Onkyo TXSR 705 and TXSR 805 AV receivers.

Manufacturer: Onkyo USA, 18 Park Way, Upper Saddle River, New Jersey 07458; 201/785-2600; www.us.onkyo.com

Prices: $900 / $1100

Source: Manufacturer Loan

I am not listing all the features, I/O connections, and specifications to save space. The complete rundown is on the Onkyo website, but I do want to take advantage of Onkyo's nifty table for high-end AV receivers, which summarizes the progression of features for Onkyo's product line. A line in the sand is drawn with the TXSR705, which raises the bar to include an Audyssey MultEQ XT room equalizer and HDMI 1.3a inputs with full decoding of Dolby and DTS high resolution signals.

The Audyssey MultEQ XT is the best Audyssey room EQ found in an AV receiver. Other product literature aside, all Audyssey MultEQ XT enabled receivers use the same algorithms and achieve similar results with similarly-calibrated microphones of similar quality.

The HDMI 1.3a inputs improve the versatility of the Onkyo receiver. Using an Oppo universal player with updated software (see Ramblings for more on the software upgrade), I decoded SACD and DVD-A without problems. Note that not all HDMI 1.3a receivers can decode SACD DSD streams. You need to check the on line instruction manual before you make your purchase.

I do not have an HD DVD or Blu-Ray player, so cannot speak to compatibility issues with high-resolution 7.1 Dolby or DTS decoding; nor can I comment about the performance when special features, such as the second audio track, are engaged on a HD disc. Check for reviews of this product in magazines and webzines that emphasize video if high-definition video is on your to-do list for an AV receiver to see if they found compatibility issues.

Based on the chart, there are minor differences between the TXSR705 and 805, except for the THX certification. The Ultra THX certification sets apart the Onkyo TX-SR805 at its price point. THX is not forthcoming with its certification criteria, but there appears to be some correlation with build quality. Moving up the line brings improved video in the form of a higher performance deinterlacing and 1080p up-conversion chip. From an audiophile's perspective, little is gained except an ability to bridge the front channels. The more advanced TX-NR905 has a networked receiver for internet radio, audio streaming, and a USB front input. HD radio is also featured. As with the Yamaha 2700 of our last issue, a comprehensive graphical user interface (GUI) is mission-critical for a networked receiver. Since I did not review the TXSR905, I cannot comment on the relative quality of the Onkyo GUI.

Other manufacturers have chosen different paths, not only from the perspective of price (others charge twice the price of the TX-NR901 for their top-of-the-line), but also improvements in the audio section may only occur in parallel with upgrades of other aspects of the unit. For example, the base receiver might be first enhanced as a networked receiver, followed by one with wireless connectivity, before the audio path is upgraded. Other manufacturers may dive right into advanced video signal processing, even to the extent of adding picture-in-picture capabilities. This is how the most video-centric (no surprise here) Sony line progresses. We are presented with a situation, very different from the past, where the distinguishing features between lines of receivers might involve one with low- and high-pass filters and the other with an added meter for center-tuning to ensure the tuning knob is properly positioned. Comparing current lineups, TX-SR805 is the most important audio upgrade offered at the second rung of the ladder. Indeed, I cannot imagine very much more could be done on the audio side given size and weight constraints of the class AB power amplifier in an AV receive (see below).

Ergonomics plays a distinct role in Onkyo's design. The row of function buttons on the front panel is far preferable to the typical rotational control. With a rotational control you have no idea what the next input will be as you move the control to the left or right. The two button listening mode switches on the front panel lets you cycle through the available decoding modes such as Dolby PLII music, Neo 6 Cinema, Onkyo original DSP modes, etc. I would like to see more buttons on the front panel to select these modes directly. The remote has a couple buttons to help in the selection process but it still is not enough.

The well-designed on-screen display is not fancy, but its man-machine interface is well conceived and virtually obsoletes the instruction book unless you are doing something complex like overlaying surround synthesis modes on a Dolby Digital encoded DVD. That said, the instruction manual is nearly silent on how to engage the XM mode, though I was able to decipher that it must be entered as an option in the tuner mode. I could not figure out category search and direct-number access, and the whereabouts of the signal strength meter required to help aim the antenna also remains a mystery to me. Adding on to this soft patch an XM display that does not list all information about the program being transmitted (the display is limited to the station number, title, and the work being played on classical stations with the performers left for you to guess), it becomes apparent that XM Satellite radio is an area of weakness for the Onkyo (I did not have access to the Sirius front-end).

