Brit 800 weird

IMO the JCM 800 is one of the best of the Marshalls in the Fractal.
I get plenty of nice 800 gain... certainly not a hellbeast of an amp, but to my understanding it wasn’t. I’ve played a few. Some have that extra something... some are dull. Cliff modeled a good one. The vertical input earlier ones seem to be the favorites. I tend to agree.
 
Omri Bazelet said:
So. I have tried a true JCM800.
And there's a certain thing I wanted to know.
When Cliff modeled it. It was based around the low input ?
Because It has way less saturation and dirt then the real one I used.
Even when I'm cranking the Master Volume all the way in the model, it is not as dirty. And the real amp was in like 1.5 master and 7 preamp gain was enough to get it distorted nicely.

I tried the 800, 800 #34 and even the 800 Mod. Same issue.
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Check your I/O settings: is your Input / Instrument Level above 5%, and Input 1 Gain set at 1.0?
 
Which real life JCM800 model did you try?

I played a post Marshall-never-told-anyone redesign JCM-800 2210 for years, and these things sounded NOTHING like the 2203/2204 or even the pre-redesign 2210s.
 
I have a 2203 circuit HV tube preamp and a Rocktron Plexi HV tube which has a 800 mode (3 gain stages into a DC Coupled Cathode Follower/Tonestack), and the Fractal JCM 800 amp model's gains are definitely on par with my various Marshall tube preamps (AS JCM 800 with the FM3 for tube power amp sim, and a Rocktron Plexi with it's 800 Mode with my AFX2 for tube power amp sim, plus a Randall MTS Super Lead/Friedman BE module).
 
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Not sure of which model of JCM800 I built but I was going off the schematic that was on a site. Tone Lizard. The site appears to be gone now. It was probably the 2203 with some mods, no big changes. In any case, it wasn’t a high gain amp. It got dirty but you would need a pedal to really make it sing.
 
skolacki said:
Not sure of which model of JCM800 I built but I was going off the schematic that was on a site. Tone Lizard. The site appears to be gone now. It was probably the 2203 with some mods, no big changes. In any case, it wasn’t a high gain amp. It got dirty but you would need a pedal to really make it sing.
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I have tried every mod from this side 25 years ago - and the stock amp always sounded better IMHO.
The amp Cliff has modelled, has a tiny bit more gain than the last stock JCM 800 MV amp I own. He took a good one.
 
Can you verify your model is a 2204/2203? In the mentioned year (1985) there were other JCM800 models available with diode clipping and probably more gain like the 2205.
 
I owned 3 800s at once time in the 90's, 2 2203 and one 2204. There can be and often are gain differences amp to amp as Marshall is famous for amp to amp differences. Components, tubes, and even the wall power all have an influence. The Fractal 800 model is on point to the 800 I still own.
 
Here's a 2204 preset for 80s thrash with a timmy boost and leon's LT TV mix 2 IR (you can get it on axe-change)
 

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Fractal 800's are really accurate to my stock 2203 and previous 2204. Main difference between 2203 and 2204 is adjusting the negative feedback. Stock they have less gain than what people think they do, bear in mind a lot of the ones out there have either been modded or components may have drifted out of spec. Very simple to tweak them for more gain
 
MirrorProfiles said:
Fractal 800's are really accurate to my stock 2203 and previous 2204. Main difference between 2203 and 2204 is adjusting the negative feedback. Stock they have less gain than what people think they do, bear in mind a lot of the ones out there have either been modded or components may have drifted out of spec. Very simple to tweak them for more gain
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Is there a list of parameters that are often adjusted for a mod? I mentioned using the Variac and saturation switch.
 
MirrorProfiles said:
Fractal 800's are really accurate to my stock 2203 and previous 2204. Main difference between 2203 and 2204 is adjusting the negative feedback. Stock they have less gain than what people think they do, bear in mind a lot of the ones out there have either been modded or components may have drifted out of spec. Very simple to tweak them for more gain
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So.. in order to achieve more gain. I need More Negative feedback?
 
FractalAudio said:
Classically people would use a boost with a JCM800. Tube Screamer, SD-1, etc.
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This is how I do it. With that you need to play with the master volume to find the sound you are looking for too. And play with the amount of distortion coming from the Booster vs the amp itself. I finally found a setting that worked for me, it took a LONG time, lots of experimenting and lots of IR combinations.

The other thing you could do is look at the JS410 models. I think the crunch models are a copy of the 2203 if I am not mistaken. And they have a lot more gain than the other models you mentioned.
 
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