Why I enjoy my Luminous Audio passive unit, vs an additional gain stage ( preamp )


This topic of preamp / passive, has been discussed, ad nauseum. So why am I posting this ?, you ask. Why not, as it is still be discussed heavily here, and elsewhere. This is a short story ( lol ), but a quick read, so be patient, and thank you, in advance, for reading. In the early eighties ( I am thinking ’84 ), PS Audio introduced the model IV preamp, which had a button on the left side of the faceplate, that showed...Gain...active / passive. Interestingly, a year or 2 prior, the CD was introduced. Prior to the cd, we audiophiles and music listeners, listened to vinyl, open reel tape, radio ( tuner ) cassette tape, and in my case, worked a bit with microphones, patch bays, mixing consoles, and dabbled in live recording ( early on ). As most of you know about me from my posts here, I own Klipsch Lascalas ( tweaked and modified ). I met Paul Klipsch, and was, from my very early beginnings, a Klipschaholic. My dad had AR3a’s, driven by a Fisher 500C. My music teacher / singing coach, had Klipsch Cornwalls ( the mid and hf horns were vertically mounted, mirror imaged, and were the only pair I had ever seen with this vertical arrangement ), which soon became mine, as he upgraded to the Khorns. My dad no longer wanted tubes, so he purchased a Sansui 8 Deluxe, and I, the 500 C. Wow !. We were both happy. The Sansui was so much a better match for driving his power hungry ARs, and I was happy with my combo ( this was the late 60s already ). Moving along to the CD era, the typical cd player, produced 2 volts output, which was enough to drive most power amplifiers directly ( just needed a way to control volume ). The early cd players, were large and heavy, and they had, as part of their designs, massive transformers and huge, hefty power supplies. Sony, if I remember (and I could be wrong ),was the 1st company, who offered a variable audio output on their players, and we, the equipment consumers, bypassed our preamps, and were running these cd players, even through receivers and integrated amps, that allowed the disconnect between the pre and power sections, going direct into the power amp sections. Getting back to the introduction of the PS Audio model IV preamp, and its gain switch. This began an onslaught of passive devices ( volume controls / switching units ), without a gain stage, to hit the market. Moving along to modern day, there are hundreds of passives available. Some dac manufacturers claim, they can drive amplifiers directly. As it turns out, within the last several years, manufacturers are now producing integrated amplifiers, sans a preamp gain stage, taking the signal of the source ( not just cd players and dacs ), but tuners, tape machines, computers, phones, outboard phono stages, cable and satellite boxes, etc., and driving the power amp directly, without the need for the extra gain stage. What I want to tell you, is this. With the right system ( and I will use my system as an example ), an extra gain stage ( preamp ), does more harm, than good. A longer signal path ( more parts, more wires, more circuits ), can only destroy finite details, can only add colorations, can only add distortions, if GAIN IS NOT NEEDED. I used to feel this is in part, to the very high sensitivity of my loudspeakers, as any of my ( what remains of my collection ) 20 or so power amps, runs them so very easily. However, I have introduced many folks to the passive band wagon, taught them what to listen for, helped them with their systems, and now, enjoy passive listening. With all types of systems. Jumping back to my Luminous Audio unit ( I am using their top single ended model, but they all share similar topology ). This is a fixed series / variable shunt device. What this means is, the signal never passes through the volume control. The signal travels through 1 high quality resistor, and the amplifier’s inputs are shunted to ground, via the potentiometer, itself. The resistors can be selected, as well as the potentiometers, depending on the model, and Luminous will impedance match your particular unit, to match your system. For a nominal fee, it can be sent back to Luminous, and be designed to match with other / different gear. The beauty of my passive unit, is, that I do not " hear it ", in my system. It is NEUTRAL. Another term popularly used, is COLORLESS. How I know this. Using a self modified Yamaha pro amp from my collection, which has input attenuators ( as all pro amps do ), I hear no difference between my dac feeding the amp directly, vs the Luminous in the system ( although, I do hear the additional 1/2 meter Audio Research Litz interconnect, needed, with the passive ). Yes, this cable has a sound ( all cables, ime, do ). I am not getting paid by Luminous, by Klipsch, by anyone, posting this. Lastly, 2 more things. I have heard a few systems, in which an active preamp was beneficial ( the added gain ), but, to my ears, some neutrality was lost. I also greatly believe ( besides the source needing to have the proper output voltage and matching impedance ), the source, whatever it would be ( let’s say a dac ), should have a very hefty, over designed, stiff and well regulated, power supply, as part of it’s analog output section, based on my listening ( many do not ). I am open to further discussions on this matter, invite questions, and share experiences. Enjoy, be well and stay safe. Always, MrD.
mrdecibel
Not seeing how balanced negates the transfer function of the cable unless you are assuming lower source and load impedance. The noise rejection is obvious of course.
So, this now 'could' mean that AES48 is not properly 'implemented' - really?
@justmetoo   It would not be the first time I've been wrong, not by a long shot!


