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All about Marshall's JVM Series
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 Post subject: Upgrade Output Transformer and add a choke (with pics)
PostPosted: Sat Sep 06, 2008 3:09 pm 
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Pub Band
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Admin: We have made this thread a sticky as the choke mod is pretty popular here, please note that it doesn't have to be
a Mercury Magnetics choke ...



I finaly did it, upgraded my JVM with a Mercury Magnetics choke, the MC-10H, and a Mercury Magnetics output tranny, the MAR-JVM100-O!
Here are the pics:

Image
There goes my warranty!!
The choke goes instead of the R106 resistor.

Image
Here you can see the difference of the two tranny's.

Image
Almost ready!

Image
The tranny didn't fit exactly, had to change the hole's!

Image
Here are the wires from the choke.

Image
Up and runnin' again!!

Good things:
The amp is smoother now, and reacts much better!
The mids are sweeeeeet!!!
The amp sounds bigger, because of the bigger and tighter lowend.
And the lowend-thump is unbelievable.
More harmonics.

Bad things:
Tranny didn't fit in the original holes.
Drilling for fitting the choke.
It's heavier now!
Warranty is gone.

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Marshalls:JVM410H (2007),JCM800 2203 (1981), JCM800 2210 (1987), Ceriatone 2555 (Marshall Silver Jubilee Clone 2010).
4xJCM800 A and B cabs, each with G12T-75 and V30's in X-patern.
FX:Roland GP100, Roland FC200.
Guitars:Gibson Les Paul 1957 VOS Goldtop, Gibson Les Paul Classic, Fender Strat hardtail 1979, Fender Baja Tele.


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 Post subject:
PostPosted: Sat Sep 06, 2008 5:40 pm 
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I can deal with the "bad" 'cause it seems like the "good" outweighs the "bad" plus I love to tinker, may have to look into this.

banana_rasta

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Marshall JVM 410H- switchable C83, choke, variable -ve, plexi, Blackface
JCM800 Super Lead MK2
JMP 50 watt
Engl Steve Morse
Bogner Shiva 20th
Orange Tiny Terror
Epiphone Valve Junior- modded
Marshall 1960 - Vintage 30's
Home built 2 x 12 - WGS Veteran 30's
Home built 1 x 12 - Rola Celestion Greenback - re-coned
Tc Electronics G-Major
Decimator Pro Rack
A bunch of pedals...
Gibson, ESP/LTD, Jackson guitars


Nothing in the world is more dangerous than sincere ignorance and conscientious stupidity.


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 Post subject:
PostPosted: Sat Sep 06, 2008 5:57 pm 
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World Tour
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Cool, and you did it yourself. [smilie=gt-happyup.gif]
I am clueless on what is on the inside. I like what you describe as the end result though. banana_rasta

Are you planing on bypassing the heater rail fuses?

How much did the parts cost you?


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 Post subject:
PostPosted: Sat Sep 06, 2008 6:42 pm 
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Yes...more info! And was it worth it to you to do it?

Sound must be great cause I love mine now!
[smilie=gt-happyup.gif]

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JVM410H - 1960A & B - Rocktron Tri-Wah
Pod XTL - Gibson Les Paul - Gibson SG - Charvel EVH - Minarik Inferno - Bernie Rico Jr. Vixen - Fender Strat - Rabies


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 Post subject:
PostPosted: Sat Sep 06, 2008 6:47 pm 
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OT is about $265, choke about $35 didn't look at the PT, probably another couple hundred so it ain't exactly cheap but probably worth it...GAS it never ends!

banana_rasta

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Marshall JVM 410H- switchable C83, choke, variable -ve, plexi, Blackface
JCM800 Super Lead MK2
JMP 50 watt
Engl Steve Morse
Bogner Shiva 20th
Orange Tiny Terror
Epiphone Valve Junior- modded
Marshall 1960 - Vintage 30's
Home built 2 x 12 - WGS Veteran 30's
Home built 1 x 12 - Rola Celestion Greenback - re-coned
Tc Electronics G-Major
Decimator Pro Rack
A bunch of pedals...
Gibson, ESP/LTD, Jackson guitars


Nothing in the world is more dangerous than sincere ignorance and conscientious stupidity.


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 Post subject:
PostPosted: Sat Sep 06, 2008 7:02 pm 
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No doubt. It never does...lol

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Pod XTL - Gibson Les Paul - Gibson SG - Charvel EVH - Minarik Inferno - Bernie Rico Jr. Vixen - Fender Strat - Rabies


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 Post subject:
PostPosted: Sat Sep 06, 2008 7:09 pm 
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Hothands, if you do, I would love to hear it! [smilie=icon_wink.gif]


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 Post subject:
PostPosted: Sat Sep 06, 2008 8:15 pm 
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[smilie=icon_cool.gif]


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 Post subject:
PostPosted: Sat Sep 06, 2008 11:02 pm 
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Nice job. Pics are great ! Thanks


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 Post subject:
PostPosted: Sun Sep 07, 2008 9:37 am 
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svdijk, great post here for those interested in these mods. I've got a Dual Rec that has a Mercury tranny and choke here waiting to be installed. Along with an NOS RFT and NOS Mullard on the way. I'm very interested in the Voodoo Amp mods for the JVM and it looks like you've got that covered for the most part. You're description of the results sums up what I am seeking in the amp. To combine that aggresive EL-34 tone with the increased low end you've described seems to me to be an absolutely killer combination. Possibly similar to the effect of me using my JVM in conjuction with my Dual Rec. Great job here! [smilie=gt-happyup.gif]

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Marshall JVM 410H+210H, 04'Gibson Custom Shop LP Standard,95'Gibson LP Standard, 93'Washburn N4 Padauk, 98'Warwick Corvette FNA, 3-4x12 Marshall cabs, X2 Digital Wireless, cases by Crown and NGM


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 Post subject:
PostPosted: Sun Sep 07, 2008 10:47 am 
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The JVM is a very service-friendly amp, so it wasn't that difficult to do the mod!
I thought of bypassing the heater fuses, but it worked oké for 1.5 years, so I leave them for now.
The output tranny was 225,- euro's and the choke 24,- euro's.
And for me it was really worth it!!!

