JCM800 with variac

  • Thread starter Thread starter Kapo_Polenton
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Kapo_Polenton
Kapo_Polenton
Well-known member
I thought this was pretty cool and it sounds pretty good to me. Anyone try it? I think the key is keeping that preamp down to control the flub and then the master volume brings up the fullness. The cascading preamp does it's thing.

Edit: not my vid, came across it online!

 
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Sounds great!! Super good idea. Surprised it seems like no else has tried it before?
 
Lightning said:
Very nice,what pickup are you using
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Good question! I edited my post as it is not my video..i was just thinking about that so i put it into youtube. Seems like it does the trick.
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Yup...Very authentic sounding. Not my thing...But a very cool thing indeed.
 
I think a lot of us have been doing this with or without variac. Those of us that play at volume usually keep the preamp knob lower because the amp is breathing. Keeps it tighter and the poweramp brings the juice. @DanTravis62 and others have been talking about this for awhile
 
Ok, so let's analyze this. I don't want to get too EVH psycho, tone chasing, etc. but that is a JCM 800 with that tone. Maybe everyone has been so focused on "Plexi" and really it cones down to a Marshall eith a variac. I'm not saying a Plexi isn't a part of that but maybe a variac was a bigger part of the Brown Sound than the other parts of the puzzle people have been analyzing to death.
 
Smash said:
I think a lot of us have been doing this with or without variac. Those of us that play at volume usually keep the preamp knob lower because the amp is breathing. Keeps it tighter and the poweramp brings the juice. @DanTravis62 and others have been talking about this for awhile
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I'm one of those too and have been saying that for a long time.. I usually use the 7 - 7 formula and go from there. Preamp 7 and MV 7 on an 800... even dial pre back to 5 at times.
 
romanianreaper said:
Ok, so let's analyze this. I don't want to get too EVH psycho, tone chasing, etc. but that is a JCM 800 with that tone. Maybe everyone has been so focused on "Plexi" and really it cones down to a Marshall eith a variac. I'm not saying a Plexi isn't a part of that but maybe a variac was a bigger part of the Brown Sound than the other parts of the puzzle
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romanianreaper said:
people have been analyzing to death.
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You aren't wrong..I often say that the 800 can be very close to a Plexi when you lower the preamp gain and crank the master. Another trick is the NFR. I drop mine to 47 or 50 instead of 100 to get rid of the tight buzzsaw gain people sometimes associate with the 2204 circuit. Just that alone will make you rethink things. But absolutely that variac squish and grind is the magic to my ears. I actually favour the 2204 circuit to the NMV circuits. I find the highs and the crashing a little too much on plexis.
 
Sounds juicy :yes:

I didn't know variac'ing a Marshall was a new thing :lol:

@Kapo_Polenton - thanks for pointing out that was not you. Some people will try to fool you.
 
I just picked up the same variac cheap.
Hooked up my jmp2203 and I gotta say it makes the world of difference for me. No im not running it at 90v to do the Evh stuff I prefer to cut my wall voltage down between 10-15v. Sounds freaking awesome.
 
tpruitt said:
I just picked up the same variac cheap.
Hooked up my jmp2203 and I gotta say it makes the world of difference for me. No im not running it at 90v to do the Evh stuff I prefer to cut my wall voltage down between 10-15v. Sounds freaking awesome.
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Nice, I plan to do the same. So what were you running it down to? The guy in the vid has it down to 75! 90 not likely going to hurt the tubes that much I don't think. if anything it's starving them I would think. Running an amp pinned is going to fry your tubes over time either way.
 
What is the spec of variac that is required for this anyway? Or am I over complicating things..
 
Kapo_Polenton said:
Good question! I edited my post as it is not my video..i was just thinking about that so i put it into youtube. Seems like it does the trick.
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I just read the YT description and there is not much info there. Do you know any specifics on the amp by chance? What year, has it been modded, etc?
 
I sometimes run a variac with my Laney GH50L, it does that thing. Mostly it's a nice way to be able to get the power amp more "in the game"
 
Youre starving the bias going to F up the tubes and amp.
 
Kapo_Polenton said:
Nice, I plan to do the same. So what were you running it down to? The guy in the vid has it down to 75! 90 not likely going to hurt the tubes that much I don't think. if anything it's starving them I would think. Running an amp pinned is going to fry your tubes over time either way.
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This is the one I got.

Vevor 2000VA 20A​

My wall voltage is around 118v so I run it down to 110v,100v if I want more brown.
I run my bias just under 70% so 32ma.
At 100v I’m around the 25ma range or a little under 60%.
 
shar-vell Dan said:
Youre starving the bias going to F up the tubes and amp.
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Evh amps come from the factory with a low ass voltage. I’ve seen them at 15ma.
Yes you should rebias if you plan on leaving it at a low voltage but mine is within range how I run it.

Actually it’s easier on the tube. And it lowers the overall volume. Which is why Evh used it to begin with.
 
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