.50 caliber tube stages

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sixstrings

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I have a .50 caliber with EL84 tubes and EQ, with metal switches (older one).

I'm aware that V1 is the driver. What are V2-V5? Is V4 for the reverb? Is V5 PI? Would the amp's reverb section sound better with a 12AT7 instead of the 12AX7?

Much thanks in advance.
 
sixstrings said:
I have a .50 caliber with EL84 tubes and EQ, with metal switches (older one).

I'm aware that V1 is the driver. What are V2-V5? Is V4 for the reverb? Is V5 PI? Would the amp's reverb section sound better with a 12AT7 instead of the 12AX7?

Much thanks in advance.

From the manual, available at the website:
"If the problem appears only in the Lead mode, then
the culprit is Vl, furthest to the right, but may also be in V2 or V3. If the problem is in the Rhythm mode
only, then V2 is usually the problem (V2 is second from the right, seen from the rear). Sometimes it also
can be V3. If the Reverb is noisy or has a problem, replace V4."
Also:
"... (D)o not change the 12AX7 tubes unless a specific problem comes up.
Their aging is very slow and you won't likely hear any improvement by changing them unless one has
become noticeably noisy."


V5 is the "driver', otherwise known as the "phase inverter".
A 12AT7 has 40% less gain than a 12AX7, so there will be 40% less reverb.
 
I dunno about 40% less reverb. FYI, my .50 Cal came with a 12at7 from the factory and even has "12at7" written in marker from the factory, so maybe that's what Boogie intended on you using for reverb. I have used a 12ax7 and it sounds no better or worse, certainly not 40% better!
 
scottcrud said:
I dunno about 40% less reverb. FYI, my .50 Cal came with a 12at7 from the factory and even has "12at7" written in marker from the factory, so maybe that's what Boogie intended on you using for reverb. I have used a 12ax7 and it sounds no better or worse, certainly not 40% better!

weird... with mine, the reverb sounds better with a 12at7... but i don't use it a lot to be honest...

for the overall sound (tone) the V1 is the most important i think... you have to put a well balanced, with the less noise tube as possible... the second most important seems to be the V5, it needs the same characteristics as V1... that's all i can say with my very little experience :?
 
Lately I've been running a RFT or Bugle Boy amperex or NOS Tesla or a NOS Beijing facility in V-1, a electro harmonix or tung sol re issue in V-2, and 12at7's in V-3- V5 and I gotta tell you, it sounds great, Might go out on a limb and say it sounds the best I've ever heard it.
 
50 Caliber:
4 x EL-84s, designed for a 12AX7 reverb tube.
50 Caliber PLUS:
2 x 6L6s, designed for a 12AT7 reverb tube.
RTM.
When Mesa actually writes the type of tube on the chassis, one may safely assume that's the tube for which the circuit was designed.
Putting a higher gain tube in a circuit designed for a lower gain device may indeed not improve the sound at all, but only increase noise and microphonics. YMMV.
Perhaps "40% more reverb" was an oversimplification, since the ear perceives changes in level on a logarithmic basis.
Nevertheless, 12AX7s still have 40% more gain than 12AT7s.
 
stupid question...I have an EL-84 50 cal...I want to retube> I'm going to buy the tubes from Boogie because I just have no idea what tubes to buy. Here is the question...4 x EL-84 + 5 x 12ax7??? Is that right?

Thanks
 
smcgov said:
stupid question...I have an EL-84 50 cal...I want to retube> I'm going to buy the tubes from Boogie because I just have no idea what tubes to buy. Here is the question...4 x EL-84 + 5 x 12ax7??? Is that right?

Thanks
You are correct, sir!
Here's the manual:
http://www.mesaboogie.com/manuals/50%20Caliber%20Series.pdf
While it's not specific, on page 5 it states:
"But do not change the 12AX7 tubes unless a specific problem comes up."
(Whatever. Keep the old ones for spares, unless they're obviously defective.)
Seems to me you can infer from this that all the pre-amp tubes are 12AX7s.
You won't blow the amp up with a 12AT7, you'll just get lower gain. You're substituting different ingredients in the tone recipe.
 
If the problem appears only in the Lead mode, then
the culprit is Vl,

i don't understand that !! it seems that the V1 influence the overall tone... i don't say that because everyone here said that the V1 is the better stage to "test" tubes... but because i experienced it myself !!
 
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