DSL15H Upgrades/Mods

Discussion in 'Marshall Amps' started by quintvisk, Apr 25, 2015.

  1. quintvisk

    quintvisk New Member

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    Hello all,
    I'm new here and I believe I looked through all the DSL15 threads so I apologize if this has been answered previously..

    I recently purchased the 15H and I quite like it but wasn't overly impressed with the red gain channel. A little too fizzy too fast.
    I checked the tubes and the bias and it was all excellent which is nice.
    I did a bit of searching and came across this forum and found a few mods (snip a cap and a resistor here and there, adjust some values etc), I dia few of them and there was a noticeable difference which was quite nice to hear.
    of course upon opening the chassis I noticed a few things (which are totally understandable at the price tag), super cheap Chinese caps was the first one that stood out to me ... also a fairly simple upgrade.
    That said, finding a parts list and or schematic for this thing is proving to be nearly impossible. I know I can measure and read codes by looking at the board but I'm far too lazy to do that without reaching out to someone else for advice first ( I mean if someone else has already done the work for me ....)

    Does any one have this information available?

    I expect nicer components will make a world of difference.
    Next step is to look for some nicer irons and see how that goes.
    For the price of these amps they are soooooooo worth modding and upgrading.
     
  2. JAC

    JAC Well-Known Member

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    There is some cool cat from the Bronx in NY that modded his to tame the fizz in the red channel. It was kind of like a work in progress but, I believe he was on the right track. I think his name is something like eggz or something like that. I'm sure someone here will jump in and help you out bro, good luck! I have the combo myself. I love the tone on these amps! I wish there was a mod to tame the fizz on the red, the way they did on the DSL5C.
     
  3. quintvisk

    quintvisk New Member

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    I've watched the Eggz videos and I did the same mods as him.
    Very simple and an excellent change to the amp, made it just a little sweeter.
    Im hoping to find the info about the caps so I can order parts soon.
     
  4. jimmyjames

    jimmyjames Well-Known Member

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    My 15H circuit is still unmodded, I only use the red channel. I have made improvements by using an attenuator and using master volume at around 12.00 (gain stays around 2/9.00); swapped power tubes for JJ 6V6s and cooled bias to 21mV each side; swapped V2 and V3 preamp tubes for electro-harmonix 12AX7s; presently using the attenuator (Aracom DAG) to reamp into an old S/S combo with 12" speaker and spring reverb. I still have a narrow window of adjustment for good tone, I'll try mods later and see where I'm at then.
     
  5. BlueCajun

    BlueCajun New Member

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    I've been meaning to do the mods myself. Another option (that I have not tried) is swapping V1 for a JJ ECC823. My understanding is that only half of V1 is used for the Ultra Gain channel. This tube has lower gain only on that particular side. So you should get lower gain on the Ultra Gain channel while leaving the Classic Gain channel unaffected. Here's a bit more info on the tube itself:
    JJ Electronic ECC823

    Good luck!
     
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  6. jimmyjames

    jimmyjames Well-Known Member

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    The 823 could be the ticket, 'tho a lot of guys don't like JJ preamps because they find them too dark/muddy sounding.
     
  7. reddog22

    reddog22 New Member

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    Hi,i've had my DSL15c for 12 months and really like it now i did a few easy mods. Firstly,this amp hissed real bad from new and i thought it was just how it was but once i checked the bias i was amazed at how bad it was done in the factory. The TAD tubes were not close at all to being matched and one tube was running very hot and the other was cold. They measured 34ma and 14ma! I could hear the hiss go as i was bringing the bias back to 22ma.
    I installed a JJ823 in V1 and that made quite a bit of difference too. The TAD tubes were eventually replaced with JJ's. The amp still worked even though the hot one blew at some stage and i didn't even know until i changed them. Also the 5w 1K Grid Resistor R36 for said tube had become brittle and fell apart too. It must've gotten extremely hot from the bias being set so hot. Very lucky i caught this in time i think.
    To finish off i swapped out the standard speaker for a Greenback and i'm really impressed with this machine now...
    Hope this helps someone out.
    Cheers
     
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  8. jimmyjames

    jimmyjames Well-Known Member

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    +1 on the Greenback, my 1x12 cab works well with the 15H
     
  9. Bloodrock

    Bloodrock Well-Known Member

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    I did the "ultra 2 to ultra 1" mod to my dsl15c. Sounded much better. I ended up getting a dsl5c just to have the effects loop tho. I've posted my mod on here a few times, it's only 4 components. If you can take the time to dig through my old posts the specs should be pretty easy to find. I don't remember them off top of my head anymore.
     
