Fosi ZA3, Go Big When You Go Home

Five Op-Amps To Play With, Including The Powered Sub

Double Your Fun With Two ZA3 In Mono Mode

Fosi expanded their imaginations and created something a little different from their previous Class-D amps with the Fosi ZA3.  This model is significantly larger than the previous ones, it takes up the space of a hardcover book as opposed to a soft cover, and there are several reasons for this.   The improved heat dissipation is an obvious one, and the active subwoofer out adds a little real estate to the PCB but the two new balanced XLR inputs really add to that extra girth.

The inside features five replaceable Op-Amps in total, left and right channel outputs, balanced input, and subwoofer output.  If you are of that persuasion, Fosi lists several alternatives on their page you could pop in, or experiment with them on your own.  Do be careful if you try this at home, Op-Amps really don’t like it if you get the chip direction wrong when you insert them, thankfully Fosi properly labelled everything.

Fosi sent one over a bit before release, they are currently taking pre-orders for a January 31st release, with a 15% discount code (PZA315) and free shipping if you indulge yourself.

A Different Take On A Fosi

The ZA3 is a little different from the previous models we’ve tested over the years, which tended towards simplicity with about the only extra feature we saw being the Bluetooth support on the BT200 Pro.  The Fosi ZA3 adds proper subwoofer support, powered as opposed to the left and right channel which have always been passive and remain so.  It also adds the aforementioned balanced XLR inputs to the RCA if you want to hook your ZA3 up to professional equipment.  You will also spot a 12V trigger on the back, so you can power on your audio source simply by powering up your Fosi.

The front sports an XLR/RCA toggle with an obvious purpose, but the Mono/Stereo switch hides a new feature.  You can buy two Fosi ZA3s and set them to mono mode, with your channel inputs split between them.   This is great if you don’t like your hearing, stereo mode can drive your two channels at 155W but in mono each channel can get up to 235W.  The power adapter has been upgraded to handle that, the 32V @ 5A brick that has shipped standard with all the previous models can be upgraded to a 48W @ 5A model, for a bit more money.

Adding To An Already Good Thing

Fosi listened to their customers in a number of ways, including making the copper dial the default and keeping the Taper A pot behind it every bit as good as on previous models.  The Fosi ZA3 will also remember the volume you last used before turning it off, so if someone happened to adjust the volume knob either inadvertently or purposefully, you won’t blow out your speakers the next time you power it up.  Fosi did also move the power to that knob, you depress it for two seconds to power on or off instead of having a dedicated power toggle.

The technical specs are similar to the Fosi V3, up to and including dropping the treble and bass controls in favour of a more natural sound.  The SINAD, SNR and THD remain essentially unchanged, which is to say they aren’t going the match an audiophile amp but for one costing just over $100 they remain very impressive.

The extra power contained in the ZA3 is dealt with by upgrading the cooling system first seen in the V3, adding vents to the side in addition to the heatspreader under the Texas Instruments TPA3255 amp chip.  With a bit of work with a TR8 bit and some pliers, you can expose the chip as well as the Op-Amps.  A bit of work with some tweezers and lining up the O1 on the board with the one on your new Op-Amp and you are ready for a new sound, or the old sound if you managed to kill one of your channels somehow.

Dual Monoblock And Active Sub Out

Audiophiles, at least some, love their Class-D monoblocks.  They will tout the benefits of separated power supplies, the ability to adjust channels independently to hear the balance as the composer intended instead of desecrating it with an amp that has two internal channels, and so on.  With the Fosi ZA3, well two of them to be technically correct, you can accomplish this as long as you take care setting it up.

Make sure that you both toggle both Fosi ZA3’s to mono mode on the front and only connect speakers to the posts specifically marked as for mono mode.  You plug the right channel RCA cable into the right channel plug on one ZA3 and take the left channel and plug it into the … right channel … on the second Fosi.  The source determines the channel, not the Fosi for this is The Way.

A YouTube test video featuring female vocals on the left and male vocals on the right was alright, however the version of On The Run from the Pink Floyd The Dark Side Of The Moon 50th Anniversary 2023 Remaster doesn’t lie.  It ran around the room just as it should.  Personally, I find the stereo mode of a single ZA3 every bit as good which can be good for your pocketbook, if not as good for Fosi.  You can see the amount of speaker wire I have connect and judge my sanity for yourself.

One thing that has always been missing from Fosi’s Class-D amps since the beginning has been subwoofer support.  While you can certainly live without one, life is better with lower frequencies and Fosi now offers a proper 2.1 system.  The ZA3 introduces a sub out, a single RCA jack which provides a mono signal to your subwoofer.  The cable you need depends on the sub you choose, one with a clearly marked mono input should work with a single to single however the Edifier T5, which this review provided a great excuse to pick up, wants a single to dual RCA cable to function.

The bass output is clear, no humming detected because of the Fosi ZA3 itself.  The quality does rely heavily on your sub, wiring and electrical load but if you can isolate them then you should be good to go.  The sub out and mono mode are mutually exclusive, when in mono mode the Fosi ZA3 will only send signal to a single channel.  If you are bound and determined to do both, ensure your sub as a pass through so you can send signal to it first and then to your two Fosi ZA3 amps.

Encore, Encore!

The first time we heard Fosi was back in 2022 with the TB10D TPA3255, an almost pocket sized amp that didn’t make much sense at first.  Why would one want a paperback sized stereo amp; how good could it be?  As it turns out, I’ve dumped my old Kenwood and have been using Fosi exclusively since I first laid ears on them.   The size is wonderful, it takes up next to no space and the sound is so much bigger than expected.

Since then they have sent three more models for review and in every case they got a bit better.  The BT20A Pro added the iconic copper coloured volume knob and Fosi realized that customers were very interested in Op-Amps.  They included the specs of the four present on the board and ensured you were aware two of them could be swapped out.  It also tossed in Bluetooth 5.0 connectivity as a very nice bonus.

Next up the V3 offered a more balanced approach, dropping treble and bass and adding better heat management with a heatsink connected to the body of the amp.  This was a definite bonus for those that know someone that loves to constantly twiddle the knobs and while I’ve never had heat issues with the previous two, better cooling is always appreciated.

The price of these previous three models never exceeded $100 MSRP, and you got great value for the money.  There are a flood of models now to check out and as long as you only need to deal with one source they will likely do wonderfully.  While we can’t speak directly to them we can tell you that the new Fosi ZA3 lives up to it’s predecessors.

The ZA3 will cost you a bit more, but also adds more flexibility internally and externally.  There are now four Op-Amps you can replace at your leisure and Fosi have added balanced XLR inputs in addition to their traditional RCA.  You can switch to mono mode, and above all else you get the convenience of controlling your subwoofer and source via the Fosi instead of having to turn them on separately.   This does bring up the price a bit, but if these options appeal to you then the extra cost is negligible.  Those who really love their volume, or arguing about peak versus RMS wattage can spend a bit more for the 48W power supply and really show off their speakers.

If you are looking for something that speaks XLR to pack with you and hook up with professionals or are looking to set up a simple 2.1 system in a small space you can’t go wrong with the Fosi ZA3.  If you don’t need the connectivity and have no dreams of buying a subwoofer in the future any of the previous models will server you well.  If you want that something more, the extra cost of this model makes financial sense.  Once again Fosi delivers exactly what we expect from them, and we look forward to the opportunity to see what they can come up with next.