---Description---Supplies--- FAQ --- Photos/Comments--- --- DSP challenge --- System --- |
Our longtime contributor and highly respected supporter of the OPLUG, known as 'Davey', sent me a DSP prototype to which I have listened now for many hours. I am quite impressed. Its performance is on par with the LX521 ASP. It is an alternative to the ASP. The only drawbacks that I see are the lack of analog input capability, which could be resolved by adding a suitable ADC module, and secondly, an input-to-output gain of less than 0 dB, which can make it impossible on some program material to drive the loudspeakers to full volume without a separate preamplifier. Construction of the DSP is literally plug-and-play due to RCA coax interconnects between modules. No soldering is required. But the DSP needs to be configured via USB from a computer. After that operation the DSP is self contained and runs independent of a computer. The proprietary LX521.xml file, which is essential to obtain the intended DSP functionality, is available for owners of LX521 Construction Plans. |
Parts/software used for construction of the prototype:
For analog input I used an ADC with S/PDIF & Toslink outputs, a SESCOM DCT-4T. It is inexpensive. It runs at 48 kHz rate, which is up-sampled to 96 kHz inside the nanoDIGI. When used for lower grade analog sources the ADC may have insignificant audible consequences. Output from high quality sources is most likely in digital format. |
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The setup by Richard Taylor can be used to implement a 2- or 3-way digital crossover with equalization for active loudspeakers. It runs on a Linux PC and uses only free, open-source software. The design goal was a small, self-contained unit that can live on a shelf beside an amplifier: it runs without need of a display, keyboard, or mouse, and it looks like this:
I am fully confident that Richard's meticulous design will match the LX521 ASP in performance.
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Solution a) is missing analog inputs and AES-EBU digital inputs. For a complete solution Tony@ miniDSP suggested to try out the miniDSP 4x10 Hd . It is a self-contained unit and with analog output for 8-channels already built-in. Davey adapted his configuration file from the nanoDIGI 2x8 to this fully assembled, yet highly flexible digital signal processing platform.
I have been listening to this processor now for a while using analog and digital outputs from the Oppo BDP-95 and Squeezebox Touch. I still use the multi-channel volume control after the miniDSP 4x10 Hd to be able to get extreme volume levels from the LX521 and AT1806 power amps. Davey has preset the unbalanced outputs to limit at 1.3 Vrms. On several occasions I amplified them by 5 dB in the MCV. But the unit can be switched to 2.5 Vrms max output. I will use that in the future and in conjunction with the internal volume control. It should eliminate any need for the MCV.
I am pleased with what I have heard so far. The miniDSP 4x10 Hd strikes me as more than an alternative to the ASP, accommodating both analog and digital sources and also providing volume control. The configuration file is available for owners of LX521 Construction Plans.
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