Integrated Amplifiers

Maybe one grows less ornery with age, or perhaps there was a nice guy inside of me waiting to crawl out from my crotchety self. It's just that, only a few years ago, the frustrating elements of AVID's Sigsum integrated amplifier would have had me cursing Editor PM for asking me to review it. So, there's minimalism here, and there's contrariness, and that's just the lack of a remote control. In a product a fiver short of £15,000.

Let's look at this in context, even though this isn't the place to argue about integrateds versus separates. You are seasoned audio enthusiasts and you know each have their strengths and weaknesses. With an integrated amp, there's no possible mismatch between preamp and power amp, you save the cost of an interconnect, etc, while separates deliver better isolation between pre and power sections, provide an easier upgrade path, and so on.

No Wallflower
You can see the dilemma this presents at £15k. Simply put, there are far too many pre/power combinations available for this money. To which you might counter: 'I only have space for one component' or 'It saves me an AC outlet'. What the Sigsum does, however, is deliver a unit so massive, so heavy, so over-engineered that it looks like it eats twee SET tube amps for breakfast.

Either way, the Sigsum is neither shy nor retiring, occupying a capacious 471x190x500mm (whd) and weighing 31kg. The first doesn't matter, because it's no worse than any high-end stereo power amp from the likes of Mark Levinson or Krell. But 31kg? I note the engraved 20mm-thick alloy front panel, the 3mm steel chassis, the huge toroidal transformer – all very reassuring, but arguably a little more voluminous than it needs to be.

Back to context. I realise most of you do not change cartridges on a daily, weekly, monthly or even annual basis. For you, the location of the phono stage DIP switches is irrelevant. But to place them under a 31kg amp? It's one thing to site them beneath MoFi's UltraPhono [HFN Mar '20]: it's the size and weight of a deck of cards. But as the user who spends £15k on an amp is also likely to have more than one cartridge, this inconvenience is unfortunate because the phono stage is truly excellent.

Its options cover pretty much all mainstream MM and MC cartridges you might encounter, offering gain settings of +40dB, +60dB and +70dB, impedance of 100, 300, 500ohm, 1kohm, 5k, 10k and 47kohm, and capacitance levels of 100, 200 and 500pF. But I let out a sigh… recalling AVID's Pulsus, on which the Sigsum's phono stage is based and which I reviewed back in 2012 – it consists of two small boxes, and it was so easy to flip over the 1kg preamp section.

Weapon Of Mas Instruction
I realise we're venturing into the let's-agree-to-disagree arena, but AVID's CEO Conrad Mas has firm beliefs here. This amp is equipped with one of the best volume controls on the market, a lovely ALPS RK50 device, each costing AVID a small fortune, so why no remote? Mas stated flatly that, for him, 'The Sigsum is all about sound and build quality'.

He further explained that none of AVID's amps offer remotes, having come to this conclusion after discussions with ALPS. Still, that doesn't explain why US tube brand VAC, which uses the same pot in its flagship Master Preamplifier [HFN Mar '21], has a remote and I don't recall that suffering for it. Mas also argues that turntables aren't remote-controlled and 'LP users are used to getting up and down, so adjusting the volume isn't an issue'. Maybe not for him.

So, once more, context. You are unlikely to site a 31kg beast of an amp next to your elbow. That said, this has a headphone output, so you'll need a long cable for your cans – or perhaps you will then place the Sigsum next to your hot seat. In which case, the remote control issue is moot.

Whining over. Sigsum – its name comes from 'the SUM of two SIGnals' – is impressively styled, easy to use (phono settings and remote control aside, that is), and provides, in addition to the phono input, two RCA line inputs and two balanced XLR inputs. Derived from AVID's Reference Pre and Mono amplifiers, the Sigsum's preamp section and phono stage reside on one PCB, while the power amp is configured as two mono modules. Power is provided by a massive circa-1kVA mains transformer, with a separate PSU supplying the phono stage.

Take A Seat...
Unpacked and located, the Sigsum is as straightforward a product to install as you could imagine, provided you set the phono stage DIPs before siting it. The back is fitted with top quality connectors for both the XLR-balanced and RCA single-ended inputs, the speaker terminals are multi-way, and the seasoned user probably won't even need to look at the owner's manual but once – to find the on/off switch underneath the unit, at the front.