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

[ILLUSTRATION OMITTED]

I evaluated the Audyssey MultEQ XT with my Phase Technology 3.1 II speakers in my large room. Entering the calibration mode is simple; connecting the microphone to the front-panel input jack turns it on. You then follow the instruction on the TV display. Figure 1 shows the uncorrected measurements (raw data and average) for the left-channel speaker followed in figure 2 by the performance of the TX-SR705 with the MultEQ XT in the signal path for the maximum allowed eight position microphone measurements taken around a couch that sits 3 people. All Audyssey MultEQ XT in receivers have the optional midrange compensation (please refer to our review of the top-of-the-line Audyssey Sound Equalizer in the prior issue of TSS). The Onkyo curve generated for the left channel and its correspondence with the Audyssey Sound Equalizer (not shown) is amazingly good below 2kHz. Above 2kHz, the Onkyo does not return to base line, but stays 3dB down. The Sound Equalizer and Onkyo regain commonality around 8kHz. Audyssey engineers with whom I spoke suspect the Onkyo supplied microphone is the source of the mismatch between 2kHz and 8kHz. This is not surprising since the Audyssey microphone included in the professional installer kit is more expensive and individually calibrated. The dip in the Onkyo response is a byproduct of a peak in the microphone response. Sourcing problems at Onkyo prevented them from sending me other microphone samples to see if they might have a flatter response. Audyssey manufactures its own low-cost microphone in the hopes of delivering a flatter microphone given the cost constraints. This Audyssey manufactured microphone is sold with some competitors' units, but not by Onkyo. All Audyssey EQ systems in AV receivers have provisions for a calibration curve that is the average response of the microphones shipped with the receiver. The calibration curve for the Onkyo microphone is different from the Audyssey-manufactured low-cost microphone, so plugging it into the Onkyo would create confusion and guarantee an error that is no fault of the Onkyo.

Moving to the right channel (figures 3 and 4), a low-frequency peak persists after equalization with the Onkyo but is smoothed out with the Audyssey's Sound Equalizer (not shown). The 2kHz-8kHz depression in the Onkyo correction is similar to that of the left channel. The MultEQ XT is less effective at the low end because the compute power is reduced by two-times relative to the stand-alone Audyssey built Sound Equalizer. All seven main channels have the same level of signal processing. As you will recall from the last issue of TSS, the Audyssey Sound Equalizer reduces processing on the rear channels.

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

More processing power will be devoted to the room equalization functions once the technology is re-scaled to 45n meter technology in the digital-signal processing (DSP) processors, however this may take over a year to happen. Despite the roughness in the lower bass frequencies, these are the best results from an AV receiver that I have seen.

The Onkyo comes surprisingly close to the $2000 Sound Equalizer, which requires professional calibration and a separate pre/pro. The loss of energy in the 2kHz-8kHz range is audible, meaning there are some situations (e.g., poorly designed speakers with frequency response deviations, rooms where optimal speaker placement is impossible, or acoustically very dead or very live rooms) in which the MultEQ XT offers manifest improvements across the full frequency range. With well-designed speakers, I wish they had a mode to stop equalization above 500Hz. Below 500Hz the room dominates the response and not the speaker until the speaker low end limit is reached. The MultEQ XT does an excellent job from 500Hz down to 100Hz and partially effective below that for the main channels. The excellent flattening of room effects in the 100Hz-500Hz region improves sound quality for any speaker.

The sub-woofer channel uses a disproportionate share of the MultEQ XT's compute power eight times that of the main channel with an upper limit of about 300Hz. I have not tested the sub-woofer channel yet, but the allocation of compute power suggests better results may be achieved when a subwoofer is in the system and the satellites have a limited bass response, putting the crossover in the 80Hz range. Audyssey picks an immutable crossover frequency for optimal performance with respect to blending the satellite and sub-woofer, making it impossible to employ full-range speakers, a sub-woofer, and a high crossover frequency. A satellite-subwoofer system used with the Onkyo TXSR 705 is in my test queue for the next issue of TSS.

