Bass Synth Pedal Review – Line 6 – How To Use Line 6 Poducts As Bass Synth Pedals

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A fat synth bass sound, played by a synthesizer or by a bass synth pedal, is probably one of my favorite sounds in music. Any song that has a synth that plays a funky and groovy bass line immediately makes me happy.
Something in that dirty electronic sound makes any song sound much better, at least to my ears.
If you like Funk, Soul and Hip Hop like me, then you probably can’t stay nonchalant
either when you hear the songs of Stevie Wonder, Parliament, Jamiroquai
and many others who give their bassist some time off and let their keyboard player play the bass lines for a few minutes.

Those keyboard players bass lines influenced a lot of my bass playing style. Quite a few times I find myself trying to adopt the motifs of this style of playing. These include a lot of slides – it’s an attempt to mimic the pitch-bend wheel that keyboards have.
But just adopting this style of playing will not change the entire sound. You also need an effect that will make the bass guitar sound like a synthesizer.

That’s why I’m always on the lookout for a good bass synth pedal.

In this review, I will go through the filters, auto-wah, and synth modulations sections of the LINE 6 products.
You can find these sounds in these LINE 6 produscts – in the “filter” section:
M5, M9, M13, HX Stomp, HX Effects, POD HD500X.

Check Prices on for these products :
M5  –
M9 –
M13 –
HX Stomp –
HX Effects –
POD HD500X –

In all of these products, this section is marked with the purple color.
All these sounds were initially made for a LINE 6 Pedal called FM4 filter modeler, which is now out of production.

Synthesizer sounds are a matter of taste and style, but in those synth pedals that are designed for bass and guitar you can always find a few sounds that are pretty much useless – either in recordings or on stage, and that’s why I’m going to focus only on specific sounds that have been useful to me.

What is the filter modeler? How does a bass synth pedal work?

The idea is that the sound effect is created by a dynamic change that is affecting a defined frequency. Imagine, for example, a Wah-Wah pedal, which you probably know. What happens when you press on the pedal is that the high frequencies open and close according to your foot movement, creating the “wah” effect.
In the same way, in a bass synth pedal, there are dynamic frequency movements, and we can handle these frequencies in all kinds of ways to change the nature of the sound.
If you’d like to dig in deeper and learn more about filter pedals, you can read this post about Envelope Filter/Auto Wah and Synth pedals.
Before I start reviewing my favorite sounds, I will go through the general settings for editing each preset –

Frequency – Determines the frequency at which the filter starts.

Q – Determines how much you boost the filter, which means that the more you rotate the knob to the right, the filter will be louder, more narrow, hence more prominent.

MIX – determines the ratio between the direct and the wet sounds.

Filter Stop Frequency – Sets the range which the filter moves between the frequencies and determines the modulation depth.

Pitch – an addition of another note that creates another layer of sound

Attack – How long does it take for the filter to appear? When the Attack knob is turned off – Instantly, when the attack knob is turned clockwise – The sound arrives in delay.

And now for the presets that I use – don’t forget we’re talking about finding sounds suitable for bass guitar. Of course, these can be used with other instruments such as guitar, but the settings will probably change. Also, note that I edit these settings while playing on a Fender Precision bass. If you own a different bass guitar, with different pickups and especially if you own an active bass guitar, your settings may be a bit different, if you wish to get to the sound that I show in the clips attached here.
And most important – I used Line 6 M5 and Line 6 M9 for this review. If you’re using a different product, the locations and names of the knobs might be different.


A dirty, funky sound that adds a beautiful electronic layer to your bass.

I can describe it as a combination of overdrive and a smooth envelope filter.
The sound will change depending on your settings – whether it’s more dirt and distortion or more “envelope-ish” feel.

Mix –
With this preset, I like to set the mix knob to a minimum level so that I can hear a lot of direct bass sound and just a little of the effect. Otherwise, the whole thing starts to go crazy. If you like noise and dirt – go for it and increase the mix level. The only problem when you increase the mix level is that you lose a lot of low frequencies – not something that bassists would appreciate.

