The Article
PA40 POWER AMPLIFIER FROM IOTAVX
9th September 2025
A stereo power amplifier in a big box and a useful upgrade tool, Paul Rigby wonders if the SA40 and even Audiolab 6000A Mk.II might benefit?
Pushing out 150W into 8 Ohms as a Class AB design, the IOTAVX PA40 power amplifier is presented in a box spanning 435 x 133 x 315mm, including the feet, with a weight of 9.6kg and a two-year warranty to boot.
Inside is a large toroidal transformer to provide low noise and stable power but we’ll see about that. Around the front is a chunky, square power button and a speaker select rotary knob because you can hook up two pairs of speakers to this one.
Around the back are sockets to connect to a pre-amp, those two banks of speaker sockets, Rec Out sockets which are nice to see for a suitable recording device and two sets of balanced inputs. This amplifier can also work stereo or brigded mode. A rocker power switch and IEC power socket are present too.
And that’s basically it in tech terms. This one is simple and to the point but how does it sound?
SOUND QUALITY
In software terms, I used my China Crisis CD of their debut album Difficult Shapes & Passive Rhythms from 1982 and the tracks Christian, Are We A Worker and Red Sails which enabled me to monitor both low and high frequencies.
The most obvious test here is to use the power amplifier to possibly upgrade IOTAVX’s own SA40 integrated amplifier. A box I reviewed on this channel only a few weeks ago – link above.
VS SA40
I reminded myself of the personality of the SA40 and recalled the good bass response, the precision of the upper mids and the low noise around the treble plus the clarity of the midrange detail. There wasn’t a lot wrong with the sound from this box. Thus, the PA40 was going to have to work to enhance the delivery of the integrated amplifier.
And did it? My goodness it did. Put it this way, listening to the PA40 hooked up to the SA40, after 15 seconds of play? I had to pause the music because I had a heap of things I wanted to say about the differences and improvements of the music delivery as a whole.
First? High-frequency noise had fallen a lot so the output sounded confidant and sure of itself while bass, because of the lower noise floor, was both firmer and better structured. Tonally, the bass was more realistic now.
The stereo image was now better centred. Nailed dead centre instead of the slight wavering I heard before. The bass guitar, which sat right at the bottom of the frequency range could now be easily followed.
The ride cymbal on the left channel was now pushed slightly forward in the mix which gave it more space to work in, enhancing its detail. Those early era synths sounded smoother while there was much more reverb in the back of the mix, adding space and air across the soundstage.
Really. I could write four sides of A4 on the improvements. As such, if you have a SA40 or are planning to buy a SA40 then strongly consider an upgrade or future upgrade when funds allow with the PA40.
But look. The PA40 is not only available to upgrade IOTAVX products. It can be fitted to other HiFi kit too.
VS AUDIOLAB 6000A MK.II
I was fortunate to still have an Audiolab 6000A Mk.II integrated amplifier in my office so I thought, why not hook the PA40 to that. Might be interesting to hear the results.
Again, did the PA40 successfully upgrade the 6000A Mk.II? Good golly Miss Molly, yes. Very much so. One of the headline features of the Mk.II is its bass. I talked a lot about it in the original review but hooking up the PA40 to the Mk.II made me think that the original integrated amp’s bass was a little narrow. Slightly claustrophobic even, because the PA40 opened up the bass on the 6000A Mk.II, pushed it left and right and infused air into it giving that bass a fresh delivery but also spreading the bass across the soundstage.
A strumming rhythm guitar also sounded much more, how can I put this, twangier? There was a really metallic bounce from this instrument now. It sounded livelier too as if the player was much more enthusiastic about what he was doing. The obvious lowering of noise increased the reverb providing a greater sense of air and space across the soundstage while instrumental separation, that sense of space between each instrument, meant that more detail could be heard wherever you decided to point your ears.
IN A SEPARATES SYSTEM
Finally? Very briefly, I wanted to hear how the PA40 would perform in a dedicated separates system so connected it to my Music First pre-amp and compared it to the much more expensive Class-A infused Valvet A1r monoblocks using vinyl as a source and Peggy Lee’s Crazy in the Heart original pressing.
And I was pleasantly surprised how well the PA40 performed. Sure, the more expensive Valvets did provide lower noise and more space around the soundstage but they are monoblocks after all.
Even so, the PA40 didn’t run as hot as the Valvets and the difference in sound wasn’t as large as I predicted making the PA40 excellent value for money for a system populated purely with separate components.
CONCLUSION
It’s a bit of a cliche but there are certain hardware upgrades where you really feel that you have to listen to your entire music collection all over again, such is the measure of improvement, right across the board.
That sense of, “I wonder what improvements I will hear with this one?” is palpable with the PA40. Of course, this power amplifier would work well with any dedicated pre-amp but is also a wonderful upgrade opportunity for any integrated amplifier that features the necessary sockets. As such, I have no problem highly recommending the PA40.
Sometimes, in HiFi, there are no-brainer components. You add them to your system without a thought because you know they will do a job. The PA40 is one of those boxes.
IOTAVX PA40 INTEGRATED AMPLIFIER
Price: €799
Website: iotavx.com
GOOD: low noise, strong stereo image, midrange detail, tonal realism
BAD: nothing
RATING: 8
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REFERENCE
Tellurium Q cabling
Blue Horizon Professional Rack System
Harmonic Resolution Systems Noise Reduction Components
Air Audio AC-2K Balanced Transformer
All vinyl cleaned via Degritter Mk.II
Chord Powerhaus M6 power block
Hi Paul,
Thanks for this review. I found it very informative and the PA40 may be just what I’m looking for to add to my Audiolab 6000a (Mk 1).
I’m assuming it would do as much (and more) for the 6000a mk1 as it did for the mk 2. I would be interested to hear your thoughts, if you would be so kind.
Kind regards,
Marcus
It would certainly help matters yes ,Marcus. The review itself describes the direction of those improvements. Not sure if that constitutes a Mk.II-a-like but sound will definitely improve.