Multi-Channel, Multi-Amplifier Audio System Using Software Crossover and Multichannel-DAC

[dualazmak]

Hello friends,

Today, one demo unit of ACCUPAHSE A-36, a pure class-A amplifier, has arrived my home for full 10-day tests and evaluation. Hopefully, I will start the evaluation of A-36 tomorrow.

BTW, in a very good timing before evaluating A-36, a top engineer from a small and excellent Japanese audio manufacturer, who is currently designing and developing a Purifi 1ET400A-based class-D amp, kindly sent me again his nice suggestions and comments on class-A and class-A(H)B paths of my amplifier exploration in this project. Please understand that his kind and honest comments are prepared for me, a non-expert end user. I am not an expert in this area, so I am a little bit afraid that the English translations below maybe somewhat inaccurate, though...

Comment-1
In the evaluation of amplifiers, it is generally important to evaluate each product individually in the environment in which it will be used. As you know some budget class-A amplifiers are apparently inferior to excellent class-D amps. On the other hand, 1ET400A is now approaching to the extreme/maximum performance of class-D approach.

Comment-2
Nowadays, there are little prominent advantages of class-A and class-AB for mid-low range, I assume. The biggest weapons or advantages of class-A and class-AB over class-D, however, are the wide-band feedback and high gain. In short, it is possible to secure the excellent characteristics (including the better phase characteristics) by applying sufficient wide-band feedback in the wide high frequencies. Excellent class-A (and class-AB) amps, therefore, still have advantages over class-D in high frequency region, usually covered by tweeters and super tweeters (i.e. above ca. 4,500 Hz?).

Comment-3
For the mid-low range, class-A and class-AB output stages require asymmetric electronic devices/circuits/elements to be placed in positive and negative voltages, resulting in asymmetric current characteristics. The voltage characteristics can be adjusted by feedback technique, but the basic (asymmetric) current characteristics remain unchanged. On the other hand, class-D has a positive and negative symmetric alignment with no emitter resistor (which somewhat interfere with the current), so class-D has relatively high instantaneous (kick) power and can provide a symmetrical current. I assume this would be the main reason that in the low frequencies of class-A and class-AB are relatively slightly cloudy, and class-D gives relatively "clear-sky" impression in low frequency.

Comment-4
We should note that an amplifier designed with relatively limited "current" would not produce enough instantaneous power. Even in case you do not need much average power in low range, if the speed of the woofer and the speed of the squawker would be rather in mismatch, the sound in that range may become more or less cloudy or blurred. It is very important to drive woofers in sync (at the same speed) with squawkers as better as possible in the overlapped range, and this means the amplifier driving woofers should have certain level of enough instantaneous/transient peak-power capabilities.

I highly appreciate having these nice technical and objective comments for my amplifier exploration, especially for my tests and evaluation of A-36 starting tomorrow. I also would like to take tpaxadpom's nice perspectives and the discussion into serious consideration throughout the coming amplifier exploration.

EDITED to add:
As for his Comment-4, I (we) already experienced and confirmed that the elimination of LC-network coils (and capacitors) in the woofer power train greatly contributes to better instantaneous/transient response of woofer in multichannel multi-amplifier system.

 

[dualazmak]

ACCUPHASE A-36 Tests and Evaluations: Part-1
In Single-Amplifier and Bi-Amplifier + LC-Network Audio System

Note: I am an end user audio enthusiast and I have no conflict of interest at all with any of the manufacturers, import companies, distributors and audio shops relevant to this post. This post is not intending to intensively share objective and/or subjective evaluations of the candidate amplifiers, but I would like to share about how I would test and try candidate amplifiers in this project.

Hello friends,

ACCUPHASE A-36 is a pure class-A power amplifier, and you may find the English Brochure and Technical Information at;

http://www.accuphase.com/cat/a-36_e.pdf
http://www.accuphase.com/technical_information/a-36_technical_information.pdf

One demo unit of A-36 is now staying at my home for tests and evaluation in this project.

The "guaranteed" specifications of A-36 are;

I cannot find English Manual at their English web site, while we can see the THD and Fq response charts in the A-36 Japanese Manual;

As usual, I started the tests and evaluation of A-36 comparing it with ACCUPHASE E-460, my reference integrated amplifier, in this setup.

The software crossover EKIO's configurations remain unchanged as I shown in my post #264.

With this setup, E-460 or A-36 at the exactly same gain/volume, I did careful listening sessions using my audio sampler music tracks.

As you may assume, the overall sound presentations/characteristics of A-36 are quite similar to those of E-460, and I could hear better resolution, cleanliness, transparency with A-36 in MID - HI range. I personally feel very much comfortable with "the sound presentation as a whole" which tpaxadpom and I briefly discussed in post #266 and post #268 in this thread.

I was a little bit surprised that A-36 gave considerably and audibly better and stable 3-D sound perspectives/positioning in all of the music tracks; the 3-D sound presentation does not change/shift at all, even I moved ca.1 m range in left-right, up-down, ahead-behind around my usual center listening position on the listening sofa.

