Feature Mods
1 | Mod | Description | Suitable for | Suffix |
2 | Tube FX loop | Adds a Tube based serial FX loop to your amp. Requires adequate power for the additional valve. Based on the popular Merlin Blencowe aka Valve Wizard Kit. | Hiwatt, Sound City, Marshall, Carlsbro and similar | |
3 | Master Volume | Adds a PPIMV to your amp. Control can go on the rear or front panel according to available space / preference | Hiwatt, Sound City, Marshall, Carlsbro and similar | |
4 | Speaker Swap | Speaker upgrades or replacement of faulty driver. See HotRox and Lean Audio for speaker suggestions | All combos and cabinets | plus speaker |
5 | Combo Speaker Cable Extension Upgrade | Upgrade the flimsy speaker lead on your combo with a low loss Van Damme OFC cable and Neutrik / Switchcraft heavy duty jack plug. Add extra length to share the cab with alternate amp head. | All combos | for 1 metre |
6 | Adjustable Bias Mod | This mod adds a bias trimmer pot inside the amp for adjustment by a qualified engineer. Great for older amps had no provision for adjusting the bias. | Selmer TnB, Some Sound City | |
7 | Fan Temperature Controller | Adds a temperature sensor to reduce fan noise at low volume levels great for home playing and recording | Bass Amps like Ampeg BA112, Hartke but would also work in PA amps |
Cosmetics
| Mod | Description | Suitable for | Price |
|---|---|---|---|
| Amp Head LED - Fixed Colour | Custom fit aligned to valves - single colour LED highlighting the tubes. Screw installed baton with custom placed coloured LEDs to highlight valves and create shadows. Comes with adaptor and can be disconnected as required. In some amps it can be powered from the amp directly too but this requires evaluation of the power capability of the amp. | Amps with see through grille like Peavey 5150, Peavey 6505, JSX, Engl | £93 |
| Amp Head LED - Variable Colour | Coloured LED strip baton mounted either up or down lighting, or shining from a corner at 45 degrees. LED strip comes with a controller to have any colour you like and comes with some effects like sequences (static is nice but the sequences are a bit annoying). Also a range of diffusers for makiing looks like a solid ray of lighting colour. | Amps with see through grille like Peavey 5150, Peavey 6505, JSX, Engl | £106 |
| Amp Head LED - Variable Colour, Sound to Light | As above but with sound to light controller for extra effects | Amps with see through grille like Peavey 5150, Peavey 6505, JSX, Engl | £122 |
| Cabinet Grille Cloth Replacement | Replace speaker grille cloth due to ageing or to achieve custom finish. Price based on Marshall black fret cloth at £15 / metre for 1 metre. | All | £97 |
| Speaker Cabinet wheels | Save your back with a set of four pop in / pop out castors. | All combos and cabinets | £103 |
Fender
Fender 90s range and onwards
| Mod | Description | Suitable for | Price |
|---|---|---|---|
| Mains Voltage Correction | Adjust your amp to the correct voltage according to your location. Essential for most Fender Amps made for the EU market to ensure long life. | Blues Deluxe/Deville, Hot Rod Deluxe / Deville, Twin, Supersonic | £10 included in service |
| Lead Dress optimisation | Most Fender Amps are noisier than they need to be. By re-dressing the leads from the transformer it is possible to reduce the amp's hum. | Blues Deluxe/Deville, Hot Rod Deluxe / Deville, Twin, Supersonic | £10 included in service |
| Chassis Dropper Fix | Dropper resistors appear is many amp circuits and their job is to provide a low voltage power supply typically of 15v for the effects loop, reverb driver chips and channel switching. The problem is that they do get very hot (80 ° deg C) which tends to damage the PCB on Fenders after about 5-10 years. When this happens, you will experience strange fault symptoms like inconsistent channel switching, loss of reverb and squealing noises. This mod replaces the dropper resistors with upgraded aluminium-clad chassis-mounted components point to point wired away from the PCB. Once the mod is applied the lifetime of the amp is no longer limited by this design weak spot permanently. | Blues Deluxe/Deville, Hot Rod Deluxe / Deville, Twin, Supersonic | £60 inc parts |
| Pro Switchcraft Input Jack upgrade | Replacement of Fenders flimsy plastic connectors with professional Switchcraft jacks as per all vintage amps. More info... | Blues Deluxe/Deville, Hot Rod Deluxe / Deville, Twin, Supersonic | £16 per jack |
| Cap Job aka re-cap | Replacement of the electrolytic capacitors that are prone to drying up and degradation over time. Worthwhile on amp after about 10 years use or as an upgrade on modern Fenders that use budget "Illinois Capacitor" brand grade parts swapping out for high end F&T low ESR caps. Includes the large power supply reservoir smoothing capacitor as well as the pre amp de-coupling capacitors, bias and cathode bypass caps. Price varies by amp size. e.g Blues Junior @ £59, Hot Rods @ £60 and Twins @ £80 | Blues Deluxe/Deville, Hot Rod Deluxe/Deville | £58 approx |
