1984 Marshall JCM 800 4104

OK I got my Girlfriend to buy this, she now has a better amp than I do, But as much as I've tried to find it on the net I can't seem to get a strait answer as too how I would increase It's distortion By way of replacing it's tubes with a different brand. I do believe it is stalk, it sounds great but even turing it up and kicking on my super overdrive in front of it that way doesn't sound right, it's heavy but strange and earsplitting like it's not compressed enough by its distortion which brings me to my question.

How do i get this thing to put out more distortion on it's own?


(I'd like to just have the overdrive pedal as a solo boost not on all the time)

No idea about tubes, but years ago I used to own an old Marshall that was the same way & used a thing called an Attenuator. It was just basically a round knob in a metal box that was on top of the amp.
You turned your amp way up past it's normal limits, and used the attenuator to control the volume. No idea what it was actually doing, but it was connected between the amp and the speakers and just allowed you to control the volume that the speakers were putting out regardless of how loud your amp was.

That sounds like a good idea, but I believe it would be more helpful to me when i like my tone when its cranked because right now I don't care for its tone at high volume enough to want to bother bringing it to a reasonable listening level.

The tone is mostly a combination of the amp, speakers and pickups on the guitar. Followed by that are a lot of other things like room acoustics, string guage, wood type on the guitar, the state that the tubes are in, cables..etc.
Then there's the whole recording side of things with boards, compressors, bit rate...and so on..

What I'd probably do is start with the cheapest solutions first and work my way up the list. So cheapest on that list is just change the room acoustics. Move the amp, maybe build a cheap 'booth' made out of insulating blankets to place around the amp if recording is your main goal. Try moving the amp into the corner of a room and use that as a bass trap to add more bottom end. If you get too much bottom end, move the amp off the floor.

If that doesn't help any, then I'd just start trying the other lower stuff on the list like changing the strings, using some decent cables, get new tubes.

If that doesn't work then it's time to start thinking about major changes like your speakers.. like, is it better to go 4X10, 2X12, Closed-Back, Open-Back, Vented.
If that doesn't work then just either admit defeat and get a new amp or consider making changes to the guitar like new pickups.

Another solution, is to stick with what you have and use a decent overdrive pedal, compressor or EQ.
If you have the cash, get yourself a decent multi-effects unit and you'll never have to worry about the sound again. Some purists argue against it, but I've always been a big fan of them and use a GT-8 and Amplitube all the time.

Hope that helps. :)

Originally Posted by: "Kevin Taylor"Another solution, is to stick with what you have and use a decent overdrive pedal, compressor or EQ.
If you have the cash, get yourself a decent multi-effects unit and you'll never have to worry about the sound again. Some purists argue against it, but I've always been a big fan of them and use a GT-8 and Amplitube all the time.

I love my StealthPlug and Amplitube combo for recording.. I've never used it in its Live (stand alone) form so I'm not sure how it goes plugged directly into an amp or PA system. I assume it would do as well as any other pre-amp that has built-in modelling and effects modulation.

But for recording.. wow.. it's not only great sounding.. it's fun and easy to use as well. I use Tracktion for the sequencing.. and that is just as fun and easy to use. When I record I like to have a direct, no-loss, digital signal to play with at the least possible cost.. and that, at the time, was StealthPlug. Later on I might get a new amp, a mic and all the rest to do that kind of recording but for now, StealthPlug/Amplitube is just perfect.

Sounds like you need a Marshall Powerbreak - it allows you to crank it to 10 and get the tubes burning at their full potential but you can control the volume externaly and bring it back to what ever level you want (bedroom level too).
If you are looking for info on tube replacement I recommend Bob at eurotubes.com He did my Mesa Boogie Triaxis and Mesa Simul Class 2:90. Just tell him the sound you want and he will spec it up. If it's a new amp it shouldn't need new tubes though...
Like Kevin said though, the pickups on your guitar and the room accoustics have a lot to do with the tone. Never used a JCM800 but the 900 has animal distortion - very powerfull!

800's have much more gain than 900's. I used to have a 900, sold it to buy a 800. I have a 1987 50 watt head, 2 channel....
The 4104 is the combo version, right?
1 or 2 channel? (can't remember what year they introduced the 2 channel model)
Does it have a master volume?

The guitars may have low output pickups, which will make a huge difference. The SG I used to have had low output pickups and I never could get as much gain as I wanted with that guitar....My LP Classic has really hot pickups and I get all the gain I need, actually turn the gain down to around 8. I also just put Seymour Duncan Blackout active pickups in my Ibanez and I have to turn the gain down to around 7.....

Gain on 10 with low output pickups is about the same as a gain setting of 6-7 with average high output pickups....just an observation I've made....

Also, an easy mod for an amp tech is to add an extra pre-amp tube. I've played through a modified 800 like this and it melted my face.....but in all honesty, this mod isn't really needed....more gain can be found in other ways.

As far as pre-amp tubes themselves, different tubes can make the difference. I just recently replaced my pre-amp tubes and found that only 2 of them provided the gain I want. So naturally, I put those 2 in the first 2 spots (2 closest to the power tubes). One tube I have is really noisy (microphonic). Microphonic tubes will not sound good in the 1st, 2nd or 5th position (at least on my amp) as those tubes make a lot of weird noises. For whatever reason, if that microphonic tube is in the 3rd or 4th spot, you can't hear it (One of these positions powers the eq I believe). The first pre-amp tube position (one closest to the power tubes) is the main tube for the overdrive. You can actually try just swapping around the pre-amp tubes that are in it now....but be careful, you can get shocked doing this....just be sure to turn the amp off with the standby switch still on to drain all the power out of the amp....It is possible to get shocked even with the amp unplugged, so be sure to drain that power.....

As far as tube brands, I recommend Tung-Sol.

Here's a website to check out that will explain the characteristics of different tube brands and types....

http://thetubestore.com

Well I have EMG's in my guitar so I I know thats not the problem. Also as I mentioned earlier I don't think an attenuator will work for me here because even when my amp is turned up to 8 it doesn't quite have enough distortion even with a Boss SD-1 on front of it.The amp on its own can only get AC/DC type distortion on its own.Ive herd that EL34 tubes break up more when you crank them than the 6550's like mine has in it.

Are EL34's that different?

Nah, the powertube section won't really affect how much gain you get, at least not a lot.....I have EL34's in my 800 though. When you referred to El-34's breaking up sooner, that's the effect they have on the speakers. They make the speakers break up sooner. If your not getting a lot of gain with the volume at 8, the powertubes aren't the problem...

I suggest swapping out the pre-amp tubes.

cool well at least I know I won't have to buy expensive power tubes for no reason now. What preamp tubes are the best to get more gain ? I've found it hard to come across a strait answer on this, people keep saying just try a bunch and personal taste and all that bull, but really taste doesn't change something thats measurable like gain so I don't know why I haven't found a strait answer yet..

It really is hard to get, or give, a straight answer...It really is personal taste and you'll have to try different tubes to find the sound you want...I've found that 2 of the same tubes of the same brand will sound different. Some will provide higher gain than others of the same make. There's usually not a huge difference in tone, but different tubes will provide subtle differences...

I recommend Tung-Sol pre-amp tubes....they provide high gain without being microphonic....

Probably no need to replace all the pre-amp tubes. Just try replacing the first 2 closest to the power tubes...those are the pre-amp tubes that provide the overdrive...

Let us know what happens if you decide to try this...

I would honestly get the amp and tubes checked out. Worst case senario is they tell you it's ok. Lack of crunch in my experience is normally a sign of something.