Some Mods for Marshall Class 5

Discussion in 'The Squawk Box' started by Lyle Caldwell, Jan 18, 2011.

  1. Splattle101

    Splattle101 V.I.P. Member

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    When was the last time Lyle swung past?
     
  2. Ejfalla

    Ejfalla Junior Member

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    Hi everyone
    I bought the Class 5 with atenuator.
    Have read every post. I am looking forward to doing ( my tech will be doing it ) Lyle's mod posted in the 1st page.

    Please somebody has the final C5 sheme ( with the mods high lighted). ??


    Thanks in advance for your replays !!
     
  3. gouna

    gouna Member

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    Hello,
    Is it normal that the "brigth switch mod" is heard only with the guitar volume pot is at maximum?
    If I lower the volume of my guitar, the effect "brigth" is no longer present (nothing to do with the wiring, I'm already in 50's gibson wired).

    Your opinions?

    Thank you. (sorry for my bad english....)
     
  4. Stormydave

    Stormydave Junior Member

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    Hi all, I'm new here and appreciate this is an old thread, but I've just acquired a Class 5 Red Roulette Head, made in 2014, issue 4 PCB and I've done the Lyle Caldwell mods to it. I have a problem that I cannot track down. After completing the mods and powering up, everything works normally i.e. amp switches on, tubes power up, there are no odd noises, but the volume level is only what it would be on 0.1w headphone mode, even with the volume pot fully up and running in the 'normal' speaker mode. The thing is driving the tubes as I can hear it distorting as the volume goes up. It sounds 'right', all pots are working and having an effect on the sound, the only issue is there's no volume to speak of. I'm hoping someone can point me in the right direction to identify what's wrong. I've done the mods exactly as described by Lyle, except I haven't fitted switches and the 68p Fizz Cap is not currently installed. Some other notes about how I've done this:

    R9 is removed
    I don't have links L19 / L18, so the 120p bright cap is fitted across lugs 1 & 2 of the volume pot
    C10 is removed and has been re-used across R12
    C13 has been removed and replaced with a link
    C20 has been replaced with what was in C13
    C2 has been replaced with what was C20
    C8 has been replaced with a 1uf electrolytic, correct polarity has been observed
    All resistors have been replaced with the values advised by Lyle

    I have checked and re-checked all connections and soldering, cannot find any bad ones. I have checked and re-checked all components, cannot find anything bad. I have checked and re-checked that I have the right bits in the right places and can't find a problem. I've also replaced all tubes, this has no effect either.

    Do any of the caps I've moved have polarity requirements?
    Can anyone suggest what might be wrong?

    Many thanks in advance of any help that can be given.
     
  5. Stormydave

    Stormydave Junior Member

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    OK, so C22 is showing nil resistance on my multimeter. Not sure if this is the problem, but I don't think it should show 0 ohms. I haven't touched this cap by the way. I've ordered 10 Wima 22n 400v caps, so I will replace everything that needs this value with these, include C22. We'll see what happens then.
     
  6. Stormydave

    Stormydave Junior Member

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    I've found the cause of the problem. The electronic components supplier had supplied the wrong resistors. What should have been 470k ohms were actually 0.47 ohms, so no wonder it wasn't working! All my work was correct, all fixed and working now.

    My god, what a difference this makes to the Amp! It is a different beast altogether, fantastic now. Also fitted the VVR Master Volume (works great) and a 190k resistor to R51, to increase the attenuated volume level to something respectable but still usable at home.

    Thanks to Lyle Caldwell for these great mods from a few years back, still as relevant today.
     
  7. greezy strings

    greezy strings Junior Member

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    Hello, 1st off thank you Lyle Caldwell for the mod info. Had it done on my class five a couple years ago and loved it.. Today after a month or two of not playing the amp.. I turned it on and noticed the tone to be very bright.. especially when the I strum hard and or volume pot on guitar is all the way up. I have to turn the treble tone pot on the amp all the way down as well as the treble on my guitars. I have tried 5 different guitars, 3 different cabs and various cables including speaker cables. I noticed that the tube in V2 position was not glowing as strong as v1 preamp tube? I took the pcb board off and went through it best I could ( far from a semi- pro but can do basic repairs.) it seemed like the r21 (which looks like has a added resistor going across it) was a little loose so I re-soldered that. otherwise I can not see anything else. I swapped out the pre amp tubes with some jj 12ax7's I have in my other amps. Same , lot of treble. I do not have a extra power tube on hand so could not switch that out.. not sure if a power tube can cause this issue. Any help would be really appreciated. I know it is a old thread so hope some of you out there are listening in. Thank you very much guys and gals.!!!
     
  8. JOESHMOE

    JOESHMOE Senior Member

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    I finally got tired of trying to make my class 5
    sound right so I traded it and $58 for a Boss
    Katana 50 and it sounds 10 times better and is
    100 times more versatile.

    Jimmy
     
  9. bulletproof

    bulletproof aka tarddoggy Premium Member V.I.P. Member

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    I still love mine....damn thing is a beast!:headbanger:
     
  10. bblooz

    bblooz Senior Member

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    Quitter!
     
  11. greezy strings

    greezy strings Junior Member

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    I really like mine pre mod and post mod.. just trying to figure out why the highs are all of a sudden bright and a bit piercing even with the treble turned all the down??? Im kinda bummed.
     
