Line 6 DL4 Delay Modeler Review

The Line 6 DL4 Stompbox Delay Modeler came out well over 10 years ago and has built up a reputation for being the go-to delay pedal. There are many popular guitarists who swear by the DL4. I finally got my hands on one so in this review, I will share with you my thoughts on the DL4 and how it compares to delay pedals available today. I will mainly compare it to the TC Electronic Flashback X4 which is the closest comparison in terms of price and features.

DL4 Features

Check out the full details of the DL4 as well as price here (link to Amazon). I’ll cover the main features worth mentioning here:

15 Delay Modelsdl4-models

The DL4 has 15 effects modeled on popular delay gear as shown on the knob to the right. They advertise 16 effects, but the loop sampler should be considered separately. The chances are if you hear delay used in a song, you can replicate it on the DL4. The DL4 processes in 24-bit true stereo which mean that the left signal stays left and the right signal stays right. In practical terms that means you could easily run two signal paths to two separate amps for a nice wide stereo effect.

Loop Sampler

As is common with feature-filled delay pedals, the DL4 has an inbuilt looper. Keep in mind that this pedal came out 1999 so while having an inbuilt looper isn’t very unique today, it was a great feature back then. The maximum recording time is 14 seconds but guitarists have figured out that if you set the looper to half speed before you record, you can double that time to 28 seconds which is far more practical. To give you a comparison, the TC Electronic Flashback X4 records up to 40 seconds which is a significant difference in terms of usefulness. As is common with loopers you have the ability to playback the loop at half speed and reverse it as well as overdub as you like.

It’s also worth mentioning that the looper works in mono so both inputs will be taken simultaneously. So if you do plan on using the DL4 in a stereo setup, be aware that the looper works in mono.

3 Programmable Presets & Tap Tempo

The first three footswitches allow you to store different presets – a very handy feature to have if you play live. The fourth footswitch is dedicated to tap tempo – again a super useful feature that’s often missing in delay pedals.

Expression Pedal Input

I did not get a chance to try this out but you can plug in an expression pedal for more control over the delay settings.

9V 1200 mA power

This is a fairly high power requirement and a problem for many guitarists. The fact that the Voodoo Labs Pedal Power 2 Plus has a dedicated position for Line 6 modelers like the DL4 should show how different this is compared to standard power requirements. Keep this in mind if you plan on adding a DL4 to your pedalboard as you probably won’t like to find out what it means to lug around a separate power pack just for this pedal.

Ease of use

Keep in mind that I got my hands on a DL4 to test out after I had already spent some time with the TC Electronic Flashback X4. So I’m constantly comparing the DL4 to the X4 in my head. While I do feel that the DL4 is easy to use, I can see how much easier it could have been.dl4-sticker

The only major problem I have with the DL4 is the labeling. When you look at the labels for the five control knobs, what do you think ‘Tweak’ or ‘Tweez’ means? The labels: ‘Delay time’, ‘Repeats’ and ‘Mix’ are pretty self-explanatory but how are you meant to know what Tweak or Tweez means? Line 6’s solution was to place a sticker on the pedal listing the functions of those dials. Handy to have if you have the sticker (shown to the right), but if you have a second-hand pedal without the sticker as I did when I tested it out, you’re left at a loss. It’s not a good sign when the manufacturer has to place a sticker on the pedal to help people understand it.

Once I looked up the functions of those two knobs – which change for each type of effect, it was fairly simple to dial in the sound I was after. For example for the delay ‘Digital w/ Mod’, the Tweak knob controls the modulation speed and the Tweez knob controls the modulation depth. This level of control isn’t available with many similar pedals such as the X4 and was a nice feature. Instead of only being able to control the basic settings such as delay time and level, you’re able to control the delay with more precision. In many types of delay this is very useful. So if you don’t like the sound of the ‘Lo Res Delay’, you can adjust the tone and resolution to your liking. Very handy if you have the sticker to tell you which knob controls what parameter.

I love the looper in the Flashback X4 because it’s a separate setting not included in the main delay type knob. That’s important to have as it means the pedal doesn’t consider ‘looper’ as a type of delay. Unfortunately, that’s exactly what the DL4 does. The Loop Sampler is just one choice in the far left knob which means when you have the looper activated, you can’t continue to play around and experiment with different delays. Bummer. An undo option is also missing which means any mistakes in your loop are permanent.

Sure the DL4 does have the half speed and reverse effects which are missing in the X4, but you need to consider whether those effects are worth more than an undo feature. To me, those effects are gimmicks that can only be used a couple of times before losing their appeal. On the other hand, an undo footswitch is a lifesaver. So if you’re considering the DL4 for the looper feature, keep in mind there are far better looper pedals out there and I personally feel the Flashback X4 incorporates the looper into the pedal far better than the DL4.



I remember when the DL4 was first released. Line 6 were seen as an innovative company, but many people didn’t take them seriously. When the DL4 came out, people started to take modeling technology (and Line 6) a bit more seriously as they heard what was possible. Thanks to 24-bit processing, the delay sounds fantastic. This is why the DL4 has been so popular over the last decade – because it sounds great. I feel a big part of the popularity is the flexibility in tweaking every parameter as you want. Search online and you can find plenty of mods people have created for the DL4 such as an inbuilt expression knob. The two knobs I complain about – Tweak and Tweez – play a massive part in the quality of the sound you can achieve with the DL4. When I went back to the Flashback X4, it became apparent how inflexible some of the delays feel when you realize you can’t tweak many of the parameters. So the DL4 scores on flexibility in tone.

