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Difference between JTM45 and Plexi?

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power stage (being 30W with KT-66 valves in JTM 45 and 50W or 100W using EL34s in plexis ) and use of vavle rectifier (in JTM45) for squishier sound are the main ones.

 

I know there are many changes ofer the years - blah di blah. But in a nutshell this is it.

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The JTM45 has split cathodes, and usually a lot more clean headroom. However a good tech can voice it to sound a little more aggressive. Also, since the JTM45 is pretty much a derivitave of a Fender Bassman, it will have very Fenderesque cleans. The Plexi will be a lot louder and aggressive when turned up.

 

I have a JTM45 and a 50 watt plexi and the plexi runs out of clean headroom very early in the volume curve. It's starts breaking up around 3 and gives up the full goods by the time the volume is 1/2 the way on. The JTm45 stays clean untill about 1/2 way and then starts gently clipping. At full bore, the JTM is a lot quieter than the 50 watt plexi.

 

I love both amps.:love:

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Probably the biggest difference on the JTM45 is the shared cathode. The 50 watt heads that debuted in 1968 used a separate cathode arrangement on the first tube, which made a huge difference in tone.

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Originally posted by Rich

The JTM45 has split cathodes,

Nope, the 45 is definitely shared. Split came in on the 68 50watters and stuck around for the remainder of the Marshall line, thanks in large part to the increased preamp gain.

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Originally posted by BerkleeBill

Nope, the 45 is definitely shared. Split came in on the 68 50watters and stuck around for the remainder of the Marshall line, thanks in large part to the increased preamp gain.

 

Thanks Bill, I got it ass backwards.:o

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the technical differences are named in this topic, but in my expierience there is quite a bit of tonal difference. The jtm45 is loose, warm and round sounding. Where a plexi is tighter, more open sounding and slightly more agressive. Very different animals, you could say that a jtm=blues and plexi=rock...

 

try them both out. Im not a big fan of the jtm45, too muddy when i played it.

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Originally posted by Negative K3 fan

the technical differences are named in this topic, but in my expierience there is quite a bit of tonal difference. The jtm45 is loose, warm and round sounding. Where a plexi is tighter, more open sounding and slightly more agressive. Very different animals, you could say that a jtm=blues and plexi=rock...


try them both out. Im not a big fan of the jtm45, too muddy when i played it.

 

My JTM was kind of muddy in stock form. My tech tightened it way up for me. I opted to keep the tube rectifier due to the sponginess often associated with them. These are very simple amps to fiddle with and see some immediate improvements in tone.

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