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PostPosted: Tue May 08, 2012 3:38 pm 
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Mark II

Joined: Thu Mar 10, 2005 12:24 pm
Posts: 128
Does anyone know where the Cathode Follower (preamp tube section), positions are on the Lonestar Classic V.2?

I've been reading where many Russian-made 12AX7 tubes are not strong enough for this slot, and that it is recommended to use a Chinese or NOS tube.

And a follow up: I've also read that Mesa has addressed this with beefier Mesa-branded 12AX7s.

I've got a call into Mesa, but I'm impatient... :wink:


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PostPosted: Thu May 10, 2012 1:13 am 
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Single Recto
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Waiting to hear more, :wink:

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PostPosted: Thu May 10, 2012 11:19 am 
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Mark II

Joined: Thu Mar 10, 2005 12:24 pm
Posts: 128
I missed the damn call from Boogie yesterday, so now waiting for second call... :evil:


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PostPosted: Thu May 10, 2012 8:20 pm 
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Dual Recto

Joined: Mon Jul 16, 2007 1:01 am
Posts: 2790
Location: SoCal
Short answer: V3

Long answer: Keep reading.

SOUND “DROP-OUTS” / INTERMITTENT SIGNAL
One Possible Cause

Many (but not all) Mesa/Boogie amplifiers have one or two “cathode follower” tube
stages in their preamps. Tube selection is CRITICAL in these stages.

Specifically, in a 12AX7 tube used as a “cathode follower”, the voltage difference
between that present at the cathode, as compared with the heater voltage, can be
withstood or tolerated by certain types of tubes, whereas other tubes will fail. The
failure of a “cathode follower“ tube will cause sound dropouts or signal loss.

For the past few years, Mesa has been using two types of 12AX7 tubes: ones
originating in Russia (Sovtek EH), and ones originating in China. The Russian (Sovtek)
tube is NOT reliable as a cathode follower. Of the tubes we are using today (March
2008), ONLY THE CHINESE 12AX7 IS RELIABLE AS A CATHODE FOLLOWER.

In conclusion, if you are troubleshooting for signal dropout in a Mesa/Boogie amp,
suspect a cathode follower tube, and try replacing it with a Mesa 12AX7 that is marked
as “CHINESE” (silk-screened on the tube itself).

Below is a partial list of Mesa amps and cathode follower tube locations:

Lone Star & LS Special: V3
M-Pulse: V2
Stiletto: V3 & V4
Venture: V2
Road King I: V3 & V4
Big Block 750: V4
Road King II: V3 & V5
Titan: V4
Roadster: V3 & V5
M2000: V2
Dual & Triple (2ch or 3ch): V3 & V4
Bass 400+: V2
Tremoverb: V3 & V4

ANOTHER POSSIBLE SCENARIO may occur in the “SPONGY” (or on some models,
“TWEED”) power setting: the reduced filament voltage may cause very low output from
a RUSSIAN preamp tube. Again, the recommended fix is to replace the “sagging” tube
with the CHINESE type of Mesa 12AX7 - which are more immune to this type of failure.


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PostPosted: Fri May 11, 2012 10:45 am 
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Mark II

Joined: Thu Mar 10, 2005 12:24 pm
Posts: 128
Thanks! Yeah, I found this explanation early when I was researching the issue. Very informative.
Still waiting for Boogie to confirm, and to see if their new production tubes will handle the slot.


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PostPosted: Tue Jun 19, 2012 9:46 am 
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Mark II

Joined: Wed Aug 19, 2009 8:51 pm
Posts: 107
I talked with MESA awhile back on this and they said they're now using JJ's in their amps and that they will work in any position, to include V3.


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