Shop Keyboard Deals, Financing, and More

AmpRX BrownBox Tube Amplifier Input Voltage Attenuator

5A Input AC Voltage Attenuator for Full-sized Tube Amplifiers, with LCD Voltmeter, 4 Selectable Input Voltages, 4 Selectable Output Voltages, Bypass, and Braced All-metal Chassis
60 Write review Item ID: BrownBox
$349.00

Earn $18 back in Bonus Bucks† OR pay $15/month with 24 month financing*

Free
Shipping
Tech Support

Free Sweetwater
Support

Free 2-year
Warranty
In Stock!

Only 8 left in stock! More on the way.
Add to Cart
Notify me about deals

Ask An Expert

Our expertly trained Sales Engineers are ready to help!

(800) 222-4700
What is a Sales Engineer?
Sweetwater Gear Exchange

Have one to sell?
Check out Sweetwater's Gear Exchange!
Learn More

Most Popular Accessories & Related Items

AmpRX BrownBox Tube Amplifier Input Voltage Attenuator
In Stock!
$349.00
Add to Cart
Add to list
Back to navigation

Written By

Our Product Research Team

Get to know them!

Optimal Voltage for Superior Tube-amp Tone

Whether you're a professional recording engineer or a consummate tone purist, if you want to get the best possible sound from your tube amp, then you need an AmpRX BrownBox voltage attenuator. All tube amps (especially vintage tube amps) are designed to run at an optimal voltage, and standard 120V/AC wall voltage is typically too high for vintage tube amps, as well as some modern designs. With its proprietary 5-amp transformer and flexible attenuation options, the AmpRX BrownBox lets you bring that voltage down to an optimal level, resulting in significantly improved amp performance.

Safe, effective, and easy to use

Another benefit of running your amp at optimal voltage is that your tubes will usually last much longer — something many of us here at Sweetwater who've paid a pretty penny for new-old-stock tubes can appreciate. The BrownBox is far safer and more effective than any standard variac, because it limits the input voltage and attenuates the output voltage. Figuring out your amp's optimal voltage is as easy as Googling the specs, and the BrownBox's onboard output voltmeter lets you see exactly what you're pulling. The BrownBox's four voltage-reduction modes let you get as close to optimal as possible, and there's a bypass setting so you can A/B the results.

AmpRX BrownBox Input Voltage Attenuator Features:

  • The perfect way to optimize the input voltage for your full-sized tube amp
  • Dramatically improves your amp's performance by providing optimized voltage
  • Optimal input voltage also extends the life of your high-performance power tubes
  • LCD voltmeter makes it easy to dial in the optimal setting for your amp
  • Selectable input voltage setting ensures safe and accurate operation
  • 5-amp, 120/122/124/126VAC input settings accommodate most wall voltages
  • Equal or attenuated output ensures that you can't accidentally overload your amp
  • Choose from 4 attenuation modes (3%, 4%, 6%, and 10%) to fine-tune your voltage
  • Bypass mode lets you easily A/B the results of your optimized amp voltage
  • Braced metal chassis and protective bar withstand the most brutal touring conditions

Additional Media

Guitar Amp Buying Guide

Warranty Info

Sweetwater's FREE 2-Year Total Confidence Coverage Warranty

Extra peace of mind at no extra cost.

  • Save money with FREE parts and labor
  • Get back to making music with the industry's fastest turnaround time
  • Fix it the first time with our award-winning, factory-certified Service Department
Learn More about Total Confidence Coverage
2 Year Total Confidence Coverage
$34.00
FREE!

Free 2-year Warranty

Sweetwater's 2-year Total Confidence Coverage™ Warranty gives you extra peace of mind at no extra cost.

Learn More about Total Confidence Coverage
Tools Icon

Save money with free parts & labor!

Fast Icon

Get back to making music with the industry's fastest turnaround time.

Award Icon

Fix it the first time with our award-winning, factory-certified Service Department.

Back to navigation

Tech Specs

  • Type: Voltage Attenuator
  • Power Handling: Up to 540W @ 120V AC (5 amp)
  • Inputs: Line voltage
  • Outputs: 2 x AC grounded outlets, 110V - 126V AC; up to 10% reduction
  • Power Source: Standard IEC AC Cable
  • Manufacturer Part Number: BB-0000-A

What Makes Our Sales Engineers Great?

Sweetwater Sales Engineers are a world-class team of experts dedicated to you. Hand selected from across the globe, each brings a wealth of experience and expertise in the world of music gear to provide you with unparalleled service completely free of charge. Friendly relationships, real trust, and the right gear are only a call or a click away!

