thegaindeli said:
JOEY B. said:
4406cuda said:
Mesa is now saying you can not use both 6L6's and EL34's at the same time in the Mark V.
I'm sure that is the standard answer to prevent anyone from switching to the 10 watt setting and potentially hurting the amp. It's a warranty thing, I understand their response. Have either of you guys read the article about how Randall Smith designed the Duo-Class for the Lonestar? :shock:
Mmmmm :?
Copied and pasted without permission.
"Randall Smith’s Unique Tweaks
“I couldn’t have come up with the Lonestar Special right out of the gate,” admits Mesa/Boogie founder Randall Smith. “This new amp pays homage to the original Mark I in having cascadable gain stages, but the Lonestar Special’s Channel Assignable Power Switching, which allows you to select a different output wattage—30, 15, or 5 watts—for both channels, has taken me more than 35 years to develop.”
Smith actually has two power-amp patents pending for the Lonestar Special—one for the Channel Assignable Power Switching, and another for the single-ended (single power tube) to push-pull (two or more power tubes) switching scheme that’s a key feature of the new amp.
“The technical issue that has always existed in trying to get push-pull and single-ended from the same circuit is the output transformer—specifically, its iron core,” explains Smith. “For single-ended operation, the transformer needs to have a gapped core that’s open on one end—like a horseshoe magnet. This keeps the DC current going through the primary windings in only one direction from saturating the magnetic core. And if the core is saturated, then it can’t handle the signal, which is AC. With a push-pull circuit, the transformer doesn’t need the gap, because the DC goes into the center tap and then comes out the two push-pull sides in opposite directions. This creates two opposite magnetic fields that cancel each other, sort of like a humbucking pickup—thus preventing core saturation.”
The problem of how to switch a push-pull circuit to single-ended operation without also switching to a different output transformer remained unsolved until the answer flashed in Smith’s head one day.
“I was swimming in my pool when I suddenly realized that I could use one of the other output tubes to trick the output transformer into thinking it was operating push-pull all the time. I jumped out of the pool, went straight to my workshop to test the theory, and on the scope I could see that it worked.
“In the 5-watt setting, the Lonestar Special is sort of operating with two tubes—except only one is on for audio, and the other is being used for DC offset on the transformer. What this does to the impedance I have no idea. It’s probably all wrong, but it’s wrong in a good way. Of course, the cool thing isn’t just the reduction in power, it’s the ability to get that second harmonic in there, which is cancelled in a push-pull circuit. It puts that halo on the sound, which is one of the main reasons why amps with single-ended output stages—such as the Fender Champ—have long been so popular with guitarists.” —AT
"
If you're not an EL34 person - stick with the 6L6's. The EL34's are a more "musical" tube than the 6L6, due to it's longer plate. Same with the JJ's 12AX7's vs Sovtek LPS 12AX7's - or Tung-Sol. IMHO - all MKV's should ship with these tubes to begin with. Someone asked me what the sound difference is?
