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PostPosted: Wed Oct 18, 2017 10:11 am 
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Location: The Last Place You Look
Pull up a chair and sit down, kids. :mrgreen:

Our story starts back in 1982.

I was in my first band with my best friends, Brian and Duff. We called ourselves Tempest initially but later changed the name to Hydra. We used that name through late '85 when we split up and went our separate ways. We were heavily influenced by The Police, Toto, Styx and a local band we all loved called Alchemy. (I ended up singing with Alchemy years later, but that's another story)

But our main influence was Rush. We worshipped the band and followed them obsessively, emulating our heroes as we gained skill and confidence. Our lives and calendars seemed to revolve around Rush. When was the new album out? When would they come to Kansas City? How hard will it be to learn those new songs?

As time went on and we started acquiring better gear, Duff decided it was time for him to have a Gibson Les Paul Custom (in ivory just like our hero, Joe Greene guitarist for Alchemy) and a Marshall stack.
Duff worked very hard to earn and save the money to buy his dream rig. And when I say "hard", I mean just that. He worked a series of jobs doing metal fabrication. That shit scared me to death. I remember vividly the day we got word that his Les Paul had arrived. Some months later he got the 4x12 cabinet and finally the amplifier, a Marshall 2204 50 watt head.

Now, we were cooking.

I always loved the sound Duff got with that rig. It was tight and tough, but sweet and fat.

Fast forward to a few moths ago.....

My good friend, Charles (a tube amp genius, for what it's worth) was looking to get rid of some stuff cluttering up his workshop. He mentioned that he had an early 80s JCM 800 2204 head cab and new chassis with transformers and filter caps that had been gathering dust waiting to be finished. Would I be interested?? Well, damn straight cowboy.

He brought it by a few weeks later and I was more than excited. The chassis was a really nice repro from Watts Tube Audio here in St Petersburg. It has the same bright yellow color that the originals had when they were new. He had sourced a PT from Pacific which is supposed to be the same one that Ken Fisher favored in his amplifiers. Unlike original transformers it has a bias tap as well as the various domestic and import voltage taps. The OT and choke came from Classic Tone in Chicago. Perfectly fine iron for the task. The filter caps were the JJs that I would have selected if I was sourcing everything myself. He had installed all this plus the tube sockets, but had not wired anything up.

At first, I thought I'd order a JCM 800 kit from Mojotone. Their kits are second to none and a really convenient way to grab it all in one shot. As I looked around my parts stock, I realized that I had nearly everything needed for the build at hand. So, after ordering some Mojo Dijon caps and deciding on a turret board from Watts I had everything I needed to get started.

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I stuck very closely to the original 2204 schematic using Ken's layout. Over the last several months I spent a lot of time listening to several Marshall 50 watt amplifiers of the era. I compiled a cross reference chart of voltage readings and component values. All of those amps sounded good in one way or another. But they each sounded distinctly different. I came away with the impression that the most important aspect other than good quality transformers and good quality capacitors was that the vast majority of the examples that sounded GREAT had resistors that were very close to specifications. I ended up using mostly carbon composition resistors. The exception is being metal films for areas where noise is a concern and metal oxide where blunt force power handling is needed.

I couldn't finish the amp without the custom plates from Mojotone, so I busied myself with the board and associated wiring. Plenty to do in the meantime.

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I've been doing this sort of thing for awhile now, so the build went relatively fast and smooth. I did end up having to reverse the B+ wires from the OT to avoid a runaway oscillation, but that happens more often than not. I used some new 20 gauge pre bonded wire from Mojotone that just works beautifully. It really sped things up a bunch. Loaded with JJ tubes (what else?) set the idle current and plugged into my 1960 Classic cab loaded with British made Celestion G12-75s.

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I'm absolutely blown away by the face and back plates from Mojotone. They simply knocked it out of the park. And they were in my hands within a week.

The "AMD" is, of course Amplifier of Mass Destruction. 8) (Actually my wife's Initials)
And the slogan "Protect The Innocent - Punish The Wicked" is one I stole from a Batman comic book and have been using for awhile now.

But, how does it sound?
In a word, spectacular.
With nothing more than a guitar and a cable you can coax all manner of different sounds out of this amplifier. It's one of those amplifiers that makes you want to play for hours. I really wish I was gigging right now. I may have to do something about that.

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My partner across the hall, Erik Rutan of Mana Recording studios is a certifiable Marshall JCM nut. He generally prefers the hundred watt models, but is always on the lookout for a 50 W that he likes. He has a number of sessions coming up in the next year where I feel like having a 50 W handy will be a good thing. We shall see.

Well, that's my story and I'm sticking to it. Cheers! 8)


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Last edited by scootercaster on Fri Oct 20, 2017 8:13 am, edited 2 times in total.

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PostPosted: Wed Oct 18, 2017 10:37 am 
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Location: Beautiful Manitoulin Island
I need to build an 800. Such a perfect sounding amplifier


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PostPosted: Wed Oct 18, 2017 12:10 pm 
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Knight of Cups wrote:
I need to build an 800. Such a perfect sounding amplifier


I recommend it highly. It's a very satisfying circuit to build and play.

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PostPosted: Wed Oct 18, 2017 12:38 pm 
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Looks fantastic by the way. :)


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PostPosted: Wed Oct 18, 2017 12:39 pm 
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Knight of Cups wrote:
Looks fantastic by the way. :)


Thank you, sir.

I think I'm finally getting the hang of this. 8)

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PostPosted: Wed Oct 18, 2017 7:24 pm 
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Beautiful job. Love 800's. Used one to record my cd in '96

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PostPosted: Wed Oct 18, 2017 7:45 pm 
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geekmacdaddy wrote:
Beautiful job. Love 800's. Used one to record my cd in '96


Many thanks, sir! I love it. :mrgreen:

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PostPosted: Wed Oct 18, 2017 7:47 pm 
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Video clip added. 8)

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PostPosted: Wed Oct 18, 2017 8:57 pm 
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Image

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PostPosted: Thu Oct 19, 2017 7:04 am 
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duhvoodooman wrote:
Image

Indeed!

Looks & sounds amazing, Scooter!

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PostPosted: Thu Oct 19, 2017 7:56 pm 
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Frag Magnet wrote:
duhvoodooman wrote:
Image

Indeed!

Looks & sounds amazing, Scooter!


Many thanks, guys!! :mrgreen:

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PostPosted: Fri Nov 03, 2017 1:23 pm 
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What a great amp! Your story gave me a whole new appreciation for the original JCM800. I can't say I worked quite as hard for the money to acquire my used 1982 JCM800 and 4x12 cab (got the whole thing for $600). They are great amps, and despite leaning towards my more clean sounding amps in preference, I can't see getting rid of the JCM. Congrats on a finished build.


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PostPosted: Fri Nov 03, 2017 4:44 pm 
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I missed the original post somehow. That, sir, is one fantastic looking and sounding Marshall. Your attention to detail on the build is impeccable as always! :)

Being a child of the 80’s myself, I’ve owned a 50w 2204 head and one of those 4210 combos with the quasi-channel-switching - both of which are among my list of gear that I’ve regretted letting go. There’s just something about those amps - even 100% stock, they sound amazing.


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