Although I have not yet performed any in-depth objective measurement with microphone and REW software, I assume this very stable 3-D sound perspective is due to A-36's excellent phase characteristics as discussed in my post #267 and post #275. ACCUPHASE said, in the A-36 Brochure, "Current feedback principle assures excellent phase characteristics in high range."

The total "sonority" of LO range by A-36 is also very nice and comfortable, but I felt a little bit lack of instantaneous/transient LO power when listening to the music tracks containing rather sharp transient LO sound. Now, I can understand well what the nice comment-4 I shared in my post #281 means; A-36's continuous average output power of 30 W/Ch into 8 Ohm and its "transient" power seem to be a little bit insufficient in driving the woofers (WOs) in this setup (still with LC-network coils and capacitors).

This finding pushed me to move on to bi-amplifier operation. The outer LC-network boxes are built in capable of bi-wiring connection from two amplifiers, one input line for WO operation and another for Beryllium squawkers (Be-SQs), Beryllium Tweeters (Be-TWs) and horn-type super tweeters (STs);

So, I can easily try bi-amplifier setup of E-460 to drive WOs, A-36 to drive Be-SQs, Be-TWs and STs as shown in this scheme;

In this bi-amplifier setup, thanks to the powerful E-460 with 180 W/Ch into 8 Ohm (my reference sound system), I have much enough instantaneous/transient power as usual which was well confirmed through the listening sessions.

As software crossover EKIO is supplying only the LO frequency of 45 - 600 Hz through the CH3+CH4 of OKTO DAC8PRO into E-460, it is possible for E-460 to directly drive WOs by bypassing the LC-network shown in this scheme;

I could achieve better and efficient transient response of woofers "directly" connected and driven by E-460.

Quite regretfully, the demo unit of Benchmark AHB2 has already left my home. Just as preparatory check and confirmation, therefore, I also dared to try YAMAHA A-S301 (a tentative budget amp, RCA inputs only) to directly drive WOs in this scheme;

I could confirm that A-S301 of 60 W/Ch into 8Ω (20Hz to 20kHz, 0.019％THD) can be tentatively used to directly drive WOs, where A-36 and E-460 will cover MD to HI frequency regions in the next full multichannel multi-amplifier tests/evaluation with no LC-network coils, capacitors nor attenuators. My next post, will be due in a few days, shall share with you such full multi-amplifier tests and evaluation including one pure class-A amplifier A-36.

Edited to add:
A-36 is not so "hot"; considerably cooler than I thought for this kind of pure class-A amp. After non-stop 5 hour continuous full range listening session in my listening room of 25 degree C (77 F) room temperature, the hottest part of the A-36's top cover is about 6 degree C above my "healthy" body temperature, i.e. it is around 43 - 44 degree C (109 - 111 F). This is a demo unit (looks very clean new one), and I hesitate to open the top cover.

 

[dualazmak]

ACCUPHASE A-36 Tests and Evaluations: Part-2
In Multichannel Multi-Amplifier Audio System

Note: I am an end user audio enthusiast and I have no conflict of interest at all with any of the manufacturers, import companies, distributors and audio shops relevant to this post. This post is not intending to intensively share objective and/or subjective evaluations of the candidate amplifiers, but I would like to share about how I would test and try candidate amplifiers in this project.

Hello friends,

Following the tests and evaluation of ACCUPHASE A-36, a pure class-A power amplifier, in single-amplifier and bi-amplifier system using LC-Network (shared in my post #282), I tested A-36 in my multichannel multi-amplifier project.

As wrote at the end of post #282, the demo unit of Benchmark AHB2 has already left my home; in this post, in addition to A-36, I utilized my reference integrated amp ACCUPHASE E-460 and tentative budget amp YAMAHA A-S301.

Since A-S301 does not have XLR balanced input, I utilized OKTO DAC8PRO's AES/EBU Digital Out (CH1+CH2) into ONKYO DAC-1000, then its RCA (L &R) output into A-S301 to drive directly the woofers (WOs).

I first tested A-36 to directly drive mid-range Beryllium squawkers (Be-SQs), while E-460 directly to Beryllium tweeters (Be-TWs) plus horn super tweeters (STs) in this Case-1 scheme;

As checked and confirmed at the end of previous post #282, A-S301 of 60 W/Ch into 8Ω (20Hz to 20kHz, 0.019％THD) can be tentatively used to directly drive WOs; the complete elimination of network coils (and capacitors) effectively contributes to the efficient drive of WOs by A-S301, so that I could test and evaluate A-36 and E-460 working on mid to high frequency.

Using this Case-1 setup, I carefully listened to all the tracks of my audio sampler music tracks. I felt very comfortable with "the sound presentation as a whole" which tpaxadpom and I briefly discussed in post #266 and post #268 in this thread. Just focused on the Be-SQs' midrange sound, however, I heard a little bit rather "warm" or "soft", but still clean and transparent, sound in comparison to the reference full-range sound given by E-460.