In summary, the TXSR 705 is the lowest priced AV Receiver that not only adopts the Audyssey Mult EQ XT, but also offers full HDMI 1.3a decoding. Accordingly, all high resolution sources are decoded digitally within the receiver and the Audyssey equalizer remains in the processing loop for any input source. For under $1,000, you can hear what SACD and DVD-A are supposed to sound like provided your speakers are in the ITU configuration. In a stereo-only system, the Audyssey remains a benefit over an unequalized room in the important 100Hz-500Hz range with a likely improvement down to 30Hz assuming a properly configured satellite-subwoofer system.

If you are only interested in stereo, I have no cost effective external DSP equalizer to suggest, even if you already have a stereo electronics with the capability to accept an external equalizer. External digital equalizers for stereo signals, let alone seven channels, are not available anywhere near the price of the TXSR 705 and there is no stereo EQ system I know of that has internal digital sub-woofer EQ and bass management. The TXSR 705 is thus a good choice for some stereo only installations especially with a satellite-subwoofer system. Just make sure you can live with the voicing above 500Hz that the Audyssey system imposes in conjunction with the Onkyo microphone frequency response errors.

The TXSR805 is well worth the $200 price increase. I am not aware of any other AV receiver or Pre/Pro built as well as the 805 (see below) although I do not have access to schematics from many current units priced over $2000. The 805's power amp is state-of-the-art for a receiver. You would need a separate power amplifier to generate more current drive or voltage swing, a situation that would arise only with inefficient speakers in very large rooms.

Thirty five years ago, multi-channel audio flopped for a variety of reasons including our old nemesis of no single standard for playback of the source material. The revival of multi-channel audio with Dolby Pro Logic shook things up twenty years thereafter; but what you bought one year was readily obsoleted by next with such advances as Dolby Digital, SACD, and DVD-A. The promise of the latter two remained unfulfilled because there was no method to hook them up with a digital cable. Yet another upgrade of universal DVD and AV receiverss was required to get the correct HDMI ports. We actually had a progression from HDMI 1.0 (no audio all) to HDMI 1.3a over a two-year period with newly minted units being issued in six-month product cycles! HDMI 1.3a may be the final interface for the highest resolution audio, including Blu-ray and HD DVD, though videophiles may be on a more accelerated trajectory.

Matching five satellite speakers to a subwoofer (bass management) without response anomalies is not solvable in the analog domain, but can be accomplished digitally. Digital EQ has evolved since its introduction in expensive standalone units in the late 1990s. After several iterations on AV receivers digital EQ systems (again on something close to a 6 month cycle) most of the performance of top tier external digital EQ systems include our recently reviewed Audyssey MultEQ XT and Trinnov (which is scheduled for release in a $2000 receiver in the middle of next year) have already started to migrate to affordable receivers such as the 705 and 805. The trajectory of improvements in digital EQ is likely to turn more shallow as the largest advances are behind us. The issue of better performing low-cost microphones has become the major impediment to the advancement of low-cost room EQ at least for the Onkyo units. The ability to select from a wider variety of target curves including one that stops EQ above 500Hz is also a remaining issue. Given what appears to be a stabilization in technology it may now be time to pick up an Onkyo 705 or 805 and hold on to it till at least the end of the decade without feeling left behind.

The Onkyo TXSR 705 / 805 may have arrived too late to save multi-channel audio in the form of SACD. For those of you who crave simultaneous video with your music, such as high-definition opera, software is not the bottleneck. Final establishment of all the operational modes possible on Blu-ray or HD DVD do, however, remain an open question. These modes should not be important for material that is music dominated. If SACD does flop and you have no interest in video you find yourself back in stereo. Even as a stereo receiver the TXSR 805 will nonetheless provide performance at near the state-of-the-art for years to come as discussed in the circuit analysis below.

The new Onkyo line is revolutionary in bringing state-of-the-art analog- and digital-signal processing for eight channels to a $1000 price point. Twenty years prior, I would have predicted the likelihood of these units as equivalent to the likelihood of a man on Mars in 2008. From George Jetson's living room to yours ... this demonstrates the remarkable decline in manufacturing cost for mass market electronics and the capability to manufacture high performance DSPs, application specific signal processors (ASSP) and digital-to-analog converters (DACs) for several dollars apiece. It is also reflects the marketability of home theater over space travel.

[ILLUSTRATION OMITTED]

Inside the TXSR 805

A state-of-the-art Pre/Pro, with full buffering of the analog inputs, requires over 80 operational amplifier sections and 26 sections alone for analog input buffering. How many times have I said that it would be impossible to use the near state-of-the-art NE5532 dual operational amplifiers in all these sections and still build a Pre/Pro for $3,000. Well, here is a complete AV receiver with NE5532 operational amplifiers in all sections, a new benchmark for the price point.

