Pubul57, you have done an excellent job of explaining the technical aspects of this subject and I as well as others have learned a great deal as a result. Given that, you now have my permission to go home and get some sleep! But I expect you to report back first thing in the morning, I don't pay time & half. In the mean time if we have any problems I will call on Herman to police this thread, as he may still may be angry.
Who is using passive preamps and why?
Seldom has there been any discussions on passive preamps in the forums and although my experience with them has been limited I have found them so far to be very enjoyable and refreshingly different. They seem to fall into their own category, somewhere between solid state and tube. Finding a preamp that is satisfing has been difficult. Some active solid state preamps can be very good but they seem to inject grain to some degree in the upper registers and some tube preamps are not too far behind. So far I think they should at least be matched up with an amp that has sufficient gain which is often overlooked. Which passives are you using and with what amp? Why do you like them?
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You all are making this appear much too complicated. I've plugged my TVC into a few friends systems and always had impressive and consistent results. I've changed amps and sources. I currently have a far from ideal load with long IC's, a 10K Zin hi-pass and parallel low-pass/bass amp. A mismatch seems to be the exception I haven't run across and I've seen some unexpected active component or amp/speaker mismatches. I have played with a couple DIY attenuators but not as a system volume control. One was for a biamp system to control gain and the other replaced a pot in an active preamp. Probably dissuaded by the negative reviews. The TVC was a fairly cheap experiment that I didn't expect to work and, if I had believed some of the "experts", shouldn't work. There's a story but I would rather not mention names. It was a DIY project and it even worked well when I had it wired wrong. That's another story, not for A'gon. Many of the RVC/attenuators have had a fairly low 10K Zin but, recently, there are more options for higher impedance up to 100K. |
Sure, it is close to a straight wire. But, they must also have a disadvantage. Alber Porter wend from Placette to DarTzeel, but why? What does a great active linestage do that the passive can't? The answer is straigtfoward when it is an issue of needing gain or impedance matching, but he did not seem to need either in his original set up. However, I'm interested in getting some insight into the resistor versus transformer issue, on the assumption that most all of us are in no need of gain for our sources and that our amps are sensitive with fairly high input impedance. |
Herman, part of you thinking is that passives in the right system are superior to actives, I wonder if it might also be true that passive resistor based attentuation is superior to tranformer or autoformer passive attentuation IN THE RIGHT SYSTEM, due to the much simpler design, or is the impedance matching that comes from TVC/AVC is simply almost always better in most systems. Modjeski, who I obviously think highly of, argues for resitor based attenuation, but that flies a bit in the face of what you will hear from most Agon passive adopters. Now Roger actually has an explanation why that I can't understand:), but it does seem to be based on some knowledge of electrical engineering of which I know almost nothing. |
I prefer the sound of an active preamp because it sounds like music.Rrog, once again a dogmatic statement that fails to take into account all factors. If you want to say you've never heard a passive that sounds like music then it appears that would be true, but I guarantee you they do in the right system as many have stated in this thread. Are you saying you have golden ears and all of us, and there are many thousands, who prefer passives in their systems don't hear well? Pubul, attenuate means to reduce or weaken so any volume control whether resistive or inductive is an attenuator. For some reason you usually see that term with stepped resistor controls and not with TVCs but they are both attenuators. . |
I am not aware of one single amplifier manufacturer that designs a matching passive preamp to compliment their amplifiers. Three manufacturers were mentioned in this thread: Roger Modjeski - Music Reference, Jack Elliano - Electra Print, and Jeffrey Jackson - Experience Music. Also, a number of manufacturers have implemented passive volume controls in their integrated amp designs. A couple that come to mind are Vinnie Rossi - Red Wine Audio and Paul Weitzel - Tube Research Labs. Ralph Karsten at Atma-Sphere offers a passive volume control upgrade for his OTL designs too. |
