JCM900 General opinions Please

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bnwitt
Senior tube assistant
Posts: 268
(2/5/04 11:09 am)
 JCM900 General opinions Please
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 I have a customer inquiry regarding changing a JCM900 from 100 Watts to 50 watts. What do you guys think about the JCM 900 in general. Is this a minor alteration or should it be a complete gutting to improve the tone of the current circuit? At this point I don't know the actual model or if it is Drake iron or not.
Barry
 
mrr3000gt
I will work on all amps
Posts: 364
(2/5/04 4:23 pm)
 JCM900 fun
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I had to fix one of these recently. I would not buy one unless it was for under 150.00.

The problem is the construction: its resistors are mostely rated at 1/4 watt, uses a cheap board mounting system, and they seem very tempermental.

The one I fixed I converted to 50 watt from 100 by removing one set of the tubes (outer pair). Now, that changes the output impedance characteristic of the output jacks (what they now mean with just two power tubes). I cant remember how it changed the jack configuration, but I remember the guy was OK to use his model 1960 Marshall 4x12 withit because he was able to run the cabinet in two different impedances (thereby supporting both the two and four power tube configurations of the head).

 
bluesbear
Hey get your own solder
Posts: 322
(2/5/04 5:21 pm)
 Re: JCM900 General opinions Please
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 I don't know anything about the construction but, in my opinion, thay sound like crap. When Mars went out of business last year, they were selling everything super cheap. My son (22 at the time) decided he had to have a Marshall. "Slash uses one!" Anyway, he called me when he got home all depressed because, in his words,"They all sound like sh*t compared to yours and you don't do Marshalls!" Needless to say, I'm working on an EL34 design. Who can resist when your son says something like that?!
Dave
 
bnwitt
Senior tube assistant
Posts: 268
(2/5/04 5:58 pm)
 Re: JCM900 General opinions Please
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 Dave and 3000,
Thanks for the feedback. That's about what I thought on the JCM900's. Seems to me I had heard that they were crap and that they sounded like crap as well. What would you think this guys tonal reaction to a 1987 50 watt hoffman "boarded" amp would be after playing a JCM 900 for several years?
Barry

Edited by: bnwitt at: 2/5/04 6:07 pm
 
Lucid Alice
Senior tube assistant
Posts: 154
(2/5/04 8:09 pm)
 Re: JCM900 General opinions Please
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 I'm not familiar with the 900 or even the 800 (am I dating myself?). But if he expects to get metal sounds out of it you will have to do a hot stage. Of course you can do the stock board and offer the hot switch mod if needed after he tries it out.

It would definitely be a step up in tonal quality. Some poor oaf will hear him playing and decide he needs to get a 900!

 
mrr3000gt
I will work on all amps
Posts: 364
(2/5/04 10:59 pm)
 Re: JCM900 General opinions Please
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Well, I did have that JCM900 around here for a couple of weeks and I did jam out on it a long time to 'test' it.

I did not think it played bad: actually, it sounded good. But its a heavier sound. It did sound better than their best AVT technology trans-tube amps they make.

From what I can tell, 1/2 of the boards being used looks like its used to make the preamp drive the hell out of the sound.

I use a master volume Hoffman Plexi-50 for playing and making noise with:
My Soundclick.com website

I use the Plexi-50 with a TS-808 pedal or a DOD-25 clone I built and I can get sounds from late '60s to Pantera. Its a real versitile amp tonewise.

I think that with a pedal, a Hoffman plexi is everything a JCM900 cant be because it can do vintage model 1987 Marshall tones as well as chainsaw noises. The JCM900 is basically a chainsaw sound/hard rock amp.

 
 
coap01
Junior tube assistant
Posts: 93
(2/5/04 11:05 pm)
 800s
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 i think you can get some good metal tones out of an 800 but you really gotta crank them up. kerry king of slayer uses 800s exclusively as well as zack wylde and those dudes are METAL
 
mrr3000gt
I will work on all amps
Posts: 365
(2/5/04 11:18 pm)
 Re: 800s
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 Coaps right:

Most heavy players use a pedal to hotten up the sound.

