Under the skin of Sony's STR-DA2400ES - chassis, sockets and solder

Tue, 12 Aug 2008, 2:48pm

We had the Sony people in the other day, bringing the new STR-DA2400ES receiver. And while we haven't got round to giving the thing the full test workout - we don't do listening or viewing with the proud (and slightly nervous) 'parents' looking on - we have now had the full technical rundown on the receiver, which Sony clearly sees as one of its key home cinema products for this autumn.

In fact, along with the receiver came what European Technical Marketing Manager Eric Kingdon called a 'Technical note': some note, running as it did to 28 pages of A4 with copious charts and diagrams! But then that's Eric for you - it's indicative of how involved he gets right down to the nuts and bolts of a product.

Or, in this case, right down to the cutting out of little copper dampers to fit on the top of the main power supply caps, in the snug workshop area at the back of the main listening room at Sony HQ in Japan.

It's there he works closely with the Chief Distinguished Engineer of Sony's audio division, Takashi Kanai, who's developed more products than most of us will ever own, and is an inveterate tweaker, not to mention a perfectionist. And if you want to know how much of a perfectionist, this is what he does as a hobby.

Aiming for Onkyo?
Anyway, back to the STR-DA2400ES, which looks like it was designed with the aim of being Sony's Onkyo-beater, It sits above the STR-DG820 in the range, and has two more models above it, the STR-DA3400ES and STR-DA5400ES, the latter being something of a 6 HDMI in/2 out monster. But at £500, the 2400 is clearly very much the core product.

And the receiver comes fully loaded, not just with features but with typical Kanai/Kingdon design tweaks. The chassis, for example, is a fairly simple sheet metal one, but it's embossed in various places to aid rigidity without adding mass, and spread the load of heavy components such as the power transformer and heatsinks.

Off-centre screws
Also in place are feet with off-centre mounting screws – because they sound better, of course – while the solid aluminium front panel has a further sub-panel behind it, thus isolating the display circuitry, a potential source of electrical noise, from the receiver's audio circuits.

Even the heatsinks have been redesigned: they're big, they're heavy and they're even sculpted to damp out resonances.

All HDMIs are not equal
The circuit layout is kept as short as possible, both on the audio and video sides, and it's interesting to see that one of the HDMI inputs is labelled "BD IN (for AUDIO)". Now there's on for the 'digits is digits' brigade - surely all four of the HDMI inputs handle audio as well as video?

Well yes, explains Kingdon, they do - it's just that the BD input is closest to the HDMI switching in the receiver, and thus sounds better, he says.

Smarter solder
Oh, and finally, let's talk solder. Yes, solder. Sony, like other companies, has had to give up the use of solder containing lead, due to regulations on the reduction of hazardous substances in products. So it switched in 2003 to lead-free solder, choosing the one with the least detrimental effect on sound quality.

Even so, the effects were there, not least because the 'safe' solder sets with a rougher surface than the original, and high frequencies tend to flow better on the surface - the so-called 'skin effect'.

So Sony has now come up with its own audiophile solder, which is almost pure tin with just 0.7% copper to lower its melting point and thus restore the smooth surface. The result, the company says, is even better than the original solder managed, with "a natural, rich texture and atmosphere" and a more enjoyable sound with voices.

That's the kind of thinking that's gone into this receiver - a mixture of getting the features right and applying some good old-fashioned audio tweakery.

It'll be fascinating to see what the review team makes of it.


Anychance that you could PDF the 28 page Sony file for download?

Sorry, but it's purely an internal technical briefing document

Hmm. I'd like to see if he could come up with a plausible explanation for subtle audio or video differences with a digital signal. Clearly HDMI signals are high bandwidth, and square waves have lots of harmonics, so a good/short cable/path is going to deliver a better signal to the other end than a poor/long one - but since this is a digital signal, all that's likely to change overall is the bit error rate, and those errors will either get fixed by error correction code if there are few enough, or not fixed if there are too many or they appear to be valid. And if they're not fixed, the error is as likely to cause a big difference to the value as a small one... so I can see how you'd get different error rates, but not how you could get that to produce subtle differences.

All that taken on board, but EK simply says that input sounds better.

And since it's not costing any more to implement, what's to worry about?

Lots Smile

I suspect the engineers actually said 'we used the shortest possible signal path for the highest quality source' which is good engineering practice, and that marketing then hyped it up to 'and it sounds better'.

If it's actually TRUE that it sounds better, then what they're saying is that the design is so broken that they can't route the other digital inputs a few cm more without degrading them badly enough to cause an audible quality loss - so that the BD input is the only one that works anything like properly!

Remember that we're talking digital switching of 1s and 0s here, so it only has to ensure that a 1 stays a 1 and a 0 stays a 0 - we're not in the analog stages where subtle differences can come into play; if the other inputs sound worse it can only be because they're trashing the input bitstream - and in only a few cm, too.

Since I reckon that's unlikely for Sony, my money's on over eager marketing bods shooting themselves in the foot by not thinking the consequences of their claims through Smile

Despite his job title, Eric is much more closely involved in the development and detailed tuning of the products from an engineering perspective.

And having spend a good deal of time with Kanai-san in his listening room, he's not the kind of person to get involved in such marketing nonsense.

So bang goes that theory, though I suspect that won't convince a paid-up 'digits is digits' believer.

So we have a real engineer saying, in effect, 'because of the way we designed the switching, the other inputs introduce a noticeable degradation in audio quality'. Seems very odd for a company as good as Sony Sad

I hope it's one of the things the review will test out - when I go shopping for an amp, I expect all the inputs to work properly... I could maybe understand minor differences for analog sources, but there's no excuse for digital.

No, he's not saying that at all, either in effect or fact.

It's just the way you're choosing to misread the comments.