The complete elimination of LC-network coils and capacitors in this multichannel multi-amplifier system makes all the speaker drivers sensitively responding to the amplifiers, in other words, the "characteristics" of each amplifier can be easily heard in this multi-amplifier setup. I could hear, therefore, relatively "warm" characters of "class-A" A-36 driving SQs. From my private "taste" and "preferences", I like the relatively slightly solid and "cooler" mid-range SQ sound given by E-460; I know well such subtle differences would be the "matter of subjective taste and preference".

Throughout the listening session, I had no complaint at all for the avearage and transient "power" of A-36 directly driving the SQs.

Then, I moved on to the Case-2 setup where A-36 to directly drive Beryllium tweeters (Be-TWs) plus horn super tweeters (STs), while E-460 directly to mid-range Beryllium squawkers (Be-SQs) in this Case-2 scheme by simply changing the EKIO's output routing and SP cable connections ;

Together with my wife who joined in the listening session, we could hear the best in all aspects elements and most comfortable "sound presentation as a whole" using this setup.

Much beyond my limited expectation, A-S301 is doing excellent job with WOs which are now easy to be driven, and the mid SQ to high TW, further to super-high ST sound is seamlessly really wonderful; we could hear considerably better resolution, cleanliness, transparency with E-460 and A-36 in MID - HI range.

I was much surprised again(!) that E-460 in mid-range plus A-36 in high-range gave considerably and audibly better and stable 3-D sound perspectives/positioning in all of the music tracks; the 3-D sound presentation does not change/shift at all, even I moved ca.1 m range in left-right, up-down, ahead-behind around my usual center listening position on the listening sofa.

Now I fully understand and agree with the nice Comment-2 shared in my post #281 where "he" said;
"The biggest weapons or advantages of class-A and class-AB over class-D, however, are the wide-band feedback and high gain. In short, it is possible to secure the excellent characteristics (including the better phase characteristics) by applying sufficient wide-band feedback in the wide high frequencies. Excellent class-A (and class-AB) amps, therefore, still have advantages over class-D in high frequency region, usually covered by tweeters and super tweeters."

I could now confirm by my (our) ears and brain, at least in my multichannel multi-amplifier project, this comment is valid and more obvious in the setup where an excellent Class-A amp is directly driving TWs+STs.

Yesterday, we did continuous, tireless, very comfortable, listening sessions for about 5 hours with this Case-2 setup. I really would like to share with you the lot of music tracks we listened and our subjective listening impressions for each of those. I should avoid, however, writing much of our pleasant and exciting subjective reports here now, since such writing should definitely prevent me from going into sleep tonight.


Let me share with you just one practical issue with this Case-2 setup which is actual "Master Volume Control and Relative Gains" in this case, since I assume many of you, especially those who visiting this thread rather recently, are interested in where and how I manage "Master Volume Control and Ralative Gains".

You would also refer to my post #191 entitled " Again, Where to Control Master Volume?" as well as several posts thereafter.

In order to share with you, and also for my "check sheet" purposes, I summarized the entire of "Master Volume Control, Relative Gains, Software Crossover configurations" in this Case-2 setup like this;

This looks somewhat complicated at your first glance, I assume. No, not at all, you can be just relaxed with this diagram!

As you can see, I am just using JRiver MC's (or Roon's) volume controller as "Master Volume Controller" in the entire multichannel multi-amplifier system. And, in the downstream, all of the red numeric numbers are the adjustable/controllable gains and/or volumes.

Please do not be frightened with the software EKIO's many gain values; they are straightforward, and, once configured, all the EKIO settings can be saved as "EKIO configuration file" of any file name like;
20200928_A-36(TW+ST)+E-460(SQ)+DAC-1000--A-S301(WO)+SONICA DAC(SW)_001.ekio
and you can open and load any of the saved EKIO configurations whenever you would launch EKIO.

DAC8PRO also "memorizes" its output master gain and individual output channel gain, even if you would do hard-off (plug-off) shutdown of DAC8PRO.

All the settings in subwoofer YAMAHA YST-SW1000 can be kept including the "volume" which I set at the 14 O'clock position (we can control it by an IR remote controller).

We should shutdown JRiver or Roon with its "volume" set to -25 dB (50 %) or less for safety in next launch. In this Case-2 setup, I am tentatively using two integrated amplifiers, E-460 and A-S301, so their volume dials should be turned to most down position on shutdown.

Consequently, as for the gain matching, all I should do on system launch is carefully dialing-up the E-460 and A-S301, to -18 dB (12 O'clock position) and to 12 O'clock position, respectively, while EKIO has been launched with one configuration file, and JRiver or Roon is playing music in small volume (less than - 25 dB, 50 %).


Well, having the tests and evaluation of A-36 in my multichannel multi-amplifier system as shared above, I am happy now that I could almost decide the possible "type" of the three amplifiers and setup diagram with such amplifiers.

In my next post, I will briefly share with you my current idea of "type" of amplifiers and their possible roles in this project.

