The Behringer TD-3-MO REVIEWED.

Behringer have introduced the TD-3-MO which is a modded out version of the TB-303 based on the highly popular Devilfish mod from Robin Whittle.  

In 2019 Behringer released the TD-3, a highly affordable clone of the classic Roland TB-303. Now they have introduced the TD-3-MO which is a modded out version of the TB-303 based on the highly popular Devilfish mod from Robin Whittle. In this article we will take a look at the additional features provided in this mod version.


Probably one of the features that stands out the most on the TD-3-MO versus the TD-3 is the inclusion of a sub oscillator. It is important to understand that a sub-oscillator is not a separate oscillator. It is always linked to an existing oscillator and usually won’t have many independent controls. On the TD-3-MO the sub-oscillator has a switch to engage it and a three position switch to set the level to low, mid or high. I personally would have preferred a continuous control for this so it can be gradually increased or decrease in level. Though what is really nice is that you can set the main oscillator’s waveform switch to OFF and just listen to the sub. In terms of the sound, it definitely adds to the tonality to have a sub oscillator mixed along with the main tone of the synth. When the filter resonance is set very high you can lose some low end so it’s good to have the option to engage the sub-oscillator.

Soft Attack 

It may be unusual to even talk about attack on a synth like this because historically the TB-303 never had an attack control. It made sense, this is a bass synthesizer so we don’t need to have any attack. On the MO version we now have control for attack time. This is not the usual attack time knob you see on typical synthesizers which usually reach values of multiple seconds. I’m not sure what the exact range is, but it is quite small. Probably in the low milliseconds range. What’s also interesting is that this attack time only affects the non-accented notes.

So you can create quite a dynamic progression where some notes have a soft attack while others don’t. A very useful and welcomed feature!

Decay (Normal & Accented)

Just like the TD-3 and the original TB-303, the TD-3-MO has a decay time control but it seems to be just affecting the VCA here. Interestingly, you get two additional decay controls which are specifically for the ‘normal’ notes and the accented notes respectively. These decay times affect the filter cutoff modulation, so the main ‘envelope’ knob needs to be up, in order to hear these in action. I’ve always preferred separate controls for amp decay vs. filter cutoff decay so this is a good addition. Though if you are coming from the perspective of the classic bass synthesizer which just had one decay control, it might be a bit confusing. These two controls again help to make the patterns sound more dynamic as you can have a different filter modulation decay time for the ‘normal’ notes vs. the accented notes.

Filter Tracking

Another welcome addition to the synth is filter tracking or key tracking, which forces the filter cutoff to change based on the notes played. So this way higher notes can be brighter and lower notes darker. At high filter tracking values the low notes can be so filtered out that they pretty much become inaudible. This is great as your pattern now has additional rests. Again, a great way to dynamically change the pattern, without having to actually go in and re-sequence the pattern. 


The TD-3 has a distortion ON/OFF switch, a control for distortion amount and a tone control. In the MO version we just get an Overdrive knob. There is no way to disengage this overdrive circuit. At lower values you will get less drive but at very low values the volume itself will cutoff.

This is more like a true overdrive control where you’re basically overdriving the circuit by adding excessive gain.
I would have liked to see an option to disengage the overdrive circuitry completely and just have the clean synth sound. None the less, distortion has always been a critical step in the bass synthesis domain so it’s good to have this built-in the system so you don’t really need to process the signal externally. 



When the resonance parameter is set to high values the synth can produce some extreme high frequency content. Acid bass lovers know about this. The muffler is designed to tone down these high frequencies especially at higher levels. There are three switches. At 0 it’s disengaged and at 1 & 2 you get two different amounts of high frequency damping. It won’t completely get rid of the high frequency squelches but bring it down enough to make a difference.

Accent Switch

This is a great live performance feature. So what this momentary switch does is that it sets all notes to accent mode, as long as the button is held down. Great way to temporarily make everything louder. Also keep in mind the separate decay control for the accented notes will kick in for all notes when this switch is held down.

Filter FM

On the TD-3-MO you can make the output of the synth as a source of modulation for the filter. This is done by increasing the Filter FM knob. Unfortunately you can’t get those extremely dissonant sounds that is typical of Filter FM because the rate of modulation is exactly the same as the frequency of the audio being processed. Though having said that, this still does add some controlled grit to the sound. 

Slide Time 

Unlike the TD-3, the MO has glide functionality. There is a knob that lets you control the glide time and you also get a 3 way switch to instantly adjust the range of the knob from slow to normal to fast. Keep in mind the slide is only active on notes that are played legato. 

Accent Sweep 

This one is a control that is a little hard to explain. It seems to be adjusting the amount of resonance in the filter. Set the resonance to a high value and change the accent sweep position from 0 to 2. You will notice on the 1 position the resonance is a lot more exaggerated while on the 2 position it’s almost negligible. Interesting control. Again a good way to quickly change up the tonality of a sequence in real time. 

CV in/Out 

In addition to all the controls, the TB-3-MO also has a bunch of CV inputs and outputs that can help when integrating this device with other analog gear such as Eurorack devices. One helpful control is the Filter FM in. Earlier I mentioned that the Filter FM is a bit subdued as it’s using the audio out as the source of FM. With the Filter FM CV in we can introduce any external audio rate signal to modulate the filter frequency and this can lead to some really dissonant tones especially when the rate of modulation is unrelated to the audio signal.

The Accent Out CV can be great to accompany the accented notes of the bass synth with any other external sound, like a percussion tone. 


 Another really great feature on this synth is the MIDI connectivity. You get 5 pin din as well as USB MIDI. The TD-3-MO is a class compliant MIDI device so no drivers are required to make the device appear in your DAW of choice.  There's Note ON/OFF and velocity control both ways (MIDI IN & OUT) and a fully controllable VCF.


TD-3 vs TD-3-MO

It possibly quite obvious that the better device might be the one with the more features. Though if you already own a TD-3, the MO version might be a good accompanying synth. The sync capabilities make sure that they play well together & you will get an additional voice to work with. The two sequencers are pretty much identical, so there isn’t much of a learning curve if you already know how to work the sequencer.


 It seems like the TD-3-MO is a Behringer-style riff on the Devilfish mod which is, BTW, fantastic to have at this amazingly low price point of $249 USD! I would have liked to see Behringer take the mod and make it even better so that people who already have the Devilfish mod might be enticed to invest in this version. But if you don't have the Devilfish mod the TD-3-MO just might be the way to go!

Find out more and where to purchase the TD-3-MO directly from the Behringer website.

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Rishabh Rajan is an award winning music producer & educator currently based in New York. He produces electronic music under the name code:MONO & hosts a YouTube channel featuring music and live mashup videos using performance controllers like the Ableton Push. He is also a sample library developer having worked with companies like Bela... Read More


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