  12. goodguy

    goodguy Junior Member

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    Love the promise of the Class 5 and never liked the sound (boxy, dull, unforgiving, tone controls don't do enough) but have held onto mine through many other amps. Slowly, slowly liking it more and more as stock but gonna dive in and do some JTM mods and see what I can get. Biggest complaint is the lack of brightness and muddy bottom. Read through entire thread and went from clear to confused to more confused so I think I will stick to a few simple basic mods and go from there. So glad I have resisted the urge to sell the amp (so many times) and have had many other nice orange and fender amps that have blown the C5 away but there is something about the C5 that makes me keep it.
     
    efstop likes this.
  13. Marshall & Moonshine

    Marshall & Moonshine Senior Member

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    You might reach out to Lyle on FB @ Psionic Audio.
    He’s a great guy, super knowledgeable and no bullshit.
    He could probably straighten you out, if you have questions.
     
  14. goodguy

    goodguy Junior Member

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    Started doing one small mod at a time.. Clipped out C10, Immediate improvement.
     
  15. goodguy

    goodguy Junior Member

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    Here are my mods for converting the Class 5 into a JTM/Bluesbreaker Tone
    I have read through 61 pages a couple times and, although awesome, is confusing as there are so many changes and half completed descriptions. Thanks to Lyle for getting me 99% of the way there... I've cobbled together bits and pieces of the suggestions on these pages and made a couple changes/additions.. sounds awesome now. These mods were the "biggest bang for the buck" IMO and allowed me to fix the issues I had with the C5. I may add the choke in the future but like what I have for now. After testing, this amp absolutely is a new animal.. keeps the C5 character, improves its shortcomings and add some serious mojo to the amp. It is like a classic collectible amp now.. the tone is amazing with strats and lp's. The success of these mods makes me now want to get another C5 (or two) make one plexi and one stock so i can compare.

    For JTM/45 Bluesbreaker Mod:
    250pf @ C14
    100pf @ V1 (across lugs 1 & 2)
    220R @ R27
    56K @ R28
    4.7uf @ C8
    Jumper C13
    Remove R9 (see below)
    Remove C10
    Remove R51
    1M @ R20

    Additional improvements (highly recommend):
    1) JTM/Plexi bright switch Mod:
    In addition to 100pf across V1 (as above), I also added a 120pf with mini spdt to switch the 120pf in series with the 100pf - this adds a really nice added touch of brightness to the amp and allows some options to stick with a more JTM brightness (100pf) or to add in a more Plexi brightness (+120pf). (highly recommend). If you do this, you must also remove R9 and add, at minimum, a 220K ohm resistor (or optionally a 470k) from V1B side of R7 to ground (read below).

    2) I also added a 1M pot in series after 220K ohm resistor (from V1B side of R7 to Ground). This allows you to vary the resistance and takes the drive/tone from a JTM (220K) to a more Plexi level. This gives some nice added drive tone depending upon the pups and pedals you use. Alternatively, you could add a mini spdt toggle going between the 220k Ohm resistor and 470K Ohm resistor (this would provide almost the same effect as pot without having to find as much space on back panel. I mounted the bright switch and pot on back panel near serial number/extension speaker output (check the back panel coverage before you drill). Use lugs 2 and 3 of pot (dont use lug 1).
    Note: I soldered a 2 conductor wire with one wire to V1B side of R7 and other wire to adjacent R10 ground side. the R7 wire side went to 220Kohm resistor and then pot then to ground at R10. Essentially you are putting variable resistance between R7 and ground (no resistance and it is way too overdriven). Tried many values of resistors and settled on 220K and 470K as the best options, like I said the pot in place of a 470K resistor is not necessary but gives a bit more fine tuning and range. Personally, If I did again, I would just do a switch between 220k and 470k as the mini switch is easier to mount and less obtrusive and you can really not tell too much difference adding a 470K ohm or 1M Ohm of resistance.

    Was going to do some more mods like Neg Feeback but Lyle said it wouldn't add very much.

    Hope this helps anyone looking to move the Class 5 into more of a JTM tone - it really rocks now and solves the issues I had with this amp. I was slowly beginning to like the stock amp so was hesitant to do these... glad I did, they were easy and really opened the amp up. Good luck.
     
    Last edited: Nov 15, 2017
  16. efstop

    efstop Senior Member

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    My C5 Ver 1 is eight years old and mint. It has been under a cover all that time, although sometimes I take off the cover, plug it in and gently strum. I live in an apartment with walls that are somewhat thin so I can't really use it at any kind of volume, and don't want to use headphones. I have thought about selling it, but I remember how much I miss the big Marshall combos I used to have. A C5 isn't close to one of those, but I'm keeping it. I have a big Psionic Audio diagram of C5 mods, but my eyes glaze over when I look at it, and don't plan on modding it, anyway.
     
  17. srvdan

    srvdan Junior Member

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    hello, i have VVR installed on my marshall class 5 by previous owner. It works, however, only when the 'master volume/ VVR' knob is after 12. Turning the knob to 9, completely turns/shuts the volume off. Also, when I put the volume to 2~3 on my guitar, I realise that the whole amp turns off instead of reducing the volume, similar to when the VVR knob is at around 9. I read some forums, and was suspecting if this was due to DC voltage leakage. Also, my class 5 is the first generation. It has rattle issues.... any suggestion how I can fix this? (i think its the EL84 thats causing the rattle).

    Any help will be appreciated!
     
  18. goodguy

    goodguy Junior Member

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    VVR Introduction

    VVR Install Instructions

    Rattle Fix
     

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