My ultimate VTPO goal is to attempt to create an illusion of a modern studio WurliTzer theatre pipe organ.

Amongst my inspirational installations were the George Wright Pasadena and elements of the Hollywood 'Philharmonic' studio recording pipe organs, the Little River Studio WurliTzer and the Castro Theatre WurliTzer. My suggestions are therefore made with those mostly dryer acoustic environments in mind which require the highest achievable tonal integrity as the samples can't hide behind a veil of reverberation.

Which Audio Device to use?

As I value sound quality, more highly than how many channels a particular device has, after experimenting with Egosys, M-Audio, Terratec, and MOTU, I found that the best compromise (and all systems are a compromise) for me, are the Echo Audiofire range. I use four Echo Audiofire 12 (AF12) in my VTPO.

However, be sure that you do not purchase the earlier AF12 units as the unattenuated ultrasonic noise from the IIR filters can wreak havoc with some older amplifiers. These earlier spec AF12s can be identified by the orientation of their firewire sockets (current spec AF12s firewire connectors are upside down). 

CONNECTIONS

AF12 to AF12 and Word Clock

With any multi-channel audio you must be scrupulous with your grounding. If you plan on deploying two, or more AF12s, to follow Echo's advice in the AF12 manual about master/slave daisy chaining multiple AF12s can, in my experience, produces too much jitter resulting in a hard cloudy sound. Unlike true high end professional sound cards, mid level soundcards like the Audiofire range, the BNC connector ground is not galvanically isolated from AC, or audio ground (indeed they are tied together on an AF12). I have found that it is better not to use a RG59 word clock cable between each AF12 and permit each unit to look after itself using its own internal clock. Quite possibly any timing difference outcome might aid the pipe illusion outcome.

My connections are all balanced, with zero ground from audio device to amplifier. Where I have an unbalanced amplifier in the configuration, like the Definitive Technology Trinity sub-woofer, I use a balanced to unbalanced transformer to isolate the audio device ground from the amplifier.

The best multi channel grounding advice that I have found anywhere is this article: http://www.soundonsound.com/sos/nov02/articles/studioinstallation1102.asp.

Pay particular attention to what the author suggests for balanced connections. As a direct consequence of this article, I recabled, and re-equipped my VTPO so that I would not have any grounds running from an AF12 to an amplifier, and the difference was staggering. Well worth the several hours work. In addition to the electronic glassiness that too many ground lines can add to a multi channel audio installation purely from the resulting ground loops (not to be confused with hum), each ground line can potentially act as an RF antenna and feed that back into all other channels making for one very ugly outcome that is a long way removed from any pipe illusion.

If you did not wish to address the word clock issues, and you required 24 channels, then with the MOTU 24 I/O you could avoid having to do anything with a word clock!  However, the MOTU's power supply is rudimentary in design when compared to the global SMPS of the Echo AF12 (I had two MOTU 24 I/O power supplies fail, and other users report similarly sad outcomes), and the sound quality is not in the same league as the AF12. However, there is a company who modifies MOTU products to improve their sound quality:  http://www.blacklionaudio.com/Modifications/MOTU+Audio+Interfaces. I can't comment on whether the outcome matches, or exceeds the audio quality of the AF12.

Wiring Strategy

Over many years of experimentation, I have come to the same conclusion that others have (including studios, PA manufacturers, and the likes of Rodgers Organ Corp) that long line level lines are superior (and often cheaper to implement) than long speakers lines. The downside is that one can't have all of the amplifiers in one place like a nice neat rack (which also creates a number of its own compromises if the amplifier shields are not providing 100% shielding, transformer magnets affect each other, and so on). One also has to take into account the fact that long line level cables can also suffer from loss of high frequencies and phase shifts unless one uses cable that is designed not to deliver such nasty outcomes over longer than usual consumer lengths. For this installation I used http://www.canare.com/ProductItemDisplay.aspx?productItemID=60 in its two and four channel versions - and excellent product. I see so many VTPO installations where loads of cash has been spent on audio devices, audio, and consoles, only to put shit cable in the path. Makes no sense to me.

AC Line and SMPS Noise

This is the final part of the equation for me. Indeed, if I hadn't installed something to address this problem, I would have, and came very close to, getting out of, multi channel VTPO altogether. When an amplifier is spending a great deal of its capability attempting to amplify crap, it does a very poor job of amplifying that which you need amplified, and the outcome is hard, congealed MUD! Each and every computer in a residence puts SMPS switching noise back on the AC line. Each and every unearthed wall wart does the same. Then, in Ruby's case, add the SMPS of each audio device, and all of the power supplies in the console. The audio devices do an excellent job of keeping their SMPS noise out of their own devices, but they then shunt that noise back down the ground, and active and neutral lines to be amplified! Even if you were running on a 100% solar system not connected to the grid (and the grid is another source of crap), a VTPO project on its own has the potential to create a lot of SMPS noise. This device saved Ruby from being sold last year http://www.thoroughbredaudio.com/SPI240AU6/index.html. $495 vs. my (or, your) total VTPO investment! Easy choice.

Hauptwerk 4.00 and audio

HW 4.00 has many new user aids. Not the least of these being the colour bars for the audio readout. Martin Dyde suggested to me during the beta testing that no instrument should ever trigger the red bars. Indeed, his stated preference was that no instrument strays outside the green bars. He also says that if this does occur, and should the obvious primary settings seem fine, that users should look at their volume settings for aux items like mix downs for sub-woofer feeds and the like. Occasionally, I could trigger a red bar, and true enough, although the cause proved to an aux mix down issue (in this situation, to the ambience system), rebalancing the relationship between the audio devices and to HW, made a slight positive difference to full ensemble at full volume. The Echo s/w mixers are a dream to use. But, then, Martin also has a preference for using the same audio device throughout due to the way in which HW 4.00 interrogates their drivers (well, that's how I understand what he meant!). So, now Ruby's audio delivers on that preference.

More to come.....................

Email: solo_tibia@yahoo.com

© Ian McLean