What are some good Fully Bypassable Marshall Plexi 1959HW Mods?

[FuriousMopar1968]

Hey Everyone!

I have a Marshall Plexi 1959HW and was curious if I were to go down the route of modding it, still on the fence about it, what are some good mods that are generally installed that modernize it? (Tighter Bass, More Drive, Boosts for extra chunky chugs, Master Volume, Etc.)

I was thinking if I did mod and it’s possible to do, I’d like to have the mods activated by push / pull pots in the 6 Knobs on the front, that way when not engaged they all bypass to that stock Plexi Sound and keep the stock Plexi look. It would be kinda like a sleeper build haha.

I have other amps that do the Modern Metal thing so it’s not a necessity and I do apologies if it’s sacrilege haha, but just wanted maybe do something cool with this head I’ve had lying around for years and definitely don’t plan to sell.

If anyone wants to share there modded Plexi tips / tales / tricks too feel free! Any and all input is greatly appreciated!

 

[FourT6and2]

Start by reading everything on Rob Robinette's website.
https://robrobinette.com/Amp_Stuff.htm

Then buy The Ultimate Tone series from London Power.
https://londonpower.com/tut-selection/

There are a bunch of other resources as well. But the sky's the limit when it comes to modding a 1959.

 

[FuriousMopar1968]

Start by reading everything on Rob Robinette's website.
https://robrobinette.com/Amp_Stuff.htm

Then buy The Ultimate Tone series from London Power.
https://londonpower.com/tut-selection/

There are a bunch of other resources as well. But the sky's the limit when it comes to modding a 1959.

Thank you, This is extremely helpful!

 

[CoreyW]

I had two mods done, master volume, with the knob placed on the back of the amp.. the tech was pretty insistent on that, and a bright cap by pass, which was put inplace of volume 1. You can always try the Mr Scary thing, I want to pick one up but have yet to do it, thats about as easy of a mod that you can do.

 

[FuriousMopar1968]

I had two mods done, master volume, with the knob placed on the back of the amp.. the tech was pretty insistent on that, and a bright cap by pass, which was put inplace of volume 1. You can always try the Mr Scary thing, I want to pick one up but have yet to do it, thats about as easy of a mod that you can do.

Thanks for info! The Mr. Scary is great with it I have one now but it gets really chaotic fast due to the Phaser Inverter getting pushed to tears. I was thinking of getting a Master Volume mod that is Pre Inverter or Post Inverter on a push/pull pot so you can toggle either depending on the needs of what your doing (Hopefully that exists haha). I’ve heard a lot of the bright cap mod how is it?

 

[CoreyW]

Thanks for info! The Mr. Scary is great with it I have one now but it gets really chaotic fast due to the Phaser Inverter getting pushed to tears. I was thinking of getting a Master Volume mod that is Pre Inverter or Post Inverter on a push/pull pot so you can toggle either depending on the needs of what your doing (Hopefully that exists haha). I’ve heard a lot of the bright cap mod how is it?

Overall, I like it.. he changed the value of the bright cap aswell.. it works really well in conjunction with the MV, I dont remember what value he put in though.

 

[FuriousMopar1968]

Overall, I like it.. he changed the value of the bright cap aswell.. it works really well in conjunction with the MV, I dont remember what value he put in though.

I gotcha, I may have to do something with this. Maybe make the treble knob a push/pull for bright cap on or off. Very cool man!

 

[CoreyW]

I gotcha, I may have to do something with this. Maybe make the treble knob a push/pull for bright cap on or off. Very cool man!

The volume 1 option is really probably the best way to do it, since the bright cap is attached to that pot already.

 

[FuriousMopar1968]

The volume 1 option is really probably the best way to do it, since the bright cap is attached to that pot already.

I gotcha, not sure how deep I want go into it yet, but was maybe thinking of making the Vol 1 Push / Pull to engage transistor clipping or something drive based. Still trying to gather ideas for the project.

 

[CoreyW]

I imagine you could remove three of the inputs, put a switch that would let you toggle between low high and jumped, then have the other two holes for a switch or pot.

 

[CoreyW]

I gotcha, not sure how deep I want go into it yet, but was maybe thinking of making the Vol 1 Push / Pull to engage transistor clipping or something drive based. Still trying to gather ideas for the project.

When Marshall announced the 1959HW modified, I started gassing hard, and do to my impatience, I found a 1959hw that was reasonably priced and decided to go from there.

During my search, I found the Metropolis amp forums… there is sooooo many posts there that will take you down so many rabbit holes, and the amount of mods you can do to one of these amps Is ridiculous.

Depending on how your set up is, you may want an FX loop, here is a link to one that I saw a lot of people recommending…

https://grangeramp.com/product/ultimate-fx-loop-2/

Personally I rarely play through a cabinet, so my MV mod isn’t really used a whole lot, but it was more of a, I might need this someday. It is usually plugged into a Suhr RL/IR, which lets me run anything I want to after the load box studio style.

 

[FuriousMopar1968]

When Marshall announced the 1959HW modified, I started gassing hard, and do to my impatience, I found a 1959hw that was reasonably priced and decided to go from there.

During my search, I found the Metropolis amp forums… there is sooooo many posts there that will take you down so many rabbit holes, and the amount of mods you can do to one of these amps Is ridiculous.

Depending on how your set up is, you may want an FX loop, here is a link to one that I saw a lot of people recommending…

https://grangeramp.com/product/ultimate-fx-loop-2/

Personally I rarely play through a cabinet, so my MV mod isn’t really used a whole lot, but it was more of a, I might need this someday. It is usually plugged into a Suhr RL/IR, which lets me run anything I want to after the load box studio style.

