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

maverickronin

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I contacted 3DConnexion a couple of years ago when I was searching for a wireless volume control. It's designed for 3D drawing and quite expensive, They didn't think it would work with JRiver, although they said they would forward my enquiry to their development team. I haven't heard anything since (not that I really expected to). It's a nice looking unit.

I have one of these, although I use it for the occasional game and not for CAD.

It's probably not what people in this thread are looking for because it doesn't actually spin like a knob. It's 6 axis joystick that be twisted, tilted, pushed down, pulled up, slid side to side, and front to back.

The included software only has presets for various CAD programs but it can be programed for anything. The downside is that the GUI for programming it is so basic as to be useless. To get it to do anything that's not built in you will need to manually edit its XML configuration files. This is a huge pain, but does work in the end.

I would not recommend it to casual users.
 

tpaxadpom

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Wow, it is like someone read my mind. I was planning to do something similar with either NS1000M or DIY speakers that use NS1000M tweeter and midrange but got side tracked with audio equipment failures and repairs. I was also thinking along Okto DAC to feed amps and subs and do all processing in software. Though your idea of comparing multichannel with classic implementation is simply awesome.
PS: Okto Research had a demo DAC that was traveling across US, though it never made it to me. I was interested in listening to this DAC first prior to committing to this project. I am really happy to see someone else is doing just that!
 
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dualazmak

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Wow, it is like someone read my mind. I was planning to do something similar with either NS1000M or DIY speakers that use NS1000M tweeter and midrange but got side tracked with audio equipment failures and repairs. I was also thinking along Okto DAC to feed amps and subs and do all processing in software. Though your idea of comparing multichannel with classic implementation is simply awesome.
PS: Okto Research had a demo DAC that was traveling across US, though it never made it to me. I was interested in listening to this DAC first prior to committing to this project. I am really happy to see someone else is doing just that!

Hello tpaxadpom,

Welcome to this multichannel project entitled "Multi-Channel, Multi-Amplifier Audio System Using Software Crossover and Multichannel-DAC" with Software Crossoover EKIO, OKTO DAC8PRO, multichannel amplifiers (not yet fully decided), renovated YAMAHA NS-1000, YAMAHA YST-SW1000 (L&R) and FOSTEX T925A.

As you may aware, so far my adventure in this multi-channel project went rather nicely, and I am on the final step to the first goal of trying and deciding the suitable multichannel amplifier(s).

You would please carefully read through this thread, and I would highly appreciate if we could share and exchange various topics and information on "software crossover" plus "multichannel-DAC" based multi-channel, multi-amplifier audio system.

Since I already found and confirmed that several "software crossover" solutions are also very much interesting and useful even for single DAC plus single amplifier system driving speaker units through LC (coils and capacitors) crossover network, any topic or discussion on "software crossover" for "single-DAC plus single amplifier" will be very much welcome.

In this thread, I also would like to share and discuss these major issues always associating with Multi-Channel, Multi-Amplifier Audio System;

- Digital I/O for software crossover within PC
- Delay, latency and synchronization issues
- Phase issues
- Master volume and gain issues

I thank you again for your kind attention on this thread.
 
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dualazmak

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Hello friends,

I assume all of you are well aware of recent amazing review by amirm on DAC8 Stero dated July 15; all the people interested in OKTO's wonderful products and activity should read that review on DAC8 Stereo.

Since I already have 8-channel DAC8PRO latest model in this project, currently I have no plan to get the DAC8 Stereo. I believe the various improved features in DAC8PRO have been fully implemented in DAC8 Stereo.
 
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dualazmak

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Completely Silent Audio (Audio-Visual) Dedicated PCs in this Project

Hello friends,

One of my audio-enthu friends contacted me inquiring about my completely silent audio (audio-visual, AV) dedicated Windows 10 PCs in this project.

