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
I have gotten a few private emails concerning the Luminous passive products, and passive, as a whole. I wanted to update this thread, as to create more interest, and truth, as to passive driven systems. There is no question, that extra gain can give you more " oomph ", but when listening to a piece of music, that has " oomph ", you begin to notice, with a good passive such as the Luminous, that there is finite information on the recordings, that can be lost, with extra gain. A longer signal path, cannot retain " what goes in = comes out ", with the most purity and clarity of the signal, and this is with a system that matches on all levels, source to amp. I would love to hear other stories here, as to those who have followed the passive path, understanding it has been discussed many times prior. There is a lot of repetition and repeat threads here, so nothing new. Enjoy, be well and stay safe. Thank you, MrD.
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


Correct, the only time balanced becomes a noise advantage MrD is if the output and the input of all stages are true balanced circuits over very long cable runs, in very noisy environments like recording studios.

And here's the BS factor for balanced claims on sound quality increases.
 Many pieces of equipment today have balanced opamps grafted onto their inputs and outputs of single ended circuits!!!, so they can advertise they have a balanced input or outputs, they are only "pseudo balanced" because they use balanced opamps like these, 
https://www.ti.com/product/DRV134

 And then in the end nearly all power amps have single ended outputs as are speakers so the whole thing becomes a "furphy", for sound quility claims, your better off sound quality wise to stay single ended all the way, unless your in a recording studio with miles of cable doing all sorts of things.

Cheers George 
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.
that has " oomph ", you begin to notice, with a good passive such as the Luminous, that there is finite information on the recordings, that can be lost, with extra gain. A longer signal path, cannot retain " what goes in = comes out ", with the most purity and clarity of the signal, and this is with a system that matches on all levels, source to amp.
@mrdecibel If your equipment doesn't support the balanced standard then you will be hearing differences between balanced cables just as you do with single ended cables. If your equipment supports the standard, then the differences between cables is vastly reduced! The benefit of balanced operation does not depend on the length of the cable- its there even if the cable is only six inches.


When you have a competent line stage that supports the balanced standard you will find that there is more 'oomph' not less (assuming that you mean more impact and more palpable images) on account of the simple fact that such a line section will not allow the interconnect cable to impose a sound.


The only way I know of to use a passive volume control and support the balanced standard at the same time involves the use of a transformer. The system we patented is the only other means I know of to support the standard and we've built versions that are strictly buffers with no gain. 


I have listened to passive units with transformers and find them to be round and colorful, meaning they are warm and the frequency extremes seem rolled of. They are not as detailed to me. Being familiar with pro gear and balanced lines, I still suggest, based on my listening, cable brands sound significantly different to me, whether they are single ended or balanced. I am not an engineer, and the reasons for this are likely many, as discussed here and elsewhete. I appreciate the feedback.
I have listened to passive units with transformers and find them to be round and colorful, meaning they are warm and the frequency extremes seem rolled of. They are not as detailed to me.
This is very true MrD of TVC passives (transformer volume controls) based volume controls.
But they "can" be liked in "some" problem systems that need some "band-aid" fix for other problems, eg harsh highs, or to warm (thicken) bass etc.

They color the sound just like any "audio based signal transformer" does, (EG: output transformers on tube amps, phono transformers, preamps etc etc), they fall short in in dynamics, detail, and frequency extreme, LF output impedances and distortions.
And the ones that are are wound with ratio taps so you can have some "extra gain" from them, they can ring like the proverbial "bell".

Cheers George