Monday, January 20, 2025

Signal Processing For BDS Correction & Sub Integration ~ miniDSP Installed In EleNanoKit System 19Jan25

The 8200R is great with the modern Russian Tung Sol 6550 power tubes and the 1960 NOS Valvo 12AU7 valves from Germany for the pre-amp, and the wireless connections with the DS200Pro are very good using BT/aptX, and the NanoOnkens with Mark Audio Pluvia 7.2HD drivers are nice full range speakers. Yet I still hear and see anomalies from my desired house curve response in the SPL frequency measurement sweeps I made. So, I re-installed my miniDSP 2x4 HD using Toslink to lash it between the BT receiver and the amp and I went to work on finding signal processing adjustments that would improve the sound further. BTW, using the optical connection of the miniDSP into the system eliminated prior issues I was having measuring the EleNanoKit with it installed. Purists don't approve but miniDSP boxes are simply amazing for this kind of work... and correcting stuff in the digital domain is very effective. Here's the experimenting underway using macOS on a Macbook Pro for both miniDSP control and REW measurements. Plus, even purists often use crossover circuits; they are basically the same in the analog realm, but not as flexibly manipulated in real time.

Eliminating Baffle Diffraction Step Loss In The NanoOnkens... I manually built a number of PEQ filters in the miniDSP to correct the NanoOnkens for some BDS loss and to account for the acoustics of the Blodgett living room "free space" placement of them. I also let REW itself automatically generate a set of PEQ filters from an analysis of the raw SPL sweep. The SPL sweeps are the last measurements shown immediately below with my filtering as well as the auto-generated filtering when applied. Both are decent compared to the raw but I think I prefer the auto-generated biquads. These sweeps are without the NanoSub active. The last pic here shows the final install... I may yet decommission the AirPort Express (not shown);  I prefer the Bluetooth wireless, even from macOS; unfortunately iOS doesn't support aptX and my workaround is to always have macOS stream the music while iOS serves as a remote control.

Line Level Subwoofer Integration... With the 2x4 HD back in the system I can also use it to deliver a line level signal to the sub, eliminating the sloppier high level connection I have been using. Though it has been nice for volume adjustments. The 2x4 HD has 4 outputs and I'm using #1 and #2 for the main full range L & R NanoOnkens; I'm using #3 and #4 to send just the L & R low frequencies (~ <110Hz) to the NanoSub line-in RCAs on the plate amp. Sub integration is pretty simple but I'll fiddle with the cutoff and gain on the plate amp to ensure balance.
The entire EleNanoKit now sounds even better, neh killer now, and with the high def wireless audio additions to the system, it's very convenient and is still very small: "nano." I swapped out the Tung Sol 6550s for the Mullard EL34s for a listen again, this time with the preferred Valvo driver tubes. The EL34s sure had thump at the low end so I did have to attenuate the subwoofer down 4dB to avoid clipping. That too was easy to do in the miniDSP gear. I may want to make a permanent adjustment on the sub actually, independent of power tube ~ work for tomorrow. The listen actually confirmed my preference for the Tung Sols.
Update 21Jan25 ~ Filter Mods & Subwoofer Integration...  With the 6550s back in for power, I tried some more passes on correction filters and subwoofer gain and cutoff and decided on my A5 version... shown here on the sub and full kit, against the raw sweep with everything flat. Sweet. But, look how dominant the room is ~ both the NanoOnkens on their own, and the NanoSub on it's own, resonate similarly and throw basically the same SPL curves from 20Hz-80Hz. It's great sounding anyway and I'm surely not gonna make any room traps or acoustic mods in my living room, as it's probably a temporary location for the EleNanoKit. Interesting though.
Update 25Jan25 ~ Adding Hardwired Full HD Digital To EleNanoKit... Ultimately I really wanted even more from the EleNanoKit and so I added a fanless, headless, mele Linux PC to run JRiver MC local to the DAC/Amp. I also wanted the DSP applied to this source, like the others, so I connected the NanoPC to the miniDSP using USB. I also added this MC32 streamer as a server in my JRemote app so I don't have to add a monitor or keyboard to the tiny PC. Now I have full 24bit/192KHz streaming to the miniDSP DAC/DSP. Woohoo. Works great.
In order to funnel all  three sources through the miniDSP for signal processing (that is local JRiver MC on USB, BT/aptX stream on optical, and AirPlay stream on analog/RCA), I need to be able to switch the miniDSP input source conveniently without connecting a PC to the USB port ~ it's in use now. I got a $7 miniDSP remote v2. I can also use it to switch among 4 different filter & routing systems if I ever need, but right now have an optimal setting in #1, as described above. Per initial system objectives, the whole kit still remains "nano."
Here's a tease of the JRemote metadata and player; it's cool enough IMO; lyrics can be displayed and it even displays JRivers calc of the dynamic range of the track.
Update 27Jan25 ~ Added ST Power Control To EleNanoKit... I was leaving all the wireless receivers, DACs, and streamer PCs powered while just turning the TU-8200R on/off manually. The subwoofer is auto-sensing so goes quiescent when there's no signal. I didn't prefer leaving all this stuff on so I added a SmartThings power outlet switch in front of all the digital gear. When I hard deliver or drop power to the kit, all seems to turn off and reboot fine... with all settings and connections as expected. I also added a secure shell server to the Linux-based streamer so I could remotely manage it without having to use a local keyboard or monitor there.

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