This is a review written by Terry Ellis February 2023.

For my video review please see my YouTube channel link here

These days, when reviewing equipment, I always ask myself the questions, “why does this HiFi product exist, why has it been designed the way it has and, most importantly, why does it sound the way it does”. Normally, with very high-end amplifiers, and I have looked at a lot of them, these questions are readily answered. Often, very high end amplifiers have what you might call their own super-power of sound, or maybe features that stand out. I think that in the modern HiFi World any expensive HiFi product needs to have at least one super-power to justify its high price when there are so many great products below, say £5k, which make you question why spend more.

Handmade in the UK

AVID HiFi are a UK based manufacturer who may be better known for their turntables and vinyl playback gear. Earlier this year I visited their factory in Huntingdon and saw them making every product they sell in house and in the main by hand. AVID are quite a unique manufacturer in that they manufacture almost the full analogue HiFi chain, turntables, cartridges, phono stages, amplifiers, speakers, cables and even racks. A couple of weeks ago I reviewed their EVO 4 speakers, which made a mark on me as they are certainly different. I have also been reviewing their flagship Integrated amplifier the Sigsum which, no surprise to me, is quite different again.

Overview

For starters, this is a large integrated amplifier. As you can see in the photo, I’m struggling to lift it. It is heavy at just over 31kg although, as I will go into later, it’s not that large and heavy for its price tag of £16,000, high end amplifiers can get very big and heavy.  Inside are some impressively large components such as an 1100VA toroidal transformer, some whopping capacitors, and a whole AVID phono stage. AVID have built one of their phono stages into the Sigsum, the Pulsus, which as a stand alone unit would cost you £2,000, so its quite a good one from their range. AVID say that it benefits both from having its own power supply and an ultra-short signal path to the amplifier.

That means you get a full set of cartridge adjustments for gain, resistance and capacitance which is accessed on the underside of the Sigsum and that means it is quite awkward to get to them to make adjustments.  Power-wise the Sigsum delivers 110 watts into 8 ohms from dual mono amplifiers. This will be enough power for most audiophiles, but it is not massive compared to other big integrated amps at this kind of money from the likes of Gryphon and McIntosh, although the Sigsum has about the same amount of capacitance as the Gryphon Diablo 300, which is impressive.

The Sigsum has a headphone amplifier built in which I didn’t test for reasons explained in a recent video. That is it for features, which seems pretty light for an integrated amplifier in 2023 but I think this tells the story of the Sigsum. It is not a typical modern integrated, it is quite “old school” in its design. The front plate is  about an inch thick with very intricate milled details that reflect the brand identity. The power button is hidden underneath, and it comes on with a ‘clunk’. The extremely useful mute button also engages with a clunk and to select between the inputs, of which there are only three results in a gratifying clunk as well. I love the feel of the controls, there is something very satisfying about adjusting the volume of the Sigsum with its stiff but smooth resistance. As there is no remote control, buyers will be using this a lot and so will learn to appreciate it.  AVID say that they did not build in a remote control system for sonic and technical reasons. I think it is because they have used a specific ALPS RK50 volume control which AVID say is one of the world’s best and they wanted it to stay sonically unmolested by a remote system.

Initially this might seem like the end of the world, but for vinyl listeners who are used to being up and down all the time anyway and, normally, record mastering is consistent and so changing volume all the time is not necessary. I’m not so sure with CD mastering, I woudl expect it to be the same in the main but for streamed music from the cloud being able to adjust the volume regularly is important. Fortunately, most streaming DACs have volume and remote control systems, and you can often change the volume without any signal degradation. Some apps have the option to auto adjust the gain of the music too so it may not be that big a deal unless, for you, it is!

Sound Quality

I have been listening to the AVID Sigsum a lot over a number of weeks with many different speakers including AVID’s own EVO 4, my own Mission 770 and, more recently, the Gryphon EOS 2 speakers ranging from about £3K to £20K. I have been comparing the Sigsum to the NAD M23 amplifier, which is an outstanding amplifier for £3,400. Remember though the NAD is only a stereo power amplifier. I have also been comparing the Sigsum to a McIntosh MA9500, which has over 300 watts of auto-former power per channel, a DAC, a phono stage, eight point tone controls, and more.  The McIntosh coming in at over 45kg makes the AVID look  and feel quite light. The Mac, whilst a big, heavy amp costs a £1,000 less than the AVID at just under £15,000.  Think what you want about modern McIntosh products, but they are a World famous company for a reason and their products certainly always set an excellent benchmark at their price points.

There are a few things which stand out to me about the Sigsum. Its very low noise floor creates a wide open soundstage with excellent space between each muscial element or instrument.  The Sigsum is also very controlled and delivers an ultra-tightly focused sound. For me it sounds like it is taking its music delivery seriously, trying to be honest and deliver the music without the amplifier adding its own character. Vocals are presented clearly and crisply, treble details can pop and shimmer and don’t ever get lost, and bass notes are, in the main, musical notes rather than just a noise, even where there is a lot of bass in the music.  All these traits really stood out when using the Sigsum to drive the AVID EVO 4 speakers, but were still very clearly present when driving the Missions and the EOS2.

For me, the super-power of the Sigsum is its ability to deliver the subtle intricate details of music, the decays, the harmonics, those extra musical details that can easily be lost but you appreciate when critically listening. One album where this stood out to me was the Mogwai Black Bird Season 1 soundtrack, with its dark and deep sustained synth notes. This is an interesting listen when you are in the right mood.