Pubul57, I don't have any direct experience with attenuators (though have done quite a bit of research on them). I have a long tome audiophile friend who has helped me for many years suggesting and auditioning gear. We have listened to alot of music together, live and recorded, and, not only do I trust his ears, but he has guided me a great deal into trusting mine. He uses attenuators - and has had the Ayre KXR, ARC Ref 5, Lamms, etc. While he says the preamps are excellent, and urged me to audition them, he uses attenuators (he only cares about sound, not how great expensive gear looks in his racks, convenience, etc). I was considering passives as my CD player was overloading my active preamp, but when I experienced the sound of my CD player direct into the amps, I just cannot believe adding any component (+ cables, etc) into that signal chain could possibly be an improvement. My decision based solely on how incredible it curently sounds and basic electronic theory. I feel the least manipulation of an audio signal, the best. While a passive would not necessarilly manipulate (definately not amplify, which usualy always distorts)the signal, it does add cables, etc (either transformers, resistors, etc) into that signal chain (and must be compatable with the rest of the gear in the chain). My turntable/preamp and my SqueezeBox/Dac still go into my active preamp - they did not sound as good direct into my amp (actually an external crossover) so definately compatability issues there. The CD player & crossover just seem to match perfectly. I really urge everyone with a CD player (or DAC) with a volume control to try the direct connection. You may be as surprised (actually, I was floored) as I was, and stil am. If I did not have volume capabilities on my crossover, I would already have a passive in my system. |
I remember Mr McCormack saying his amps were designed with a high input impedance so they would work well with passive and tube preamps. After talking with him several time about preamps I got the feeling he prefers the sound of passives, though he will tell you there is a difference in the way the two present the sound. Its just a matter of how you like your sound (do you prefer your coffee with creme or without). I was at that point at one time, I liked the slam or greater impact in the bass region that his active offered but I also liked the openness that the passive had. The Ultra upgrade to my TLC gave me both, at first I thought it was the buffered output but then I remembered trying that before the mod and it wasn't the same. Phd, I have no intention on selling any of my gear I've worked to hard and sacrificed to much to get where I am with it today. Plus I like the flexibility I have with the McCormack gear in my two channel/Home theater setup. I would like to apologize to everyone one for the bad grammar in my earlier post, I thought I read through it better. I promise no more drinking and posting. The good thing is I don't have to worry about he telephone polls jumping out in front of my words. LOL Great conversation everyone and Happy Listening. |
There is at leat one fella that designs a passive preamp around his amps, Roger Modjeski if Music Reference - a "simple" resistor-based attenuator - of course it is house with an active phono stage. He is adamant about the superiority of a passive linestage, which get's my attention knowing is perfectly capable of designing any kind of premaplification he wants. I still use an active preamp with his amps though.... |
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I agree completely, which is why discussions and assessments of of amps, speakers,cables, tubes etc. outside of complete system context (let alone personal taste)while useful as a guide, are no substitute for listening to something in your room with your other equipment - which is why I always say "with my amp and my speakers, this preamp....." |
Pubul, I see your point, they do have limitations, or perhaps better put they require careful implementation, but that could be argued for just about anything. After years of experimenting I've found that a couple of stages of triode amplification and very high efficiency speakers is what floats my boat. I would venture to say that if more people heard one properly implemented they would agree. This type of system is a perfect candidate for a passive pre. . |
Herman, isn't the other side of your argument that passives simply don't work right in too many setups? A similar problem to a discussion about the virtues of SETs (If this is right, and that is right, then they are wonderful, otherwise...). Not about laying blame, but the fact is that the problem is the passive if it can't work for certain types of sources and amps, though when it appropriate it can work very well indeed, but the passives do have their inherent limitations for being a SOTA solution in many cases. |
I have friends who have been using attenuators since the 80s, and will never go back to an active preamp-and they have access to mega buck gear. I just bypassed my preamp with my cd player and will (probably)never add a preamp again. System synergy is key-as it always is. Most of the passives I have seen have a liberal trial policy. Impedance and output voltages, length of cables, etc., are key. |
Rrog, just because you tried numerous times doesn't mean you ever tried a combination that was suitable for the purpose. There is absolutely no reason a source component can't have an output stage that is capable of driving an amp directly and many do. Having a 7 Volt output is only part of the story since it could also have a high output impedance and therefore be incapable of properly driving a low impedance passive and/or amp. No disrespect intended but statements like yours which fail to properly explore all of the facets involved and dismiss topologies which are proven to work when properly implemented only add to the confusion of those who are trying to get the big picture. . |
