rectos came with the 5U4's stock, and I just wondered if that had just a little (I know the circuitry is completely different in a 3 channel) bit to do with the different tonal characteristics of the 3 channel heads...just a thought. lol.

-AJH

 

[edgarallanpoe]

The rectifier tube is not part of the tone chain so I would say that it has very little to do with the tone. My guess is that they changed because they were a pain in the *** to change when they blew. I know in my Tremoverb, I had to remove the top vent unit to change the rec tubes because they were right up against the top of the amp. The GBs are shorter which makes them easier to change if there is a problem. I swap my rec tubes for NOS because they last longer and are much more consistent, it has nothing to do with tone because the rec tube isn't part of the signal path.

 

[Elpelotero]

The rectifier tube is not part of the tone chain so I would say that it has very little to do with the tone. My guess is that they changed because they were a pain in the *** to change when they blew. I know in my Tremoverb, I had to remove the top vent unit to change the rec tubes because they were right up against the top of the amp. The GBs are shorter which makes them easier to change if there is a problem. I swap my rec tubes for NOS because they last longer and are much more consistent, it has nothing to do with tone because the rec tube isn't part of the signal path.

not true....the 5U4G's in my 2ch rectos are much tighter than the 5U4GB's. I've compared pretty much every tube I have in all my amps and I still prefer the 6l6 str 420's and the 5U4G's.

If you guys want more info, there's a great description on Mesa's website under all the stuff about tubes.

In the 3ch heads, the 5U4G's add some clarity and tightness, but the sound is still not anywhere near what you get out of an old 2ch. So it's not so much the tubes as it is the circuit board revisions.

MesaEngrl, I know you're a Metallica guy, so you would probably like 5U4g or GZ 34, etc.

 

[MesaENGR412]

yeah, I have the GZ34's in my Triple right now and they work great. I was just wondering about the Coke Bottle 5U4's because i was reading in the catalog and saw them and just wondered what you guys thought. Thanks for the info buds.

-AJH

 

[sgtbaker]

Do you have to bias the amp to change from 5U4's to GZ34's? I'm sorta new to tube amps.

 

[waassaabee]

yeah, I have the GZ34's in my Triple right now and they work great..

****.. Now I've got to buy a triple.. :wink:

 

[ThunderMonkey]

Do you have to bias the amp to change from 5U4's to GZ34's? I'm sorta new to tube amps.

No, again rectifier tubes change (rectify) incoming AC power to DC, that's all, no need to bias them....you do get a performance reaction from using them, especially high gain crunch settings, you get a "power" sag reaction.
Especially nice if you play more doomy/stoner rock type stuff.

 

[sgtbaker]

I wanna try out GZ34's in my Stiletto

 

[Guitarzan]

I like them both! I have the 5U4's in one Recto and the GZ's in another.

 

[ThunderMonkey]

I like them both! I have the 5U4's in one Recto and the GZ's in another.

NICE !
I like the 5U4's response better than the 5U4GB's in my 93.
Has everything to do with circuit board revision I suppose.

I'd like to try the GZ34's :!:

 

[Russ]

I have Mesa 5U4's sitting next to NOS Phillips 7581's. That makes my '94 DR awesome. I haven't pulled the 420's out of my Mark IV yet to try them in the DR though. I have been wanting to swap them and hear the 7581's in the Mark IV also.

 

[MesaENGR412]

Nice Russ! Let us know when you do that!

-AJH

 

[Nigel.Wambuto]

The rectifier tube is not part of the tone chain so I would say that it has very little to do with the tone. My guess is that they changed because they were a pain in the *** to change when they blew. I know in my Tremoverb, I had to remove the top vent unit to change the rec tubes because they were right up against the top of the amp. The GBs are shorter which makes them easier to change if there is a problem. I swap my rec tubes for NOS because they last longer and are much more consistent, it has nothing to do with tone because the rec tube isn't part of the signal path.

not true....the 5U4G's in my 2ch rectos are much tighter than the 5U4GB's. I've compared pretty much every tube I have in all my amps and I still prefer the 6l6 str 420's and the 5U4G's.

If you guys want more info, there's a great description on Mesa's website under all the stuff about tubes.

Nothing on Mesa's site explains any potential sonic differences between the Chinese "Coke bottle" 5U4G and the Russian 5U4BG. That's because there are none. Though your anecdotal evidence may suggest otherwise, again, the rectifier tube is not part of the signal path. Both types share the same specs; a 5U4G or 5U4GB close to design center will drop the same amount of voltage, resulting in the identical sag (or "tightness"). There may be a difference in response if one of the tubes is out of spec, however.