Just got this of ebay. Wow, loud is an understatement. It is louder than a JCM 800 bass series 1992 I use. Or at least the volume is more sensitive. Was hoping for earlier breakup than the Bass series at lower volumes. It goes from off to almost full volume between 0 & maybe 2. After 2 or 3 the volume does not change much. Maybe there is something wrong tube wise, I hate to take it in my local shop after just getting it. For they usually have a 2 to 3 week turn around. Seems like there was a mod at one point, which could be a whole nother can-o-worms. There is a hole in the back panel with no knob. I bet it was a master violume mod that has been reversed. Hoping for the best when they open Her up.
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JCM 800 1987 model
- Thread starter kilsin
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plexilespaul
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not sure there is anything wrong with it. these amps are loud as f....k.
had the 100 watter
beautifull amp...helped john sykes get his point across
That's exactly what a very large bright cap will do. It probably has a 5000pF that you can either remove or replace with a smaller value like 1000pF or less.
Rockett Crawford
Member
Doesn't sound right to me. I own pretty much this exact head - 2204. I think mine is 1986. The master volume on mine goes up pretty steadily until it reaches 5 and from there it seems to get just a little louder, but mostly just gets more breakup in the main tubes. I wouldn't be surprised if someone had replaced your 1 meg master pot with the wrong taper or something like that.
Model 1987 doesn't have a master volume like a 2204. Different amps.
Schematics do show a 5000pF bright cap for the JCM 800 1987. That's why the volume acts that way. If you don't like it, it's extremely easy to change; no need to take it to a tech.
V-man
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Totally different animals. See below.
I have a 1984 JCM Super Bass and a 2008 1959RR.
Plexifier has explained perfectly what is going on with the bright cap. Most latter-day "plexis" have this cap, and it gives you earlier break up (at the cost of headroom). Yes, it's loud as balls and is an amp made EXCLUSIVELY for those who can/will go balls to the wall or who can live with attenuated tone. My 1959 loses neighborhood playability somewhere between 0 and 2, so it is my office toy that gets pushed past 6 when everybody leaves.
The JCM Super Bass on the other hand, really isn't a loud amp to me. It has nothing but headroom and zero (or for a Marshall, near-zero) breakup/distortion. For some odd reason, once it gets boosted with a pedal, it suddenly gets loud as hell.
What you have there are two very cool, and rare Non-Master Volume Marshalls. they are definitely eccentric amps. If you can deal with the volume of the 1987, you have perfect bookends: for clean(ish) playing, plug in the Super Bass at any volume. For rich, overdriven rock plug in the 1987 and set it to 2. For balls to the wall (without breaking down the walls) set either between 0-2 and boost with the dirt that works best for the amp.
If this setup is problematic somehow, a 2203 or 2204 is probably what you're looking for.
Rockett Crawford
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Yea, you're right. I didn't look at the front very closely. Looks like there may be 4 inputs. Not a 2204.
DSL100 Dude
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Nature of the beast with the 1987's. It's ok though because they put out in a sweet way when ya get around 8 on the volume.
it sounds a flabby or farty to me on 8 or maybe even past 6 I'd say. Was thinking this type of Marshall would sound great cranked, even if the volume was ureasonable.
It's crazy to me how a 50 watt can be just as loud (or possibly louder in this case) as a 100 watt marshall. A nice Fender clone amplifier builder explained to me that the difference is only a couple db Between 50 & 100 watts. He had a 34 watt JMP clone that I'm sorta wishing I woulda bought instead. I was affraid of the resale value being too low if it could not keep up with the band, since it was not a genuine Marshall. I was/am being asked to turn down a lot with the 800 bass series. Thought this one might be perfect.
changing the brite cap sounds appealing. What value did they put in the earlier models?
It's crazy to me how a 50 watt can be just as loud (or possibly louder in this case) as a 100 watt marshall. A nice Fender clone amplifier builder explained to me that the difference is only a couple db Between 50 & 100 watts. He had a 34 watt JMP clone that I'm sorta wishing I woulda bought instead. I was affraid of the resale value being too low if it could not keep up with the band, since it was not a genuine Marshall. I was/am being asked to turn down a lot with the 800 bass series. Thought this one might be perfect.
changing the brite cap sounds appealing. What value did they put in the earlier models?
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CKCinMass
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The caps look original. Wouldn't hurt to replace all of the electrolytic caps in that amp. (Yes I know that replacing the caps would not affect the original issue noted - It's just a good idea to replace any electolytic caps that are that old - just my 2 cents).
They've used a lot of different bright cap values on different models from none to 5000pF.
The cap bypasses the volume pot so the tone and overdrive levels depend on both the cap value and the volume setting. The lower the volume, the more effect the bright cap has. The larger the cap, the more mid and low frequencies are passed, which gives you earlier overdrive. Small caps pass only treble. Once the volume is above about 8, larger caps help tighten up the bass response.
Here's a rough guide:
100pF - adds brightness with volume below 3; above that, gradually does less
250pF - brighter sounding than 100pF at same volumes and affects tone up to about 5 on the volume
500pF - brighter still and starts adding what some find to be harsh upper-mids
1000pF - adds in a lot more mids for earlier overdrive (common value on preamp pot of 2203/2204 amps)
5000pF - passes frequencies down into bass range (on/off volume behavior)
In general, I prefer small bright caps (250pF or less) on non-master amps because I like to add just a little sparkle or chime to clean tones without making the overdrive much brighter. On a 2203 I like the stock value of 1000pF because it adds some grind and tightens up the bass.
DSL100 Dude
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Yeah, it sounds like a total piece of crap. I will do you a favor and take it off your hands for you so you don't have to deal with that flabby, farty tone anymore.
TradAmpGuy
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250-500 pF seems to work real well with these amps. It allows you to get great cleans on the lower 1/3 of the volume, great crunch up through the next 1/3 and dimed is heavenly. A cap job will prolly take care of the fartiness when cranked. Your best bet is to have it gone over and tuned up for best tone and reliability.
The difference between a 50 watt and 100 watt amp is twice the power or a 3db increase in output... it's louder but not by much. In order for something to sound twice as loud, you need an increase of 10 db or 10x the power. So, to get twice the volume of a 5o watt amp you would need 500 watts. What a 100 watter will give you though is a tighter and punchier bottom end.
The difference between a 50 watt and 100 watt amp is twice the power or a 3db increase in output... it's louder but not by much. In order for something to sound twice as loud, you need an increase of 10 db or 10x the power. So, to get twice the volume of a 5o watt amp you would need 500 watts. What a 100 watter will give you though is a tighter and punchier bottom end.
Having a great time with the new amp at rehearsal. The tone is real nice IMO. It still is a beast volume wise tho.
What speakers should I pair with it? Vintage 30's? Greenbacks? What was standard back in the day (meaning the 60's when the original 1987 was produced), and what do people use now with the reissues and what not? Seems like there was a lot of alnico stuff goin on then right?
What speakers should I pair with it? Vintage 30's? Greenbacks? What was standard back in the day (meaning the 60's when the original 1987 was produced), and what do people use now with the reissues and what not? Seems like there was a lot of alnico stuff goin on then right?
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