MASS III (150w) Attenuator

Designed for use with 80w amplifiers and lower.


Footswitch Bypass * 

Footswitch Bypass

Attenuator FAQ * 

Attenuator FAQ

Rackmount Wings * 

Rackmount Wings

Cables * 


This attenuator has three knobs for tonal control. The main volume is controlled by the TREBLE knob. Then to control the mids and bass, use the MIDDLE knob and BASS knob. The middle and bass controls are always dependent on the main volume control. Be aware that the higher the setting on the main knob, the less the effect of the other knobs. For instance, if you turn the main knob all the way to 10, you’ll notice very little change in the tone as you turn the other knobs compensation from one end to the other. The line out signal EQ is dependent on your amplifier settings, with only a volume and tone control on the unit.

May be used on 4, 8, and 16 ohm amplifiers. This MASS III is unique in that it has an actual tone stack for the speaker signal — BASS – MIDS – TREBLE. It also has the internal speaker motor for the load, and has a variable line out signal with volume and tone. The unit has two speaker output jacks to support multiple cabinets. The three tone controls can take the signal from whisper quiet to full on with slight humps in the bass, mids, and treble.

Like all Weber attenuators, you can turn all attenuator controls to zero, pull the speaker, and just use the line out, making the MASS III a dummy load.

Additionally, the MASS III has an active bypass circuit with a footswitch so you can run attenuated or bypassed. The power pack for the switching relays is a 7.5VDC wall wart. With no power applied, the attenuator is still usable. The power is just for the footswitch circuitry. We include the power plug but the footswitch itself is not included. You can use any latching footswitch, including one incorporated in a multi-effect floor unit.

Optional wings may be employed for rackmounting the MASS III. Attach these wings to the sides of your attenuator, and you can mount it in a standard 19″ rack.  Uses two rack spaces. Must place the attenuator on the topmost spaces of the rack to allow proper ventilation.

This item is hand-built to order, to ensure the best attention to detail is paid to its construction.  We build them one at a time, on a table – not hundreds at a time on an assembly line.  This allows us to reduce the margin for error and produce an overall higher-quality product.  Please allow at least 7-10 business days for your order to be built and then shipped.

IMPORTANT NOTE ABOUT HIGH GAIN AMPS*: *if you have a Fender or similar amp, and play with cleaner tones, this part does not apply to you. High gain amps such as Marshall or clones (with heavy distortion) are hard on attenuators. Unfortunately, an amp’s volume dial is not a good indicator of how much power is being produced.  Many amps can reach full power at 3 or 4 on the volume dial, so it is a good suggestion to get an attenuator with 4x the power handling. For example, if you have a 50w high gain amp, you should opt for the MASS 200. If you have a 100w amp, you should still go with the MASS 200 but you should not crank the amp. 

1) do not attenuate too far down. this puts a lot of power through a very small section of the volume rheostat which can cause it to fail

2) also do not turn your amp all the way up.  even if you’re just knocking a little off the top with the attenuator, it’s a good idea to keep the amp somewhere in the middle at most.  it’s best to find the lowest volume on the amp that is the acceptable tone to you, and then use the attenuator to bring it the rest of the way.

CABLES: for combo amps, most people like to set the unit on top of the amp. sometimes there is enough slack in the speaker wire to reach and sometimes there isn’t. these cables will make it work for you: GMC2P and GMC2E If the speaker is hardwired, then you need the PV30MH.  (click the links to view them, and add to your order if you need them.)







More often than not, your amp’s output is more than your ears can handle.  To maintain the tone of a cranked amp with saturated tubes and output transformers, a device called an <strong>attenuator</strong> is placed between the output of your amp and the speaker.  Weber offers a variety of attenuators for different applications.

<p class=”p1″><strong>Please read and consider the following prior to ordering an attenuator:</strong></p>

<p class=”p1″><em>(The following text is reprinted with permission from Eurotubes.)</em></p>

<p class=”p1″>Here are some facts to consider when using an attenuator. Attenuators do work. They are not the cause of transformer failures. An attenuator can only simulate two out of the four components that are involved when you crank up an amp. The four components are <strong>#1</strong> preamp tube distortion, <strong>#2</strong> power tube distortion, <strong>#3</strong> speaker distortion and <strong>#4</strong> the physical movement of air that your speakers produce at high volumes. So the two components missing are speaker distortion and the physical movement of air and these are huge components! So if you’re playing at moderate volumes and just want to tame the amp down to get a bit of power tube breakup then an attenuator is a great tool, but do not expect to be able to dime your amp and then use any attenuator on the market to get the exact same sound from your amp at whisper quiet volumes. You can’t get there from here. You would be better off with a one watt amp.</p>

