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BSG Technologies QOL Signal Completion Preamplifier Review

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BSG QOL Signal Processor PreamplifierSignal Processing for Audiophiles

I have always been interested in listening to alternate and supplemental ways of reproducing audio signals. In 1980, I first began playing with some of them, most notably the dbx Dynamic Range Expander, which sought to restore the pianissimos and the fortissimos of live music by “stretching out” the dynamic compression added during the process of making records. I also used a graphic equalizer, analog, of course, in those days, for a year or so to modify the bass produced by the speakers I owned at the time. One aspect of equalization that bears on the discussion to follow is that equalizers intentionally shift phase, then recombine the phase-shifted signal with the original signal. Unfortunately, many of these devices were complicated to use and often required you to reset the processor for each new album. Moreover, the sonic results were often very mixed, especially for users who did not understand the sonic effect of adjusting each band of equalization.

When digital sound processors first came out some years later, it was interesting to see how the presentation of the music could be radically altered to attempt to recreate various different performance venues, such as “concert hall,” “outdoor” or “nightclub.” However, it was quite rare for the resulting sound to be very realistic, and these various settings often changed tonality in ways that detracted from the music. The results of digital processing became more palatable when multi-channel surround sound processors became available. The processed sound was much more enjoyable and accurate. Unfortunately, this required three more speakers, plus a subwoofer or two, and well-mastered surround sound music was limited. Moreover, many serious 2-channel audiophiles wanted a way to improve their 2-channel recordings and didn’t want to add surround sound.

At roughly the same time that multi-channel digital processing was developing, digital room correction was coming into the picture. Tact, Lyngdorf, Behringer, KRK Systems and DEQX, to mention a few of the most prominent manufacturers, developed systems that measured room response and altered the signal to account for the inevitable anomalies. Some also added speaker correction, in addition to room correction. In most cases the results were very good, and in some cases spectacular. In my own case, I have used the Lyngdorf RP-1 to great effect for several years. With a few mods and tweaks designed to make it more transparent, it addressed some major issues I had with how my B&W 800Ds interacted with the room, and thereby created a much more realistic listening experience.

The upshot of all this is that when I had a chance to review the QOL Signal Completion Device I already had experience and interest in signal processing devices, and had some vague idea that some of them accomplished their intended effects by use of phase shifting. Furthermore, after reading through the BSG Technologies website, I understood that BSG is attempting to accomplish something other than room correction or speaker correction. They are trying to “correct” the recording itself by bringing out information which is buried in the recording but not being reproduced when played. To accomplish this, BSG focuses on the phase relationships which are not revealed when playing recorded music through current playback devices. As a shorthand description, I’ll refer to this below as “proper phasing.”

Getting in Phase

So what do I mean by “proper phasing”? According to BSG, and others, proper phasing is one of several aspects of audio reproduction which must be present to get accurate sound. Many of us have had the experience of improperly inverting one set of speaker cables and noticing that the bass lost force, volume and definition. The effect is very obvious and any listener can immediately hear the difference. Inversion of the cables resulted in inverted phase, or as we usually refer to it, “out of phase” sound.

Of course, this example suggests that phase is like an on/off switch – you’re either in phase or out of phase, and when you’re “in phase” everything is cool and you don’t need to think about it anymore. Actually, that is not the case. A cursory search on Google for the words “phase shifting” and/or “flanging” will turn up several articles that explain the effects of these techniques for shaping the sound of a recording. As someone who does not have technical training, one article that I found interesting is http://www.ethanwiner.com/EQPhase.html, which discusses phase shifting that occurs in equalization and distinguishes it from phasing and flanging processes in mastering recordings.

There are also other more subtle examples of inverted phase. Many audiophiles have for years claimed that they can tell when the phase of some versions of CDs has been inverted during the mastering process, and I have personally heard demonstrations of the same CDs, one mastered in proper phase while the other was inverted. There is no denying that when CDs played back with proper phase sound better – specifically, more realistic and “live.” Several audio devices incorporate circuits that let you flip the devices’ polarity to correct for phase-inverted music.

BSG explains that live musical information is composed of three main components – magnitude, more often called “volume” or “ampliftude”, with all its gradations; frequency – treble, bass, midrange notes and their harmonics; and phase – cues that tell us where instruments are and where the boundaries of the venue are located. With that in mind, here’s something from the BSG Technologies website that discusses what the QOL is designed to accomplish:

“Electronics do not work like the human ear/brain. As a result of cancellation effects within electronics, the phase information is not reproduced. In an over- simplified analysis this is as basic as the fact that, in algebra, +1 and -1 = 0, not 2; in physics, likewise, for every action there is an equal and opposite reaction.