I appreciated all these attributes, particularly at lower volumes, but did find the mid / upper bass of the Sigsum to be a little shy in producing the solidity, impact and warmth I prefer.  The amplifier is excellent for driving speakers to produce a lot of deep / sub bass, but the mid bass presence or fullness was not as prominent as I like. I think I know why and it is to allow for an open sound at all times. When switching to the NAD M23 it is a great amplifier in this regard, but comparing to the big Mcintosh MA9500 is also a little lighter in the mid bass than I feel is ideal for me. However, the overall sound balance of the MA9500 is a warmer and richer listen.

Using a digital source (I tried several), the Sigsum seemed to push the mid-range details a little forward in the sound stage which may be perceived that way because the upper bass is a little lighter. For some music like Melody Gardot Live in Europe, this sounded great because you feel closer and more connected to the live singer. However with other music, such as some electronica I listen to, Faithless – All Blessed, for example, I found it to work less well because it overemphasised the tops of the vocals a little too much.  This had me ringing the changes for the digital source and I was favouring one with a warmer and bolder sound, maybe an R2R DAC like a Denafrips Pontus II, or the Metrum Acoustics Pavanne would be a good choice for synergy rather than an ESS Sabre or an FPGA, especially at louder listening volumes.

Switching to my AVID Ingenium turntable, with the Goldring E3 cartridge as the source, the tonal balance of the Sigsum made more sense to me. It sounded more evenly balanced and with a little less mid-range push although, for me, that characteristic was still there, just not as obvious.

Interestingly, in my initial testing of the built in phono stage, the Pulsus, I was comparing it to AVID’s Pellar phono stage, which is one down in their range and costs £1,000.  I could hear where the built in Pulsus sounded clearer and cleaner than the Pellar. This was for the better as it allowed for a more open and clearer see-through soundstage, so I could hear more of the strength of the Sigsum.  However, the Pellar sounded fuller and thicker, to me which I know is not as good but, nevertheless, I preferred it and it was a little more pleasing to listen to with the Mission 770 and EVO 4 speakers.

Swapping out speakers for the Gryphon EOS2 things were clearly different. This was not just because of their own sound but where they have to be placed in my room. The EOS2 deliver a bolder more bass heavy sound and with these speakers I preferred the clarity of the built in Pulsus phono stage.

Comparisons

Given the closeness of the prices, for me the big comparison here is between the Sigsum and the McIntosh MA9500.

Reflecting on the specification, the McIntosh does sound the more powerful of the two amplifiers. It sounds more solid and secure, more full in terms of tone and bigger sounding overall. These traits carried over when comparing the built in moving magnet phono stages, with the Mcintosh again sounding warmer and bolder but with less refinement and precision.

There is a very noticeable difference in the bass between these two amplifiers. The McIntosh is again bolder and more rounded in its bass delivery, which made the imaging from the Gryphon EOS2 speakers more three-dimensional in the room. I noticed this with Joe Bonamassa-High Water Everywhere, but this was at the expense of some soundstage space noticeable in other music.

The Sigsum always sounds wide open and extremely precisely focused for the small details.  Vocals sounded more bloomed from the MC and with less focus, but more rounded and full and likely more pleasing to listen to across more varied music. The MA9500 just has more grunt to its sound and its very impressive in that regard.  The treble from the Sigsum however never gets lost, it can from the Mc at times at louder volumes

For the modern and electronic type of music I often listen to, and with the Gryphon EOS2, speakers I preferred the McIntosh because the warmer boulder bigger sound always wins me over with that music genre. However, if I was a classical music listener, I think it could be the other way round.

The McIntosh does have a built-in DAC with a HDMI input and that makes it a more flexible amplifier for a modern lifestyle as you can easily attach it a TV. You can do this with the Avid too of course but you would have to buy a unit to do the conversion, but I don’t think the Sigsum has really been designed with that intended use in mind.  The Sigsum is very much a two channel HiFi integrated amplfiier and, to my mind, no doubt heavily vinyl playback orientated, given the rest of the AVID product portfolio.

The McIntosh is definaetly not perfect, the buttons on the front feel a bit cheap, not nice and solid aluminium, like on the Sigsum. It doesn’t have the same luxury knob feeling, and I am not a lover of the McIntosh’s visual design and do prefer the look of the Sigsum. But VU meters are always cool, I just wish they were bigger!

Conclusion

To sum things up, the Sigsum is a very fine amplifier which will tick many key boxes for many audiophiles. However, with the competition at its price, I think this could be an integrated amplifier with more of a niche appeal. The McIntosh, I think, proves this point because it very obviously looking to offer something for nearly everyone as its features have wide appeal. The Sigsum feels like the more specialist amplifier,  aimed more at high a end Vinyilista’s who have maybe spent a lot of money and time on their turntable setup, and preserving the integrity of the musical details from an expensive arm, cartridge and record becomes very important and they may not want an amplifier with any character to get in the way.

My only regret for this review is not having a better turntable setup to test with the Sigsum as that is probably where the true strength or, super-power, of this amplifier and phono stage combination lies.

An Essential Audition Award is granted in recognition of a products high performance but with a certain uniqueness that makes auditioning even more essential.

For the full specification of the AVID Sigsum please see their website linked here