Discontinued – We no longer modify these amplifiers.Various factory issues have proven time consuming to resolve/repair. To date we have absorbed a great deal of time/cost associated with repair(s) of these models, however we can no longer continue to do so & nor do we wish to charge customers for costly repairs. Please note; our Mods do not cause/contribute to noted factory issues. All warranties for Voodoo Mods still apply.
Sorry no exceptions - Any and all units shipped in after 01-09-12 will be returned at sender's expense.
We recommend the Marshall JVM205 / JVM210. By comparison the JVM205/210 is more reliable, parts are readily available and we have several professional musicians touring/using these.
Marshall JCM900 4100 "Rock" Mods 
Standard Mod™ $249.00
Deluxe Mod™ $528.00
Platinum Modified™ $862.00 FREE SHIPPING!
Platinum Modified™ $872.00 International Customers!
"This is our original Mod for the JCM900 4100 Series - Great Rock tones!"
Standard Mod™ $249.00
Circuitry Modifications
Description / Specs:
- All Modifications are exclusive to Voodoo Amps®
- This is the original Mod we designed for the JCM900 4100
- Increased gain / distortion
- No matter how much gain you use you can still hear all the notes within the chords
- When you turn the gain control to 10 - it's all useable
- Increased sustain - Smoother & more liquid like
- Faster attack - tracks every note you play immediately
- Improved harmonic content
- Harmonics will leap off from the fretboard with ease
- Vibrato & bends feel smoother
- You will not have to struggle or fight the amp
- EQ sections are more active, flexible & musical
- Dramatically improved bottom end - Tight / responsive & fun to play on
- Over all frequency response is better balanced / more even sounding
- Cranked tones at lower volumes
- Will cut through & sit in the mix much better live as well as in the recording studio
- Note: Channel 1 makes for a better crunch channel verses a clean channel
- Recommended Voodoo Add-On™ controls; Bottom, Push/Pull Bottom & Global
- All features will function the same - Features are not removed nor disengaged
- We do not offer Modifications or upgrades to the fx-loop, switching circuitry or reverb
- All components used are high quality & are chosen for quality of tone, feel & reliability
- Please list "Rock Mod" in the notes section of the Mod-Form
- Voodoo Mods™ retain your amps resale value verses decreasing it
- Approximate turn-around time 5-7 days - rush service is available
Deluxe Mod™ $528.00 
Output Transformer Upgrade to Standard Mod™
Description/Specs:
- Includes Standard Mod™ (see above)
- Incudes Upgraded Mercury Magnetics VA-4100-O Voodoo-Designed™ Output Transformer
- $229.00 & $50.00 Installation fee (included)
- Vastly increased sustain - leads are much more liquid like & fluid
- Effortless Pinch / artificial harmonics
- Greatly improved articulation & definition
- Increased / richer bass response
- Increased even-order harmonics (IE: sounds much more musical)
- Massive rhythm tones - when you hit a chord it's there immediately
- Increased headroom (cleans stay cleaner & louder at gigging/stage volumes)
- Approximate turn-around time 5-7 days - rush service is available
- Transformer FAQ's
Platinum Mod™ $852.00 
FREE SHIPPING!
Power Transformer Upgrade to Deluxe Mod™
- Includes Deluxe Mod™
- Includes Upgraded Mercury Magnetics VA-4100-P Voodoo-Designed™ Power Transformer
- $259.00 & $75.00 Installation fee (included)
- 120V 60Hz Operation
- Improved power regulation
- Reduced noise and hum
- Improved feel & tone - Smoother feel & easier to play
- A must for touring musicians, engineers and producers!
- Platinum Mod™ will give you the best tone, feel and performance
- Average turn-around time 5-7 days - rush service is available
- Transformer FAQ's
- Voodoo Amps® World AC Voltage Guide
Platinum Mod™ $872.00 International Customers!
Power Transformer Upgrade to Deluxe Mod™
- No need for step-down transformers that can harm your amp!
- Includes Deluxe Mod™
- Includes Upgraded Mercury Magnetics VA-4100-PE Voodoo-Designed™ Power Transformer
- $269.00 & $75.00 Installation fee (included)
- Specify your voltage - 100V, 220V, 230V, 240V & More!
- Improved power regulation
- Reduced noise and hum
- Improved feel & tone - Smoother feel & easier to play
- A must for touring musicians, engineers and producers!
- Platinum Mod™ will give you the best tone, feel and performance
- Average turn-around time 5-7 days - rush service is available
- Save money! Buy from Ebay USA, have it shipped directly to us & we will ship it you!
- Save money on shipping! We offer several shipping options, please Email us for an estimate!
- Transformer FAQ's
- Voodoo Amps® World AC Voltage Guide
Mod-Form / Mod Process & FAQ's / Packing & Shipping / Reviews / Contact
"Get inspired - upgrade your tone now!"
Voodoo Amps® is the Leader in Tube Amp Mods & Upgrades
Pricing, features & specifications subject to change without notice