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 Post subject: Triode / Pentode switch
PostPosted: Fri Dec 08, 2017 10:08 pm 
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Bottle Rocket
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This is possibly a stupid question. I have been silently waiting for someone else to ask but it hasn't come up in any of the discussions. The JP2C is supposed to be a reissue with John Petrucci's suggestions for a better modern version.

I have no complaints with it at all. It sounds and plays great!

I can't help wondering though if some of the magic "feel" and response was due to the original's being wired in triode?

Has this crossed anyone else's mind?

Is it possible to have this done as a mod on a switch?

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PostPosted: Sat Dec 09, 2017 11:32 pm 
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Mark III

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The magic or feel, like anything, can be a preference thing. Beauty is in the eyes of the beholder. In John Petrucci's case, he prefers pentode 100 watt c+'s over the simul class triode c+'s. James Hetfield prefers the triode wired simul class. Feel is one of those things that have to be experienced by playing. A few mark series amps gives you the option of pentode or triode. Making it easy to find your preference. But back when the c+'s were being made, you had to get your hands on one of each to feel those differences and find what works best for you. The pentode/triode is no small tweak either. As the manual says, it can make or break the feel, and players often find what works best and leave it that way.

I guess there is room for mesa to release a simul class version of the JP2C. At least a lot people here on the board want it. It's also been called the James Hetfield signature c+. Even if it doesn't have Hetfield's name on it, the fact that it is simul class alone would make a lot of Mark fans drool. It seems the majority of c+ fans prefer the feel of the simul class c+'s over the pentode wired 100 watt c+, but that doesn't make one better than the other. It's the individual player that decides that.

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PostPosted: Thu Dec 14, 2017 8:19 pm 
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Triple Recto

Joined: Fri Feb 22, 2013 7:31 am
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I think it is one reason why I like the JP-2C as the Class A/B amps tend to become my favorites. Probably because none of them have the tube sing issue like the Simul-Class amps I had starting from the Mark III, Mark IV and the Mark V. It is not rattle but actual vibrations of the tube innards resonating identical to the guitar signal. Only present at reduced volume but sometimes becomes apparent at higher volumes on the clean channel. Mark V seems to be more prone to this than the IV and the III. Still the tone at 45W is great so not complaints on that.

JP-2C is a beast all on its own, and if it sounded like the Mark V I would have sold it as that would have been disappointing. I think my V is a lemon, should have asked for yellow Tolex. Still that would be wild though, black grill and yellow skin with the black leather corners. Perhaps if Zakk Wylde had a signature amp it would be something like that... Wonder if he would want his speaker in it (EV black Label).

All the Pentode switch does is connects the screen resistor to a different voltage level. Pentode is at plate level and triode is at a reduced voltage by 3 volts or more. Something like that anyway.

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PostPosted: Thu Dec 21, 2017 12:55 pm 
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Mark III

Joined: Mon Sep 29, 2014 12:17 pm
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There's no Triode/Pentode switch because that's a feature they had on their SimulClass amps, but the 60/100W versions are fixed in Pentode.

You could probably mod in a Triode/Pentode switch... but it might not work how you'd expect. On the SimulClass amps it's only the "Class A" tubes which were wired Triode, or could switch on the switchable amps. Since the 60/100W version doesn't have a set of Class A tubes it won't do the same thing if you set either just one pair to switch, or if you switched all 4. You might like the results, you might not, but it wouldn't do the same thing the SimulClass amps do when you switch it.

And unfortunately, I think for now the SimulClass, Triode IIC+ reissue is called the Mark V. But if the JP proves popular enough maybe they'll diversify it. At the very least use that new Transformer on the next Mark iteration.

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PostPosted: Wed Mar 07, 2018 6:26 am 
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Triple Recto

Joined: Fri Feb 22, 2013 7:31 am
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If the JP-2C was a Simul-Class amp, I probably would have returned it. However since the amp is much louder than the Mark V I probably would not notice the tubes singing in the background unless I was using the clean channel. Perhaps I am picky but I can do without the tube sing (you know you have it when the class A tubes are rattling off the same frequencies as the guitar signal and it gets annoying, had this with the Mark III, Mark IV and is present in the Mark V. Note that it was not as apparent if I used the EL34 in the class A positions on the Mark III and Mark IV. Tube vibration or tube sing issue does not happen with the JP-2C, Roadster, RA100, TC-50 or TC-100 which are class A/B amps. Also note it is not the same thing as tube rattle as the amp can be isolated from the speaker cab and the noise stays with the amp).

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