 

[dualazmak]

Possible "Type" of Three Amplifiers in Current Multichannel Multi-Amplifier Project

Note: I am an end user audio enthusiast and I have no conflict of interest at all with any of the manufacturers, import companies, distributors and audio shops relevant to this post. This post is not intending to intensively share objective and/or subjective evaluations of the candidate amplifiers, but I would like to share about how I would test and try candidate amplifiers in this project.

Hello friends,

Now, I feel that I could move one step up in this project, especially moving forward on the amplifier exploration.

I assume this schematic diagram is self-explanatory for all of you;

I need enough instantaneous/transient power for excellent amplifier driving my WOs.

With the amplifier driving SQs, I need "better" overall sound characteristics/presentations well fit for my taste and preferences so far I acquired through my long journey in Hi-Fi audio.

I very much like the hi-range sound presentations given by an excellent Hi-Fi pure class-A amplifier, as I shared in the previous post #282 and post #283.

The durability, long-tern stability, warranty, future service and repair, parts availability, etc. are also very important factors for my possible decisions on amplifiers.

The entire of "Master Volume Control, Relative Gains, Software Crossover configurations" in this setup is like this;

Possible "the simpler, the better" configurations of software crossover EKIO would be;

I will not write too much in this post about the bases behind my above present idea/plan; I believe the whole of this thread started on April 9 is converging into these possible setup in my "specific" and "unique" multichannel multi-amplifier project.

Your kind attention and suggestions/comments on the above will be much appreciated.

I myself, would like to take interlude/intermezzo discussion and thinking period again for a while, and I also would like to further evaluate, listen to A-36 carefully until its scheduled departure in early next week.

 

[mitchco]

@dualazmak I must say, I love your diagrams!

 

[dualazmak]

Hello friends,

Just for your info, an interesting discussion has been started today at post #1,771 of the DAC8PRO review thread on possible new DSP software/firmware development dedicated to DAC8PRO and DAC8 STEREO.

 

[dualazmak]

Note: I am an end user audio enthusiast and I have no conflict of interest at all with any of the manufacturers, import companies, distributors and audio shops relevant to this post. This post is not intending to share objective and/or subjective evaluations of the candidate amplifiers, but I would like to share about how I would test and try candidate amplifiers in this unique project.

hello friends,

In my above post #284, I wrote and shared my current idea of the selection of "type" of amplifiers and EKIO plus DAP8PRO configurations in my multichannel multi-amplifier project.

BTW, in my post #228, I shared my tests and evaluations of rather heavy duty Hypex NC400 based DENTEC DP-NC400-4-EXP class-D amplifiers in my project. Furthermore, I wrote in my post #251 that I also would like to test and evaluate TEAC AP-505 class-D power amp (and/or its integrated version AX-505) in my project;
https://teac.jp/int/product/ap-505/top
https://teac.jp/int/product/ax-505/top

Although quite belated, just last weekend, I could successfully arrange the demo units of AP-505 and AX-505 will be available soon at my home for my tests and evaluation for full 14 days.

I would like to share my coming experiences with AP-505 and AX-505 in my unique project, partly together with my Accuphae E-460, hopefully within 4 - 6 weeks.

 

[forart.it]

Hi there, very interesting project mate !

While we strongly suggest to release it under a free license, we've collected "some" web resources for our own similar project:

• Multiamp & DSP projects
• OPEN SOURCE AMPLIFIERS PROJECTS

We hope that new collaborations can born from ideas's exchange.

 

[dualazmak]

Hi there, very interesting project mate !

While we strongly suggest to release it under a free license, we've collected "some" web resources for our own similar project:

• Multiamp & DSP projects
• OPEN SOURCE AMPLIFIERS PROJECTS

We hope that new collaborations can born from ideas's exchange.

Hello forart.it,

Thank you for your visiting here.

Since I am now restricting myself to share my progress in current multichannel multiamplifier project only here on this thread in ASR Forum, you would please, if you would like to do so, share the top page link of this thread at any of audio forums where you would assume it worthwhile, and please invite your friends to this thread.

 

[dualazmak]

TEAC AX-505 and AP-505; Tests and Evaluations: Part-1
In Single-Amplifier and Bi-Amplifier + LC-Network Audio System

Note: I am an end user audio enthusiast and I have no conflict of interest at all with any of the manufacturers, import companies, distributors and audio shops relevant to this post. This post is not intending to intensively share objective and/or subjective evaluations of the candidate amplifiers, but I would like to share about how I would test and try candidate amplifiers in this project.

