Do you want to get "state-of-the art" DAC, which was born in almost professional DIY project (actually just a bit worse because we don't use all OPA627 due to the high level of cost, but still very close to it, as OPA2134 is not the worst choice). Take a look over there and it will be clear what we are talking about ... it is in German, but everyone can use babelfish or something similar to translate it, right?

Thanks to Geo, who provided some pictures of new flagship receiver 59TXi (European version should be AX10Ai, though as the previous models, a multichannel amplifier).

The modification of this receiver is exactly the same as for 49TXi. The DACs board, being marked as AWK7773 instead of AWK7725 in 49TXi, has the same DACs PCM1704, the same OPA JRC5534 and JRC2068 and looks very similar. As it had been mentioned before, PCM1704 is a Sign-Magnitude DAC (R-2R multi-bit) and it is doubtful which one is better for 59TXi - PCM1704 or DSD1792 due to the exceptional sound quality, produced by multi-bit DACs. However, at least we missed an interesting opportunity with PCM1704: similar to as in 49TXi, DSD stream is processed through i-link with conversion to 32 - bit, though instead of 88.2 kHz (2FS) to 176.4 kHz (4FS) PCM signal in the receiver, SM5819A chip does it perfectly.

Such a modification will probably set 59TXi at the position of one of the best AV processors in the world, with it's 32-bit 96 kHz DSP processing (it uses ADSP21161 Melody - 100 DSP instead of used in 49TXi ADSP21065), i-link and new Advanced MCACC. It has the new quite nice remote control. Here we can see 59TXi's back side with the new Pioneer Pro-R04U Media receiver and DV-59AVi DVD player at CES2004.

Pioneer 59TXi/AX10Ai modification

59TXi (AX10Ai) has i-link, quite good clock with the stable quartz oscillator, (the schematics, supporting AV/C command mode is implemented in Ice-Lynx Micro chip - the receiver of i-link signal) - it is necessary to have such stable clock for PQLS (Pioneer quartz lock system, equal to AV/C command mode) support, as in other case the sync process between player and receiver can have problems. The power supply is also good enough - we have separate filtering circuits (with Oscon capacitors) for each DAC and separate stabilizing ICs for DAC supplying voltages and finally fast Shottky diodes KCH30A15 in the bridge rectifier. It also has very good Sign-Magnitude (multi-bit) DAC - used in many High-End devices with the proven SQ - PCM1704. They also have pretty good Burr Brown OPA2134 in the output stage (at the main board), so our task is much easier with the high level of SQ improvement - we need to modify the DAC board, or I/V and post filter stages. JRC5534 is used in I/V converter stage with 13V/mks slew rate (actually one of the best, if not the best for I/V in the mass production consumer electronics industry, but not good at the real High-End level) and JRC2068 with 6V/mks slew rate (take a look in the IC database - many famous brands use them even in I/V stage of pretty expensive products) in the post filter and in the digital volume adjustment stage, all on the DACs PCB (the picture is zoomed to let you get the details). We need to decide what are the best OPAs to make such kind of upgrade. For I/V we had two candidates - AD825 (often used in CDPs modifications due to the great performance and lower cost) and the most expensive OPA627. We had a lot of discussions in different forums and finally we had to make the comparison how they sound, and the final decision was - OPA627. They sound "warmer", and with the high resolution of DSP processing of 59TXi (AX10Ai) it is a bit better. Though one may prefer the more refined sound of AD825. We also have the new op amps AD8610/8620 and AD8065/8066, they are very good, but oyou need to take in mind the supplying voltage (a lot of people recommend to use AD8065 with +/-12 V max), and it requires some exchanges in the circuit design, so we didn't try them yet. It is doubtful though, that the difference with OPA627 may be high, we have different opinions about it in DIY forums, but all reports confirmed only minor difference, some people still prefer OPA627 and others AD8065, so we will try to compare them later. Concerning the exchange of JRC2068, the decision was pretty easy - OPA2134, High-End producers use it in Lexicon MC-12 everywhere, the same OPA2134 they use in Anthem AVM20, then this is a good enough op amp for a post filter. We could use again OPA627 (only single version available, so it is necessary to have the special dual-to-single PCB adaptors), but this exchange will be significantly more expensive, and from our point of view the effect is not worth it. The confirmation of our decision is shown in the datasheet of PCM1704, the combination of OPA627 in I/V plus OPA2134 in post filter is recommended by Burr Brown engineers, (C) Texas Instrument. Very important issue is the removing of digital noises from the ground bus and power supply buses, but this was not necessary in 49TXi, it had been designed with high level of engineering approach, the stated -105dB S/N level confirms this as well, but more important are the schematic decisions for UHF noises and interferences removal:

To be sure that this modification is sonically reasonable , we have made it first for 2 channels only. The result was amazing - in stereo mode (not Direct mode as we had M&K monitors with frequency response starting from 72Hz and used M&K sub for low frequencies) it was like a wizard removed some kind of "veil" from the sound image, it became to be much more natural, "open air" came from nowhere and gave us exactly the SQ that we wanted to get for a long time from our system. It sounds quite close to the best systems we have even heard - like MBL Top Line with Radialstrahler ... We do not claim that they are the same, it is not possible, but we miss MUCH less in the modified system that we have heard before in MBL ... the transparency, soft high frequencies with a lot of details, excellent SQ playing different music styles from voice vocal and classic till hard rock, etc. The highest difference in comparison of modified and unmodified 49TXi was with Russian Choral singing (CD) - a lot of voices were flying around like butterflies without any interference to each other, producing harmony and almost mystical feelings.

