What dtermines DAC and DSP quality in surround receivers?


New member
Username: Bayboy101

Post Number: 1
Registered: Nov-05
I've just jumped into the HT arena and started researching the specs of different surround receivers. Can someone explain what are the primary variables involved in DSP and DAC processors? I've seen Analog Devices Hammerhead SHARC processors and Burr-Brown DAC's mentioned within specs of some of the higher-end units. Can anyone provide clarification?

New member
Username: Bvg

Arvada, CO

Post Number: 3
Registered: May-06

I am also new to HT, and to a lesser extent to audiophile gear in general, but here's my understanding thusfar:

If you're concerned with audio fidelity, Burr-Brown is a good name. So is Crystal. I've demoed units with and without, and you can clearly hear the difference. Not all BB's are created equal, as you might imagine, but it's a good start. Trust your ears. There's no substitute for a great DAC driven by clean op amps.

Build a collection of demo CD's and DVD's, and go fishing. I like Nora Jones, Keb Mo, Peter Cincotti, Dire Straits, and Annie Lenox, for instance. YMMV. On the DVD side, there's The Polar Express and Private Ryan, each with revealing scenes.

In addition to the DAC's, the quality of the power supply will matter, as does the pre-amp section. If the manufacturer is claiming, say, "125 watts into 7 channels", take a look at the UL rating on the power supply on the back. You will often find it rated to a mere 500 watts or so. Last I checked, 125 x 7 makes 875, and you haven't accounted for heat loss, DSP or pre-amp stages yet, as I understand matters.

As a rule of thumb, I've taken to adding a channel to however many I'm looking to drive, and dividing the power supply rating by that figure. So on a 7.1 unit, divide our 500 watts above by 8. You really have somewhere near 60 watts a channel, if you're driving all 7 simultaneously. If you're only using 5 channels, divide by 6, etc. Think of the wpc spec quoted by the manufacturer as an "up to" figure, as in "up to x watts per channel, provided there isn't too much other stuff going on this instant."

Don't get too hung up on this, but do be aware that spec's are really misleading. 60 watts a channel is plenty for many applications, especially if you have a powered subwoofer doing the heavy lifting in the bass region, so that your HT amp can hand those frequencies off. Woofers suck current big time, and lesser power supplies just run out of kahunas, so to speak.

More sensitive speakers help, too. Look for a sensitivity rating of at least 88 dB on your sats. That's the sound level at 1 meter that they'll produce when fed 1 watt of power. (No, sound levels don't rise linearly with power increases.)

An easy check of the pre-amp section is to run up the power level with no input. Silence is golden. Airplane sounds not so much. Enabling the DSP always raises the noise floor in the units I've demoed. The question is how much.

As far as the DSP section you mentioned goes, I'll leave that to more seasoned folks.

Hope this helps.

Bronze Member
Username: Ravbains


Post Number: 89
Registered: Mar-06
I agree with Aragorn, very good advice.

Don't get hung up on specifications, or technicalities like DSP throughput. Often there is no close correlation between specs/technicalities and real world performnce.

Find a good dealer, who will demo equipment you have shortlisted. Take your time, since it is often a learning process in itself just to realise what is good and what is bad. Often at the start of the process we dont have clear ideas of our own likes and dis-likes.

Take your time, and ultimately trust your own eyes and ears.....

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