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  10. jimmyjames

    jimmyjames Well-Known Member

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    Tried the green channel the other day, with my (Maxon) Ibanez SD-9 and ST-L in front. Not bad at all :cool:
     
  11. Grogshla

    Grogshla Active Member

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    dont mod. just learn to dial in the right eq add a booster out the front and away you go.
     
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  12. mtm105

    mtm105 Well-Known Member

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    sage advise.

    or put pedal EQ in front.

    I also add BOSS Bassman pedal to take out some of the ice picks.
     
  13. jimmyjames

    jimmyjames Well-Known Member

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    My present home setup is Maxon/Ibanez GE9 graphic EQ pedal>Max/Ibz PQ9 parametric EQ> E/H Soul Food (clean boost mainly, minimal gain setting)>Yamaha THR10 (beige one, most versatile pedal I've ever had :cool:, Brit Hi setting with moderate gain, headphone out to)>DSL15H (Green channel with gain 8-10 for humbuckers, Red channel with gain around 2 and vol around 7-8 for SSS Strat)>Aracom DAG attenuator>4x12 Greenback cab. I go for '70s tones, Motorhead is as gainy as I wanna get. I can tweak the various stages to get the speakers involved without getting scary loud, and dial in a closer sound for what I'm playing. I wouldn't go out and buy a lot of surplus gear to help an amp work for me, had this stuff anyway, and it works well together. For a lot of versatility otherwise, I would need to get several amps, or go down the AxeFX or similar road.
     
  14. Jonesy Live

    Jonesy Live New Member

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    I own a dsl14h and love the classic gain channel while hating the ultra gain. I finally resolved to have the ultra gain modded and saw a good YouTube video that helped convince me. I took it to the Soundroom in Chesterfield Missouri and for $140 they made it sound GREAT!
    1) R82 (150K Ohm) was added to input of VR3
    2) C75 was replaced and a 10meg Ohm resistor was added in series on wiper of VR3.
    3) C34 was replaced and a 10K Ohm resistor added in series to ground on Cathode V1 (B).
    4) R40 was changed from 1.8K to 2.7K Ohm in Cathode of V1 (B)
    3) C76 (VR3 bypass cap) was changed from 470pF to 120pF.
    Bias was set to approx 66% of max plate dissipation
     
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  15. Moony

    Moony Well-Known Member

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    Welcome to Marshall Forum! :)

    May I ask - replaced with what?
     
  16. acosta

    acosta New Member

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    Is it necessary to remove the circuit board to do R82?
     
  17. ck516

    ck516 New Member

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    The RoHS 'lead-free' solder on my DSL15 was conductive epoxy and not solder. When heated, it stuck to everything, a circuit pad came up (with a 15 Watt iron!!) and a sloppy mess ensued. So, On future changes/mods, I did not pull the PCB but clipped one lead of the component, moved it out of the way and soldered, WITH LEAD SOLDER, onto the old stem and the still connected component stem. MUCH easier and less chance of damage along the way.
     
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  18. ck516

    ck516 New Member

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    I made the Johnny Eggz mods on my DSL15C and changed the speaker to a 12H30. It sounds like it was supposed to. When I did calculations and looked up other Marshall circuits, I found this Chinese design was just NUTS in some places. So, doing correct calculations and making the circuits match other classic Marshall designs is why the changes are what they are. Remember to use Silver Mica capacitor for C76 and metal film resistors for low noise. R29 is a wire-wound resistor and is in place of a choke. Seems to work.
    I tried MANY 6V6 type power tubes and came back to the TAD as they are more open, airy and an articulate high end. An old NOS RCA pair were the worst (imagine that!). All biased at 70% plate dissipation.
    Mods were:
    R40 Change to 5.6K
    C58 Change to 2n2
    R82 add 150K
    C76 Change to 220p
    C75 clip one leg and lift.
    C34 clip one leg and lift.
     
    Last edited: Nov 16, 2019
  19. Peter McAteer

    Peter McAteer Member

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    I put a JJ EC823 in V1. Took all of 10 minutes, no soldering needed, and tamed that nasty/useless red channel. Today my DSL15H went into the shop to get a Metropolous FX loop installed. After that I think I'm done with mods on this one.
     
  20. Peter McAteer

    Peter McAteer Member

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    Was that Anthony Jarrah's video?
     

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