| Princeton 112 Clean Volume Abruptness Mod and Drive Channel Fizz Taming Mod | See Princeton Mod Post for details | Princeton 112+ | £24 |
| Princeton 112 Master Volume Pot Mod | See Princeton Mod Post for details | Princeton 112+ | £24 |
| Master Volume Control | The Fender Hot Rod is just way too loud. The volume control is hard to control at lower levels. Fender addressed this a little bit in the Hot Rod III by using slightly different taper pots but it is not a significant improvement. One solution is to add a removable master volume in the effect loop, called the Lion Tamer. This plug-in module works well but it is a flimsy solution and more importantly you lose the access to the effects loop. Instead fitting a permanent MV control you retain access to the effects loop and gain complete control of the amp. The control is added to the front paned just above the effects loop and massively improves the versatility of these popular amps. See the video clip here for a demo. Hot Rod master Volume demo video here | Blues Deluxe/Deville, Hot Rod Deluxe/Deville | £49 |
| Negative Feedback Control | The Hot Rods have global negative feedback like most amps, but oldder amps like a Tweed do not. This mod gives you control on the amount of negative feed back and adds a control giving to the stock HotRod on mimnimum and full-tilt tweed bark at maximum levels. Great mod combined with the master volume. | Hot Rod Deluxe / Deville | £39 |
Fender Blues Junior
One of the most popular amps ever made has a long list of mods so many that it deserves its own table.
| Mod | Description | Suitable for | Price |
|---|---|---|---|
| Mains Voltage Correction | Ensure long life of your power valves and 5% cooler running of your FBJ by correcting the mains operating voltage setting of your amp. Essential for most Fender Amps made for the EU market (factory set for 230v) but in the in UK should be adjusted for 240v operation. | I, II, III and IV | £12 included for free in service |
| Lead Dress optimisation | Most Fender Amps are noisier than they need to be. By re-dressing the leads from the transformer it is possible to reduce the amp's hum. | I, II, III and IV | £12 included for free in service |
| Bias Reduction | Circuit mod to reduce the power valve's bias current by around 10-15% and ensures maximum valve life. | I, II, III but not IV | £12 included for free in service |
| Fully Adjustable Bias | This mod adds an adjustable internal bias control to the amp. This gives full control over the amps bias and allows you to lower it or push the bias depending upon you preference of tone or appetite for buying new valves. | I, II, III but not IV | £29 |
| Billm Style Basic Mods | Includes: Full F&T re-cap - including stiffened (reservoir cap) Twin style tone stack using Orange Drop caps, Mid mod Bias reduction mod Anti oscillation mod (earlier models only) Master volume range fix | I, II, III and IV | £90 |
| Presence Control | Adds a presence control to your Fender blues junior right above the fat button. | I, II, III and IV | £27 |
| Sparkle Control | Adds a pull / push pot in between the mid and master volume control which tames some of the brightness especially on the Fender blues Junior III variant. I don't find the mod that effective but people ask for it form time to time. | I, II, III and IV | £27 |
| Pro Switchcraft Input Jack upgrade | Replace the cheap plastic jack socket with nickel plated Switchcraft jack as per all high end vintage Fender amps. Essential upgrade for amps that are used in gigging environments. | I, II, III and IV | £16 |
| FBJ History | FBJ I (Green board from 1995 made in USA ) FBJ II (Cream Board from early 2000s made in Mexico) FBJ III is clearly marked as version III on the rear and made in 2010 FBJ IV is not marked but is sold after about 2019 (tbc) Special editions made with fancy speakers and made from wood rather than particle board. https://en.wikipedia.org/wiki/Fender_Blues_Junior | ||
| Cap Job aka re-cap | Replacement of the electrolytic capacitors that are prone to drying up and degradation over time. Worthwhile on amp after about 10 years use or as an upgrade on modern Fenders that use budget "Illinois Capacitor" brand grade parts swapping out for high end F&T low ESR caps. Includes the large power supply reservoir smoothing capacitor as well as the pre amp de-coupling capacitors, bias and cathode bypass caps. Price varies by amp size. e.g Blues Junior @ £59, Hot Rods @ £60 and Twins @ £80 | All models | £44 |
Vintage Fender and Reissue Mods
| Mod | Description | Suitable for | Price |
|---|---|---|---|
| Reverb and Tremolo on Both channels Mod | Changes the amp so that Reverb and Tremolo are on both channels a la RobRobinette | AB763 type circuits i.e. Fender amps with boring normal channel 1 and exciting reverb and tremolo channel 2 which is a long list of amps including Twin Reverb, Deluxe Reverb (65 and 68 Reissue), Vibroverb, Vibrolux, Tremolux, Bandmaster, Showman etc | £65 |
