Greetings,

Today we’re checking out something I’ve had no prior experience with, an op-amp swap!

Burson Audio is an Australian company founded over 20 years ago who specialize in the design and construction of audio equipment and various components within. When Carlos from Burson Audio reached out to see if I would be interested in checking out the V5i for use in my Walnut devices, I had to do some research. Swapping op-amps was an aspect of the hobby I was aware of through forum discussion where people showed off their swaps and other various upgrades to budget devices like the Walnut V2S, but it wasn’t anything I had personally participated in. My device use is generally a little more straightforward, with my efforts towards modding going to headphones instead.

The Walnut V2S and F1 are awesome little devices and quite capable for the price, but they’re also a little rough sounding in the treble and lack depth in the low end. If the V5i could address this it would make for a very appealing upgrade, though in truth it costs more than either one of the players used during my testing. I decided to dig a little further to see if it would be worth both my time and Burson’s to send the V5i to someone with no hands on experience in this particular field.

Checking out the V5i product page (https://www.bursonaudio.com/products/supreme-sound-opamp-v5i/), it was touted to be fast, dynamic, and transparent. Fast and transparent were, for the most part, already addressed by the Walnut bros’ stock op-amps, though I found dynamics lacking, particularly in terms of bass. Both of Walnut’s devices have a clear mid-range and treble bias in stock form, making them best suited for pairing with neutral, warm, and/or dark headphones which manage or compensate for the aggressive treble and edgy nature of their presentation. The V5i sounded like just the thing to deal with this. I replied to Carlos to advise I’d be interested, and two weeks ago a V5i dual-SS op-amp showed up on my doorstep.

**Keep in mind that this is a purely subjective review. There are no measurements, there are no in-depth comparisons with competing products. I don’t have any experience in this area of the hobby beyond this, though I’m definitely going to be diving in further after this experience. Op-amp swapping was fun and seems to be a great way to give new life to an old device.**

Installed in the Walnut F1 and V2S:

Starting with the Walnut F1, note that my testing only applies to the 3.5mm unbalanced output. Also note that I didn’t realize the V5i would be so tall. With it and the battery in place, the top half of the case no longer fits. If you decide to get this op-amp for use in the F1 you’re going to have to fabricate a new way to fit the device back together. Of course, you could always run it with the internals exposed, though that probably isn’t the most brilliant idea in the world.

The stock OPA2604 op-amp is described on a certain retailer’s site as having a “warm and delicate” sound with a low frequency that has “quality and quantity”. I personally wouldn’t agree with any of that, unless talking about low end quality, at least not when it’s plugged into the F1. The stock sound is fairly cold and treble aggressive. You need to use the built in EQ presets to bring up the low end and make it sound anywhere close to warm and delicate. That, or pop in the V5i. With Burson’s op-amp in play, the F1 took on warmer sound with a stronger, punchier mid-bass presence. An increase in sound stage width was immediately apparent, as was the V5i’s reset on your default position relative to the music. Where the stock op-amp is fairly intimate, the V5i sets you back a couple more rows, pulling you away from the artist and giving the F1 a more open and spacious sound. It’s not a night and day difference, but it is noticeable and makes for a much better listening experience, especially once you realize the F1’s edginess in stock form is mostly gone.

The V2S comes with the Texas Instruments (TI) NE5532P, which from what I understand is a pretty well-respected op-amp. Still, replacing it nets similar changes as those experienced with the F1, though not quite as drastic. With the V5i installed, the V2S ends up having a more organic presentation. Texas Instruments’ op-amp applied a colder, more digital feel to the music. I heard a similar improvement in sound stage width, though without as much change to your “sitting position” within the music. There was also improvement in instrument separation and layering.

The most notable thing to come away from my testing was that the V5i gave both players a richer output with a fuller and more robust bass presentation, smoother treble, and a larger sound stage. They come across more open and dynamic with the V5i, and simply put, sound a heck of a lot better. Before, I wouldn’t have bothered pairing either with treble prominent earphones like the ADVANCED GT3 or Echobox Finder X1[i]. With the V5i in place, treble heavy gear is no longer a painful experience.

Packaging and Build Quality:

The V5i arrives in a nice little plastic case sealed shut via a plastic lock and a Burson Audio branded sticker. Inside, the V5i is set within a secure foam block with cutouts present for two op-amps. This case is a great way to ship the V5i because not only do you have a custom tailored area to store it when not in use or during transit, but you also have a place to store the op-amp the V5i replaces, as well as an extra.

The V5i is interesting in that it is a hybrid op-amp; part integrated circuit, part discrete. This probably explains the size since under that sturdy metal casing, which I’m guessing doubles as a heat sink given this little guy gets somewhat toasty during operation, are two micro chips. The 8 pins are gold plated and also pretty tough, unlike the pins on the stock op-amps which required the most deft of touches to keep from bending. It all looks and feels well constructed and durable, handy given the way I conducted testing.

How I Tested and Compared Stock op-amps vs. V5i:

It was very scientific *cough-sarcasm-cough*. First, I removed the top half of the shell of the Walnut device I was testing. I then listened to a song with the stock op-amp. Once that was up, I unplugged the battery and carefully pried the stock op-amp up and out with an itty bitty screwdriver, careful not to bend anything. Then I popped in the V5i, making sure the half-moons were lined up. The battery was reinstalled and I proceeded to listen to the song again. During my listening I noted a few key moments. I would return to these, quickly unplug the battery, swap op-amps, plug the battery back in and listen to that moment. This would be done three or four times per op-amp to note the differences, then I would move on to the next track.

Some Test Tracks:

First up was BT’s “Angels On My Broken Windowsill” from his experimental opus ‘If The Stars Are Eternal Then So Are You And I’. This song was used to test dynamics, sound stage, instrument separation, and layering.

Next was Supertramp’s “Rudy” from ‘Crime of the Century’ for male vocals, timbre, and general tone.

Last was The Crystal Method’s “Grace feat. LeAnn Rimes” for femal vocals, sibilance, and general treble edginess.

I also ran through my regular gamut of tracks for more general testing when I wanted to sit and enjoy the sound of the V5i without analyzing every little aspect.

Final Thoughts:

I wasn’t really sure how much of a difference a new op-amp would make to the Walnut Bros, but after spending some time with the V5i in place I came away impressed. It gives both of these devices more well-rounded signatures than they have in stock form. It warms them up to give them a full, dynamic sound with more refined highs, a thicker mid-range, and a more robust low end.

At 39 USD it may seem weird to spend more on a single component simply to enhance a device that costs less than 35 USD. This hobby isn’t always logical and you don’t always do things because price dictates it. If that were the case, then no one would be “upgrading” their budget earphones with cables costing twice as much, or more. When it comes to these Walnut devices, they are desired for their simplicity, durability, and ease of use. They are basic devices, free of complication, and I’ve gotten plenty of use out of them in stock form. The V5i is a great way to improve their sound quality, bringing new life to a device that maybe you were otherwise ready to move on from. And when that time to move on inevitably comes, the V5i will be right there with you.

Thanks for reading!

– B9Scrambler

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