Hello friends,

As pre-announced in my post #287, the demo units of TEAC Integrated Amplifier AX-505 and Power Amplifier AP-505 arrived at my home for tests and evaluations in my current project;

You may find info including the specs on AX-505 and AP-505, ultra-compact amplifiers, at TEAC's international sites;
https://teac.jp/int/product/ap-505/top
https://teac.jp/int/product/ax-505/top

These pages in English are also available for your reference;
https://hifiheaven.net/shop/TEAC-AP-505-Ultra-Compact-Stereo-Power-Amplifier-Black
https://hifiheaven.net/shop/TEAC-AX-505-Stereo-Integrated-Amplifier-Black?search=AX-505

Both AX-505 and AP-505 are really compact Class-D amps with Hypex Ncore module specially tuned by TEAC; I do not know the details of TEAC's special tunings, and I heard somewhere in Japan that base module could be Hypex NC122MP but I am not sure about that; I hesitate to open the top covers of these demo units. They are using MUSES Op-amps in the analog section, and high capacity (even in these compact sizes) toroidal power transformer and SBDs (Schottky barrier diodes); as I am not an expert in amplifier design, I do not know the pros and cons of SBDs in the power train.

As usual, I started the tests and evaluations in single amplifier + LC-network setup comparing them with my reference amplifier ACCUPHASE E-460.

As I shared repeatedly, the reference sound system with E-460 is like this;

Please refer to my post #284 for the details of software crossover EKIO's configurations (which I am also using even in this single-amplifier setup) and master volume and relative gain controls.

Also please refer to my post #248 and post #251 for the 22 Ohm parallel resistors in SP lines (for Be-SQ, Be-TW and ST) for fine tuning.

I first tested AX-505 integrated amplifier in this scheme as the replacement of E-460;

As you may assume, I easily found/heard that it is "unfair" to compare AX-505, very compact "integrated" amplifier, with my reference E-460, rather heavy duty high-end integrated amp, in this setup; in comparison with E-460, AX-505's light duty preamp section gave audibly somewhat inferior quality in every terms of the "total sound characteristics and representation" which I do not describe here in detail.

I would say, if I do not have the reference sound system with E-460, then AX-505 would be acceptable even in this setup. Furthermore, in case if I will consider renovation of my desktop audio system in my office upstairs (currently I am using still wonderful Klipsch Promedia 2.1 THX), TEAC AX-505 should be an excellent choice of amplifier, I believe.

Consequently, I regretfully excluded AX-505 in my present tests and evaluations in this and coming posts.

I moved-on to test and evaluate AP-505, very compact power amplifier, in the above setup diagram.

As the first listening impression, I was really surprised by the "sound quality and representation as a whole" given by AP-505, such a tiny compact amp, especially and very fortunately the "taste, characteristics and quality" of the given sound by AP-505 are quite similar to those given by E-460.

I was really happy to perform intensive listening sessions with AP-505 listening to all of my audio sampler music tracks for three times; in usual sound volume, then rather small volume, and finally really loud large volume (not in midnight but in daytime). I found that one rare case drawback of AP-505 in this single-amp setup still using LC-network would be a little bit inferior low frequency transient peak power in large volume listening to full orchestra fff transient sound such as "Dance of the Knights" in Prokofiev's "Romeo and Juliet" by Montreal Symphony Orchestra conducted by Chales Dutoit (POCL-1082 430 279-2 London-Polydor).

This finding encouraged me to test AP-505 in another setup where AP-505 to directly and dedicatedly drive WOs (woofers) bypassing the LC-network coils and capacitors, and E-460 to drive Be-SQs, Be-TWs and STs still through LC-network, as in this diagram;

I did two cycles of the same listening sessions in usual volume and again in large loud volume. I should not write too much about my subjective observations, but it is really amazing that, even with its relatively small 90 W + 90 W (8 Ohm, 1kHz, JEITA) power spec, how nicely AP-505 drives and controls the WOs which are now easier to be driven thanks to the elimination of the LC-network. It looks E-460 is now also very happy to drive Be-SQs + Be-TWs + STs, with no control nor power consumption for WOs.

Furthermore, the AP-505 to E-460 crossover, i.e. crossover at around 500 Hz by LR -12 dB filters, is really smooth and natural between the two amplifiers.

If I would have one more AP-505 at now, I definitely might have tried mono-block BTL drive of L & R WOs using the two unit of AP-505 in BTL mode with spec of 250 W (8 Ohm, 1kHz, JEITA).

In any way, I will continue my intensive listening sessions in this bi-amplifier setup (still using LC-network for MD-HI-SH sound) for the coming a few days, then during the weekend, I will move-on to tests and evaluations of AP-505 in multichannel multi-amplifier configuration fully bypassing/eliminating the LC-network.

Edited to add one topic:
It is interesting to know that TEAC is offering firmware update for AP-505 power amplifier;
https://teac.jp/int/support/news/6356
Firmware V1.03 as of October 5, 2020
Improved a noise issue coming from loudspeakers when using dimmer function.
even though I will not apply this update to the AP-505 demo unit (manufactured in 2019) which I am testing now... Fortunately, I have no such noise issue in my tests and evaluations, as I do not use the dimmer function.

 

[dualazmak]

TEAC AX-505 and AP-505; Tests and Evaluations: Part-2
In Multichannel Multi-Amplifier Audio System

Note: I am an end user audio enthusiast and I have no conflict of interest at all with any of the manufacturers, import companies, distributors and audio shops relevant to this post. This post is not intending to intensively share objective and/or subjective evaluations of the candidate amplifiers, but I would like to share about how I would test and try candidate amplifiers in this project.