Thank you so much for all the information and help! I’m definitely falling through that rabbit hole myself at the moment too haha. I guess ultimately I like to do my take on a Fortin Meshuggah-like Modern Metal thing but only utilizing all push/pull pots for the front six knobs and a rear panel master volume, when all knobs are push in its stock Plexi. I’m sure it’s ambitious but that the fun part haha

 

[harddriver]

For gain mods you can mod the 1959 circuit to a 1959 Bright channel and 2203 on a simple push pull switch so that would be fully bypassable per your request. Also you can do a cascade one wire mod on a simple push pull switch as well. Now how much gain you add to the circuits is another rabbit hole entirely but this should provide you with a base idea.

 

[FuriousMopar1968]

For gain mods you can mod the 1959 circuit to a 1959 Bright channel and 2203 on a simple push pull switch so that would be fully bypassable per your request. Also you can do a cascade one wire mod on a simple push pull switch as well. Now how much gain you add to the circuits is another rabbit hole entirely but this should provide you with a base idea.

Thank you! These will be incredibly helpful! Here’s a jot down of ideas of was thinking of maybe trying to find if they exist:

1. Presence Knob - Some kind of Mod to add fixed Depth (Maybe like a Deep on IIC+)
2. Middle Knob - Some kind of Mod to shift Mid Freq Sweep (Maybe Shift from 500-800hz to 250-500hz)
3. Treble Knob - Mod to Tame Brightness (Bright Cap?)
4. Bass Knob - Mod to Tighten Bass (Modern Metal Chug Style)
5. Channel Vol 1 Knob - Add Clipping (Transistor Style)
6. Channel Vol 2 Knob - Add Gain Stage (GZ Add a Stage / Jose Mod)

-All 4 Inputs stock, allowing for Jumping and all normal stock uses of Amp.

-All 6 Knobs be push / pull pots, and when pushed is restored to original circuit.

-Ideally still able to run Legendary Tone Hot Mod / Mr. Scary, if possible.

-Amp will look stock, minus one knob on back for Master Volume, replacing one of the Speaker input holes. (Also Push / Pull pot when Pushed it’s a Type 2 PPIMV and Pulled its a José Mod Master Volume if possible.)

 

[harddriver]

Thank you! These will be incredibly helpful! Here’s a jot down of ideas of was thinking of maybe trying to find if they exist:

1. Presence Knob - Some kind of Mod to add fixed Depth (Maybe like a Deep on IIC+)
2. Middle Knob - Some kind of Mod to shift Mid Freq Sweep (Maybe Shift from 500-800hz to 250-500hz)
3. Treble Knob - Mod to Tame Brightness (Bright Cap?)
4. Bass Knob - Mod to Tighten Bass (Modern Metal Chug Style)
5. Channel Vol 1 Knob - Add Clipping (Transistor Style)
6. Channel Vol 2 Knob - Add Gain Stage (GZ Add a Stage / Jose Mod)

-All 4 Inputs stock, allowing for Jumping and all normal stock uses of Amp.

-All 6 Knobs be push / pull pots, and when pushed is restored to original circuit.

-Ideally still able to run Legendary Tone Hot Mod / Mr. Scary, if possible.

-Amp will look stock, minus one knob on back for Master Volume, replacing one of the Speaker input holes. (Also Push / Pull pot when Pushed it’s a Type 2 PPIMV and Pulled its a José Mod Master Volume if possible.)

You can make it a simple or as complicated as you wish but with all those metal type mods you will essentially lose the sweetness of what a two gain stage plexi bright channel provides.

As you add more gain to the circuit you will have to deal with alot of issues extra gain brings with it. Wiring routing and lead dress, dealing with oscillations and parasitic oscillations, layout of the circuit.

Just giving you some things to consider while you design what you want. My Cameron HG jose does not sound or have the characteristics of my 1968 stock plexi so keep that in mind, there are tradeoffs with everything especially in amp circuits.

 

[FuriousMopar1968]

You can make it a simple or as complicated as you wish but with all those metal type mods you will essentially lose the sweetness of what a two gain stage plexi bright channel provides.

As you add more gain to the circuit you will have to deal with alot of issues extra gain brings with it. Wiring routing and lead dress, dealing with oscillations and parasitic oscillations, layout of the circuit.

Just giving you some things to consider while you design what you want. My Cameron HG jose does not sound or have the characteristics of my 1968 stock plexi so keep that in mind, there are tradeoffs with everything especially in amp circuits.

I hear you, the ideal end result is when all knobs are pushed in it’s as close to a true bypass as possible. We’ll see what ends up being possible to do at the end of the day too. Thank you again for the help!

 

[Smash]

Not what you are asking for...But if I had a 1959HW, I would send it to @glpg80
He has some shit going on that I have got to fucking try.

 

[FourT6and2]

Thank you so much for all the information and help! I’m definitely falling through that rabbit hole myself at the moment too haha. I guess ultimately I like to do my take on a Fortin Meshuggah-like Modern Metal thing but only utilizing all push/pull pots for the front six knobs and a rear panel master volume, when all knobs are push in its stock Plexi. I’m sure it’s ambitious but that the fun part haha

That should be pretty easy. The Meshuggah is just an 800 circuit with diode clipping. Typical Jose mod type of thing. Ceriatone has a layout you can use on their website.

 

[FourT6and2]

You can also add extra tube stages, which IMO sound better than diodes.

 

[harddriver]

This Xenrelic guy had some interesting designs going on to give you some more ideas. Here's an SLO layout as well.