Marshall JCM900 4100.. Just a few questions..

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Chadk808

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I've had this amp for almost a year now. It doesn't get a crazy amount of use, but I do use it. I run it through a Mesa 4x12 cab.

The sound is a little bit on the thinner side, and i hear that may be because of old tubes, so I usually have my bass up pretty high.. I should probably point out the fact that I know jack about electronics.. :scared:

Anyway, I'm planning on getting it retubed and rebiased and just completely "tuned up" because I just want it to be in great working order and not have to worry about it blowing up or anything. I've been reading up and found that the 4100 isn't necessarily the most popular model. I've read a few posts recommending rebiasing and switching to EL34's instead of the 6L6's. I'm just looking for nice, strong tone. Any advice/tips??

Also, does the gain channel run on tubes?? Or just the clean channel??

Thanks!!!

Chad
 
I used to own one. Was never too thrilled with it to be honest, but had 5881's in there. I've played and have heard that the EL34 version is better - it is. I don't think you can just put 34's in there, though. Pretty sure you'd have to have the output transformer swapped as well...
 
I had a hard time getting a good hi gain tone out the one I had. I loved the clean tones though. I usually ran the treble and presence all the way off, dimed the bass, and used the mids to control the brightness. But it still had to be ear bleeding loud to sound good so I let it go. Mine was a 5881 model.
 
Welcome to the forum btw. I had a JCM 900 Dual reverb, not sure what model #. I thought it was the shit back in the day (shrill as hell though), but it got stolen. If you want a retube/rebias and a tune up go for it. I would not dump a lot of money into changing the tube type and changing out the transformers, etc in an amp. At that point to me you are not tweaking, you are trying to change the fundamental nature of the amp. If you are happy with it keep it and get it in as good a shape as possible. If you are fundamentally dissatisfied with it, you are probably going to stay that way until you get what you want so I would figure out what that is and work towards that. Some people like tweaking around on their stuff. That's fine if you enjoy the tweaking process but since you mentioned a general lack of knowledge regarding electronics I take it that you are more in the get my tone and play camp. Also, don't overlook speakers. If it is a combo with that 75W celestion it is shrill and thin sounding to me by nature. Wish I had back some of the money I have spent trying to polish turds
 
Cool, thanks for the tips guys.

Hmm, not sure what I'm gonna do yet. I might just retube it with 5881's and sell it or try to completely overhaul it.. Gotta give it some thought.

Can anyone tell me if the gain channel on this amp uses the tubes to run it or just the clean channel??? I've heard that certain 2-channel "tube" amps only use the tubes to run the clean channel.

Thanks again! This forum seems cool as hell


Chad
 
The other guitarist in my band plays a 4100, and he sounds great. Runs it thru a Marshall slant with 75 watt celesions, and has a big, fat, thick, gainy rock tone.
 
the gain uses tthe pre amp tubes same as the clean, but it has diode clipping as well which isnt very popular.. they can be a harsh thinner sounding marshall, but ive also known dudes that make them sound good. maybe look into a known amp modder and get it re-done..?
 
Awesome! Thanks again guys. I appreciate the input. I learned more about my amp in the past 24 hours than I've known the entire time I've had it. :)
 
I always like the 900 series. I can't remember which I had though. I am pretty sure I had one of the heads and I know I had the combo. I was always able to get great sounds from.
 
i Got one going through my bogner cab,,,,,sounds fkn awesome....i prefer it to the SLO I had but the SLO Had the extra gain i need...but that Marshall edge cant beat it
 
Lots of great amps use diode clipping, so don't let that discourage you from getting a good tone. The CCV, and Silver Anniversary Marshalls use diode clipping, and they sound great. Just keep tweaking it!
 
any tube recommendations for a Less stiff more liquid lead feel?
 
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