Anyone buying a receiver should consider this new technology!


New member
Username: Edison

Post Number: 27
Registered: 12-2003
Pioneer Sa-xr45 for $300 is a surround digital receiver, and many audiophiles are getting them. Some even compare it to the world class Krell amps.

Upgrade the electric chord for better sound.

Looks slim and stylish too - saves space.

Google search for best price.

New member
Username: Edison

Post Number: 28
Registered: 12-2003
Here is a picture of it - good price on it as well.

New member
Username: Elitefan1

Post Number: 42
Registered: 12-2003
This is a Panasonic, not a Pioneer. It will be interesting to see what develops with this "digital" format. I have seen another brand like this also, I think but can't remember whose.

This is like the thread with the Harmon Kardon DPR 1001 further down. The specs say this thing weighs 9 pounds and puts out 100 wpc x 6?

This must have the same IC amps that Hawk was speaking about in the DPR 1001 thread, and seems hard to believe it would sound like a Krell.

Is there some new technology with all these digital receivers?

New member
Username: Andrew1165

Post Number: 2
Registered: 12-2003
There are class D amplifiers that are often used in professional equipment. Instead of amplifying input signal (class A, B, or AB amplifiers) so that output signal shape follows exactly the shape of input signal and therefore has to waste a lot of energy amplifying DC component of the signal barely achieving 50-60% efficiency at best, class D amplifiers output very short pulses of same [and very high] frequency, same magnitude and varying widths [proportional to input signal] performing what's known as pulse-width modulation. Because class D amplifiers utilize high-efficiency MOSFETs with exceptionally low resistance, they're extremely efficient: e.g. a transistor dissipating only 1-3 watts may easily drive 300-1000W load [e.g. right now I keep in hand a tiny mosfet 1/8"x1/8" in size that can drive 750W load dissipating less than 1W]. So they don't need massive radiators and the like.

Similar technology is used in power supply: switching/impulse power supplies [e.g. widely used in computers] don't need large transformers because, using similar technique, they increase frequency of input power from 50/60Hz to 20-200KHz and thus dramatically increase transformer core utilization.

I think that in very observable future majority of amplifiers will converge to class D, and old-fashioned power supplies with monster transformers will be replaced with impulse PSs.

Thank you,


New member
Username: Feminazi

Post Number: 11
Registered: 12-2003
Here is what Consumer Guide says about it. Not a real reference on audio . . .but they it is decent for the money, if a bit laid back.

New member
Username: Gman

Post Number: 35
Registered: 12-2003
Currently the digital amp modules that are made by one of three companies that sell them to HK and Panasonic are mostly inadequate for big surround sound. The technology has been used in other small systems (from car stereos to and miniaturized consumer electronics, etc). D2Audio is currently selling its modules to HK and they have some amazing abilities, along with a couple of glaring shortcomings for high powered reproductive sound. Texas Instruments sells theirs to Panny and Orient Power in Hong Kong builds them for many foreign and US companies in various consumer products that need to save a lot of size and weight. One TI model is the first to supply 70 watts at 4 ohms with around 0.2% distortion---and sold in lots of 1,000 these amp modules cost $3.95 EACH.

Once they work some kinks out, digital amps will be everywhere--for a few reasons. A biggie is it saves receiver and amp companies a lot of money in sheet metal. These amps allow for the receivers to be 1/4 or so the size of current models. Bean counters love this--and many consumers love this. They are great amps for TV's, plasma sets, anywhere you want small but effective amplification.

The following is from an electronic engineering magazine for household devices. It is worth reading.
With any new technology, quality is the result of smart innovation and exceptional engineering. While Class-D amplifiers have been a novelty in most markets for many years, true analog-equivalent performance has been difficult and costly to achieve. Customers are not willing to trade quality for smaller and lighter components. A new generation of digital amplifiers now exists that overcomes the foibles of previous Class-D experiments.

By incorporating DSP technology into the digital amplifier switching circuit, quantum leaps in performance can be realized. Digital amplifiers work on the principle of Pulse Width Modulation (PWM). In this scheme, the analog signal is encoded into a digital pulse, whose varying width correlates to the amplitude of the signal; essentially, a wider pulse yields a louder signal. On paper, this technique works well. In the real world, things are less than ideal. The PWM signal, switching at 500 KHz to 1 MHz, has artifacts that add noise and distortion to the audio signal. These artifacts are caused by FET switching-overshoot in the carrier signal, ringing in the same carrier signal and overall non-linearity of such a fast signal. That's why less elegant Class-D amplifiers often exhibit unacceptable specs and undesirable sound.