Well you would think with minimal parts and no active circuitry (non-buffered designs) a passive would be low maintenance, but I've run into a few scenarios where owners of both Sonic Euphoria and Promitheus expressed issues related to noise/hum. I imagine you can occasionally get a bad transformer, or in the case of my Lightspeed a bad opto-coupler. So they are not maintenance free. Also, I'm already gray so that probably increases my risk:) |
Using Mod Squad Line Drive with Bryston 3B-ST and some fairly sensitive Mirage OM-10...cables by Tara Labs. Best sound I have ever had. My previous preamp, a Sonic Frontiers SFL-1 sounded good too though but I like the fact I don't have to turn anything off when I take a break. Tube preamps I would normally turn off when not in use. |
Right now I have a McCormack DNA-1 Deluxe Gold with the Jensen's transformer inputs. At one point I had a pair of DNA-1 mono-blocks then switched to a pair of DNA-1 Deluxe Golds that I used to vertically bi-amp a pair of Vandersteen 3A Sig/2Wq combo. But the pair Gold's and a 2Wq and I were "lost" during my move here to Canada. My plan was to mono-block the Golds and do the Platinum upgrades. So right now I'm in the process of rebuilding. I heard this combo (VRE-1 and custom 0.5 mono's) at Steve's work shop a few years back and was blown away by what I heard. As a matter fact the pair of amps I heard Steve had for sale here on Agon. If I had had the cash back then I would have bought them. By the way the volume control in the Ultra is a Shallco stepped attenuator built to Steve's spec's and assembled with Audio Note resistors by Kris. Kris told me to be able to use this attenuator they had to bypass the passive output on the TLC and just use the buffered output. I wished I could have made a direct comparison between the before and after but the packers came a week after I got it back from SMc Audio. I hooked it up to make sure everything worked and could hear the difference just as soon as I fired it up. Took a while to get everything unpacked here in Canada, but this is a total different setup from what I had and I'm still rebuilding. I will tell you this is not the same TLC-1 that left my system. Wow sorry I got so long winded but I really enjoy the TLC now. By the way if you are ever in the area please drop me a line and we'll set up a session. You can enjoy some of the wine from some of the 32 wineries we have around here. Its not the Niagara region either. |
Dave Slagle is selling them too now: http://intactaudio.com/atten.html I spoke to Jeffrey about redoing my Slagle box. He is very detailed and does great wood work. I still may pursue this with him but for now need to finish my balance passive project. I've been hearing a lot about the Sonic Euphoria. They have a balanced version I'd like to try. However, I'd be concerned about support as I don't think they are manufactured anymore. |
Anthony, I know what you mean about the RM10MKII, why I had to come back to it. It maybe be in some ways, a greater piece of design than my RM9SEs (5x$$$). Becuase I do think Roger is a genius at this stuff, and he insists that I am crazy to use anything but a passive preamp, I may go there yet again. Herman, thanks for the link. |
Jeffrey uses the Slagle autoformers in his designs. Another person who on his site specifically states what we have probably stated an number of times here and in other passive threads: http://www.jeffreywjackson.com/preamplifiers.htm |
Pubul57, the engineers among us can give sound scientific reasons why resistors should outperform transformers just as they can explain why transistors should outperform tubes. However, there is a large contingency out here who swear by these supposed inferior devices. My personal experience with a PLacette confirms that a resistor based device can be excellent as well as the TVCs. One problem with the Placette's is their 9K impedance which poses a problem for many systems. If interested in a TVC check out Jeffrey Jackson's work. http://www.jeffreywjackson.com/Passive_Aggressive.htm . |
Paul, After listening to the RM-10 MkII for the last few days I'm beginning to believe Roger is the genius he thinks he is ;) I haven't even tube swapped yet and I may not. I may try my hand at building one of his PITB's, but after I build my balanced passive though. I have the parts now, just need to put it together. I live near Jack Elliano of Electra Print and I'm using his transformers and schematic for the project. He's been kind enough to allow me access to his workshop to build it as well. Great guy, very knowledgeable and some excellent SET amp designs, with which he uses passive preamps. If all goes well the Lightspeed may be available soon. Of course if you ever just want to listen to it let me know. |
Phd, Not to make this sound bad but once you hear the Ultra the stock really sounds veiled in comparison. The transparency in the soundstage just opens up to reveal layers upon layers of information. Just to tempt your taste buds if you happen to live anywhere around the Lake Ontario/Toronto area we could arrange a listening session and compare notes. |