I am actually using two DIY assembled silent audio (and AV) dedicated PCs in this project. Of course the PCs in our listening room should have enough processing power for operations of Windows 10, JRiver and/or Roon, software crossover such as EKIO, web browsing including YouTube and other streaming audio and AV services. Furthermore, it is critical and the must that the PCs should be completely silent in our listening room for Hi-Fi audio enjoyments.

Consequently, the audio (AV) dedicated PC in our listening room should be fan-less, spindle-less (HDD-less); "fan-less" means no chassis fan, no fan in PSU (power supply unit), and no CPU cooling fan.

The CPU should have enough but not over-spec processing power at low temperature operation. In this line, I selected and have been using Intel Core i7-2600S (LGA1155, 4-core 8-thread, 32 nm, 8 MB Intel Smart Cache, 2.80 GHz, Turbo Boost 3.80 Ghz, TDP 65 W) with Intel HD 2000 Graphic Processor in it.

My two completely silent PCs in this project are;
WS000706.JPG


The left Silent PC:
Chassis:
NoFan (NoFen) with Fanless 400W PSU, no chassis fan
PSU: Nofan P-400A Silent 400W Fanless
M/B: ASUS P8Z68-V PRO GEN3
CPU: Interl Core i7 2600S (LGA1155, 4-core 8-thread, 32 nm, 8 MB Intel Smart Cache, 2.80 GHz, Turbo Boost 3.80 Ghz, TDP 65 W, with Intel HD 2000 GPU)
CPU Cooler: Huge fan-less natural air-flow CPU cooler
GPU: CPU incorporated Intel HD 2000
MEM: 16 GB (DDR3 1066)
SSD-1: SATA-6Gb/s (AHCI) 128 GB for OS & Software, etc.
Windows 10 Pro 64 bit, JRiver MC26, Roon, Chrome, EKIO, ESET Internet Security, etc.
SSD-2: SATA-6Gb/s (AHCI) 2 TB for data, non-compressed music library
LAN: Giga bit wired home LAN with high-speed optical Internet access

The right Silent PC:
Chassis:
HUSH-ATX with Fanless 240W PSU, no chassis fan
(Unfortunately, HUSH-ATX in Germany has disappeared from the market)
PSU: Fanless 240W Full ATX 2.03 Standard. Auto-switching 90-250VAC
M/B: GIGABYTE Z77MX-D3H
CPU: Interl Core i7 2600S (LGA1155, 4-core 8-thread, 32 nm, 8 MB Intel Smart Cache, 2.80 GHz, Turbo Boost 3.80 Ghz, TDP 65 W, with Intel HD 2000 GPU)
CPU Cooler: Large fan-less heat sink connected to HUSH-ATX Chassis through two heat pipes
Chipset Cooler: dedicated heat sink connected to HUSH-ATX Chassis through one heat pipe
GPU: CPU incorporated Intel HD 2000
MEM: 16 GB (DDR3 1066)
SSD-1: SATA-6Gb/s (AHCI) 128 GB for OS & Software, etc.
Windows 10 Pro 64 bit, JRiver MC26, Roon, Chrome, EKIO, ESET Internet Security, etc.
SSD-2: SATA-6Gb/s (AHCI) 2 TB for data, non-compressed music library
LAN: Giga bit wired home LAN with high-speed optical Internet access

I can use either of these two PCs anytime in this project with one wireless mouse, one wireless keyboard and one TFT PC monitor (1920 x 1080 pixel, 64 x 38 cm); I can select either of the PCs using a simple KVM changer. In front of my listening sofa, the mouse and keyboard are on low (45 cm) living table, and the PC monitor is placed on the floor with 10 cm height Styrol block; they do not interfere with the sound from the SPs to my ears.

The temperature of CPU never goes over 50 degree C even in full operation of JRiver or Room and software crossover EKIO. The total CPU usage is always below 50 %.

