The Line 6 DL4 Delay Modeler has become a staple on many guitarist’s pedalboards – from professionals to bedroom rockers. It packs 15 different delays into a four stomp box – enabling you to have anything from Floydish tape echos one second to reverse Hendrix solos the next. Expression Pedal control allows you to morph between two different saved settings in the one preset. For example, heel down of the expression pedal can be saved for 50% Repeats and 50% Mix and toe down can be saved for 100% Repeats and 100% Mix. This lets you ride the pedal into oscillation and back it off when it starts to run away.  The three presets give you your favourite sounds one-click away while the fourth switch is a tap tempo control. But perhaps the hidden gem in this versatile pedal is the excellent 14-second looper which lets you record a phrase and manipulate it via a one-shot, reverse, half-time or double-time speeds.

Line 6 also offers more Modelers in this four-button stompbox format: The MM4 is a Modulation Modeler that contains classic emulations of phasers, flangers, tremolos etc. The FM4 is a Filter Modeler and changes the guitar into a vintage synth with a step of a switch. A Distortion Modeler, the DM4, recreates many of the hard-to attain fuzzes, overdrives and distortions. The discontinued AM4, Amplifier Modeler, can also be found on eBay from time to time.

As much loved as the pedal is, it has gained a bad reputation as unreliable due to some design limitations. Firstly, the switches used are not on/off switches, but spring actuators that “click” a surface mount switch on and off. These switches feel unsturdy and are normally the first things to break. Secondly, many users noticed a volume drop when activating the pedal. The output level was affected by component values in the buffer circuit with varied levels of “drop” in different pedals.

The DIY community was pleased when pedal designer Jeorge Tripps (Way Huge, Line 6, Dunlop) released information in tackling these initial limitations, it led to a number of pedal makers and modders to offering their services to improve the Line 6 Modelers. Robert Keeley offers a hi-fi mod involving the replacement of IC chips for Burr Brown’s and some part-time modders (DRASP at Harmony Central Effects Forum) improving on the flexibility of the pedal. After intensive experimenting successes (and failures), cubisteffects now offers a number of modifications to the Line 6 Modelers.

cubisteffects offers not only a modification to rectify the initial design flaws but also has a number of modifications that can improve the flexibility of the unit, and some that push the pedal to become a new experimental tool.


The Standard Modification involves three changes;

  1. SWITCHES - The spring actuators are removed and momentary SPST “soft-touch” switches are installed. These switches are screwed to the pedal chassis and are wired to the place of the switch providing thousands of clicks without touching the PCB.
  2. VOLUME DROP – Selected capacitors and resistors are removed and, if required, replaced with metal film components.
  3. LEDs – The four red LEDs are replaced with superbright, waterclear LEDs of your choice.


A rugged 24mm Alpha pot is placed on the bottom right of the pedal, adjacent to the tap tempo switch. This allows you to use the Expression Pedal controls without having an expression pedal take up pedalboard real estate. The modification enables you to save and morph between two settings per preset by rolling your foot over the knob. Settings are saved as per the Line 6 instruction manual. The knob can be put on either side of the pedal.


This modification involves re-routing the output of the Modeler back into the input, and the new output selected by a switch on the top of the chassis. This is a feedback loop, and causes spontaneous bursts of noise, squeals, oscillations, drones – all depending on the setting selected. This modification is definitely for the more adventurous musician, but with every effect, the feedback can be used subtly. Most times the feedback can be deafeningly loud, so I have installed a separate BLEND knob to dial in the volume you be used with caution. The second knob controls the INTENSITY of the feedback allowing control of the amount, pitch, speed of the feedback depending on the delay setting.. A superbright, waterclear LED indicates whether the feedback loop is on or off.

Below is a demo:

Other modifications offered are:


This preset lets you save two different settings per preset as per the Expression Mod. However unlike the Expression Mod, the two settings are selected via a stomp switch. This allows you to instantly switch between two settings without the need for an expression pedal. The selected preset is indicated by a superbright, waterclear LED.


WARNING: Volatile and extreme modification. Not for the faint-hearted.
This mod involves two circuit bends that work around the same principle as the Feedback Mod but are much more pronounced and distorted. Crackling, white noise, fuzzed loops can all be activated via two independent toggle switches with a knob controlling the output volume for both. Superbright, waterclear LEDs indicate whether bend is on or off (but you can clearly hear them if they are on!)


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  1. aaron says:

    how much does that cost to modify the dl4…

    cause for me I’ a real experimental atmospheric type, and on the auto volume I would like to have a little more mod with it…by making this change will in inhance this

  2. Hi Aaron, you can check the my Pricing page ( for costs of each mod. If you are the experimental musician, the Feedback and Expresion mods are right up your alley. Some great atmospheric sounds and loops can be created, especially in the Auto-Volume and Reverse settings. If you wanted that bit extra you should check out the Distortion Circuit Bends as well. You can find my email address in my Contact Page ( for more info. Cheers.

  3. Jim says:

    Dear Cubistefeects,

    What is the turn around on your dL4 standard mod?



  4. cubisteffects says:

    Hi Jim,
    I ask for two weeks for all repairs/modifications, but turn them around in a week if I have the time.

  5. I’m super blown away that you offer these mods. Absolutely fantastic!!! I was thinking about the replacing the switches, but these modifications sound quite cool.


  6. cubisteffects says:

    Thanks Hank. The switches are defiitely worth changing.