Thus, no matter how well audio products reproduce frequencies and magnitude (and these days, many of them do very well), we will be robbed of realism and naturalism unless the phase information within all signals can also be reproduced. If the phase information is missing or otherwise distorted, the sounds to be reproduced will likewise be distorted and unrealistic.”

……

The only way to get natural, complete information requires uncovering and reproducing the natural phase information that has been hidden and buried in every signal, but, until now, not retrieved and reproduced by electronics. After more than seven years of research and experimentation, we have succeeded in uncovering and reproducing the information that has been hidden and buried within every audio signal! For the first time, ALL the fundamental elements of sound can be retrieved and reproduced. ”

Sounds interesting, doesn’t it? I certainly thought so.

The QOL Arrives

The QOL has seven pushbuttons on the front panel. Four of them select one of the four inputs of the QOL, one is for mono operation, one bypasses the QOL’s processing functions, and the last is the power switch. On the back, you will find four pairs of both RCA and XLR inputs, two pairs of both RCA and XLR outputs, the power inlet and a voltage selector.

You have several options on how you configure your system with the QOL. The typical configuration involves placing the QOL between your preamp and amp(s). A second
is routing the QOL’s processing through a tape loop or external processor loop of your preamp. A third is to install the QOL between sources and preamp. There are also several suggested ways to install the QOL in a home theater system, even though the QOL is basically a two-channel device. In my case, I used the QOL in several configurations, including one without a preamp in the system. I will describe my results in each setup.

Initial Impressions

I decided to start by simply inserting the QOL right before my amps, which resulted in the following configuration, starting from the source through amps: modified Qsonix Q-105 server > Empirical Audio Pace Car Reclocker > MBL 1611f (with volume control option) > Lyngdorf RP-1 > QOL > Electrocompaniet amps.

The most immediate effect of engaging the QOL was a 2-3 dB increase in apparent volume. This was a bit disconcerting, because increasing volume generally causes most people to prefer the louder recording. Of course, this has nothing to do with any improvement in the sound – it’s just that the gut reaction to “louder” is usually “better.” However, switching the bypass function of the QOL in and out quickly demonstrated that something more than a volume increase was at work. The soundstage clearly seemed wider and deeper, and certain instruments that were previously muted and in the background became more prominent, and in a good way.

In order to account for the added volume of each recording, I initiated a testing sequence that reduced the system volume by approximately 3 dB when the QOL was active. All my subsequent comparisons used this system of reducing the system gain, and the comments that follow all are based upon this general 3dB reduction in system gain whenever the OL was engaged. I then began playing music in earnest, periodically switching the QOL BYPASS switch in and out to compare the sound. It quickly became clear that several things were occurring simultaneously.

First, the soundstage wasn’t necessarily “wider” in the strict sense of the word. However, the far edges of the soundstage, especially the upper and lower corners of the extremes of the soundstage, contained much more musical information than they did without the QOL. The music coming from the far left and right of the soundstage was just as prominent as it was in the middle, and the side walls of the venue could be “visualized.”

A similar phenomenon occurred with the depth of the soundstage, but in this case it also really did add significant depth to the perceived stage. To be specific, the perceived depths of the soundstage often improved significantly; an apparent depth of 15 feet became an apparent depth of 30 feet. In addition, it wasn’t just that things gained depth – the rear boundary of the recording venue actually manifested itself on many recordings. By that, I mean that you actually had a sense of the sound bouncing off the back wall. The combined effect of the improvements to the back and sides of the soundstage created an acute sense of the scale of the recording venue. This was especially the case on live recordings, and repeated itself on every recording I listened to. In some cases it was merely a pleasant improvement, but in a significant minority of cases, it was stunning.

The third thing that occurred was the emergence of instruments often lost in loud multi-instrument recordings. Cymbals, chimes, wood blocks, mariachis, tambourines and similar instruments got equal billing with kick drums, bass, piano and other bigger instruments. When I say “equal billing,” I don’t mean cymbals became as loud as the piano. Rather, I mean that instead of having to strain to hear them, they became distinct, while maintaining an appropriate relationship with the other instruments.

Finally, while the QOL’s effect created a much more defined performance venue and brought out previously repressed instruments, the instruments on the soundstage seemed to become a bit more amorphous – there seemed to be less “space” between each performer on the stage. At first I felt ambiguous about this effect, but over the course of the next two weeks somewhat grudgingly concluded that the QOL’s effect made for a more realistic reproduction of the performance.

