AudioCircle
Industry Circles => Hollis Audio Labs => Topic started by: HAL on 13 Mar 2020, 06:02 pm
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The Danville Signal Processing dspNexus 2x8 prototype is here and making music. Unit has two new AKM AK4493 and two new AK4499 DAC boards installed. The ADC is the great sounding AK5397.
Starting with the new headphone amp capability using Windows 7 and Audio Weaver for first testing. Using my HiFiMan HE500 headphones and sounding very good and no problem with plenty of headphone drive.
A new HAL MS-5 Music Server running Windows 10 is built and getting loaded with software to run the dspNexus 2x8 for the testing with the Monoliths and Magnetar speakers.
This unit has a powered mic input on front with separate ADC for measurements.
The Raspberry Pi 4 2GB is installed and as software updates are made it will be running Raspbian Buster OS and measurement software like Room EQ Wizard. The I2S bus is connected to the DSP and clocking will be from the DSP low noise clocks. Will be testing with Linux based music players like Audacious and Audacity for recording.
This chassis is only for the prototype. Production units will have a new style of case similar to the one from the AXPONA2019 show.
(https://www.audiocircle.com/image.php?id=205858)
(https://www.audiocircle.com/image.php?id=205859)
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Always at the cutting edge, aren't you? 8)
Rocket Ronny
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The dspNexus 2x8 prototype system is now running The Monoliths speakers with the bottom half of the 6x12 servo sub arrays.
For this listening, the AKM AK4499 DAC's are driving the BOSC amps for both the BG NEO10 midrange and GR-NEO3 tweeter planars and the AK4493 DAC's are driving the Rythmik HX300 servo subs.
Getting the levels adjusted and so far very good sound quality!
(https://www.audiocircle.com/image.php?id=206075)
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Great to see it up and running.
Any reason why 2 different DAC chips were used ?
Will that cause any timing issues ?
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This is a prototype to let us listen to both styles of DAC's. Since they are modular, they can be changed at any time by opening the chassis and swapping DAC modules once purchased.
Once production is going, I will get more DAC modules for trials with systems needing more than 4 channels. The DAC filter delays are not making any problems in The Monoliths speakers with the 3x12 servo subs for listening to this 3-way stereo setup.
The baseline dspNexus 2x8 is to have the AK4493 DAC modules. The upgrade system will have the AK4499 DAC modules. Price increases from the baseline DAC's to the upgrade system DAC's. The final prices are TBD at this time.
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The production dspNexus 2x8 chassis front panel is now installed.
The dspMusik 2x8 and dspMusik 2x16 in comparison to the dspNexus 2x8 system.
(https://www.audiocircle.com/image.php?id=207812)
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Long delay of an update due to the Covid19 trials and tribulations for 2020.
Since AKM had a silicon foundry fire recently, there is a now a long delay for new AKM DAC's and ADC's. Danville has a supply of parts for units for a good period of time. Also there will be other options for DAC's and ADC's being developed as the unit is fully modular for DSP's, ADC's and DAC's. The unit now has AKM AK4493 and AK4499 DAC modules and AKM AK5397 ADC module. All excellent sounding units with Class A output stage.
The recent trials are with the headphone amp function with different headphones. Working with Audeze and will have a pair of LCD-MX4 phones for testing this week along with Sennheiser HD650 and HiFiMan HE500 phones.
Next stage is bring up the RPi4 for room measurements, music playback over I2S Bus from files. Then when Audio Weaver 8.x is integrated adding capability for room correction. The DSP crossover function is already working well using the original Audio Weaver 5.16 implementation.
The user will now have direct access contiol to crossover functions, DAC and ADC filter selection, volume control, input selection system gain and other parameters via the IR remote control.
More updates as I get them and will pass them on.
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The new version of the software will be coming soon for Alpha testing.
With this software version the RPi4 will be operational and interfaces to the DSP by I2S Bus and SPI Bus for audio connection and control. So now there are separate data and low phase noise clocks moving the audio data from the player to the DSP processing and HiRez DAC's.
This is the full version dspNexus 2x8 system, so the next speaker and servo sub project will utilize all 8 channels for a stereo setup. That speaker design is in work now.
This design will follow the new Magnetar speaker due mid April to start listening trials.
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For anyone thinking about DSP crossovers, here are a few reasons that the dspNexus can be superior to passive crossovers.
1) Not all DSP crossovers are created equally. The Audio Weaver program used for dspNexus system has custom designed filter topologies
2) By removing the passive crossover between the amp and speaker driver, it is now being controlled the most directly as possible for any back EMF generated. Any passive crossover reduces the control on the driver back EMF due to the parasitic losses in the circuit. Even speaker cable length has a similar effect on the back EMF control.
3) Using short speaker cables (in the case of the Magnetar speaker using 18in speaker cable) gives greater control of the speaker driver.
4) Passive crossovers are sensitive to component actual values (component tolerances) and each channel can have different frequency responses. This affects the speakers overall frequency response and both channels will be different.
5) Passive crossovers channel to channel matching varies also due to the component tolerances. This affects stereo imaging.
6) Since passive components have parasitic losses (all passive components are not pure L, R or C) the response of the crossover will vary away from the design parameters.
7) A DSP crossover's channels will have the same frequency and phase response, if that is what the user sets up.
8 ) A DSP crossover can give time delay between channels to compensate for distance offsets between drivers. The higher the sample frequency the smaller the time difference that can be compensated.
9) Using memory the time delays can account for feet of offset between a main speaker and subwoofer to optimize their placement to work with room acoustics.
10) Using techniques like minimum phase response correction, room acoustics and speaker response can be adjusted for better room integration.
Hopefully that will give some insight into why DSP crossovers are very popular with proaudio active speakers for things like control room monitoring for music mastering.
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The updated dspNexus 2x8 system is installed and beginning trials with the AGN Line Array speakers.
The software block diagram has been updated to use the new functions of the dspNexus. This includes the internal RPi4 via I2S Bus directly to the DSP for music replay and measurements.
The RPi4 on this system has JRiver MC28 and REW 5.20 installed for use.
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I'm going to follow this conversation since I am interested in how this DSP compares to others such as the MiniDSP.
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If you are looking for more information on the dspNexus 2x8, here is the webpage for the system.
https://danvillesignal.com/dspnexus-dsp-audio-processor
i have been using the predecessor the dspMusik 2x8 over different revisions for many years.
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The latest update from Danville Signal is that dspNexus 2x8 DSP crossover system metal work is complete and in house.
They are targeting early 2023 as the system release time.
The system will be released with the 21469 dspBlok for DSP use. They are still working on the 21569 port for the next generation DSP.
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in a chip shortage world, progress is slow, but this is a step in the right direction
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Yes, it has been bad since AKM foundry was down, but luckily that has turned around and the newer generation Analog Devices DSP's are available.
Other devices are still out and had to be new designs to change parts.
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The prototype dspNexus 2x8 is getting a firmware update to test the latest functions and remote operation. This is beta testing at this point. There is new AudioWeaver code to support many new functions for the remote control. Also has a simplified menu structure for both the remote and rotary encoder on the unit.
Once this is tested, will then be ready for the production dspNexus 2x8.
Plan is still to have the dspNexus 2x8 production release before AXPONA 2023. Will keep everyone posted on that occuring.
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The dspNexus 2x8 firmware update is done and the system is running with the new remote and rotary encoder features. Will be beta testing them over the next few days to verify operation.
I can compare the direct output of the system to the internal headphone system with this setup. A check to see if the upgraded power supply upgrade is doing well.
(https://www.audiocircle.com/image.php?id=250502)