I would appreciate if I could hear what type of silent or quiet PC and/or Mac you are using in your audio system; such info exchange would be valuable for many people visiting here and having interests in multichannel audio and audio-visual system.

BTW, at my home office upstairs, I am also using two of very powerful but quiet DIY assembled Intel Xeon (12-core, 24-thread)+NVIDIA GTX TITAN based PC-Workstation with dual EIZO FlexScan EV2750 monitors (i.e. 5120 x 1440 pixel, 120 x 33 cm desktop area), but any description and introduction of these PC-Workstations are out of the scope of this thread of my audio multichannel project.
 
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John1959

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Hi Dualazmak, nice to read about that good old Hush enclosure! I still have one, a small version. Completely fanless too, a mini-ITX format based on VIA-Epia platform. I used this PC to play audio files when 99% of the people still used CD's and a CD player (about 15 years ago I think). Unfortunately, this unit didn't have enough processing power to decode high res mpeg files also, so I decided to upgrade to a "normal" (not fanless but pretty quiet) PC as a "Mediacenter". The motherboard failed also, BTW. I still have the enclosure though, which looks and feels more like a high end amp than a PC. Maybe I will put some Hypex of Purifi amps in it some day!

hush-technologies-hush-mini-itx.jpg
 
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dualazmak

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Hi Dualazmak, nice to read about that good old Hush enclosure! I still have one, a small version. Completely fanless too, a mini-ITX format based on VIA-Epia platform. I used this PC to play audio files when 99% of the people still used CD's and a CD player (about 15 years ago I think). Unfortunately, this unit didn't have enough processing power to decode high res mpeg files also, so I decided to upgrade to a "normal" (not fanless but pretty quiet) PC as a "Mediacenter". The motherboard failed also, BTW. I still have the enclosure though, which looks and feels more like a high end amp than a PC. Maybe I will put some Hypex of Purifi amps in it some day!

Hello John1959,

Very nice to hear so! My completely silent two audio dedicated PCs with "NoFan (NoFen) chassis+silent PS" and "HUSH-ATX chassis+silent PS" are still working just fine in this project.

I agree with you, however, so many super-quiet low rpm CPU and chassis fans are available now in the DIY PC market with which you may build almost silent PCs. Of course, SSDs are silent, and it is also important to use very quiet or silent PS in your PC at our listening room.... I suggest that you would also take care of cooling of chipset on your M/B to ensure long durability of the motherboard.
 
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dualazmak

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Trials with Hypex NC400 based DENTEC DP-NC400-4-EXP Multichannel Amplifiers

Quick and Brief Conclusion:
The total sound quality with DENTEC DP-NC400-EXP was really wonderful and very nice fit for my multi-channel project, and it is definitely the top-ranked candidate for introduction into my system, even though it is really expensive.

Hello friends,

As I pre-announced here in this thread, Mr. Fujimoto, President of SOUND DEN Sound Pro Shop, kindly visited my home yesterday with two of DENTEC DP-NC400-4-EXP on his car. DP-NC400-4-EXP has 4 (four) Hypex NC400 amp modules in it, and the amp and the wiring are very carefully fine tuned-up by Mr. Fujimoto and DENTEC people including cryogenic treatments and some of the thick pure silver wiring (I do not know the effectiveness, though).

DENTEC DP-NC400-4-EXP (still not yet shown at their web site) is the new version/model of their DP-NC400-4, and the new DP-NC400-4-EXP has its "heavy-duty transformer plus large capacitors type" power supply (PS) in external PS Units. The one PS Unit supplies DC power for two NC400 modules, so, therefore, two PS Units are needed for one DP-NC400-4-EXP main instrument. This new concept and design of external PS Units will enable future reasonable(?) upgrade with possible new Hypex amp modules keeping the PS Units would remain unchanged, he said.
WS000724.JPG