The issue a lot of people have with the DL4 is that you can easily hear a volume drop when you plug it in – especially if you play a high gain signal. It’s also important to note that while the DL4 is True Bypass, it can be switched over to Alternate Bypass. With True Bypass the delay effect will stop as soon as you turn the effect off. The downside is that you may notice a volume drop when the unit is on. Alternate Bypass will avoid the volume drop issue, but it does mean the DL4 is affecting your tone even when the effect is turned off. This is discussed at length in this article explaining Buffered and True Bypass.

The advantage to setting the pedal to Alternate Bypass is that when you turn the effect off, the delay trails off rather than cutting out completely. You switch between the two modes by holding down the A and C footswitches for three seconds before you insert the left mono input lead. For many guitarists, this issue is what stops them from using the DL4 and I can understand why.


The risk with brand new products is that you don’t really know how long they will last or if there are problems with the design or build that won’t appear until years later. The good thing with the DL4 is that it has already been out for more than a decade so any possible problems are easy to find. Some guitarists found that the footswitches could eventually wear out the PCB underneath. So if you choose to buy an early model from 2000-2003, be wary of this problem. From what I have heard Line 6 have improved the internal construction so this problem doesn’t occur anymore.

Apart from some issues pre-2003, the DL4 is fairly reliable and I have not heard of any issues from new pedals bought today.

Overall impression

The DL4 is a great piece of gear without any doubts. Although I’ve known about it since it came out, this was the first time I managed to get my hands on one. So I can imagine how it would have stood out when first released over a decade ago. However today we have a massive range of very high-quality delay pedals available with a wide range of features and price levels. I know that the DL4 will suit a lot of guitarists and many are extremely happy with the DL4. On the other hand, I know some people will see limitations in the DL4 when comparing it to other pedals available today.

As I was familiar with the Flashback X4 before trying the DL4, the biggest limitations I felt with the DL4 was the looper and the inability to edit presets on an app or software. The looper felt like a tacked-on feature where on the X4 it feels well thought out and far more useful. The reason I feel having an editor or app to set up presets is important is that it allows you to have more control over the presets. With the DL4 you cannot set a specific delay time in ms. You can with the X4 if you use the software or app. For many guitarists, this isn’t important so it’s up to you to decide whether those features are important to you or not.

Overall, I can see why the DL4 has been so popular and despite it’s limitations today, it’s still a fantastic delay pedal.

Check out the price and full details of the DL4 here.


  • Great control over delay parameters
  • Tap tempo footswitch and three presets
  • Wide range of delay types at 24-bit


  • Tweak and Tweez controls are confusing without the sticker explaining the functions
  • The looper’s time of 14 seconds (28 if recorded at half speed) limits it’s usefulness
  • You might notice a volume and tone drop when the unit is activated
  • Uncommon power requirements
  • No undo function on the looper

Who is it for?

If you want control over a wide range of delay types, the DL4 will probably meet your needs. In addition to being able to control delay time, feedback and level, you are also able to control the delay model parameters. This allows you to dial in the perfect delay type for any situation. It’s a level of control not available on many other delay pedals. So if you want control over the delay effect, the DL4 is worth considering.

Who isn’t it for?

Remember that the DL4 is well over a decade old so there are a lot of other pedals that have come along since then with more features and better quality. Throughout this review I have compared the DL4 to the TC Electronic Flashback X4 because it’s a very close comparison. I typically recommend the X4 over the DL4 simply because the looper is far superior and the features of the X4 overcome some limitations with the DL4. If you want a delay pedal with a better looper and the ability to customize presets on an app or editor, then I recommend the X4 over the DL4. The other advantage to the X4 is that you won’t experience tone loss like you do with the DL4.

I also don’t recommend the DL4 for guitarists looking for a simple delay pedal that doesn’t take up too much space. It should be obvious that this pedal does not suit that need. Instead, consider something like the MXR Carbon Copy or the Flashback Mini.

How to get the most out of the DL4

I’m currently compiling a list of tricks, tips and effects you can use in your playing based on the effects on the DL4. Subscribe to my newsletter to be notified when it is available.

Alternatives to the DL4

TC Electronic Flashback X4: it should be clear by now that I recommend the X4 over the DL4. For the same price you can get a pedal that was developed a decade later than the DL4 with a better quality looper and better features. Read through my review on the X4 and you’ll quickly figure out which one will suit you best.

It’s also worth mentioning that Line 6’s newer range of stompbox modelers such as the M9 or M13 take the delay models from the DL4 as well as their other modeling pedals all in one unit. So if you like Line 6’s products and want to use the DL4’s delay types with a newer piece of gear, check those pedals out. You will find the same delay models along with a large list of other effects and a better quality looper.

If you’re looking to buy a delay best but aren’t sure whether this is the best one for you, check out my Buyer’s Guide on finding the Best Delay Pedal. It explains how to find the best delay pedal for your needs.

See information on pricing, availability and other reviews here.

Review Date
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Line 6 DL4 Stompbox Delay Modeler
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Line 6 DL4 Stompbox Delay Modeler