Stop Freq –
My suggestion is to set it to a near minimum level, or it would sound like an extreme modulation effect. Somewhat like a heavy tremolo.

Pitch –
As in most cases, I like to set the pitch knob to the middle, i.e., one octave above. Any other interval sounds useless to me.
The pitch setting is not so precise with the M-SERIES pedals, and you have to tune it by ear.

Freq –
Anything between the middle and the high end would be nice. If you turn the knob to the left, to the lower frequencies, then you lose all the effect of the effect (-:

Q –
Here I prefer to broaden the filter, meaning that the knob will set to minimal condition, but not completely turned off. The more we turn it to the right, the more we hear the “Wah Wah” sound and less of the dirt.

When should you use this sound? – when you want to imitate vintage analog synths like those they used in soul and funk music from the seventies (for example, in Stevie Wonder songs).

Synth string

This sound adds a lot of width to the bass. Imagine it as a dirty electronic string section (this is the best description I could think of). It works well with long notes or repetitive rhythmic grooves.
If you turn this knob, you will hear the way that the filter operates on the low or high frequencies. The effect will “open up” as we turn the knob to the right. Play with it and choose according to your taste.

Pitch –
Once again, I prefer to set it to one octave above.

Attack –
I usually play with the attack turned off, which means that the sound of the filter doubles the bass immediately. But opening the attack can create an exciting effect, especially if you play electronic or psychedelic music.

Mix –
Here, too, I add just a little of the filter sound to the bass to not lose the original bass sound. Try turning the knob to get some more noise.

Stop Freq –
I prefer the moderate range. But if you’re looking for a modulation effect – go for it and turn the knob.

When should you use this sound? – in electronic music: trance, techno, etc. or in reggae/dub/drum n bass.



The guys at Line 6 moduled some of the best analog synthesizers of the seventies: Moog Modular, Oberheim, Arp, And created a single preset that combines some of their sounds.

The lower left knob acts as a selector switch between the different sounds and synth modes, and there are eight modes in total.
My favorite preset is Wave 5. It sounds Very similar to an analog vintage synth.
My settings with the WAVE 5 sound:
Pitch – set to the middle, and plays one octave down
Freq – about 40 percent
Q – about 25 percent
Mix – Here too I only push the knob a little to the left.

I’ve found two more sounds that I like: Wave 1 and Wave 4 Which remind me of a few Jamiroquai songs.
We can leave the above settings as they are, and just add more wet sound to the mix.

Tron Up / Tron Down

These are Envelope Filters/Auto-Wahs, based on the vintage Mu-Tron III pedal.
In my opinion, Line 6 has managed to turn these two presets into an excellent envelope filter effect that any bassist who likes Bootsy Collins or Flea must have and that no bass synth pedal would be complete without it. Tron Up will give you the classic envelope sound. Tron Down adds some electronic vibe, and is more suitable for slapping or any other hard core picking.

Mode – Low/High. Low works best for bass.

Filter – LP / BP / HP. LP (LOW PASS FILTER) works best for bass. A low pass filter is a filter that cuts the high frequencies and only allows low frequencies to pass.

Freq – set at about 60 percent.

Q – set to 90-100% – that is, a narrow filter.

Mix – above 75%.

Check Prices on for Line 6 products with these tones :
M5  –
M9 –
M13 –
HX Stomp –
HX Effects –
POD HD500X –

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This Post Has 4 Comments

  1. tony6fingers

    i just got a m13 yesterday. do you know any les claypool sounds? any at would be nice. please keep your demos coming and ill record some of the things i do.

    1. idogomusic

      Hi Tony,
      Thank you for your comment and congrats on your new M13! How do you like it so far?
      I’m not that familiar with Claypool’s music to know what is “his sound.”
      But let me know if you find something interesting.

  2. bassKasper

    Hey, thank you very much!!!
    I got the pod go and struggled as an absolut beginner with the effects. I searched for some synth and funk sounds but couldn’t figure out which I need or how to set them.
    Your explanation gave me the right direction so set my own sound.

  3. Fab

    I just got one for $100 on Boxing day. Wondering if anyone knows what effects to use to get that John Taylor tone from Duran Duran

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