WS000725.JPG


Before to try and listen to the sound of DP-NC400-4-EXP in my stereo 5-way (10-channel) multi-channel system, Mr. Fujimoto and I carefully listened to my reference sound with DAC8PRO in single DAC mode and ACCUPHASE E-460 integrated amp plus the renovated LC-network as show below. As described before, the RCA input into sub-woofers YAMAHA YST-SW1000 was achieved by ONKYO DAC-1000(S) through sync AES/EBU (CH1+CH2) connection from DAC8PRO.
WS000726.JPG


We very carefully listened to the reference sound of some of my Audio Sampler music tracks, and to his reference CD tracks recorded at their DENTEC Recording Studio. Then, he became much interested in the performance and sound quality of DAC8PRO (still only one in Japan, I believe) which he tried for the first time.

Next, I changed the connections at the SP Cabling Board into mutli-channel, multi-amplifier routes;
WS000727.JPG


And we carefully connected 8 XLR cables from DAC8RPO into two of DP-NC400-4-EXP, and also connected the 16 SP cables to the binding posts of two of DP-NC400-4-EXP. He preferred that one to drive L-channel SPs, and another one to drive R-channel SPs, as shown below;
WS000728.JPG


Now I set the software EKIO's configurations as follows which mimics the original LC crossover network of YAMAHA NS-1000;
WS000729.JPG
and;
WS000730.JPG


After careful listening sessions to the multi-channel sound of some of my Audio Sampler music tracks, and to his reference CD tracks, we also tried the second EKIO configuration using 48 dB/Oct LR filters for the crossover of woofers to Be-squawkers at rather low ca. 475 Hz as follows;
WS000731.JPG

and;
WS000732.JPG


Using above described procedures, we carefully compared the reference sound and the DP-NC400-4-EXP multi-channel sound in two different EKIO configurations.

Very regretfully, Mr. Fujimoto and the two DP-NC400-4-EXPs could stay at my home only for half a day; even though we could have the intensive ear-listening sessions, no measurement session with REW and ECM8000 microphone was performed this time.

OK, now what would be my (our) impressions on the sound quality with two DP-NC400-4-EXPs in my multi-channel system?

Here, I should not describe too much about our subjective impressions, but let me say that the total sound quality with DP-NC400-4-EXPs is just amazingly nice and wonderful in comparison with my reference sound of single amp system.

We agreed that my reference sound with ACCUPHASAE E-460 is still also very nice, and two DP-NC400-4-EXPs in multi-channel system gives audibly better responses of the SP Units (thanks to the elimination of the LC-network) and the S/N and distortion features are below audible level even in pianissimo small volume and also in rather large sound volume, just the same as in the reference sound.

We also found and confirmed that EKIO's crossover functionality is really wonderful and accurate with no deterioration of sound quality played by JRiver in 192 kHz 24 bit.

Also, thanks to the fine-tuned DP-NC400-4-EXPs, together with the still very nice cabinet and SP units of YAMAHA NS-1000, the audible 3D sound perspectives and phase features are just perfect in any way; even when we moved, left and right, up and down, front and back, around my usual listening position, the nice 3D and phase features of the sound remained unchanged.

This is my first experience in listening to Hypex or Purifi Class-D amplifier(s), and I was really impressed by the sound quality of Hypex NC400, fine-tuned by DENTEC, especially the smooth, very clear and clean but not "dry", I may say a kind of "rich", sound which is my happy surprise, as I have been thinking of somewhat dry or crispy sound with Class-D amps including NC400.

I heard that the two of DP-NC400-4-EXPs came to my home were already under the purchase order from one Japanese audio enthusiast, and this was the one of the reasons that they could stay at my home only half a day yesterday with careful handling of Mr. Fujimoto.

In conclusion, the total sound quality with DENTEC DP-NC400-EXP was really wonderful and very nice fit for my multi-channel project, and it is definitely the top-ranked candidate for introduction into my system, even though it is really expensive.

