Real Tube vs Tube Emulation

Eden’s GlowPlug Tube Warmer pedal passes your signal through a real 12AX7 tube, while Tech 21’s SansAmp VT Bass DI is a modern classic in tube emulation. Let’s battle…



For this particular shootout, we will focus on some very specific areas, which also means leaving out some features. The key focus is on comparing the basic ‘tube’ sound of each pedal – the actual tube in the Eden Glowplug versus the tube emulation circuit of the SansAmp VT Bass DI.

There are two main parameters for each pedal that are named differently, but share somewhat similar functionality. On the Glowplug the WARMTH control sets how hard you drive the internal 12AX7 tube, and the DRIVE knob on the SansAmp does the same, only the range is wider and at the outer extreme you get more overdrive than the Glowplug can deliver.

Further, both pedals can combine the FX signal with the dry signal. On the Eden Glowplug, the control is named MIX, whereas the Tech 21 SansAmp calls this feature BLEND. They do exactly the same thing, though.

The Glowplug also has a Crossover feature, but in all clips, this knob is set right at noon with a crossover frequency at 180 Hz. The SansAmp has a lot of additional controls – the EQ is set completely flat, the ‘Bite’ is off and the Character is set at noon in all sound clips.





NOTE! Please use headphones or ‘real’ speakers. You simply can’t judge low-end material on laptop, tablet or phone speakers…!


Subtle Tube. But All Tube.

In this round, we use a passive Fender Precision bass and both pedals are set to 100% wet mix, which means that none of the dry signal is blended in. But the WARMTH and DRIVE knobs are turned all the way down, so while it’s an all-tube scenario, the tubes are not driven very hard. First a dry version, followed by each of the shootout contestants.


A Litte More. And A Little Less.

Now, we’ll turn up the heat a little, pushing the WARMTH and DRIVE knobs to 25%, but at the same time back the MIX / BLEND knobs down to 50%, leaving us with an even blend of the FX and dry signals.


Halfway There x 2

In this example, we swap the P bass for a Fender Jazz bass, and also use a pick, so there is a new DRY sound clip that you should listen to first as a reference. The pedals are now set to 50% on the WARMTH and DRIVE parameters as well as on the MIX and BLEND.


Full-on Tube. Subtle Blend.

Now, the WARMTH and DRIVE knobs are cranked all the way up, but the BLEND and MIX knobs are backed down to 25%.


More details and sound clips here: Eden Glowplug Review / Tech 21 SansAmp VT Bass DI Review.



As you have probably noticed, the SansAmp adds a lot more dirt as the DRIVE knob is turned, compared to the WARMTH control on the Glowplug. This is also why we decided not to do a full-on example at a 100% wet mix as the difference would be too big to deliver a meaningful comparison.

While the pedals can indeed be used for a similar task – adding tube-like tone to your sound – the pedals are quite different by nature. The Glowplug is more of a One Trick Pony, where the SansAmp VT Bass DI is a complete set of tools that also offer 3-band EQ, speaker simulation and DI functionality, as well as further tonal varieties via the BITE and CHARACTER parameters. Therefore, the SansAmp is also a more expensive pedal.

Which one you prefer is of course a subjective matter (as always). The difference is subtle – especially when the DRIVE knob is not set too high on the SansAmp – but it is definitely there. If have not noticed this in the first two rounds of sound clips, you probably haven’t used headphones or a pair of good speakers. To our ears the Glowplug (and the actual tube) sounds a little more ’round’, but that does not necessarily equals better, though. Again, it all comes down to a matter of opinion.

but depending on what your needs are, one may be bette fitted for you than the other. Say, you already have a dedicated drive pedal on your board and some kind of preamp pedal with a DI output (or have DI on your amp), all you need might be that one real tube in the Glowplug to add some vintage-y flavor once in a while.

But if you’re looking for one pedal to handle many different tasks, and maybe don’t use overdrive as one of your main effects, the VT Bass is a great place to start. This is not meant as if the overdrive in the VT Bass is poor by any means, but if you plan to use the pedal as an always-on, main tone-shaping pedal, you can’t punch in and out the overdrive as you please. You need to turn the knob for more dirt, and that will affect your overall output volume quite a bit, which means it is not suited for on-the-fly dialing between overdrive and clean tones.

If you would like to dig in deeper and learn more about these pedals, as well as listen to much more detailed sound clips of each, please check out the full reviews: Eden Glowplug Review / Tech 21 SansAmp VT Bass DI Review.



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