Active From a Young Age

I have been a huge advocate of onboard preamps going back almost to the time I began playing, more than 20 years ago. And I say going almost that far back simply because the first two basses I had as a know-nothing teenager happened to be all passive – and I didn’t yet know that “passive” or “active” were words you used to talk about these massive, heavy things, rather than attitudes or people.

But the next bass I picked up – which would be the first for me in many ways (first real instrument of quality, first modern design, first 5-string) – provided me my first experience with the all-mighty power and glory of the active circuit. Suddenly, I could sound however I liked to, wherever I was playing! Playing through the school band’s shoddy old amp? Still sounded like me. Playing directly into a patch bay and recording right into a Tascam DA-88? Yep, still sounded like me. Nevermind that I still didn’t know very much and essentially dimed every EQ control on the thing! What I didn’t know at the time was that my low impedance output signal was not

being degraded by cable runs of various length, and the character of my sound wasn’t being partially informed by the impedance of the input stage of whatever I plugged into next. I went on to experiment with preamps made by Ibanez, Bartolini, Aguilar, Audere, MEC, Seymour Duncan, and probably others I’m forgetting.

Fast forwarding to now; there are really not very many reasons these days to not have both your passive and active bases covered with the same instrument. Most preamps I’ve tried can be bypassed to go fully passive, with the caveat being that your pickups are passive and not running through any type of active buffer on their way to the blend or volume pot(s). Heck, you can even add a passive tone control to most any preamp-loaded bass with passive pickups, so assuming you’re able to find a spot for a mini switch or replace a standard pot with a push/pull one, you can have a traditional, fully passive signal path AND an active one, with all the benefits of both at the flick of a switch.


Full Control

The Noll TCM 4 XM is the first 4-band, onboard preamp I’ve had first-hand experience with that allows for this “having-your-cake-and-eating-it-too” scenario. In contrast, I’ve also had great experiences with an Audere Classic 4-band, but due to that product’s active pickup mixing and grounding scenario (in which the pickup grounds are separated from the common ground), it’s not easily doable to have a switchable, truly passive setup. The Noll TCM 4 XM does indeed allow for switching to full passive, and the configuration I opted to go for was: combination single-shaft passive tone/active treble control, bass control, and stacked high-mid and low-mid. I opted to keep the combination MEC volume/blend/DPDT switch I had already installed to keep all that functionality with limited cavity space. I installed the system into my Warwick Streamer Stage II 6-string, being fed by Delano SBC-6H dual-coil pickups, each of which have a dedicated series/single/parallel switch. I also decided to keep the cool rechargeable Fishman Universal Battery Pack system with USB-charging ability that came as part of the newly redesigned Warwick/MEC preamp for 2016. This component simply takes the place of the battery and provides the same 9-volt power supply as a battery would; it’s not involved with the audio path in any way.


Navigate to on desktop to watch a fully annotated video comparing the Noll TCM 4 XM and Aguilar OBP-3 under nearly identical circumstances. Fingerstyle and slapping examples are given with various EQ settings using both preamps. Note: annotations will not display on mobile.

Manufacture:Noll Electronic
Model:TCM 4 XM
Country of Origin:Germany
Stated Input Impedance:>1 MOhm
Stated Output Impedance:<10 KOhm
Stated Input Sensitivity:max. 450mV @ 9V
Stated Output Voltage:max. 4.5V @ 9V
Stated S-N-Ratio:96dB (1kHz/5Vss)
Bass Control:+/- 15 dB @ 40Hz
Low Midrange Control:+/- 15 dB @ 400Hz
High Midrange Control:+/- 15 dB @ 1,3KHz
Treble Control:+/- 15 dB @ 4,2KHz
Operating Voltage:+9V (+18V optional)
Power Consumption:typ. 1.5mA @ 9V / 450h Batt. Life
Dimensions:45mm x 30mm x16mm
Price (Street): $160.16

Right off the bat, I dug the Noll’s frequency centers. For a 4-band EQ, they’re very well thought-out. From lowest to highest, they are: 40Hz, 400Hz, 1.3kHz, 4.2kHz. This means there are a little more than three octaves between the peak of the bass and low-mid filters, a little less than two octaves between the two mids, and a little less than two octaves between the high-mid and treble. This means the frequency bands are spread widely enough to avoid too much interaction with each other, but also to provide just enough interaction to not sound artificial. The low frequency is listed as being the same as that of my old standby, the venerable Aguilar OBP-3. However, whereas seasoned users of that particular preamp may be aware that a little boost or cut on that low EQ filter goes a substantially long way, I found the Noll’s control to be more even and easier to dial in a useful amount of bottom (nearly all the way through the pot’s rotation). That was a recurrent theme with all of the Noll’s EQ controls.

