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
@atmasphere Welcome to my post, and thank you for the feedback. My other cable is in fact another of the same cable, and of the same length. I like the sound of these cables. I am yet to hear a cable that does not have a sound ( after an extensive break in ( another topic I will discuss at some point, also ad nauseum ). If I like something I put in my system, I give it some break in time, but generally do not need much time to make my final judgements. My Yamaha amps ( and other pro amps ), with it's input attenuators, easily allows me to hear the quality of a preamp, or passive unit, because I can go source / dac direct into it. My currently enjoyed amp at this particular time, is an original Edge M8, by the 1st company of Tom Maker. It is single ended, only. His newer stuff, Maker Audio, is balanced, and I am familiar with balanced connections, and the benefits of use. I totally went over this amp, and it is a dream to listen through. As we have discussed before on other preamp / passive threads, we always differed in opinion on this subject. Georgehifi is another, who is in my camp. I am completely fine with this, as I know many prefer a preamp, but few, ime, actually need one. As far as cables are concerned, and I am speaking of balanced cables as well, they all have different SQ characteristics, from each other, and from the various levels within the same brand. Power cables ( I build my own ), that will be another discussion, also discussed ad nauseum. There is a YT video, from " The British Audiophile ", " Hi Fi Cables, Myths and Misconceptions ", which is very informative. He is intelligent, and speaks with etiquette, as I find most Brits. I am glad you stopped by. All is good with our differences of opinion. As you may know, since my beginnings here on the ' Gon, I have always stated what SQ characteristics I enjoy, and I understand more than most, the variety of listeners that there are. It is what makes our audio world go round and round. Enjoy, be well and stay safe. Always, MrD.
As far as cables are concerned, and I am speaking of balanced cables as well, they all have different SQ characteristics, from each other, and from the various levels within the same brand.
One of the reasons for balanced line is that it is a technology that virtually eliminates artifact from the cable itself. But if the equipment used with it does not support the balanced standard, you will certainly hear different sound qualities from various cables! FWIW, a passive balanced volume control system (at least none that I know of) can support the balanced line standards because it has to reference ground in order to work. When you are running balanced line, ground is supposed to be ignored. This is why (until we came along) if a system supported the standard, transformers were in use. Transformers allow the circuit driving the balanced line to not have any connection to ground.

So the logical inference here is that the equipment you've heard so far simply does not support the standard. Beyond that though it appears that your method is pretty sound.
All good. I have heard the Benchmark gear ( at another listener’s home ), which I understand conforms 100%. We did a cable shoot out, and the sq differences between cables were quite apparent to me ( I brought over some 1 meter Silnote Audio balanced cables I purchased from Mark, at Silnote ). On another visit, I did bring over two self modified Yamaha amps for comparison, and found them to be quite competitive to the Benchmark, for neutrality. The Benchmark preamp is quite amazing, in it's neutrality. It surprised me. 
The Benchmark is an excellent amp.

The thing driving the interconnect cable is where the difficulty lies in supporting the standard. Its pretty easy to do in an amplifier- you can do it with a differential input, which can be done with an opamp easily enough. But to drive the balanced line so that neither the non-inverted phase or inverted phase references ground (the interconnect shield)- that's a bit of a trick. How its done in studio equipment is with a small output transformer that has no center tap. It has a simple secondary winding that has one side tied to pin 2 of the XLR and the other side of the winding tied to pin 3. Pin1 is tied to chassis and no connection to the transformer whatsoever. This is done to prevent ground loops but it also prevents the cable construction from influencing the sound. However for the latter its not enough to not reference ground- the circuit also has to be low impedance. For many years the standard was 600 ohms but these days is a bit higher: if your balanced source is going to support the standard, it should be able to drive 1000 ohms without bandwidth or distortion issues.

We patented a way to do this that is direct-coupled, which to my knowledge is the only other way to support the standard. Any system that employs dual out-of-phase single-ended outputs has to reference ground and so does not support the standard.


Clearly a passive simply cannot support the standard- and so the interconnect cable will impose a coloration, and quite often one that varies with volume. With many sources that employ an output coupling capacitor, it can cause a bass rolloff if the volume is set to anything less than full. This does not happen with all sources, but if it works out that way, the choice of passive volume control will have no effect!
My passive is single ended, and I am fine with it. Given everything you say, which is quite informative, still leaves me with 2 conclusions. The 1st is, balanced lines are useful, and necessary, when the lines are long, and / or there is an abundance of electrical, magnetic, or rf noise, contaminating the area ( which is truly likely in most circumstances ), balanced has a lower noise floor, resulting in a blacker background while listening. The 2nd is, there are very apparent sonic differences between cable brands, and as I mentioned, those models within the brands line. Balanced cables, as well as single ended cables, all sound different, and matching them to systems, can create a better synergy between the components, and sound shape the presentation, for the listener. Should this be the case, I do not know. But keep in mind.....I am one, who hears improvements, with an upgraded fuse ( another discussion ). I put a brick ( from your local garden / home improvement store, covered in a small towel ( towel to protect the equipment ), on top of an amp, preamp, transport, etc., and it changes the sound........anyway, thank you again, for your information and involvement with the discussion. You seem to be the only one, thus far. Enjoy, be well and stay safe. Always, MrD.