The HDMI receiver is a Silicon Image SiI9134. The information on this chip is limited to a two page product sheet on the web site. Manufacturers who deploy the chip are privy to the details. I thus have limited things to say about it beyond the functionality described in the Onkyo instruction manual. The SPDIF signals are decoded by a Cirrus CS42516 Codec chip. The chip has a two-channel analog-to-digital converter (ADC) which converts analog input signals to digital. It also has six audio DACs that go unused. The worst-case distortion is--94dB with an unweighted dynamic range of 105dB.

The complex stereo analog switch matrix takes in thirteen (!) stereo analog inputs and assigns the main analog bus or the receivers to two other zones. Zones two and three have separate volume and tone functions in the analog domain on a small part of an Onkyo R2S15211FP custom chip. We will meet this part again as the heart of the analog signal processing in the TXSR 705. Only analog inputs can be switched to zones 2 and 3, so you must hook up the two channel outputs of your CD player, DVD player, and any other device that also has an SPDIF/ HDMI port. As an aside, the 705 has only two zones and the second zone has tone controls.

[ILLUSTRATION OMITTED]

The matrix is a phalanx of assorted passive CMOS switches including the large (close to 90 analog switches) custom Toshiba part TC94A46 and the smaller New Japan Radio NJU731X series analog switches. The supply rails to the switches and operational amplifiers are a full +/- 15 volts. These high voltage rails in conjunction with the high quality ICs assure high dynamic range and low distortion.

A CMOS tape assignment switch is always required at tape outputs to prevent an analog loop from a given recorder's tape in to tape out. The tape outputs should be buffered to prevent frequency roll-off from long cables or the loading of a recorder when it is turned. This is not done in the 805. The signal that drives the CMOS tape assignment switch is buffered so the tape recorder loading does not affect the performance of the signal that emerges from the analog switch matrix.

The output of the switch matrix can be sent directly to the analog volume controls in the stereo direct mode or to the input to the stereo analog-to-digital converter (discussed above) that allows analog stereo signals to use the digital signal processors for bass management and room equalization. Between the output of the switch matrix and the ADC input are two electrolytic DC blocking caps. Such capacitors are said to color the sound although I am not one of those that agrees, provided the capacitors are of good quality.

The phono section is a marked improvement from what I have seen on other AV receivers. The NE5532 is coupled to a discrete differential pair in front for low noise and high gain. No moving coil option is available. Moving up to an external phono equalizer like the Parasound Z phono improves RIAA accuracy, but the sonic difference is less evident than with almost all other AV receivers.

The headphone amplifier also gets the deluxe treatment. A discrete class AB output stage following a NE5532 insures the lowest impedance headphones are driven with low distortion.

The power amplifier is decked out with secondary circuit components to yield low total harmonic distortion at 20kHz and in high-frequency intermodulation distortion tests. A current source sets the bias on differential pair and an additional pair of transistors act as a cascode for improved linearity and bandwidth of the differential stage. The second voltage gain stage is in a complementary configuration. The critical buffer between the first and second stage is balanced. In Onkyo speak, this stage is called "dual push-pull amplifier design," referring to the second voltage gain stage with the accompanying unit gain input buffer.

The unity voltage gain output stage begins with a highly linear common-emitter-common-collector compound pair followed by emitter-follower transistors connected to the speakers. The total output stage is one form of a compound triple. Such stages are always part of a high-end power amplifier design because they reduce the load on the second voltage gain stage and increase the capability to drive large amounts of current to the load.

A pair of high performance (a rare find in an AV receiver where single devices are the norm) 2sa1962 2sc5242 complementary devices (these are Toshiba triple-diffused devices) are the output transistors. They have a unity gain bandwidth of 30MHz. The maximum safe operating area current for an isolated 1msec pulse is 30mA per device (60mA total). Continuous DC is half that value with 10 volts across the collector--emitter junction at room temperature. Sitting on +/- 65V rails and with the common emitter-common collector (CE-CC) predriver at the bases, this output stage delivers lots of current over a wide span of voltage. The internal heat sinks are not up to the job without a fan. It is just not possible, in a power amp with this much current sinking, to put enough aluminum in any rationally-sized AV receiver to passively cool the output transistors. The bias circuit, which sets the ideal current of the output stage, is very complex and it appears to have been designed to reduce distortion by preventing the transistor not driving the load from completely cutting off. This used to be called a sliding class A bias system in the 80s