  7. Seo says:

    Do you ship abroad? if so, how’s the cost of shipping?
    and payment? do you accept the credit card or just accept bank wire and Western Union?


  8. cubisteffects says:

    I do ship abroad if the shipping costs are okay with you.
    Contact me by email ( for payment questions.
    Thanks Seo.

  9. jc says:

    do the feedback and/or distortion mods work when the DL-4 is in loop mode?
    if so, could you explain / give examples how each function in that mode? and do you have sound clips for that?



  10. cubisteffects says:

    Hi jc,
    The feedback mods effects the delay signal in looper mode. If you have no delay set when looping then it won’t. I find having the Expression mod useful in Looper mode as you can record your overdubs, then by fully turning the Exp knob you have a delayed signal. By activating the Feedback/Distortion bend mod the feedback effects the delay and a whole noisy layer can be improvised on top of your overdubs.
    I will be making video demos in the New Year so keep posted for those.

  11. sean says:

    Hey I just bought my first Dl4 during the holidays, and was aware of the some of the problems it had. one question about the volume drop, when installed will it help with the over all tone perhaps making it sound less digital. also i noticed that when it is disengaged there is just something missing form the sound. will it help there as well and if not is there a way to make it hard wire true bypass? thanks

  12. cubisteffects says:

    Hey Sean,
    The volume drop does make the pedal sound more open, more “alive”. It is still a digital pedal but the slight boost gives the tone more of a clarity. As for bypass, the xx4 pedals use relay switching so true bypass is not an option. If you hold down the first and third buttons while plugging in the input, you can change between two modes of bypass. Try that and see if there is any difference.

  13. casey says:

    hey man. if i get the twin preset mod instead of the expression mod, does the “switch” that you mentioned come with? thanks

  14. cubisteffects says:

    Yes, the switch is needed to alternate between the two settings.

  15. Tim Clarke says:

    To anyone reading this page,

    I strongly urge all DL-4 owners to get the Standard Mod done. The new switches are much more responsive – it makes the DL-4 a far more usable pedal. Christian knows what he’s doing!


    Tim Clarke
    Hidden Shoal Recordings

  16. tim says:

    can you do a 9volt mod so i can run with a standard boss type adapter?

  17. cubisteffects says:

    The Line 6 modelers use an AC adaptor or DC adaptor with a tip positive plug.
    Standard Boss adaptors are tip negative.
    Unfortunately, the DC jack is soldered straight to the PCB so the polarity of the tip can not be modded easily but I believe you can buy One Spot adaptors that can change your tip neg to tip pos.

  18. domesticatedrobot says:

    I’m interested in some of your mods for a DL4, but I’m also quite interested in the Keeley hifi mod. Would it be possible to have you do a different version of your standard mod where you replace the IC chips for Burr Brown’s? Essentially, I want a DL4 with the hifi mod but with the stomp switches you use, and your feedback mod. Also, is there any reason not to get both the feedback mod and the distortion circuit bend mods on the same pedal?

  19. domesticatedrobot says:

    I just watched your Filter Modeler feedback mod demo. Freakin’ rad. How about a feedback mod demo for the DL4?

  20. cubisteffects says:

    I don’t offer the Burr Brown mod as that is something that I think Mr. Keeley can do better than I :)
    Also, the distortion circuit bends use the same territory as the feedback mod so it works out better on the pedal to have one or the other.

  21. cubisteffects says:

    I plan on updating all mods with videos in the near future. Subscribe to my YouTube channel here: for notice for when I do.

  22. doug says:

    hello. i was wondering what the differences between your standard mod and robert keeley’s mod. also, if i were to ship you a dl4 with the keeley mod would you still be able to perform the expression mod? thanks! -doug

  23. cubisteffects says:

    Hi Doug,
    No I do not replace any op-amps in the Line 6 modelers.
    I have done it before, but in my humble opinion, I found the change subtle in relation to the labour involved. So to keep my price affordable I chose not to offer it. And I respect that it is Keeley’s signature on the mod, so that factored into my decision as well.
    Thanks for the question,

  24. james says:

    Hi, my dl4 power jack burned up and i was wondering if this is something that can be fixed. the board has a tiny smudge of black but its not to serious and the capacitors next to it burned up i know you cant say for sure but do you thinks its fixable or am i just wasting my time ?

  25. faizal says:

    i love the idea of the twin mode preset, how does it work. Could you talk more about this, and is it possible to just get a new DL-4 from you straight instead of sending mine? Thanks for the head up.

  26. cubisteffects says:

    It may be fixable – I have repaired worst in the past :|
    Feel free to email me any time.

  27. cubisteffects says:

    I’ll do a demo in the next week showing the DL4 mods in detail. I do sell some DL4s from time to time so keep a look out on my Twitter/Facebook page.

  28. Martin says:

    Hi there!

    I havent gone thru whole page but here is my Q: my Loop seems to be working very quietly. How so? How do I fix this?

    Thank you


  29. HI- do you know which unit Reggie Watts uses? he’s got some sort of capacitance modfication.
    i’m a performance artist wanting to expand my repertoire. i’d appreciate any thoughts you might have. i’d be using my hands, not my foot.

  30. cubisteffects says:

    Hi Martin,
    You can change the level of your loop by increasing the MIX knob to maximum.

  31. cubisteffects says:

    I think Reggie uses a couple of DL4s and an EHX 2880. I have both and they are both great units for what they do

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