The reasons why I did the mod, was that I was looking for more lowend in the OD1 and OD2 channels, and a thighter bass-response in the crunch-channel.
And the feedback of the amp was not very musical to my ears.
All those things are solved now for more then 100%!!
Even the OD2 channel is awesome now, and reminds me of a Mesa Mark 4, but with a thighter lowend!!

I was very used to my good old JCM800 2210 (alsow with MM ot and choke!), and missed some things in my JVM, like the nice feedback, and very big sound, but now the JVM can sound like that amp, and do a lot more then the JCM800!!

Don't get me wrong, I always liked the JVM from the beginning, just tweaking it, like I did 21 years ago, when I bought my first Marshall, the JCM800 2210, that I still own!!

_________________
Marshalls:JVM410H (2007),JCM800 2203 (1981), JCM800 2210 (1987), Ceriatone 2555 (Marshall Silver Jubilee Clone 2010).
4xJCM800 A and B cabs, each with G12T-75 and V30's in X-patern.
FX:Roland GP100, Roland FC200.
Guitars:Gibson Les Paul 1957 VOS Goldtop, Gibson Les Paul Classic, Fender Strat hardtail 1979, Fender Baja Tele.


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 Post subject:
PostPosted: Sun Sep 07, 2008 2:11 pm 
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Location: Baltimore, Md
Todd Zila wrote:
Hothands, if you do, I would love to hear it! [smilie=icon_wink.gif]



Soon as I recover from my latest spending spree I'm going to do it!
Keep you posted.

banana_rasta

_________________
Marshall JVM 410H- switchable C83, choke, variable -ve, plexi, Blackface
JCM800 Super Lead MK2
JMP 50 watt
Engl Steve Morse
Bogner Shiva 20th
Orange Tiny Terror
Epiphone Valve Junior- modded
Marshall 1960 - Vintage 30's
Home built 2 x 12 - WGS Veteran 30's
Home built 1 x 12 - Rola Celestion Greenback - re-coned
Tc Electronics G-Major
Decimator Pro Rack
A bunch of pedals...
Gibson, ESP/LTD, Jackson guitars


Nothing in the world is more dangerous than sincere ignorance and conscientious stupidity.


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 Post subject:
PostPosted: Sun Sep 07, 2008 3:12 pm 
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I might do this in say June 2010. But I'd really like to hear a modded one side by side with an unmodded one and see if you can get the unmodded one to sound close with something like an EQ or KT77s (I think that's the tube sub????) first.

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Randall MTS Lynch Box (Modules: JTM (Marshally crunch); Brahma (Lynch Dokken); SL+ (Marshally); Deluxe (Fender); KH1 (Fender); Grail (Mesa DR); Mr. Scary (Soldano)); Fender HR Deville
ESP Alexi V; G&L Legacy; Gibson J45; Epi LP Special (P90s); Gibson SG Std
Memberships -- League of Pentatonic Players; League of Vocal Assassins


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 Post subject:
PostPosted: Sun Sep 07, 2008 3:51 pm 
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RachelMorgan wrote:
I might do this in say June 2010. But I'd really like to hear a modded one side by side with an unmodded one and see if you can get the unmodded one to sound close with something like an EQ or KT77s (I think that's the tube sub????) first.


In the pix svdijk has KT77's in already ... so svdijk did you try the modded amp with Kt77's and EL34's to try both ?

I guess you did the mods at the same time but I just wondered how much difference the choke made too as that's a cheap mod to do ?

Finally are you sans c83 on this amp too ?

cheers

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::: JVM410 head,modded:- 4H choke, Caseys Mods :- Plexi cap, -ve feedback, Dual Rectifier, Blackface, Anti Stiffness, 1 wire Randy Rhoads, Plexi
::: AFD100, DSL100W head (no C83), Fender Champ 12
::: 1960AV w/greenbacks, homemade 2x12 Celestion Golds (100W)
::: Gibson Les Paul Standard, Dimarzio SD bridge Pup,Standard neck Pup. Tokai Strat with Dimarzio SD, Alhambra Acoustic fishman Pup
::: PodXTLive fully loaded, Vox V848 Clyde McCoy Wah Wah


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 Post subject:
PostPosted: Sun Sep 07, 2008 5:58 pm 
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Hey Svdijk, fabulous work!

Not being a technical person, I have a couple of queries.

1. It looks like the JVM has 2 transformers (1 on the left and one on the right). Is this the case?

2. In simple terms, what is a choke, and what is its purpose.


Looks like a great mod that is worth considering.

Cheers

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Gibson SG Standard, Orville Les Paul (Standard & Custom), Ibanez 1570 Prestige, Schecter Genesis, Epiphone Les Paul Bass
Marshall JVM410, Line 6 Spidervalve MkII HD100, Orange Dual Terror, Marshall 1936 (GT1275's), Marshall 8412 (Mesa Black Shadows + Celestion Neos), Vox 2x12 (Greenbacks), TC Electronic Nova System, Ibanez Screaming Demon Wah, Ibanez SD-9, Boss MT-2, Decimator G-String, Boss NS2, Sennheiser Freeport Wireless


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