(800) 222-4700
Contact Your Sales Engineer
Back to navigation

Customer Reviews

4.9 out of 5

Customer Added Media

Write your review

Get genuine feel and tone of your amp

First of all this is extremely well-made it's built like a tank. Most importantly though, you are allowed to warm up the filaments of your tubes and the internal parts of the amplifier at lower voltage and lower amps which really does provide longevity for the parts. If you have vintage amplifiers that run at lower VAC and require lower amps it's the perfect tool for that. Additionally, you can use it with modern amplifiers creating a different feel allowing the amp to breathe while introducing a slight bit of compression and a touch of sag without harming the amplifier. The bonus is that many of the components including the tubes will last longer the only thing I would say is you may be required to check the tubes and adjust the bias accordingly if you intend to run it at some extreme (cold). I've also noticed that playing live for extended periods that the amplifiers don't run as physically hot (I've heard some times that the amplifiers will get so hot because of the incoming voltage from the outlets in bars and other places being too high that you can't even touch them after playing for 2 to 3 hours even with some breaks with the amp on standby. I have experienced this similarly with my Marshall amplifiers. Generally, it's a very amazing piece of equipment that I think is overlooked largely due to the price as well as some people believing it to be snake oil, but for the quality and service you get I believe it's worth it. As always Sweetwater has been amazing generally I run mine at 117 or 115 and that seems to be where I get the best results you will notice also that your outlets will run anywhere from 119-122 or even 123 Depending on your outlets the edge of your house and how dirty the local power is. All in all a great product I use everyday.
by Sweetwater Customer on

Believe the hype, it’s worth every cent!!

All the previous reviews are spot on except it really does not automatically regulate your voltage, if your supply line is moving around, you still need to change it but it does allow to manually lower the voltage in steps down to as much as 10% or bypass so you'll be able to A/B pretty easily. As I said you'll still need to monitor the voltage periodically because of your supply is anything like mine then it can drift up and down pretty quickly depending on the grid load. The voltage at my house never goes below 120 VAC and can be as high as 123 VAC. I hear a big improvement in tone at around 115 VAC and this is in all my tube amps including my newer Two Rock CRS. Also should mention that my amps were all biased at around 120 VAC and so by effectively lowering the plate voltage it means a colder bias. Even if your biased at 115 VAC, your going to want a way to be at 115 VAC to align to your bias setpoint. Oh and one more thing, I used to just leave my amp on and used the rocker switch on my brown box to power on my amp but over time the switch failed but I was easily able to order a new switch for around $3 and solder it, nowadays I plug everything into a power strip and use its rocker switch, that's also makes it easier to jump into practice too. Lastly the owner, Patrick Geraghty, is a great guy and will also provide support if you need it.
by Coolbreeze from Dallas on
Music background: Blues based music of all genres

Essential for the gigging guitarist with a tube amp!

I was surprised to see 125V at my house. Playing out with it, I have seen 120 to 128V at clubs. I exclusively use tube amps, but not vintage. Regardless, they are designed to run at 117V. I set it to 117V or the next notch below. The sound is clearer, sweeter and slightly lower volume than in bypass. It also does a great "brown sound" if you want to run it at 110V or lower (not how I use it). It believe it will extend the life of the tubes and amp components while delivering the proper sound of your amp. The only thing that could be better about it would be if it were smaller (not sure if that is possible). Highly recommend!
by CC from Scottsdale, AZ on

I’m convinced!

I bought this after I purchased a Friedman small box 50 amp from SweetWater.
I tested the voltage in my house and it was 124-126 volts! And that got me to thinking maybe that's why my rig sounded not as good in some of the places I played and sure enough that's what it was.
This fixed the inconsistencies of different voltages plus I think things like tubes and other electronic components will last longer if you have the specified correct voltage!
And if you have a old Fender amp from the 60's I think this is a must!
by Mitch Willis from North Georgia on
Music background: Pro 57 years

Fantastic tool for tube amps

If you love your tube amps but sometimes struggle to replicate an awesome sound you had going yesterday, at your house, etc. it's possible that your wall voltage is high. I got this just to try it and my amp sounded great anyway... but the wall voltage was 121 and dropping it to 117 made a huge difference in how the amp sounded. Our rehearsal space was 123 and I'd always wondered why my amp sounded a little sterile there. Brought the brown box tonight and cut the voltage to 116 and it sounded amazing. If you don't consistently have the right voltage this is probably worth it - makes a VERY noticeable difference even on modern amps.
by Cabot Nunlist from WILBRAHAM, MA on
Music background: Hobby player and occasional gigs
See also: Attenuators, AmpRX, AmpRX Attenuators & Simulators
Close Close $2,000 Pick Your PRS Giveaway -- input your email address below to enter or click here to learn more.

See giveaway details & rules or check out our past winners!

Enter Now

Success!

Your email, has been entered to win this giveaway. Good Luck!