The 15,000 ufD primary capacitor on the unregulated power supplies and the power transformer itself prevent seven hungry output stages from approaching the maximum safe operating voltage of the transistors when driven continuously. As expounded upon in past issues, eighty pounds of transformer and heat sinks are needed to pull this off. Stereo is a different matter. They rate the amplifier in stereo under FTC conditions as capable of 160 Watts 20HZ-20kHz at 0.1% distortion into 6 ohms. What other $1100 AV receiver has an FTC rating into 6 ohms. Dynamic power is specified as 300 watts for a single channel into 3 ohms although dynamic power is not defined. The number is consistent with the design of the output stage of this receiver.

No wonder Onkyo can bridge these power amps in stereo given their current sinking capabilities, but the option is only available in the higher-grade TSRX875. It is a shame the option was excluded from the TX805. There is no specification for the TXSR 875 amplifier in bridge mode; it should be over 200 watts under FTC conditions into an 8 ohm load but I cannot say for sure. Below an 8 ohm impedance, performance may decline since the effective impedance each side of the bridge amplifier sees is half of the actual value of the load. Without manufacturer specs, we are in limbo here.

On the digital side, there are three (!) TI digital signal processors (DSP): a TMS320DAC710, a TMS320D708, and a TMS320D707. The digital-to-analog converters (DACs) are premium TI PCM1796. The chip has a DSD input to allow for direct support of data coming off an SACD. The Onkyo has a pass-through mode that allows the DSD output of the HDMI receiver to go direct to the DAC in the direct mode. The instruction book is cloudy on exactly what switches have to be thrown to get into DSD pass-through. All the room EQ and bass management is lost in this mode since the DSPs are bypassed. This pass-through's apparent utility is to only a handful of people who claim DSD is audibly superior to 24bit/96kHz PCM. When the DSP is engaged, the DSD stream is converted to PCM. It is unclear from the HDMI receivers two-page data sheet whether this conversion occurs in the HDMI chip or the TI DSP chips.

Excellent performance is achieved by the Texas Instruments Stereo DAC used in the 805. While a couple notches down from the very top of the line, TI DACs performance is extremely impressive with minimal worst case distortion of 0.001% at 1kHz and worst-case dynamic range of 120dB A weighted. The distortion spec is for the chip operating at 44 kHz and doubles when the chip is processing at a 88kbit/ sec data. The digital interpolation filter has fast and slow roll-off modes. I am not sure which mode Onkyo uses. Stop band attenuation is -100dB in the sharp roll-off mode.

No sample-rate converter is present between the DSPs and the DACs, marking it as the only place where Onkyo is outdone by the competition. The sample-rate converter reduces clock jitter and it is unclear at this point how much jitter is generated by an HDMI receiver, at least with the limited information Silicon Image posts on its web site. To get a better handle on the effect of jitter from the HDMI chip under real-world conditions on the distortion at the output of the DAC, we would have to take measures that require equipment to drive test tones into the HDMI input--Audio Precision is just about to introduce test equipment for this purpose, but do not expect T$S to purchase one-off extravagances in the mid five figures.

Both the TXSR705/805 have ten DACs, not the prerequisite eight (F C R SW SR SL SRB SRL). At first, I thought the extra two had something to do with the second room option; but, they do not connect to the second room bus. The extra two signals produced by the DACs are called c2 (center 2) and sw2 (sub woofer 2). These are fed into a mixer to produce a two-channel analog output from the multi-channel HDMI or SPDIF entering the receiver. This mode appears to be used only when the front speakers are active in the room. The c2 and sw2 feed the left-channel mixer. The regular center and subwoofer signals go to the right-channel mixer and nowhere else. Adding an extra pair of DACs and the associated analog support circuitry is expensive. Normally the standard center and subwoofer signals could be adopted for both the left and right channel mixers and I am uncertain what additional functions are being accomplished here to require this complex implementation. Obviously, the Onkyo engineers implemented the design for good reason, but they have yet to respond to my inquiries.