Previous generations of Class-D amplifiers have tried to Band-Aid these inherent design challenges. Some of these patches were successful, but they always add complexity, cost and size to the overall design, often defeating the inherent benefits of Class D. Additionally, designers have always been challenged by the required low-pass filter, which acts as an audio integrator in the Class-D topology.

This filter is inherently susceptible to variations based on the speaker load to which it is connected. While some previous Class-D designs may perform adequately with a nominal 8-ohm load, they can lose significant bandwidth when driving a nominal 4-ohm load. Or they may shut down altogether when driving low loads that are typically found when paralleling together two speakers on an output channel.

The new generation of digital amplifiers has a DSP to correct for these artifacts and load dependencies. This DSP can analyze the internal PWM switching signal of the amplifier, making corrections that greatly lower both the noise floor and total harmonic distortion. While older Class-D designs struggled to get 85dB SNR this new generation of digital amplifier can achieve 110dB SNR or better. Likewise, older and simpler Class-D amplifiers often were rated at one percent or even 10 percent distortion, 0.01 percent THD+N is now possible with well-designed digital amplifiers.

To accommodate for a wide variety of speakers, these new intelligent digital amplifiers offer "speaker compensation."

All speakers have varying resistances based on frequency. An eight-ohm speaker may range from 3.2 Ohms up to 16 Ohms or more at various frequencies. Resistance is typically high at the crossover frequency. Speaker compensation is a technique whereby the amplifier can actually read this resistance "fingerprint" and EQ accordingly. Additionally, bass management can be easily and correctly set up based on the attached speaker's low-frequency capability.

Not only can these digital amplifiers now respond to various loads, but they can also accommodate the wide variety of digital music formats and sample rate directly. Whether 44.1KHz, 48KHz, 96KHz or even 192KHz sample rates are provided, the new digital amplifier can synchronize appropriately without the need to decimate or downgrade the signal. This solves a major problem that has concerned audiophiles.

Perhaps the most compelling aspect of DSP is the ability for the amplifier to exhibit intelligence based on the environment. As we look into 2004 we know that receiver manufacturers will be offering "intelligent digital amplifiers" including new features not possible with old analog amplifier technology. One such feature is room equalization. This feature is already being tested in the analog domain in a few high-end A/V receivers using complex and discreet DSPs. However, the most logical and most effective place for EQ to take place is within the amplifier itself. With a 56-bit DSP, extremely precise frequency response analysis can be achieved and very accurate and effective EQ compensations can be made.


So it is pretty safe to assume that we will all be using digital amps (even in high end apps) in the not too distant future. I can't wait for great technology to improve to the point of being masterful. Let us all hope that the major consumer electric component companies communicate all their needs and desires to the digital amp manufacturers so we can all enjoy a 7 channel 200-300 watt per channel amps that perform better than all current amps while keeping their power high, that the size is just small enough tgo keep all the numerous connections we need or want, and weigh under 30 lbs--so none of us gets a hernia. IT WILL HAPPEN.

Poor standard amp manufacturers. If they are light on their feet and smart--they too can survive and even thrive if the add value and interesting and useful features.


New member
Username: Hawk

Post Number: 34
Registered: 12-2003
I have heard this Panasonic receiver and I was not impressed, at all. In fact, it didn't sound as good as the Onkyo TX-SR501 I compared it to. To compare the Panasonic to Krell is simply ludicrous.

The big mass market audio companies are looking at so-called "digital amps" merely as a means of cutting manufacturing costs, not to provide you with quality sound. I have heard several of these so-called all digital receivers and they suck, to put it bluntly. No, Sony has taken the lead on this as Sony's audio equipment division is losing money hand over fist and it is all marketing hype, including well planted stories in the press. Now, we may well all have digital amps in the future, as suggested by G-Man, but we are a long way from there right now and I am not going to hold my breath.

New member
Username: John_a

Post Number: 45
Registered: 12-2003
Pulse Width Modulation is the method of encoding used in Super Audio Compact Disc, too. And Sony is pushing both. Why? Is there a link?

The Harman Kardon incarnation has some strong support on the thread H/K DPR 1001
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