Universal Audio OX Amp-Top Box

Plug into this reactive load box to push your tube amp into sweet distortion at any volume -- and shape your tone with Universal Audio's speaker cab models.

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Overall User Ratings (based on 4 ratings)
  • Overall:
    4 out of 5 stars
  • Sound:
    3.5 out of 5 stars
  • Features:
    4 out of 5 stars
  • Ease of Use:
    4 out of 5 stars
  • Quality:
    4 out of 5 stars
  • Value:
    3.5 out of 5 stars
  • Manufacturer Support:
    4 out of 5 stars
  • The Wow Factor:
    3.5 out of 5 stars
Overall: 4 out of 5 stars
(4) (see rating details)
Submitted January 15, 2023 by a customer from

"OX has been good to me."

Overall: 5 out of 5 stars
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Verified Customer zZounds has verified that this reviewer made a purchase from us.
UA is a company that charges a premium, yes. But I feel I’ve gotten excellent value unavailable anywhere with every purchase including The OX. This attenuator has worked great, I haven’t experienced the microphone distortion. I’m running modern guitars through modern amps with fresh tubes. With included presets sound comes out of the optical and into my x8p as a beautiful soundscape. If you understand a little more and go beyond presets, there is quite a bit to adjust to your liking. I’ve laid down quite a few tracks that got a tone and effect with a desired separation at a minimum of effort. If you use the cone cry feature with some understanding as well. You can replicate and amp that barks and squeals, as intended. Not microphonic. Now I’ll add that I run a clean amp platform and pedals for beyond that. I reuse power section. El34, EL84, 6L6 AND then switch out the pre’s. The victory v4 series all four (kraken, sheriff, countess, copper) so 5150, modern Marshall, plexi, and ac30 essentially. Again great results on all of it. Ran for several years now. Very satisfied with the product. As with everything, there can be an amount of user error. I haven’t met anyone with a bad ox experience. Different gear has different quarks. Learn your gear, and you can love it for what it is then.
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Submitted January 19, 2018 by jim walker in New york, NY

"Universal Audio OX Vs. Two Notes Torpedo Studio"