The PCM1796 produces a current output. No operational amplifiers in the signal path are on the PCM1796 die because they could not be designed in a way that would not degrade the chips' performance. The external current-to-voltage conversion for the DAC is balanced with two 5532 sections doing the work. Following the I/V converters is a balance to a single-ended converter which uses NE5532 operational amplifier sections. The electronics discussed above also provide the reconstruction filtering. An electrolytic capacitor removes DC offset voltages at the output.

In between the electronics described above and the digital volume control is the dreaded CMOS switch matrix that selects the DAC out, the eight-channel analog input, or the stereo analog signal direct from the analog switch matrix for direct mode. Why can we not declare victory with HDMI and SPDIF and blow away the whole analog pass-through, giving us a direct shot between the DAC and the analog volume control. I do not think the extra electronics is audible, but its removal would make it hard for even the most picky audiophile to complain about the signal path of the 805 from DAC out to preamp out.

At least the analog high-pass filter that gums up the interface from the DAC front channels to the volume control appears to have been thrown overboard. Given the absence of a high-pass analog filter in the analog signal path, it appears the Onkyo's do not have analog bass management in the direct analog path as an option. I am waiting for Onkyo to confirm this. With the Audyssey bass management system on board, I expect the Onkyo engineers decided too much performance would be lost by bypassing the DSPs and managing the bass crossover for the front and right satellite speakers to the subwoofer in the analog domain.

The single-ended signal enters the highest-performance Cirrus digital volume control available (CS3318). This unit handles all eight channels and has internal active operation amplifiers. It is limited to +/- 8.5 volt rails. The CS3318 is the top-of-the-line Cirrus digital volume control with a worst-case THD of 0.0063% and a dynamic range of 121dB. The Cirrus chip drives the preamp outputs directly with only one electrolytic capacitor between the RCA plugs and the Cirrus chip. The muting function at the preamp output is done by a relay like the pro stuff. You see why, to my mind, the useless analog switches and active opamps that are placed between the reconstruction filter and the volume control are the only thing that prevents this design from going head to head with $3000 preamp processors and maybe units at twice that price when the input is from a digital source SPDIF and HDMI with respect to an analog source. The lack of the sample rate converter is the only other missing item between the Onkyo and the big buck high end stuff.

For $1100, this is a magnificent assortment of state-of-the-art and near state-of-the-art parts. It is professional quality to the preamp outputs, although the digital inputs are not what a studio uses (they have to have no encryption for obvious reasons) and the outputs would have to be balanced.

Inside the TX705

The two Onkyo units are almost identical with respect to digital audio and video signal processing, meaning the $200 price reduction has to come from the analog side of the receiver. The power amplifier is simplified. Gone are the buffer between the first and second gain stages, the complementary second voltage gain stage, and the cascode in the first voltage gain stage. A single emitter follower drives a single set of 2sa1962 and 2sc5242 output devices, curbing the unit's capacity to drive current into a low impedance load with only one output transistor per side and only a single current gain stage driving them. The simplification of the voltage gain stage section increases distortion near full power. A simple single transistor bias circuit sets the idle current

A single Cirrus CS42528 Codec chip replaces the five stereo DACs in the 805. Worst-case full-scale THD is -94dB and the worst-case unweighted dynamic range is 108dB. The DAC has an on-board current to voltage converter unlike the TI DACs used in the 805. For ultimate performance, all operational amplifiers should be discrete devices but internal opamps are not the performance limiting factor for the CS42528. The stereo ADC in the codec, used to encode the analog stereo input signals, has a worst-case THD of -94dB and an unweighted worst-case dynamic range of 105dB.

Almost all the rest of the analog signal processing from the analog input switch matrix to the analog volume controls is done by an Onkyo custom chip R2S15211FP. Now center stage, we saw a small section of this chip used in the second and third zone outputs of the 805. With the exception of a circuit discussed below, discrete operational amplifiers (NJM 4580 typically found in AV receivers) are used only for the balanced signal-ended converter at the output of the DAC.

It is impossible to cram the almost ninety discrete operational amplifier sections of the 805 into the R2S15211FP. Fewer active elements are available for buffering signals, but the signal path often remains on the chip to which significantly reduces inter-stage loading. The performance of each operational amplifier is reduced compared to the NE5532. Complex operational amplifiers consume too much silicon. To gain performance in a large scale analog chip, opamps can be customized for individual functions. Active sections that need low noise operational amplifiers get one opamp designed for that purpose; active sections that must drive a low impedance load get another type for that function. Also, most inter-stage connections can be direct, without DC blocking capacitors in the signal path. Additional circuitry in a large scale analog IC can reduce the intrinsic DC offset of an opamp so the capacitors are not needed.

