Is an AV amp really good enough for hifi?
Now, you'll know that I'm not a great believer in huge sonic differences between amplifiers, but I feel I have to chip-in here. I have an (Arcam, about six years old) AV amp and its sonic performance is ruined by the digital hash from all of that computer circuitry which is crammed into the space no bigger than a standard hifi amp. You should see how densely packed the electronics are - there is barely an inch to spare.
Originally Posted by Labarum
And the consequence? Either via RF transmission and/or via the audio signal and/or via the PSU the digital circuits superimpose a continuous and loud mid and high frequency twittering which is completely unacceptable above about 1/4 volume. I do not know if this is typical of modern AV amps. I can say that this digital burbling was evident from new with my amp and is a design issue - hardly surprising bearing in mind how much digital technology is incorporated. We bought it for our last appearance at the London hifi show and, well, the issues noted above were a disappointment for such a well respected brand.
So, my advice - based on the likely AV amplifier's designer's objective to cram the unit with (digital) features - is don't expect hifi performance from any AV amp. I conceded that if you pay top dollars for a big (Japanese) brand AV amp then they will surely have the R&D resources to invest in sophisticated design and testing and may/will minimise the breakthrough issue, but at the budget end of the AV market you just cannot expect all those features and high fidelity performance.
The less digital circuitry in an amp the better chance that all the design effort will be on maximising the audio, analogue side.
P.S. Discussing this with Andy (Prodn. Manager) this morning he says that his old Sony AV amp built before HDMI as is my Arcam - never showed this problem. Maybe my experience is the consequence of subcontract-to-China-on-a-fixed-price and was the best they could do for the money. He's now using a Rega Brio 3 apm with his C7ES3s at home and very happy. And of course, such a simple amp concentrates all the circuitry on the audio performance. Obvious really.
P.P.S. In the hierarchy of design complexity, RF products (mobile phones, satellite comms, radio communications) are the most difficult because the frequencies are so high that signals do not obey nice, convenient, predictable PCB rules. So much depends on the skill of the RF designer to draw on his experience of what circuit layout (let alone functionality) will give the best result. Can you imagine how complex and difficult it is to design even $10 mobile phones? Re-position just one component or PCB track barely 0.1mm and the product may not work (see Apple's iPhone problems). In all digital consumer products every single tiny wire and PCB track acts as its own mini radio transmitter. So it is no surprise that an AV amp has to optimise the design for the fast, digital signals and accept that the analogue audio side must inevitably be compromised.
Alan A. Shaw
Harbeth Audio UK