Have Passive Preamps Finally Come of Age?
It will also pass clean 1080p component video or coaxial 24/192 digital & DSD. Let me rephrase that a bit. (deleted my above prior post) Wrote it too fast and slightly incomplete. Some capacity for AC, as in HF alternating current. More like ’RF capable’, would be the better analogy. Lowe current, low voltage, but Radio Frequency. Similar in bit bandwidth, as well. Very high bit bandwidth, essentially. |
Your right MrD, they can’t. Some preamps are designed to have very large s/n ratios and very large voltage swing range capacity. And then the designer of the circuit puts sort of passive volume pot implementation -in front of the high gain preamp. This results in a far higher level of signal quality on the output, with regard to preserving micro differentials in the signal, which is where the music works for the human ear. Some tube preamps are more likely to be designed this way. Or, some preamps are designed so the volume pot is part of the gain of the circuit itself. I believe that Charles Hansen made a version of such topology in one of his SS preamp designs with Ayre. A switched resistor circuit where each step was optimized to provide best low distortion and highest fidelity. Not just individually gain stepped but individually tweaked on each of those steps. (IIRC, that is, source: interview with Charles at Stereophile) The one you take note of, which is the most common way to do it for reasons of a ’safe’ output section, is also the lowest fidelity way to set up a preamp circuit topology. The variable loading does indeed change the transient distortion of the circuit, and it also makes the output sensitive to the cables and input it is hooked up to, in a way that is non linear as one scales through the volume settings. eg, the one with the hardset gain with the input being varied via a potentiometer at the start, that one... is more linear and constant in it’s coloring of the sound signature, as one scales through volume level changes. Most (IIRC) of the Bruce Moore tube circuits were set up this way. There is a danger aspect as a potential problem, though, as the full gain is always applied to the amplifier inputs, via the preamp circuit. So, one can accept the cheaper and easier to implement most common design method (volume pot just before preamp output) and have mediocre warmed over sound quality ...or.... play in the danger zone and have a notably greater fidelity in ways that matter to the human ear. (volume pot at front of full gain output) I made that trade off over 30 years ago, and the cost of problems that have happened, over the years, was less than the cost of one single item upgrade. Less safeties on the system (DC or full scale output issues, etc) and more care needs to be taken, but....the pay off was over 30 years long, on a key point in fidelity. And that was priceless. Priceless. Essentially, it’s too bad more people don’t understand how fidelity in audio works. It’s not all that simple... After trying every active topology known to humanity, I gave up at the max grade preamp level of a customized three chassis MFA ’Venusian’ preamp (capable of over 165Vp-p into a standard load!), and went to passive circuits, but only when done via the liquid metal design we have on offer. IMO and IME, active is too complex and too colored. All of them. 100% of them. Even simple buffer circuits, even though they generally exhibit the least harm... In my personal experience a liquid metal passive preamp defeats all passive contenders and all active contenders at any price. At the $10k level, at the $50k level, no matter. Additionally, the consensus on that, within the group of people who have actually heard such an arrangement of gear with the given specific passive preamp... is rather high. With zero caveats. How? the liquid metal does not behave like wire, on the fundamental scale of what impedance in dynamic living terms --actually is. high correlation on it being best? let me clarify: Hundreds of people, and maybe three or five disagree. But this as a pronouncement, depends upon the rest of the system, all the individual components, of source, cables, speakers, etc.....and most importantly...the wiring of the mind and ears of the listener....all being up to snuff, in being at the center of the maelstrom of what each is required to do with regard to projecting and exhibiting (and hearing/realizing) the maximum fidelity of signal. |
08-08-2018 1:35am celander My Teo Audio Liquid Pre passiveA very good passive, and from what my sources tell me, it’s a 23 position "shunt" type passive volume control, 1 fixed series resistor, and 1 variable shunt resistor (48 total), not the best way of doing a passive volume control, the "ladder" is best, "series" being the worst. We are notoriously tight lipped due to the nature of intellectual theft which both Taras and I have endured far too many times over the years. I could name you more than one company that has come into the world (and audio world) based on intellectual theft from one or either of us. Yelled at and slapped around as charlatans on the front..while the thieves slip around the back and steal the tech and ideas away and make a living off of it. This is why incorrect information can be out there, and we won’t correct people. Too much information. The questions are all about getting responses.. so the data can be mined. Just to make a total mess of common logic (gained from much experience by the whole industry) in the audio world, I’ll say one thing one time about our tech to illustrate how impervious it is to impedance function. The stepped attenuator in the Teo Passive Liquid Pre, is a 23 position series unit. One interesting thing, is that it does not change in sonic character as one raises and lowers the levels on it. Owners note this specific point as it is part and parcel of the problem of passive preamps, but in our case, is non existent. Which is totally backward to how one understands what a series implementation will do. Which you basically said, George. Yet it still works gang-busters and and the top of the quality chain in passive or active preamps. How is that? The preamp can, when the attenuation is set to the max pas through, pass either 1080p component video (would need a second unit to pass the third signal, component has three signal lines) OR Digital audio signals in a coaxial configuration.. It is literally, by all science and physics a totally different handling of the living dynamically changing impedance of a constantly shifting signal. that is what the fluid metal is: it is not your father’s impedance. Period. The end. Finito. No question, no argument possible. The physics, if you actually know it..is quite clear. Anyone arguing beyond that, really does not know their impedance at the molecular level and everything else required to understand this question and answer set about the fundamental nature of conductivity, LCR, and signal. THAT, as an exclusive patent that locks the entire industry (all of them) out of this area of implementation (we were there first, at a ground level and grabbed the whole area)..that is why the audio cable industry recognized this. It is also why an unnamed maker of world class audio cables..came into our display room at the 2009 Montreal audio show...and shook our hand with a big grin on his face. He warned us that the entire industry of high end audio cables felt quite threatened by us and that we need to ’watch our backs’. The only thing that has saved them, is that we are not super ambitious and gung-ho to push huge coin into a huge push. But we have been threatened and cut down in various ways by various manufacturers in the cable world, in ways that are libelous to speak of, even if it is true. People are slowly getting it, this problem of how basic LCR tells only a very small part of the story of why things sound the way they do. We’ve make a big jump, here (in all technological ways) . The tech is not easily understood and this is added to the audio problem of some thinking that having good hearing and being able to hear such things - is crazy. Which is really pear shaped in the final analysis, it’s like beating up people because they are smart. Same-same. We’ve latched on to a partial explanation of one aspect of part of a question: the the application of LCR to audio. It is the nature of humans to be dogmatic and biblical, it’s a social fabric coherence function buried in our subconscious origins of thought. And it screws up our logic function, all the time. LCR is just a echo back of the smallest part of the possible components of analysis. Yet some dunderheads crown it as king, and try to kill in it’s name... when it can’t even tie it’s own shoes. The insanity is.. they they don’t even know what it means. The map is not the territory. Things change in physics, by the minute, these days. Same for medical research. This is not the world of a bunch of older audiophiles, who are slowing down in their life pedaling speed. The universe is now an information field, time is not linear, spooky action at a distance is fully realized, and immorality is here, in the genetic and real sense. And much much more. WAKE UP. PAY ATTENTION. Like Max Planck said, "Science advances - funeral by funeral". (when the nasty nay sayers die and their grip and voice finally leaves the stage, we can get on with moving forward) |
