Looking for Valve recomendaions for MKIV

Lights Out · Oct 6, 2005

Hi
Im new to this forum, I have recently bought my first booge & found this site . I have found some interesting info already & would like to ask some questions about these great amps !

I have been getting some dips in Volume while playing my Boogie MKIV
So Im thinking its time to re-valve

I Bought it second Hand so I dont know how old the Valves are in the amp. (There all Mesa labled Tubes)

I would Like some recomendations on valves Pre & Poweramp
And does anyone use EL34's in the outside Two sockets .

I have some New JJ E34L's that have been in my Marshall for a few weeks I would like to try , can I just wack those in or do they need to be Matched specially to boogie Specs ?

Thanks

Boogiebabies · Oct 6, 2005

My rig is a 1993 Mk IV EV12L 1X12 Combo through a matching MK IV Era
Thiele. The pre's are V1 and V5 GT 12AX7M's. The V2,3 and 4 are Ruby 12AX7C9 Chinese. The powere tubes are GT 6L6GE's and GT 6CA7GE's in the outer sockets. A tremendous combination and by far the best sounding MK IV I have ever heard. The power tubes are all #6 and draw around 24ma across the board at idle in the MK IV.

As far as the JJ's. You need to know what they would draw before just popping them in. If they draw a naturally high plate current they could bias way above MPD and blow up the tubes and the screen grid resistors and possibly the output transformer. Adversely, they could draw cold or right on Mesa specs. Without a bias meter you cannot tell. Tubes also draw more bias when they are played at a decent volume so if you pop the JJ's in and they draw a static 60ma, they may spike as high as 80-90ma during load. I would just be causious.

Lights Out · Oct 6, 2005

Thanks for that .
I see your a Groove Tube fan , I havent used them for years & didnt like there results last time I used them , but that was over a Decade ago.
Some local tech just used what ever he had in stock, they might not have been the right ones for the amp Im guessing.

Did you discuss with them that sound you were looking for etc...
And what did the set end up costing ?

Monsta-Tone · Oct 7, 2005

I tried a set of JJ E34L's that are a few years old but still dead on, no drifting yet. They sounded incredible. Bias was exactly -28 ma on both of them.

As for getting the tubes exactly at -24 ma, this is entirely subjective. If you replace the tubes in an amp, there is a range of acceptable Bias that you have to stay within in order for your amp to sound and work right. You can be at the top, bottom, or anywhere in the middle of this range. Where you are within this range will affect the way the amplifier sounds & reacts to your playing. Just because a manufacturer likes his amps to be set exactly at a certain Bias does not mean that you can't experiment with your own amp's tubes.

Boogie Babies is absolutely correct about what can happen if you drift too far from the prefered Bias range.

I ordered a complete re-tube kit from Bob @ Eurotubes with Hi-Gain JJ 12AX7's & a quad of JJ 6V6's. I''ll post my findings next week.

Tuna141 · Oct 7, 2005

Boogiebabies,

The powere tubes are GT 6L6GE's and GT 6CA7GE's in the outer sockets. A tremendous combination and by far the best sounding MK IV I have ever heard.

How do the 6CA7GE's differ from regular 6L6's? Why do you use them only in the outermost pair? Is there a definite difference on tone between these and 6L6's?

Thanks.