Hello friends,

Following my tests and evaluations in single-amplifier and bi-amplifier + LC-network audio system as shared in my post #290, I tested and evaluated TEAC AX-505 and AP-505 in my multichannel multi-amplifier system.

Even though I wrote in my post #290 that "I regretfully excluded AX-505 in my present tests and evaluations in this and coming posts", I first tested AP-505 and AX-505 in tentative multi-amplifier Case-1 setup;

In this Case-1 setup;

AX-505, an integrated Class-D amp, to cover HI (High) and SH (Super-High) ranges driving Be-TWs (Be-Tweeters) and STs (hone Super Tweeters),

AP-505 to cover LO (Low) range driving WOs (Woofers),

ACCUPHASE E-460 to cover MD (Mid) range driving Be-SQs (Be-Squawkers)

I found again the problem of AX-505 in this kind of multi-amplifier system mainly due to its relatively low sensitivity of XLR balanced input. In TEAC's Spec page for AX-505, only "Max input level of 3 Vms" is declared and there is no sensitivity descriptions. In TEAC's Spec page for AP-505, on the other hand, they indicated "Sensitivity 1.3 V, Impedance 10 kOhm or higher).

In this multi-amplifier setup, in order to achieve adequate level matching with AP-505 and E-460, I needed to increase the gains of the software crossover's HI and SH covered by AX-505 to -2 dB and -4 dB respectively (they are usually -9 dB and -13 dB respectively in my reference system with E-460), and furthermore, I also needed to set the AX-505's volume dial to rather high -4 dB position;

These inevitable high gain and high volume settings with AX-505 covering HI and SH regions caused very faint high-frequency hiss noises to tweeters and super tweeters which only can be heard when I contact my ear directly to the drivers. For double check, I asked my wife to check it by contacting her ear to the drivers, and she also could hear the faint high-fq hiss noises on Be-TW and ST.

For honors of AX-505, I should say that the hiss could not be heard at all at our typical listening position of about 3.5 - 4.0 m away from the SPs.

In any way, I concluded again that "for this type of multichannel and multi-amplifier system" the use of AX-505 integrated amp would not be feasible mainly due to its low sensitivity of XLR balanced input.

Consequently, I rolled back the EKIO's configuration into the usual one as shown below;

And then I moved-on to the tests and evaluations of AP-505 together with ACCUPHASE E-460 and the tentative budget (but rather nice) Class-AB amplifier YAMAHA A-S301 which does not have balanced XLR input but featuring excellent unbalanced RCA input; the first tested and evaluated setup is shown in this Case-2 diagram;

In this Case-2 setup;

AP-505 to cover HI (over 6,000 Hz) and SH (over ca. 8,800 Hz) ranges driving Be-TWs and STs,

ACCUPHASE E-460 to cover MD (500 - 6,000 Hz) range driving Be-SQs,

A-S301 to cover LO (45 - 500 Hz) range driving WOs,

As I wrote at the end of post #282 and in post #283, A-S301 of 60 W/Ch into 8 Ohm (20Hz to 20kHz, 0.019% THD) can be tentatively used to directly drive WOs; the complete elimination of network coils (and capacitors) effectively contributes to the efficient drive of WOs by A-S301, so that I could test and evaluate E-460 and AP-505 working on MD and HI-SH frequency, respectively.

The HI-SH sound given by AP-505 in this setup is quite nice and acceptable for my ears and brain. In comparison with my memory sound given by ACCUPHASE A-36 which I shared as Case-2 in my post #283, however, I prefer A-36 (pure Class-A amp) better than AP-505 (Class-D) in terms of smooth sound continuity from MD range by E-460 (Class-AB). I also feel that A-36 gave more stable and non-shifted(?) phase characteristics in HI-SH sound which was more comfortable for my ears especially in the long continuous listening sessions.

Above feeling and impressions encouraged me to test the Case-3 setup in this diagram;

In this Case-3 setup;

A-S301 to cover HI (over 6,000 Hz) and SH (over ca. 8,800 Hz) ranges driving Be-TWs and STs,

ACCUPHASE E-460 to cover MD (500 - 6,000 Hz)range driving Be-SQs,

AP-505 to cover LO (45 - 500 Hz) range driving WOs,

Now I can hear significantly better HI-SH sound given by A-S301 of 60 W/Ch into 8 Ohm (20 Hz to 20 kHz, 0.019%THD) with smooth transit from MD sound by E-460, and AP-505, 90 W+90 W (8 Ohm, 1kHz, JEITA) and 0.0015% THD (8 Ohm, 1 kHz, 12.5 W, JEITA), is really nicely, much better than my expectations, driving and controlling the WOs, thanks to the complete elimination of the LC-coils and capacitors.