I can say that the 1959 bassman is not a good choice if you are a heavy player. I got one to overdrive with two distortion pedals on it, but at that point, you are not in the 'tone zone' of the bassman.
 
bnwitt
Senior tube assistant
Posts: 271
(2/6/04 12:29 am)
 Re: 800s
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 Guys,
this information is very helpful for someone who has been into Fenders more than Marshalls. Thanks a ton for the feedback. I have really started to appreciate the Marshall tone since I built my first 1987 plexi (hoffman 50 watt) and now I am building an 18 watt which I hope to add to my line up.
Barry
 
mrr3000gt
I will work on all amps
Posts: 367
(2/6/04 12:43 am)
 Re: 800s
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 A little 18 watt combo would be cool. I'd probably use that one more often.
 
Ritchie200
Senior tube assistant
Posts: 161
(2/6/04 1:08 am)
 Re: 800s
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 Hey guys,
I worked on two 900's last year and if I am not mistaken, they have a 50/100 switch built in!?!? I guess my question would be why your customer requested this mod? Or am I going daft! Or was that the 5150's..... Darn, I can't remember. The PCB crap all kind of runs together. Anyway, IMHO, I thought the distortion sounded pretty flat - almost solid state'ish. I thought the whole amp sounded kind of ehhhh... I was not impressed at all. The 800's are a different animal! THey seem richer in overtones and more versatile tone-wise.
Hey Dave, have your son buy one of the Marshall repro-head cabs and you can put the good stuff inside! THat way he will sound good and still have the big "M" on the outside! Come now, you were his age.....a few years ago. Remember, image is EVERYTHING! It sounds like you raised him right, he appreciates good tone!
Jim
 
bluesbear
Hey get your own solder
Posts: 323
(2/6/04 9:04 am)
 Re: 800s
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 "Remember, image is EVERYTHING!"

That's true, even when you know better! Now that I'm retired, I'm trying to play more. Everyone else in my band still works and can't play enough to satisfy me. I'm the best blues guitarist in town....but that's not good enough. I play '70's Yamaha's. I just think they're WAY better than Gibsons or Fenders. I just bought a Tele and now I'm social acceptable to the blues nazis, as I call them. Plenty of jobs. Weird!

"It sounds like you raised him right, he appreciates good tone!"

Believe it or not, when he was in high school, he was in an ELEVEN piece band with a five piece horn section doing blues and southern soul (Otis Redding, Barcays, etc) versions of Beatles and Led Zeppelin songs. Amazingly, the were real popular. It seems that even kids who claim to like bozo music prefer real music, as long as it's kids their own age playing it. I think that's the key.
Dave
 
coap01
Junior tube assistant
Posts: 94
(2/6/04 9:59 am)
 5150
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dazco6550
Junior tube assistant
Posts: 17
(2/6/04 11:59 am)
 .
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 Hmmm......well, i've had 3 800's and 3 900's. The 900's evoke wildly varying opinions, and the reasons are because 1)they have diode clipping which causes them to sound much different at bedroom levels that at stage levels where the gain can come down because of the extra ouput stage grind you get live. So those who play them at home are likely to have a very different opinion than those who gig with them. 2)one 900 can vary wildly from the next. One of the dual reverb 900's i had was crap. I could not get it to sound good anywhere, and it was piercing, and i had to keep the treble at 0 or close to it ! The other dual reverb was fat and rich and unlike my 800's NEVER mushed out onstage, which my 800's did often horribly after they got real warm. I always kept them biased correctly and with good tubes.....usually the old double getter teasla 34LS.

Point is, if you get one thats not a lemon (which it seems a lot are) and you use it live and use it to it's best advantage, they can not only sound good but great. I have tapes of my band at various stages over the last couple decades, and the best tone on tape is from the gigs where i used the good 900! I assure you that if you listened to them you'd agree. The 800's were better sounding amps in a side by side comparrison, no doubt ! But like many amps they sound a lot different live where other instruments tend to mask certain frequencies.The 900's always cut thru much better and stayed tighter than the 800's with few exceptions. Usually on slow tunes where there's a lot of space and the tone isn't being tread on by the