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Channel D Pure Vinyl Music Server Software and Seta Phono Stage and Lynx Hilo DAC

A Computer-Based Active Crossover for Sanders Sound Speakers

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System Set-up and Operation

As my friends will attest, I am not particularly computer savvy.  Rob was extremely helpful in getting the new system it up and running though in point of fact, it is not that complicated.  While Rob might have gone the extra yard because I am a reviewer, I must emphasize that he provides excellent support for all customers.  Rob answers telephone inquiries personally and, via a link on his website, he can gain remote access to a customer’s computer, and thereby help them with set-up, or to trouble shoot a problem.

Because the Hilo contains the ADC, it serves as the hub for all analogue sources.  In my case, both the SETA phonostage and my CD optical transport are connected to the Hilo via single-ended (RCA) interconnects.  The Hilo is connected to the Mac Mini via a USB cable which, as I learned, conducts information in both directions (i.e., from the Hilo to the Mac Mini, and from the Mac Mini to the Hilo).  I use balanced interconnects to connect the outputs of the Hilo to my four Merrill Audio Veritas monoblock amps; specifically, I use the Hilo’s XLR outputs for the amps driving the Sanders Sound electrostat panels, and the TRS outputs on the Hilo for the amps driving the Sanders Sound woofers.

Source selection is controlled by Channel D Pure Vinyl.  To access files stored on the hard drive (irrespective of whether those files were ripped from a CD, down-loaded, or digitized from vinyl), one clicks on the iTunes icon.  (More on the use of iTunes below).  The selected track is digitally processed, then sent via the USB cable to the Hilo’s DACs.  To access analogue sources, one clicks on the button labeled “analogue,” which opens up a screen with boxes labeled (in my setup) “CD” and “Turntable.”  (These labels are applied during initial system set-up and provide communication with the Hilo, which is where this source selection actually occurs.) Selecting the “Turntable” option opens Channel D Pure Vinyl’s patented graphical interface for vinyl playback.

Cross-over functions are selected in a window in Channel D Pure Vinyl.  The functions include cross-over point and slopes, as well as relative volume of the upper and lower frequencies (the latter allowing the user to match the volume of the panel and the woofer based on room acoustics, musical selections, and personal taste).  Channel D Pure Vinyl also allows time alignment, which is extremely important when the sound radiating devices (speakers) are not the same distance from the listener (time coincident).  For example, we used this function to time align the electrostat panel with the woofer, using the interval previously determined by Roger Sanders.  This function can similarly be used to time align a main speaker with a subwoofer, to compensate for any difference in physical distance from the listener.

As mentioned earlier, because the Sanders Sound panel is a dipole, it is necessary to use a shelf function to compensate for dipole cancellations.  The frequencies at which cancellation occur are a function of panel width; in the Sanders Sound speakers, this is at approximately 2 kHz and below.  The shelf function thus attenuates frequencies above 2 kHz, so as to ensure flat frequency response.  Channel D Pure Vinyl does not have this capability, so Rob recommended a plug-in from Fab Filter (http://www.fabfilter.com).  This program is very powerful and, in conjunction with Channel D Pure Vinyl, extremely user friendly.  To create a filter one opens a window in Channel D Pure Vinyl, selects the appropriate program (in my case, Fab Filter) from the pull down menu and voila, a new curve (frequency vs. dB) appears graphically in its own small window (superimposed on the other open windows).  The curve starts out flat but by clicking and dragging a portion of the curve, one can change its shape to whatever is required.  Alternatively, the shape can be altered by graphical buttons which allow control over (1) center frequency of the curve, (2) its amplitude, and (3) it’s Q (i..e, width).  A wonderful feature is that Fab Filter allows the curves to be altered in real time (while listening), and one can open numerous curves, which makes experimentation easy.  One can quickly generate a family of curves, each of which can be turned on or off in Channel D Pure Vinyl simply by checking the appropriate boxes.

As discussed in my earlier interview with Rob Robinson (see above for link), Channel D Pure Vinyl (and Pure Music) uses iTunes as a library.  Whereas certain competitor’s products sit atop iTunes and secondarily try to improve on its sonics, Channel D software does not use iTunes at all for playback. It took me a while to get used to the differences between iTunes and the PC-based software programs with which I was familiar.  Unexpectedly, I found iTunes less intuitive, and more temperamental, than JRivers.  Your mileage may vary.

Earlier in this article I mentioned that performing the cross-over in the computer introduced two problems that did not exist when the cross-over was performed in the Behringer.  The first problem was the need for a DAC with four output channels, which was solved with the Hilo.  The second problem relates to volume control.  You may have noted that the Hilo connects directly to my amps, without a preamp.  The reason for this is that a 2-channel preamp will not work in the system.  How then can one control volume?  Rob’s idea was to control volume in the digital domain, which is easily accomplished in his software (which provides both “up” an “down” buttons, as well as a slider).  Rob explained that when using a digital volume control with a 24 bit signal source, it is reasonable to apply up to about 12 dB of attenuation without any audible degradation, compared to an all-analog volume control (which also has its own trade-offs).  To accomplish this properly, the system’s analog “gain structure” has to be correctly managed.  Ron further explained that this subject is one of the most fundamental and important issues in an all-digital playback system for obtaining the best possible sound.  (Interested readers are directed to the Channel D website, under the topic “Digital Volume Controls”: > http://www.channld.com/computeraudio.html.)  With most of my recordings I stayed in this range (or at last, near it), though some that were recorded especially loud did require a bit more.  This was certainly not a deal breaker, though it is something to keep in mind.

Also as  mentioned above, I used an iPad for remote operation.  This worked fine for track selection, but volume control left something to be desired.  The mobile iTunes app has only a slider (i.e., no up/down buttons), and the wireless communication has a bit of a lag time to it.  For these reasons it was difficult to precisely control the volume, and most times I did not use the remote, opting instead to take the few steps to the computer to control volume.  Of course, this problem can be solved by keeping a monitor, keyboard and mouse near the seating position (as Rob does).

One Response to Channel D Pure Vinyl Music Server Software and Seta Phono Stage and Lynx Hilo DAC


  1. Stephen Mollner says:

    Hi Larry,

    Steve from Los Angeles here. Like you, I own the Sanders System. Also, I setup and perform the Sanders demo in Newport Beach and Chicago. I had dinner with you and Roger in Denver a couple of years ago… Anyway, here is my point…Like most audio enthusiasts, including Roger, I am interested in having the best audio experience possible at home… That is not to say that it cannot be improved upon…However, that said, have you subjected your new crossover setup to tightly controlled, double-blind testing at the Sanders facility? Assuming the new crossover setup meets the Sander’s BQC’s, you could put this matter to rest by bringing it with you to RMAF this year and going to the Sanders facility! I will be helping at the RMAF this year and look forward to this evaluation. Since Roger only uses a PC, you may need to bring along your Mac Mini.

    Best,
    Stephen

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