In this setup, together with SWs (sub-woofer YAMAHA YST-SW1000s), I did intensive listening sessions repeatedly for 3 days using my audio sampler music tracks. We found and confirmed that even with the full orchestra fff transient sound such as "Dance of the Knights" in Prokofiev's "Romeo and Juliet" by Montreal Symphony Orchestra conducted by Chales Dutoit (POCL-1082 430 279-2 London-Polydor), the total sound quality and presentation was really nice and amazing. I was much impressed by the clean and high-speed WO sound given by AP-505, really compact Class-D amp.

Again, if I would have one more AP-505 in this test session, I definitely might have evaluated AP-505 in mono BTL mode of 250 W (8 Ohm, 1kHz, JEITA) in driving WOs.

In conclusion, TEAC AP-505, especially in its mono BTL mode, can be one of my preferences to drive WOs in present multichannel multi-amplifier system.

In my next post, I will write and share again about my current amplifier selection possibilities/plans in this multichannel multi-amplifier project.

 

[dualazmak]

Possible Plans for Amplifiers in Current Multichannel Multi-Amplifier Project

Note: I am an end user audio enthusiast and I have no conflict of interest at all with any of the manufacturers, import companies, distributors and audio shops relevant to this post. This post is not intending to intensively share objective and/or subjective evaluations of the candidate amplifiers, but I would like to share about how I would test and try candidate amplifiers in this project.

Hello friends,

During the past five months, I have tested and evaluated these amplifiers in this multichannel multi-amplifier project;

ACCUPHASE E-460 Class-AB stereo integrated amp (as my reference sound system)

YAMAHA MX-A5200 Class-AB 11-Ch AV amp

DENTEC DP-NC400-4-EXP Class-D 4-Ch power amp, two units

BENCHMARK AHB2 Class-A(H)B stereo power amp

YAMAHA A-S301 Class-AB budget stereo integrated amp (only for tentative use)

ROTEL RB-1582 MkII Class-AB stereo power amp

ACCUPHASE A-36 Class-A stereo power amp

TEAC AX-505 Class-D stereo integrated amp

TEAC AP-505 Class-D stereo power amp

In my post #251, I also wrote the possibility of testing SOULNOTE A-0, but now I decided to skip this amp mainly because of its relatively low driving power of 10 W/Ch for 8 Ohm SPs.

As a follow-up of my post #284 where I shared possible "type" of three amplifiers in this multichannel multi-amplifier project, this post is intending to share my latest selections/plans of amps with identification of possible individual amplifier.

In my post #284, I showed my preference of amp "type" selection using this diagram;

After you would kindly read through my recent amplifier explorations, you may easily assume my selection of individual amplifier in this diagram could be this Plan-1;

Since the Japan domestic sales of AHB2 has just started in July through one sole import company and distribution channels/shops, the price of AHB2 is still rather high of ca. JPYen 440,000 (or USD 4,190 by JPYen 105/USD) inclusive of VAT and shipment. Even though the sole import company declares one-year warranty and possible repair arrangements (by sending back to Benchmark in NY?), we are not yet fully sure for these service system and arrangements on AHB2.

Consequently, I feel it would be better for me to postpone my purchase of AHB2 in Japan for some while, about one or two years, to see the business continuity and the real implementation of the service system on AHB2. It may be also possible that updated new version of AHB2 MkII (?) would be released during the coming a few years, I would really expect it.

Until I would actually introduce AHB2 in my project, now I believe I may use two of AP-505 in mono BTL mode as shown in this Plan-2 diagram;

Just for your reference, the price of TEAC AP-505 in Japan is around JPYen 128,400 (or USD 1,223) inclusive of VAT and shipment; the two units of AP-505 costs JPYen 256,800 which is much less than the price JPYen 440,000 for one AHB2 at present.

The current price of ACCUPHASE A-36 in Japan is still/always rather expensive around JPYen 450,000 (USD 4,286) inclusive of VAT and shipment (as usual in Japan for ACCUPHASE products, but fortunately it is cheaper than abroad).

Furthermore, current price of ACCUPHASE P-4500 Class-AB power amp in Japan is around JPYen 600,000 (USD 5,714) inclusive of VAT and shipment.

The Master Volume, Relative Gains and Software Crossover EKIO's Configurations in this setup would be;

And EKIO's Filters, Fq Response, Total Phase, Theoretical Delay, etc. based on my "The Simpler, The Better" concept would be;

Finally, I have also drawn my ultimate (dream?) amplifier Plan-3 in this project like this;

I would highly appreciate having your comments and/or suggestions on these amplifier plans in this project.

 

[dualazmak]

Hello friends,

As you may find in my recent posts, I have almost decided to use one or two Class-D amps in my current project.

In very nice timing with my plans, I just found the start of the business of Buckeye Amps in the US. Their (his) updated pricelist is also interesting and attractive. Since I am planning to use one or two Class-D amp(s) for only woofers (45 - 600 Hz), I would little concern about the Mid-High frequency characteristics and/or phase feature of the amp(s), and their NC5021MP line-up would perfectly match with my project.

Consequently, for the time being, I would like to carefully watch the startup and evaluations/reviews of Buckeye Amps...
Of course, I will soon ask Buckeye Amps regarding their policy and arrangements for international shipments especially to here in Japan.

