1969 Marshall Plexi vs. 1978 MKII 50W Metalpanel

  • Thread starter Thread starter EddyLenz
  • Start date Start date
They both sound great but the 69 just has that raw beautiful tone nice job! Great playing also, it has been so long since I have heard that Journey song it really takes me back to some good memories.
 
The 69 just seems to have more of a 3D thing going on. Almost sounds double tracked compared to the 78.
Both are great but your 69 is better for this tone.
 
psychodave said:
Sounds great.

I’m more curious about using an attenuator with the 69! I’ve tried a few attenuators over the years and after a few minutes they all get crazy hot and I just don’t trust them. My 67 Plexi isn’t replaceable.
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IF your 67 PT is getting really hot Dave then your power tubes are pulling alot of current. Are the attenuators themselves getting hot or is the Power transformer in the amp getting hot?

The Rivera Rockcrusher is one overbuilt MOFO and probably one of the best built ones out there IMHO and I have tried them all except the Aracom and the Scumback Decibel. Cranking my 68 plexi in to it regularly and it barely gets lukewarm if at all but I am also variacing down at least to 80-90 volts when doing so of which you could do the same if you are concerned with you 67. Remember a 67 plexi really want to see about 105-110 VAC max because that was standard for the power grid back then with average swings down to 100VAC at times.

I still use my old THD to shave off a -8 DB with my 50 watter but it is not built as well as the Rivera, the Rivera Rockcrusher(full size) is about three time the size of the THD. It's as big as my Two rack space Matrix GT1000FX power amp to give you an idea of size. IF you variac the 67 down some and then use an attenuator neither the PT or the Attenuator should be getting extremely hot, some heat is expected but really hot is not good......
 
They both sound great, but I prefer the plexi. It sounds bigger and sweeter.
 
harddriver said:
IF your 67 PT is getting really hot Dave then your power tubes are pulling alot of current. Are the attenuators themselves getting hot or is the Power transformer in the amp getting hot?

The Rivera Rockcrusher is one overbuilt MOFO and probably one of the best built ones out there IMHO and I have tried them all except the Aracom and the Scumback Decibel. Cranking my 68 plexi in to it regularly and it barely gets lukewarm if at all but I am also variacing down at least to 80-90 volts when doing so of which you could do the same if you are concerned with you 67. Remember a 67 plexi really want to see about 105-110 VAC max because that was standard for the power grid back then with average swings down to 100VAC at times.

I still use my old THD to shave off a -8 DB with my 50 watter but it is not built as well as the Rivera, the Rivera Rockcrusher(full size) is about three time the size of the THD. It's as big as my Two rack space Matrix GT1000FX power amp to give you an idea of size. IF you variac the 67 down some and then use an attenuator neither the PT or the Attenuator should be getting extremely hot, some heat is expected but really hot is not good......
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My Plexi doesn’t get hot, the attenuators do. I had the Alex attenuator, Powerstation V1 and a custom attenuator made by Cameron. After 10 minutes all got stupid hot. ? I’m not attenuating to bedroom volumes either. Keep in mind my Plexi is freaking loud. Loudest amp I’ve ever played. I’ve blown 30 watt Celestion speakers while running two 4x12’s. ?
 
psychodave said:
My Plexi doesn’t get hot, the attenuators do. I had the Alex attenuator, Powerstation V1 and a custom attenuator made by Cameron. After 10 minutes all got stupid hot. ? I’m not attenuating to bedroom volumes either. Keep in mind my Plexi is freaking loud. Loudest amp I’ve ever played. I’ve blown 30 watt Celestion speakers while running two 4x12’s. ?
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It's nothing for an old Marshall to put out 150 Watts RMS at high volume not to mention the peak square wave transients in the distortion waves, the square waves are usually what blows speakers in addition to the excessive wattage .

If you need or want to curb some volume and run it straight up NMV then I would look into the Rivera full size Rock Crusher the load resistors are huge and the rockcrusher is a reactive load. I use mine a -8DB @ 16 ohms to quiet down my 68 and also use a 16 ohm 400 watt resistive load that I built in parallel for an over all impedance load of 8ohms, I intentionally use the resistive load to pull some wattage away parasitically from the Rockcrusher. This setup has worked great for years for me and neither the Rivera or my resisitive load gets luke warm with my plexi cranked but I am variaced down pretty hard at 80-90 sometimes 70-75 VAC. No hot Power transformers, attenuators or blown tubes and I 've been doing it this way for 10+ years. I even pull two power tubes just to save tubes and I run my plexi output transformer at 4 ohm in to the 8 ohm total load.

Rivera rates the Rockcrusher are 120 watts but I would say it has to be almost double that but I sure he only wants 100 Watt raging Marshalls or the like running through it and not 150 Watt Bass amps. Like any other attenuator any attenuation below -8/-12DB the Fletcher Munson curve issues show up to the human ears but I have heard recorded clips and to the microphone it's more transparent than to the human ear IMHO.

Your 4x12 speakers might appreciate a good attenuator and a variac to some degree when you run that beast....:unsure::2thumbsup::p
 
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Oh yeah... the 69 is my overall favorite for all the obvious reasons but the 78 wasn't bad at all it just missed some of the atttak grind and compression. You can tell the 69 feels better to play just by listening to how Eddy's playing style changed between the two amps, it seems Eddy had to work harder to get what he wanted out of the 78.:yes:
 
harddriver said:
Oh yeah... the 69 is my overall favorite for all the obvious reasons but the 78 wasn't bad at all it just missed some of the atttak grind and compression. You can tell the 69 feels better to play just by listening to how Eddy's playing style changed between the two amps, it seems Eddy had to work harder to get what he wanted out of the 78.:yes:
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Yeah, the 69 is much more fun to play.
 
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