BTW, Mr. Fujimoto looks to be much interested in DAC8PRO; I also told him that DAC8 Stereo is now also available, and I will soon send him the links of OKTO RESEARCH as well as amirm's nice reviews on DAC8PRO and on DAC8 Stereo.
 
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Dion_Sinewave

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I am using 6 channels of NC400 in a 4 way active system (With powered subs) and can’t believe how good the modules are. All of my class A/B amps will be replaced by Hypex in the future - I thing they are a big step forward.
I love this thread and look forward to each update :)
 
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dualazmak

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I am using 6 channels of NC400 in a 4 way active system (With powered subs) and can’t believe how good the modules are. All of my class A/B amps will be replaced by Hypex in the future - I thing they are a big step forward.
I love this thread and look forward to each update :)

Hello Dion_Sinewave,

Thank you for your kind attention on this thread. I also read several of your posts with great interests.

I was quite lucky and happy having the opportunity of free trials with DP-NC4004-EXP. As you aware, I have so far tried YAMAHA MX-A5200 (AV multichannel amp) and DP-NC400-4-EXP (Hypex NC400 modules), and I learned a lot that I should be very much careful in making final decision on multichannel amps in my current project.

Very fortunately, my current reference system with DAC8PRO in dual DAC mode (CH1+CH2 for sub-woofers, and CH3+CH4 for all the other SPs) with ACCUPHASE E-460 integrated amp still gives very nice sound quality with which I fully enjoy music until my final decision on the introduction of multichannel amp(s) in my system. This means I may take enough time and intensive reaserch/trials on various amps for multichannel utilization.

Now, I am seriously considering and exploring possibilities of (hopefully free) trials with Purifi 1ET400A amps, and also with Benchmark AHB2. So far, I could not find, however, such free trial route and arrangements with Purifi 1ET400A based amps in Japan. As for Benchmark AHB2, I know that Benchmark is offering free trial of AHB2, but it is limited only within the USA, and not available in Japan, quite regretfully.

I just started to think about possible personal contacts with Apollon Audio in Austria as well as with Benckmark in the USA for possibilities of trials at my home, since I well learned that the candidate amps should be tested at my home in my exact multichannel system in intensive comparison with my reference sound. I assume you would kindly agree with my policy and direction towards the final decision on multichannel amplifier(s).
 
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dualazmak

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Dion_Sinewave

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Hello Dion_Sinewave and friends,

I just found that Benchmark very recently has assigned its sole dealer, Emilai Inc., in Tokyo Japan!
https://www.benchmarkmedia.jp/products/

They said that demo AHB2 is now available also in Japan;
https://www.benchmarkmedia.jp/dearlers/

I just placed my request for trial of demo AHB2 at my home, preferably 4 units at once, with my project info;
https://www.benchmarkmedia.jp/contact/contact-before/

Fantastic! AHB2 is a dream amp, I look forward eagerly to your review.
 

Dion_Sinewave

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I switched from my 4 way stack of Rotel amps to Hypex NC400 x 6, and can’t believe the improvements.
Though your Accuphase amp is a beautiful piece of gear, and a big step up from my Rotels.


.
62EDF608-9639-4EBA-B225-6494D9680AF5.jpeg
 
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dualazmak

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An Interlude again, in the Project:

Reference Sound Quality Improvements by Complete Physical Elimination (Bypass) of Attenuators in Single Ampifier+LC-Network System while Software Crossover EKIO mimics Attenuators

Hello friends,

In my post #130, I showed and shared that software crossover EKIO's gain settings can perfectly mimic the attenuator adjustments for NS-1000's Beryllium squawkers (Be-SQ), Beryllium tweeters (Be-TW) and super tweeter (ST) FOSTEX T925A.