Overall: 5 out of 5 stars
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My review of the new UAD OX Verses the Two Notes Torpedo Studio/Live/Cab/Captor Disclosure - I have been using the Two Notes Studio for a year+. And just received the OX yesterday and unboxed & played for 2 hrs. Enough for a basic review for sure. Note I am a guitar player recording in my home studio and not getting paid to do this review. Just wanted to share my experiences after learning plenty on the UAD forum from others. Two Notes Two Notes was kind of the only game in town unless you wanted to cobble together your own Smart reactive load (i.e. SUHR) and then add your own IRs (Celestion, Red Wirez, Ownhammer, etc). Setup - TN Studio Balanced analogue outs into UAD Apollo 8p and listened thru Yamaha HS8 FRFR monitors and headphones. Pros -Two Notes is an open platform, i.e. use your Impulse Responses ( IR's) or the Wall Of Sound IRs. Some of which are quite good. -I get to blast my amp(s) and feel the amp while keeping my destroying my hearing. -Neighbors and family can't hear me blasting amps at midnight. Cons -Two Notes Studio is just too finicky for me. I can't get consistent results. Respectfully, some people disagree with my experience. They says "any good sound requires a lot of tweaking." Agreed but... -After spending time to tweak a good cabinet sound, changing to a different cabinet requires you to start all over again. Frustrating. -The 2 most important controls Input and Output volume are totally inconsistent and results become finicky. -While Two Notes's generic effects are okay but not the same high quality as UAD models for the recording chain. i.e. mic-pres, mic , reverb, compressors, delay. -Two Notes is small company and their support is lacking. UAD / OX Summary: -Just received it today. I unboxed and played for 2 hrs...enough to do a basic review. By the way, the box is as cool as any Apple product packing ...perhaps better. See pics. In summary its simply a great amp add-on. It just works out of the box and sounds clean and/or gristly while capturing the live feel of my amp & guitar. Feels 99% as responsive as playing thru an amp on the edge of breakup I could hear the Cone Cry on higher bend notes. Unbelievable that UA captured that. Setup - Alessandro 15 watt Vox Clone and Fender 1960 Tweed Deluxe, OX Analogue Balanced out into UAD Apollo 8p and listened thru Yamaha HS8 FRFR monitors and headphones. I didnt play thru amps own speaker purposefully to try it at reasonable volume at night at home. PROs -It just works easily. Steps are so basic. 1) Connect Amp out into OX with correct Ohm matched. Plug in headphones or Line out to monitors via Apollo 8p, Turn on Ox, Turn on Amp, Play Guitar. -The Default Cabinets are Great Sounding: 1) Marshall green back, 2) Tweed alnico, 3) Vox 2x12, 4) Tweed 4x10 Bassman, 5) Blackface Champ/Princeton and 6) 2 x12 Divided by 13. Not sure what the last cab is. (See pics for details) -The 2 Fender Tweeds, Champ and Vox models are just fantastic. Sparkly and clean and will light on fire when the volume turned up and extra "gristle" is needed. The Marshall cab is good but I am not a Marshall player. Rig 6 ( 2x12 cab) is good too and has a bit of plate reverb and delay. -UAD says there are 17 cabinets in total using the Ipad or desktop app. But the app wasnt available yet. -The UAD platform is rock solid and captures the soul of the best studio gear.... Some of which i didnt know existed until I became a UAD user a few yrs ago. -Leverages the great sounding modeled gear as a foundation for its recording chain that includes mic-pre, mic , pristine plate reverb, compressors (1176) , LA2, Fairchild, Tape saturation, blah, blah, blah Cons -The number of cabinets are 6 by default but a total of 17 says UA. UA will need to add (or sell) a few more classic cabinets/mic models. My vote is for Fender Dual Showman, 15 inch tweed Jenson, Fuchs ODS, BuzzyFeiten, Two Rock. Or partner with Celestion to mike up the best of. -The cabinet models are less flexible compared to the more open Two Notes platform where you can use 3rd party impulse responses. Some people have invested time /money in impulse responses and not sure yet if this is possible w/ the OX. -Its not rack mountable. So must be placed on top of something i.e. Rack, amp head, etc. -A bit pricey. Although its priced similar to the other complete solutions - i.e. Two Notes Studio of Live. Note: The App to control is not available yet. UA said dealers shipped the OX a week early to time with Namm 2018. Summary Comparison - The UA OX will likely disrupt the market for Two Notes' higher end products (Studio and Live) priced at in the same range.... $1000- $1700. That said, the Two notes inexpensive Captor line is affordable but stripped down version for live & studio work. But overall, the Two Notes Studio is too finicky. Its hard to get consistent results perhaps due to having too many options. It takes too much time to dial in a great sound. The settings change drastically with every cabinet change . But since its an open platform you can add your own Impulse Responses (IRs) . That said, the OX may be able to be used with IRs by disabling the speaker setting. I will followup and check if this is possible since there are cabinet models in the Fuchs amp. Anyway, I prefer to have the mikes placed by an expert (i.e. UAD) and just give me the whole model so i can start playing & recording. Support...Two Notes is smaller company than UAD, their support is lacking. Video & Pictures Below: This Shawn Tubbs demo video shows off a lot of what it can do.

Musical Background:

30 yrs as guitarist /recording music .

Musical Style:

Blues, Rock, Jazz
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Submitted April 26, 2023 by a customer from


Overall: 2.5 out of 5 stars
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Verified Customer zZounds has verified that this reviewer made a purchase from us.
Mine won’t connect to wifi , there is a problem with the wifi chip within the unit itself . Everything I’ve gotten from zZounds is either broke or breaks within a couple weeks or months of owning it . Customer support is rude and I wouldn’t recommend buying from zZounds, even if they offer financing .
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Submitted May 22, 2021 by a customer from

"Do not buy for attenuation."

Overall: 0.5 out of 5 stars
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Verified Customer zZounds has verified that this reviewer made a purchase from us.
The attenuation make your tube amp components emanate microphonic distortion. I found it completely unacceptable for bedroom playing and find it somewhat insulting that UA is claims my amp has always made these noises and I simply did not notice. I would hear that even with the amp dimed(I wear ear plugs AND over ear protection when playing that loud. You can hear little noises over the wall of guitar.) UA will have to earn my trust again before I buy anything UA because they just sapped all their good will with me.
I can’t believe UA would think I would want my guitar amp to make noises like that…and that I would just ignore them while I play LMAO. Keep your half baked beta test.
The modeling was fine. Nothing special. The vibrational noise coming from the components of my tube amp was unacceptable. BS that my amp makes that when I’m not use an attenuators. Also never heard other attenuators do this.
I will be building a recording studio from scratch instead of using this.
Manufacturer Support
UA has an trickle on their website explains away the microphonic distortion as normal. I won’t even attempt troubleshoot this issue with a company that is so scummy as to blame their customers for their own short comings.
The Wow Factor
The hype is real. But it left me disappointed and down right upset. It’s main purpose as an attenuator is just pointless because of all the microphonic noise coming from the components. I can’t mic my attenuated amp with that noise in the room!
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