To meet AES48 the output of the source (preamp, in this case) does not reference ground. In order to see if your equipment supports the standard, a simple test can be conducted.


You'll need an amp with a single-ended input and a cable that goes from XLR at the preamp end to the RCA of the amp. Its important for this test that pin 3 of the XLR on the cable not be connected to anything, so pin 2 is signal and pin 1 is ground. 


Plug it all in and run the preamp and amp. Do you have a buzz? If no, the standard isn't supported. The reason there is no buzz is because the output of the XLR is referencing ground- so there are are return currents passed through the shield of the cable to complete the circuit. A circuit that supports the standard will not have a path through ground to complete the circuit- and so it will buzz unless pin 3 is tied to ground or some conversion from balanced to single-ended is made (for example, through an output transformer).



.since you think that hardly any one has heard a "properly done balanced system".........why do you keep talking about it? Are you just trying to get people to buy your gear? So they will finally hear what balanced can do? Most people do not want your gear.....so, no matter what you say about cables......they are all going to hear all the differences in cables that are very obvious to any who listen. So it is silly to keep saying that balanced cables have no sound since everyone but you hears something different.....I exaggerate.....maybe a couple of people agree with you.....he he.
Still not seeing how this negates the transfer function of the cable.
One aspect of the balanced line standard is in fact that it is low impedance- there is in essence a termination standard, whereas with single-ended there is not. The low impedance aspect is as important as the aspect of not referencing ground- it swamps cable 'transfer function' (which is the capacitance and inductance of the cable).


And of course *everyone* has heard balanced cables set up properly- they are in most recordings. Mercury used to park their recording truck behind Northrup Auditorium in Minneapolis to record the Minneapolis Symphony. The mic cables had to run nearly 200 feet. I experience this when I was playing in the St. Paul Civic Symphony back in the early 1970s. One of our performances was being recorded and I saw the mics hanging over the orchestra when we were warming up. The cables went into the cloud ceiling then down to a booth off to the side of the auditorium. I investigated and got to hear the mic feed over headphones. That and prior work in the studio is why I know this system works. Its why we made the first balanced line products for home stereo use. In the 1950s when hifi was getting going, the cost of transformers was not cheap and consumer equipment was. The RCA connector was originally used in televisions between the tuner and IF amplifiers; it was cheap and wide bandwidth; that is the main reason they are in use today. But high end audio is all about how far you can push it to get your system to sound like music instead of electronics- the balanced line system is a nice step in that direction as it removes cable artifact.


Many recording engineers of course have heard balanced cables set up correctly- which is why if you talk to them they will tell you cables don't make a difference. Audiophiles often assume they are talking about single-ended cables; audio engineers often assume audiophiles are talking about balanced cables. So there appears a sort of disconnect that makes it seem to audiophiles as if engineers don't have good ears or something. Its not the case- just apples and oranges.


I talk about 'properly done balanced system' because once you hear it there is no going back. There are balanced cables made today that cost over $1000/foot; if you subscribe to the Veblen Effect (consciously or unconsciously) you might be convinced that cables costing this much are some of the best made anywhere. One of the advantages of balanced operation is you can run long runs, allowing you to place your amps as close to the speakers as you can to minimize the effect of the speaker cables. Imagine a 30 foot run of cable that's $1000/foot; now imagine a system that negates cable artifacts allowing you to run the same length with inexpensive cables and no audible difference. In case anyone has a problem working this out, setting up a balanced line system that works properly is a lot cheaper, and you don't have to think about a cable investment loosing its value in an incredibly short time...


Thank you atmasphere, that is what I assumed the answer was.

One aspect of the balanced line standard is in fact that it is low impedance- there is in essence a termination standard, whereas with single-ended there is not. The low impedance aspect is as important as the aspect of not referencing ground- it swamps cable 'transfer function' (which is the capacitance and inductance of the cable).