In my single amplifier+LC-network reference sound system, I now almost always use EKIO's 10-channel configurations with such gains simulating the preferable attenuator settings, and the real settings in physical attenuators are now normal position (no attenuation) for Be-SQ and Be-TW, and max position (again no attenuation) for ST as shown below;
WS000726.JPG


Here, such physical attenuators, however, still exist in the LC-network box, and the SP level sound signals go through the attenuators into SP units, even though all the attenuators have been fully overhauled in August last year.

It is well known that, in general, we should better to replace attenuators with fixed-value resistors after we could find and fix the attenuator settings and could measure the attenuation value in Ohm unit. Having the full utilization of digital software crossover which well simulates the attenuators by gain control, however, we can just physically eliminate (or bypass) the attenuators (and fixed-value attenuation resistors) for better sound quality.

Although a little bit belated, I did such DIY today to fully eliminate (bypass) all the attenuators in the LC-network box expecting some improvements in sound quality;
WS000735.JPG


WS000736.JPG


In this DIY, I installed connection terminals, as you can see in the photos, for future possibility of rolling back to attenuator utilization, such possibility would be minimal though, I think.

Even though I have not yet performed any objective measurement of the improvement using REW+ECM8000 microphone, the audible improvements of the sound are exceeding my expectations in terms of sound cleanliness, transparency, transient responses, 3D perspectives, phase features and stability, and perhaps S/N and distortion, in SQ, TW and ST sound.

In my first post in this thread, I wrote;

Since I already found and confirmed that several "software crossover" solutions are also very much interesting and useful even for single DAC plus single amplifier system driving speaker units through LC (coils and capacitors) crossover network, any topic or discussion on "software crossover" for "single-DAC plus single amplifier" will be very much welcome.

Now, I would like to repeat this message here; software crossover, EKIO in this project, is also a very nice solution for sound improvements even in "single-DAC plus single amplifier audio system" by physically eliminating all the attenuators in the SP level signals.

In conclusion today, now I have further improved sound quality in my reference sound system, and this reference sound would be my new standard for further exploration of multichannel amplifier(s).
 
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dualazmak

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Hello friends,

Regarding my post above, with careful consideration and listening tests, I changed the "attenuator bypass wiring" into this way ;
WS000740.JPG


With this bypass wiring, attenuation is fully canceled while the amplifier still can "see" the 8 Ohm attenuators in the circuit. I believe, this should be better way to fully cancel attenuation with no change of impedance (attenuator+SP Unit) against amplifier.
 
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dualazmak

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One Naive but Important Question:

Is it Feasible (Preferable) or Not to have 8 Ohm Resistors Parallel with SP Units in Multichannel System with Rather Powerful Hi-Fi Amplifiers?

Through my recent DIY (post #234 and #235) to fully eliminate (bypass) SP level attenuators in the single-amplifier + LC-network reference sound system expecting total sound quality improvements, I learned that better sound improvements were obtained when the 8 ohm attenuators were maintained within the circuit , in comparison to the complete physical removal of the attenuators.

Above finding would be probably due to YAMAHA's original extremely careful fine-tuning of NS-1000 with the total "fixed impedance" of the LC-network+attenuators+SP Units, since the above preservation of the 8 ohm attenuators within the circuit maintains the total impedance unchanged even if the attenuation is now fully canceled (the sound signal does not go through the attenuator).

This result brings another naive but important question to me; Is it Feasible (Preferable) or Not to have 8 Ohm Resistors Parallel with SP Units in Multichannel System with Rather Powerful Hi-Fi Amplifiers?

Of course I know that, in principle, 8-ohm resistor in parallel with SP units would just give extra workload to the amplifier, and it would not affect the sound quality of the SP unit.

In some cases, especially if a rather powerful Hi-Fi amplifier (such as Benchmark AHB2) would dedicatory and directly drive a high efficiency mid-range or tweeter, the intentional addition of a 8-ohm resistor in parallel within the circuit may be (I assume) preferable for stable operation of the amplifier, and also for steady universal "burn-in" of the multiple amplifiers, as show below;
WS000753.JPG


In this scheme, I plan to use exactly the same rather powerful four (4) Hi-Fi amplifiers, and I would like to burn-in the amps universally through my daily listening sessions. (I even plan to rotate these four amps periodically to dirve WO, Be-SQ, Be-TW and ST.)