My ambiguous feelings about this effect mirror a debate I periodically have with myself about whether I prefer the “neutral/focus” or “neutral/global ” setting of my Lyngdorf RP-1. The neutral/focus setting on the RP-1 produces a razor-sharp image of each performer on the soundstage, which allows you to close your eyes and visualize each performer on the stage. The downside is that not all live music sounds like that all the time. It may be that the Chicago Symphony sounds like that in Symphony Hall, and Patricia Barber sounds like that when her band plays at the Green Mill, but even if you are in the “sweet spot” listening to the Dave Mathews Band in a halfway-decent venue like the House of Blues, you definitely can’t close your eyes and visualize the placement of performers; and if it’s outdoors in Alpine Valley, don’t even think about it. In those cases the “neutral/global” setting of the Lyngdorf more accurately reproduces how the Dave Mathews Band actually sounds live. When used in conjunction with the Lyngdorf RP-1 in neutral/focus mode, the QOL took the RP-1’s razor-sharp images and blurred them a bit, thus accounting for the fact that live music is affected by the venue’s walls, floor and ceiling. Don’t get me wrong, Carlos Santana and his electric guitar are still clearly located in the correct spot on the stage, but instead of his guitar coming directly at you like a laser, it comes at you both directly and as echoes off the walls. It is more realistic.

3 Responses to BSG Technologies QOL Signal Completion Preamplifier Review


  1. Jon2020 says:

    I had an opportunity to bring home a unit for an audition in my system some time back. For me, to my ears, the cons add up to more than the pros. So, I returned the loan unit to the dealer.
    The one most important aspect of the sound that deterred me from an outright purchase was the unrealistic expansion of image size of every instrument. Although the soundstage has expanded, so too have the piano, guitar, saxophone, violins and whatever else that is playing together in a band or orchestra to the point that each of them seems to extend from the far side of the left to the far side of the right of my room boundaries. May be seductive initially but it just doesn’t sound real and right.
    Other aspects of my personal experience with the qol :-
    1) The S/N ratio is indeed rather low as previously posted; I can hear more hiss and noise from my speakers in between tracks and during soft passages. With the qol out of the chain, the added noise was gone
    2} When I cranked up the volume with the qol in place, there is a point where distortion can be easily heard and things start to sound ragged
    3) To reiterate, image size is stretched to the point of unbelievability. A glaring example is when the tenor sax is playing, it is as if I am standing at the “cusp of the crucible” so to speak, staring down into the deep belly of the sax – totally unreal
    4) The bypass mode is not a true absolute bypass. Remove the qol from the chain altogether and the comparison is startling – one gets easily seduced by the immediate signal gain and think, ah, instruments have more body but take it out of the chain, and gradually crank up your system. You will realise a similar gain in instrument body but without the image stretching effect.

  2. Jon Goh says:

    Some aspects of my personal experience with the BSG qol in my home system :-
    1) The S/N ratio is indeed rather low; I can hear more hiss and noise from my speakers in between tracks and during soft passages. With the qol out of the chain, the added noise was gone
    2} When I cranked up the volume with the qol in place, there is a point where distortion can be easily heard and things start to sound ragged
    3) Image size is stretched to the point of unbelievability. A glaring example is when the tenor sax is playing, it is as if I am standing at the “cusp of the crucible” so to speak, staring down into the deep belly of the sax – totally unreal
    4) The bypass mode is not a true absolute bypass. Remove the qol from the chain altogether and the comparison is startling – one gets easily seduced by the immediate signal gain and think, ah, instruments have more body but take it out of the chain, and gradually crank up your system. You will realise a similar gain in instrument body but without the image stretching effect.

    I could not bear with all of the above and so returned the loaner unit.

    • Ed Momkus says:

      I assume both of these comments come from the same person, so my response will treat than as the same.

      Hi Jon – I did not have the same result as you did with noise or image size. One of the things I mentioned in my review was that I tried the QOL in several different locations in my reproduction chain. I found that it worked differently in each and settled on the best configuration. This configuration produced no additional noise. However, I did get some noise in other configurations, though not very noticeable. One thing I found I had to pay attention to was proper grounding, and I don’t know whether that might have affected your system.

      I also did not have your issue with image size. I have an extremely large soundstage in my main listening room – 28 feet – and the performers are all “right-sized”. In my system the QOL illuminated the far corners of the soundstage and fleshed out the performers, but did not stretch them. What associated equipment did you use?

      Ed Momkus

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