<p class=”p1″>So, now some answers. Catastrophic power tube failure will cause transformer and screen grid resistor failures. The reason you will read and hear horror stories from un-knowledgeable attenuator users is because they do not understand how attenuators work and the stress they put on your tubes. If in fact, a player chooses to run his amp cranked all the way on and attenuate the volume down to a whisper, then in most cases power tubes will only go a few months. Power tubes will die in one of two ways. The first and most pleasant is by simply fading and dying. The second and more popular way is to go out in a blaze of glory which is what I referred to above as a catastrophic failure which can and most often will, take out screen grid resistors.</p>

<p class=”p1″>Tubes sound great when they are really working hard but the harder you work them the faster they wear out. If you understand this and either use the attenuator sparingly or change your tubes regularly then your amp will not suffer damage.</p>

<p class=”p1″>If you are going to dime your amp out and attenuate it down to very quiet volumes then we recommend using an attenuator that is rated for twice the power of your amp’s rated output.</p>

<p class=”p1″>If you are simply going to dial an amp up to where it starts to breakup in the clean channel and then knock it down a few dB so the club owner and the sound man are happy, then using a 50 watt attenuator for a 50 watt amp will be ok.</p>


<strong>A note about the power level:</strong> <em>You should select an attenuator that can handle at least as much power as your amp puts out.* (see <a href=”https://tedweber.com/attenuator-faq”>FAQ</a>)</em>

Amplifiers are generally designed to operate clean, and most manufacturers specify the output power as clean power. When you run the amp full blast, the output devices actually become more efficient because distortion is not considered. Under those conditions, the amp may be capable of putting out as much as 50% more power than its rated clean power. Be aware of that when choosing an attenuator, because the idea of using an attenuator is to run the amp full blast into power tube distortion and then controlling the level going to the speaker. If you are going to dime a 50 watt amp, you should choose a 100 watt attenuator.

<strong>Understanding Attenuators</strong>

<em>An article by Michael Farnsworth</em>

This is a wonderful article written by one of our customers, which explains attenuators in even more depth.

<a href=”/understanding-attenuators”>CLICK HERE TO READ IT</a>

3 reviews for MASS III (150w) Attenuator

  1. Steve in VA

    When I decided that it was time to get an attenuator, I did my research first. After understanding what my options were, I decided not to go with a purely resistive based load…I wanted the load to be a a speaker motor for the amp to interact with. That pretty much narrowed my choice down to one of the Weber models and I finally settled on the Mass III. So I ordered one with a balanced line out and also got a set of rack ears for it so I could (eventually) mount it securely.

    A week later, I received an email that my Mass III had shipped. I was surprised because the expectation had been set that it took 7-10 business days just to build…it had only been 5 business days. So 12 calendar days (8 business days) later, the FedEx man left a package at my door. At first there was dismay: the box, clearly marked "Fragile" in big, bold letters had obviously been dropped from a decent height. One side and corner was completely smashed in. No way was this Weber’s fault, this happened in the hands of FedEx. So before I opened it, I took few pictures of the box, as delivered….just in case. Upon opening the box however, the attenuator itself was packed on the opposite side of where the damage on the box was. WHEW! Overall, the box was packed so securely that nothing else was damaged either. All the accessories were there, including the foot-switch, power supply (for the switch) and rack ears. There was also a Weber sticker, a Weber amp/cab badge and a Weber beer cozy. Nice.

    Once it was unpacked, it was time to get to know it and what it could do. For all the tests, I used the following:
    – Blackstar HT-20H: As implied, it’s only 20 watt head, but it’s been upgraded with Mercury Magnetic output and power transformers as well as a set of SED Winged C power tubes biased very warm. It’s a very good sounding amp at volume and even at 20 watts, it’s loud as hell.
    – A home built 2×12 cab: Made of cedar, finger jointed at the corners, covered in blue snakeskin tolex with Eminence Patriot Texas Heats inside
    – A custom Ibanez RG470: Most snobs would turn their nose up at this guitar, but it plays extremely well. Both the tremolo and all the electronics have also been completely replaced and the latter heavily customized…making it one of my favorite axes.

    I started by setting the channel and master volumes on the head to zero and all the Mass controls wide open. I then connected the footswitch and power supply to the Mass (to be 100% clear, the Mass does not require power….the power connection is only needed if you want to use the bypass foot-switch). Then, using a speaker cable, I connected the 16 ohm out from the head to the Mass III and used another speaker cable to connect the cab to the Mass. After double checking all the connections and settings, I flipped the head on and gave it a minute or so to warm up.