 

[dualazmak]

Hello friends,

Just for your (our) reference, on amirm's nice review thread on Apollon Hypex NC2K Amplifier, several people had an interesting and intensive discussion on durability and stability of Class-D amplifiers (Hypex and/or Purifi modules) and Hypex SMPS Power Supply modules, especially on the quality and reliability of the capacitors in these amp and PS modules.

 

[Jukebox]

Hopefully, my next two or three posts will be due on September 19 or 20 sharing the tests and evaluations on ROTEL RB-1582 MkII together with Benchmark AHB2 in my single amplifier system and also in multichannel multi-amplifier system.

Any info about the Rotel RB 1582?

 

[dualazmak]

Any info about the Rotel RB 1582?

As you can find in my post #263, #264 and #265, I tested and evaluated ROTEL RB1582 MkII, and did not test ROTEL RB1582. The reason is quite simple that ROTEL RB1582 MKII has balanced XLR input, but RB1582 has only RCA unbalanced input.

In my amplifier exploration, I have been (and will be) sticking to XLR input capable amps for connections from DAC8PRO.

 

[dualazmak]

Hello friends,

One of the visitors to this thread contacted me inquiring simple and "at-a-glance" diagrams for JRiver into EKIO and ROON into EKIO in Windows 10 Pro 64 bit PC via VB Audio Hi-Fi Cable under ASIO4ALL, and also VB Audio Hi-Fi Cable into EKIO then output into DAC8PRO using the DIYINHK USB ASIO driver.

I would like to share the following simple diagrams with all of you assuming some of you are also interested in these "all in ASIO I/O routings".

As these are all in ASIO and independent from Windows kernel sound services, I recommend you to "Sound Off" all the Windows kernel speakers while you would enjoy music with JRiver MC or ROON in these multichannel multi-amplifier USB ASIO I/O routings.

You would please refer to my post #225 where I described and shared about "Completely Silent Audio (Audio-Visual) Dedicated PCs in this Project".

I hope the following diagrams are self-explanatory for you;

JRiver MC27 to EKIO via VB-Audio Hi-Fi Cable under ASIO4ALL;

ROON to EKIO via VB-Audio Hi-Fi Cable under ASIO4ALL:

(Edit: The below diagram has been already corrected as I wrote in my post #301)
VB-Audio Hi-Fi Cable into EKIO under ASIO4ALL (Common for ROON and JRiver MC) then into DAC8PRO;

In case if you would like to use another/other DAC(s) together with DAC8PRO, then you need to check/enable the specific ASIO output route(s) in the ASIO4ALL-EKIO panel. After that, new DAC(s) will appear in the pulldown list for the EKIO's output channels.


VB-Audio ASIO BRIDGE’s behavior while ROON (or JRiver MC) and EKIO are playing;

DIYNHK Control Panel while EKIO is playing;

 

[dualazmak]

Hello friends,

After I posted the above #297, two visitors contacted me by PM inquiring the type and physical configuration of my Windows 10 Pro 64 bit PCs dedicating for current audio system.

You would please refer to my post #225 where I described and shared about "Completely Silent Audio (Audio-Visual) Dedicated PCs in this Project".

 

[Vit]

After using all the information kindly displayed by Dualazmak I now have music with JRiver and Roon on a 2 channel DAC AK4490.
I am very happy ! : D
I can only say that Dualazmak was right, EKIO is very good.
Everything is intuitive and simple and I find everything well thought out and versatile.
I'm glad I went this way and thank you for all the support!
Now I will connect with DAC8PRO and deal with filters for a 3-way open baffle system (Beyma TPL200 / H, AE TD8M, 2 x AE15 Dipole)
As amplifiers I will use 2 pcs Pass XA30.8, and for bass a class D amp with a power of 400Watt.
Thank you again for all the support and all the information presented here !
Best regards

 

[dualazmak]

After using all the information kindly displayed by Dualazmak I now have music with JRiver and Roon on a 2 channel DAC AK4490.
I am very happy ! : D
I can only say that Dualazmak was right, EKIO is very good.
Everything is intuitive and simple and I find everything well thought out and versatile.
I'm glad I went this way and thank you for all the support!
Now I will connect with DAC8PRO and deal with filters for a 3-way open baffle system (Beyma TPL200 / H, AE TD8M, 2 x AE15 Dipole)
As amplifiers I will use 2 pcs Pass XA30.8, and for bass a class D amp with a power of 400Watt.
Thank you again for all the support and all the information presented here !
Best regards

Hello Vit, welcome to this thread.

I am very happy hearing that my I/O routing info is somewhat useful and valuable for your multichannel setup.

I now well understand that your 3-way open baffle system with nice drivers and Pass XA30.8 + class-D amps would be very interesting and attractive setup of digital crossover using EKIO and DAC8PRO, not only for myself but also for many people visiting this thread.

I really hope much good luck for your multichannel multi-amplifier project with DAC8PRO and very nice flexible software crossover EKIO.