My main question here is;
Is it Feasible (Preferable) or Not to have 8 Ohm Resistors Parallel with SP Units in Multichannel System with Rather Powerful Hi-Fi Amplifiers which dedicatory and directly drive high efficiency SP units like YAMAHA's Be-SQ and Be-TW as well as FOSTEX T925A Super tweeter?

When I googled by "resistor parallel speaker amplifier impedance", I could find several discussions on this issue in several audio forums. I assume, however, the preference (Yes or No) would vary depending on the exact audio system to be applied, and I would highly appreciate having your thoughts and suggestions on this issue.
 
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dualazmak

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In my speaker cabling boards, I already have the "golden" 8 Ohm 100 W resistors which I have been using as "dummy speakers" for "silent" burning-in of my amplifiers and LC-network capacitors;
WS000727.JPG


The golden "dummy speaker" 8 Ohm 100 W resistor is ARCOL HS100 8R F;
https://www.mouser.jp/new/arcol/arcol-hs-power-resistors/
https://www.mouser.jp/datasheet/2/303/HS-Datasheet3-779273.pdf

and I have open space to add one more ARCOL HS100 8R F on each of the L and R SP Cabling Boards.

I can easily add and test these 8 Ohm 100 W resistors in parallel at the multi-amplifier cabling terminals for Be-SQ, Be-TW and ST as shown in the scheme in my one above post.
 

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gene_stl

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The main disadvantage of leaving that power resistor in the circuit is that it will waste something close to half your power. With modern power amps this is not much of a problem since power amp watts are getting like memory and bandwidth, ie fairly low cost. And most power amps today exceed the desireable input of Yamaha drivers so it may afford a slight safety factor.

It MAY improve the damping factor slightly but probably not audibly. By paralleling with the low amplifier impedance but locally rather than through speaker cables. a very small amount.

If the power amp you are using has some residual zero crossing notch distortion having a power wasting resistor might push the amp into the no notch region. You mentioned the Benchmark amp which probably has no zero crossing notch distortion. It is reported to have feed forward correction.

I would guess it would be very hard to hear the difference between switching it in and out if you were able to level adjust simultaneously.

On your series capacitors have you considered using one on each side of the driver in order to present the amplifier with a more symmetric circuit? Also I used to and will use again a series fuse. I used one quarter amp fuses and never blew them which was surprising even when listening loud for a good while they never blew. Both on the tweeter and upper midranges. I am interested in more modern speaker (driver) protection boards, especially to protect the drivers against output stage failure. Tom Christiansen has some interesting ones using MOSFET switches iirc.

https://neurochrome.com/collections/protection-control
 
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dualazmak

dualazmak

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Hello Gene,

You wrote:
On your series capacitors have you considered using one on each side of the driver in order to present the amplifier with a more symmetric circuit?

I have already designed and prepared both of the L & R "LC-Network+Attenuators Box" and the "L & R SP Cabling Board" as symmetric as possible, and placed them as symmtric as possible bsides the SP Units;
WS000736.JPG

and;
WS000401.JPG

(I fully open the grass slide doors behind the SPs when I intensively listen to the audio system.)

What do you mean by "a more symmetric circuit"?

In any way, thank you for your info and the link which I am now carefully learning and investigating.

I agree with you that Benchmark AHB2 has almost no zero crossing notch distortion. I assume that the parallel 8 ohm resister's constant extra load to each of the three AHB2s (driving BE-SQ, BE-TW and T925A ST) would be nice for stable operation of the amps and also for universal constant burning-in, although I need to pay a little bit additional cost for electricity consumption!
 
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