| Fender Deluxe Reverb 68 Custom Noise Reduction Mods | As per the videos of PsionicAudtio on youtube to reduce the amp's hiss and background noise by 50%, Correct the channel bridging of reverb and tremolo. Point to point volume pot bypassing PCB for vintage channel. Plate resistor upgrade. Custom 68 Noise Reduction Video | Fender Deluxe Reverb 68 Custom | £75 |
| Fender Deluxe Reverb 68 Custom NFB control | Adds a toggle, or rotary switch to change the NFB as per either the 65 or 68 Deluxe Reverb. This is a further noise reduction mod. NFB control demo | Fender Deluxe Reverb 68 Custom | £38 |
| Middle Control, on either or both channels | Adds a pot to the rear of the amp and widens the tone range of Fender's much loved Deluxe Reverb to cover the range between stock, Twin and Tweed tonestack. Middle Control demo | Deluxe Reverb, 65 Deluxe Reverb and 68 Custom Re-issues | £46 |
| Bassman 50 - Bass channel to guitar voicing mod | Make the bass channel same as guitar channel for extra versatility. | Bassman 50 / AA270 circuit | £65 |
| Cap Job aka re-cap | Not exactly a mod but an option to help restore bass response on old amps, reducing noise and to pre-empt failure. Performed using high end F&T capacitors it is considered an upgrade for bass response. | Deluxe Reverb | £50 |
| Cap Job aka re-cap | ditto above | Twin, Supersonic | £61 |
Marshall
| Mod | Description | Suitable for | Price |
|---|---|---|---|
| Marshall JTM30/60 Overheating Mod | Chassis ventilation mod. Adds a small gap of 7mm at the rear of chassis to allow heat to escape but prevent small fingers entering. | Marshall JTM30, JTM60 | £32 |
| Marshall JTM30/60 Common Sense DI connector | Changes the DI so that you can use it without getting your connector stuck. | Marshall JTM30, JTM60 | £18 |
| Marshall JTM60 Gunnar Tone Mods | The Gunnar mod removes the clipping diodes from the amp’s fizzy drive channel, rebalances the gain to provide a classic valve blues breaker tone. https://soundcloud.com/user-284115725/marshall-jtm60-stock-v-gunnar-mods | Marshall JTM60 only | £103 |
| Marshall DSL401 Overheating | Cool running bridge rectifier mod Reduced bias current mod. Increased Ventillation | Marshall JCM2000 DSL401 | £26 |
| Eddie Van Halen 3 x Mods (Fat Cap, Mid Pot and Negative Feedback) | Middle Pot change Adds a mini toggle switch to the rear panel to switch in or out a filter capacitor on V2 cathode. Rolls off slight amount of high frequency - hence fatter sound. Adds a rotary switch to the rear to switch between three levels of Negative Feedback in to the power amp. More NFB gives a more refined HiFi sounding amp and less NFB gives more brashness and bark. Requires chassis alterations. | 1959SLP, Plexi and similar | £72 |
Other Amps
| Mod | Description | Suitable for | Price |
|---|---|---|---|
| AC30 TB/TBX Mag 7 Mods | Application of 7 magnificent mods described on YouTube by Psionic Audio reduce noise, increase reliability of these wonderful reissue AC30s made by Marshall from around 1993. | Vox AC30 TB / TBX | £120 |
| Roland JC120 Noise Reduction | Roland Jazz Chorus amps are renowned for their crystal clear tone and also their irritating hiss. By slight restructuring of the pre-amp gain this can be cured and works on JC120, JC77 & JC55. Also has side effect of making the volume control some what more gradual. Overall tone and maximum volume is not impacted. | Roland Jazz Chorus | £100 |
| Roland Street Cube Headphones / Line out switch | Is it possible to modify the Headphone Jack socket on my Street Cube to become a Line Out socket i.e. so that when a cable is plugged into the Headphone jack, you can still hear the signal coming through the main speakers? In addition can a switch be installed to switch back and forth between “Line Out” with speakers sounding and “Headphones” with speakers muted? I have found a youtube video that purports to show how to carry out this modification. https://www.youtube.com/watch?v=kylovLsBwBY Fast Track required" |
Custom Builds and Conversions
| Mod | Description | Suitable for | Price |
|---|---|---|---|
| Harp Amp Conversions | Alnico Magnet Harp Conversions – Tried and tested on VHT, Harley Bentons and Epiphone amps. These kits alter the voicing of the amp to give you the honk you are looking for. | VHT, Harley Benton, Epiphone | Kits are about £50 fitting is £150 |
If you have read about other mods and want to know more or whether I have tried please drop me a line. I have just mentioned a few popular ones on this page…
Notes:
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- Modification included with all service or repair jobs free of charge unless specifically not required.
- Modifiations to amps invalidate manufacturer’s warranty; so please consider carefullly.
Updated 30/04/2025
16:46.