Our soldering expertise (more then 20 years of experience, over 12 years professional) allowed to make the exchange without any damages of PCB or chips - here is an example. One has to be very careful, doing this, because an overheating in the process of soldering can make non-predictable results. To make sure that we didn't fool ourselves with the results (we know that it is so easy to make the subjective opinion) we had made the measurements, using RMAA ver 5.3 software. The results are as follows:

Testing chain: 49TXi modified Direct (59TXi should be the same, as it uses the same DACs board)
Sampling mode: 24-bit, 96 kHz
THX 1kHz -3dB, IMD 19kHz and 20kHz -7dB below FS

Summary

FS - level of clipping. Here are the old measurements, if anyone is interested to compare.

Those results are superior even in comparison with the good professional soundcard, for example ESI Waveterminal 192X:
http://audio.rightmark.org/test/esi...l192x-2496.html
Or AudioTrack ProDigy 192 (semi-professional):
http://audio.rightmark.org/test/aud...gy192-2496.html
I am not even talking about such devices as Audigy 2 ...
http://www.extremetech.com/article2...,1151975,00.asp
Noise level, dB (A): -96.5 Excellent
Dynamic range, dB (A): 94.1 Very Good
THD, %: 0.0037 Very Good
IMD, %: 0.0096 Very Good
Stereo crosstalk, dB: -88.4 Excellent

Test conditions:
Output level of volume control in 49TXi was +12dB.
Connection: SPDIF output of Lynx L22-> SPDIF in 49TXi (used DVD/LD digital input 1), stable clock of Lynx L22 is almost equal to i-link (though anyway worse, because of PLL clock restoring in the receiver, it means the results through i-link should be even better). Analog outputs of 49TXi (pre-out, FR and FL) -> analog inputs of Lynx L22; this is the required loop. Level of the input signal -3.1dB below FS.
I used the most difficult conditions: 24 bit 96kHz signal (equal to DVD-A Advanced resolution multi-channel signal), CCIF professional IMD test (19kHz and 20kHz both -7dB below FS) instead of less difficult SMPTE IMD test.

Old Audigy had been replaced with Lynx L22, as planned (one of the best sound cards for measurements available). The current results are even better then for a High-End processor; take a look here (this is a PDF file, so will take some time to download) for a comparison. With Lynx measurements are not simply better, they are awesome! Please note, that we got "excellent" and "very good" results in RMAA measurements, which it stated for SOUNDCARDs, not for processors, and processors in receivers are more complicated devices as they operate in worse conditions.Our subjective listening tests had been confirmed by objective measurements.

The best for modification are receivers with i-link - they require less work (Pioneer 59TXi, Pioneer 49TXi, Pioneer 55TXi, Yamaha Z9), though we have made the mods for High-End processors and some modern receivers with very useful specific functions. For example Yamaha 2400 with it's room acoustic calibration system YPAO. Please take a look at the cost section of the webpage to get the information about our current offers.

You could make the upgrade by yourself, in this case ALEX HARDWARE IS NOT RESPONSIBLE FOR ANY DAMAGES TO YOUR RECEIVER (before doing anything, read the DISCLAIMER, please) and you will not be included in the database for the future upgrades. Our prices are competitive that it would make no sense for anyone to attempt to self modify and risk damaging the equipment. It is also risky to remove the DAC board as well, therefore, if you are not sure that you can safely do it by yourself, we recommend that you send to us your receiver for upgrade, with your board or ours. The instruction on how to remove the DACs board are provided below, and the installation of the board is is not too difficult. However, we do recommend it to anyone with no professional training.

All procedures have to be done WITH DISCONNECTED POWER OUTLET, this means that YOU HAVE TO DISCONNECT the power cord from the AC power supply! YOU CAN'T DO ANYTHING BEFORE THAT. Only then remove the upper cover, as shown here (13 screws have to be removed, 3 from the back side and 10 from the top). Then remove the right side aluminum plate (only 2 screws have to be removed). Now remove the shield from DACs board (6 screws have to be removed). Now you can see the DACs board, as shown here . Now be careful not to damage anything with the screwdriver! Remove screws 2,3 from the DACs board. Now there is the most difficult and important operation - to disconnect two interboard connectors 4,5. You need to carefully disconnect one by one from one side (get up the fixing part of the connector, as shown here, the result of your action will look like this); then from another side, don't try to do it simultaneously. They are fixed in their places to avoid disconnection due to vibrations, points 10,11. Now you have them completely disconnected - 4,5. The final stage of this operation is the removal of the DACs board. Be careful - slightly moving the board from side to side as shown at 12,14, pull it up, while keeping the distance 13 not more then 12 mm (1/2") to avoid the breaking of the bottom connectors. They are fixed in their places as well as previous ones, as shown here - 9.

When you will insert the DACs board back (after the modification) , please pay attention to insert the connectors exactly at their places - directing the 7,8 in the appropriate holes in the relative bottom connectors (2) on the PCB in your receiver. Don't put a lot of pressure, you will feel a slight "click" when the connectors are fixed in their correct positions.

The end result is as you have bought a system that is at least twice as expensive. In addition you will now have the only processor (except of the new coming Integra Research AV processor, which is not available yet) on the market (even compare to those selling at double the price) that has an i-link.

Enjoy!