The 805's two extra channels (center channel 2 and subwoofer 2) are present in the 705. They need to add extra DAC (Cirrus CS4898) converts them to analog and a couple of discrete operational amplifiers sum them into the left and right front channels. I have no idea what these channels are for and would prefer them to disappear; the money saved could be redeployed to upgrade other parts of the analog signal path.

The 705 has no phono stage and the headphones are driven from the front channel power amps. The power amp output is attenuated before it goes to the headphone jack.

Overall, this type of construction is typical of an AV receiver in the $900 price range, but comparable receivers in this price range lack the all important HDMI 1.3a decoding for high resolution audio (be careful, a HDMI 1.3a input may be on the back of a competitive unit but it is just a pass-through if the unit is priced below $900, and the high resolution 7.1 audio is not decoded). Also a far less sophisticated room EQ than the Audyssey MultEQ XT might be seen. Some competitive units in this price range may have Audyssey MultEQ, but that missing XT is a BIG deal.

The extra $200 for the TXSR 805 adds many high performance analog components as we have seen above, I know of no other similarly-priced receiver brand that offers similar build quality since I have not come across any AV receiver schematic at any price that looks as good as the 805. Again I caution I have not seen all the competitors schematics but I would be very surprised that a competitor exists at this time anywhere near this price point with respect to audio signal processing 

The ability of the 805s power amplifiers to sink current into tricky speaker loads is the key improvement. Overall, THD and signal-to-noise ratio (SNR) are about 1 to 2 effective bits higher in the 805, coming very close to the intrinsic resolution on the best SACDs and DVD-As. The audibility of this reduced distortion and noise is at best case minimal, and likely inaudible with background noise in a room not stuck at the bottom of cave, and with the speaker distortion an order of magnitude worse than what comes from the 705. I would sleep soundly if I could budget $900 for the 705AV receiver, but stretching an extra $200 does come with some pretty hefty audiophile bragging rights in the form of the 805.

                             TX-SR705       TX-SRS05

Power (8 ohms, 20-20k Hz,    100 watts/ch   130 watts/ch
0.05% 2-ch driven, FTC

THX Certification            Select2        Ultra2

Dual PUSH-PULL amplifier                    x
design

Toroidal transformer

Front L/R Bi-Amping          x              x

Bridging- a for Front L/R

VLSC (Vector Linear
Shaping Circuity)

HDMI v1.3a in/out            3/1            3/1

480i--480p deinterlacing     Faroudja       Faroudja
                             DCDi           DCDi

1080p upconversion

DTS-HD, Dolby TrueHD/DDI+    x              x
decoding

Satellite Radio ready        XM and         XM and
                             Sirius         Sirius
Neural TFIX Surround

HD Radio tuner               x              x

Audysseey Auto calibration   MultEQ XT      MultEQ XT

Onkyo RIND                   x              x

Powered Zone 2               x              x

Zone 3 line out                             x

Streaming Audio (Micro-
soft's PlaysForSure)

Ethernet for Internet
Radio

MSRP                         $899           $1,099

                             TX-SR875       TX-NR905

Power (8 ohms, 20-20k Hz,    140 watts/ch   140 watts/ch
0.05% 2-ch driven, FTC

THX Certification            Ultra2         Ultra2

Dual PUSH-PULL amplifier     X              x
design

Toroidal transformer                        x

Front L/R Bi-Amping          X              x

Bridging- a for Front L/R    X              x

VLSC (Vector Linear          x (all         x (all
Shaping Circuity)            channels)      channels)

HDMI v1.3a in/out             4/1            4/2

480i--480p deinterlacing     HQV Reon-      HQV Reon-
                             VX             VX

1080p upconversion           HQV Reon-      HQV Reon-
                             VX             VX

DTS-HD, Dolby TrueHD/DDI+    X              x
decoding

Satellite Radio ready        XM and         XM and
                             Sirius         Sirius
Neural TFIX Surround

HD Radio tuner               X              x

Audysseey Auto calibration   MultEQ XT      MultEQ XT

Onkyo RIND                   X              x

Powered Zone 2               X              x

Zone 3 line out              X              x

Streaming Audio (Micro-                     x
soft's PlaysForSure

Ethernet for Internet
Radio                                       x

MSRP                         $1,699         $2,099