The Noll’s low-mid is also centered at the same frequency as one of the Aguilar’s mid options, at 400Hz. While I have grown fond of a slightly lower center for a low-mid control, I found the Noll’s to be very effective at cutting out or adding in what I’ll refer to as “bulk” – basically, the stuff I don’t want much of when going for a modern tone with both pickups, or the stuff I sometimes want more of when using just the bridge pickup. The high-mid control is perhaps the best-voiced EQ filter on the preamp, being situated perfectly to either cut out honk and clank in a bass that has built-in leanings towards that side of the sonic spectrum, or to add in a nice amount of attack when using duller strings or rolled-off tone on the neck pickup. In fact, it is actually due to the two mid frequency filters of the Noll TCM 4 XM that I discovered my new-found love for the series option with the Delano pickups. Cutting the low-mid

generously and the high-mid just a bit, with both pickups full-on, allowed me to choose a coil configuration that emphasized the general voicing I like from the Delano dual-coils, while removing the excess, fattening mid frequencies that are a hallmark of that coil configuration, and which I’m personally not too fond of. The effect was a wonderful opening-up of the sonic range the pickups and strings had to offer, with the resonant peak of the pickups remaining low enough as to not be too harsh in the upper register. Finally, the treble control, being voiced well-lower than many other popular 3 or 4-band EQs, performed exceedingly well at cutting harshness, or adding both zing and presence.

A note on the combined passive tone/active treble control: these things are incredible! I would like to see them adopted much more widely. This is not a stacked pot, as is the low-mid/high-mid, but rather a pot with a single shaft to turn, that’s connected to a dual-ganged pot body (really, two separate pots in one housing, like a blend control). The passive tone is fully rolled-off from one extreme of the rotation and increases to fully on at the center-detented position; the active treble stays completely neutral and flat during this part of the rotation. Then, from the center to the other extreme, the passive tone stays full-on while the active treble control is engaged from flat to fully boosted. This means that you’re never using the active treble control to cut high frequencies, preferring the passive tone’s warmth and familiar variable peak and slope to attenuate them, instead. It also means that you cannot simultaneously roll off the passive tone while boosting the active treble, but my guess would be that this is an acceptable trade-off for most players.

Solid Take

The Noll preamp came impeccably pre-wired and uses high-quality MEC and Alpha potentiometers and flexible, clearly color-coded wire. But a word to the cavity space-conscious; the module itself is considerably larger than that of the Aguilar OBP-3 or Delano Sonar. You’ll want to make sure you have room to stow it and that you can get the cover back on and flush before you begin surgery. I had a brief moment of panic when I realized that my initial desired installation location wouldn’t work, due to conflicting with the Fishman battery system mounted to the cavity plate. While that may not be your specific concern, make sure you’ve got a good spot, before you get too deep into the project. I found communication with Noll to be quick and effective during my initial phase of interest in the product, and shipping was very fast, especially considering that it came directly from Germany. While I prefer the more gentle slope at which the EQ controls work from their center

detents, some others may not feel comfortable, at first, with needing to turn a knob further than they’re used to in order to get the same response. But to keep perspective, all the EQ controls are listed at +/- 15 dB, which compares similarly to other popular preamps.

If you’re in the USA, you may not yet be familiar with the Noll name or be able to source them from a local retailer as easily as something domestic, but you just might find that the imported stuff can be the good stuff! Noll has been well-received in Europe and around the world for quite some time. And while the market for onboard preamps has grown more diverse with lots of great options to choose from, the number of companies making 4-band preamps is notably much smaller. With the Noll being both affordable and highly configurable for your specific needs, I would definitely recommend trying the TCM 4 XM in your bass of choice. Of course, not every preamp will work for every bass/set of pickups/preferred strings/player, and tone is the most subjective thing we can discuss. But you’ll never know if it might help you discover your new favorite tone until you try it! In the USA, Noll preamps can be purchased from Best Bass Gear (