    Once the amp was warmed up, I set the attenuator to bypass. Starting on clean, I turned the channel volume all the way up and slowly brought the up the master volume to about 6. That’s a pretty loud setting, but it’s also where I start to get power tube breakup with this amp. After double checking to make sure the Mass was wide open, I turned bypass to off and slowly started rolling back the "Bass" knob to start attenuating. Once I had attenuated the volume level a litle lower, I would ease up the master volume on the amp. Within a few minutes I had the amp wide open and was heavily overdriving the clean channel. I was getting the sweet, crunchy gig level tone out of the amp that I loved…and there was no apparent loss of fidelity either….just volume reduction. It was still loud, but not "pissing off the neighbors" loud.

    I stood there, right in front of the cab, and just jammed on the tones I was hearing for about 45 minutes. I would not have been able to do that un-attenuated…not right in front of the cab. Nice.

    Next, I decided to test the line out. I therefore connected the line out on the Mass directly to my audio interface (balanced TRS to balanced XLR). I then fully attenuated the amp and jacked a pair of headphones into the interface. The raw, unprocessed sound is decent, although somewhat "fuzzy" in the high end. That’s not the fault of the Mass though. That’s just what the output of the amp sounds like without a speaker processing/filtering it. It wasn’t necessarily bad, like fizzy would be. I therefore inserted my Peavey EQ. With some copious EQ settings, I was able to tame the fuzz and make it sound pretty damn good (just to be clear, you don’t need a hardware EQ…a DAW plugin would work just fine either as an insert or used post prod). After hooking up the laptop and pulling some test tracks, I was pretty impressed. I would not solely rely on it for recording, but coupled with a mic or two, it gives me another blending/mixing option. Nice.

    The only "complaint" I have (and complaint is a very strong word here) is that the footswitch cable is somewhat thin. I don’t think it would hold up very long to prolonged stage use. To be clear, this is a very minor issue. The Mass III itself is built like a tank. The rack ears are boxed on the edges for strength and powder coated. Even the footswitch itself seems to be a very sturdy…just not the cable. It’s thin. Again, this is an extremely minor issue as A) I do not plan on using the footswitch; B) any standard latching footswitch can be used; and, most importantly C) the cable works just fine.

    Overall, I am ecstatic with my Weber Mass III. Whether it’s jamming, recording, gigging or just playing at home, I will use this thing all the time. I don’t know why I didn’t buy one sooner. Granted, I’m going to be driving my amps harder so have to change tubes more often, but that’s a small price to pay.

    In addition, Weber’s customer service is top notch. When I first got the Mass and tried it, I was confused about the bypass switch on the unit (not the foot-switch). It’s labeled "On" (up position) and "Bypass" (down position). I noticed that when the switch was set to "Bypass" the Mass was attenuating but when it’s set to "On", it was bypassed. That seemed backwards, so I emailed Weber about it. I received a response in less than two hours from Mr. C.J. Sutton. As it turns out, "Bypass" is the label for the switch. So when it’s set to "On" (up) it means Bypass is On. The down position is therefore Bypass turned off. So that cleared up my confusion. A few days later, when I was rack mounting the Mass, I had a question about voltage requirements for the foot-switch. I emailed C.J. again and he was extremely responsive and helpful in getting me the answers I needed. Thanks again C.J.!

    Bottom line, if you are on the market for an attenuator, I highly recommend the Mass III. The Mass was significantly less money than some of the alternatives I considered and will be able to fully attenuate up to a 100W amp. I can also say for a fact that the build quality of the Weber is excellent, so it’s either the same or better than the alternatives. Finally, those same alternatives are resistor based…not speaker motor based. Better amp response, excellent build quality and less money…where’s the downside again? Also, like I said earlier, customer support is top notch. Thumbs up to Weber as a whole!

  2. Michael

    I use the Mass III to tame my Hot Rod Deville and I could not be happier! It does absolutely everything I had hoped, just better! For recording in an apartment, I run the balanced line out into my interface, use a speaker simulator plug in, and turn the thing up. I have incredible delicious tone in my headphones, and my neighbors wouldn’t have the slightest idea that a 60 watt monster is roaring right next to them. I’m equally impressed at how great it sounds using it to just dip my volume for practices. The 3 band eq really lets you dial in exactly what you want at any volume, and the transparency is unreal! You guys build a heck of a product, fan for life right here. Thank you!

  3. Jacob (verified owner)

    I ordered a Weber MASS III guitar amp attenuator the evening of 21 April 2020 (during the height of the COVID-19 crisis) for use primarily with my Mesa Boogie Mark IV combo, serial number 356. Given its value and difficulty of replacement, I’m very cautious with my Boogie.

    Not only has the MASS III been *EXACTLY* what I hoped (no tone suck at all to my ears!), it was hand-built-to-order and delivered to my door on 5 May – 2 weeks to the day from receiving my order confirmation, with which I also received a personal thank-you email from T.A. Weber himself.

    Two thumbs way up!

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