"seldom any discussion" ????????????
This has been debated to death. Do a search on passive and you will find hundreds of threads about this topic. I can't imagine anything will come up in this thread that hasn't been stated many times before.
I think the WHY is pretty basic. After following basic steps re.length of ics;the sound is as pure as anything you could imagine; at their cost.---(They are cheap compared to most active pres.)
Have to agree with Herman, the topic seems to come up once a month.
When discussing passives you need to break them out into a few different camps. There are those that use resistors to attenuate the volume, those that use transformers, and those that use autoformers (a transformer with a single winding). Within the resistor camp there is a sub group that used opto-couplers in the design, thus eliminating any effect the switch may have on the sound.
While the benefit of a pure signal at a fraction of the cost of an active preamp is an ideal goal of a passive preamp. The reality is some cost more, much more. Audio Consulting is a good example. Not only that, but passives, while providing a high level of transparency, can induce their own coloration and sonic signature. One example would be Audio Consulting's copper and Silver Rock transformers. The silver wound sounding more detailed and transparent IMO. Another example were S&B transformers of which there were the MkI - MkIII series. I preferred the copper MkI versions of these transformers as there was just a touch of warmth added to the sound. Resistor colorations are also possible - Vishay, Mills, Caddock, Tantalum, etc. Then there are the switches.
So all in all, while we hear how transparent and pure the signal can be with passives, there are some caveats to that. For me, the big issue is reduced noise. I also feel the level of transparency cannot be beat versus actives. If you have enough gain from your source and the rest of your system is passive friendly then a passive preamp may make sense. However, if you're someone who prefers coloration and what some will say is more "weight" to the sound (maybe its just another form of pleasing distortion), then I doubt a passive will be your cup of tea. Better to "tune" your system to you liking in other ways.
In my system the passives I have/had are:
S&B MkI TVC (custom built by K&K Audio)
Lightspeed Attenuator (boutique unit built by George Stantschleff)
Slagleman Autoformer Volume Control (prototype built by John Chapman)
The S&B was used with the solid state TRL D-225. The other two have been used with VAC Auricle Musicblocs, VAC Vintage Williamsom 35/35, and now a Music Reference RM-10 MkII. All of these passives worked fine with the respective amps.
Passives are wimpy sounding...
Yeah TVC,Placette,whatever passive is passive and you lack dynamics and bass that you can get out of decent pre.Still some folks cup of tea not mine having had one.Think amp matching is essential.Maybe the best hybrid of two ideas was Placette active.Look it up.
Why? A lot of bang for the buck. Why not? Good actives still sound better to my ears, an others, in more systems. But you can undoubtedy have SOTA with a passive approach, but you might prefer the flavoring provided by actives, especially with tubes.
Phd, I once had a Placette passive preamp for several years after previously using active tube preamps, I got rid of it and went back to active tubes, why? Because I agree with some of what has been stated above, the lack of deep base, not nearly as dynamic, and everything started to sound the same IMHO. Also the amp to be used with one, needs to have a low voltage input for full output in order to match well with a passive.
I have a Herron Audio VTSP-3 preamp which to my ears is musical, quiet and dynamic and it's tonality is as true to the instrument or voice as any preamp that I have heard or tried. I suggest that you try one before you make any decision to go passive. See if you can borrow a demo from a dealer because it does take time to break in. I do not think that you would be disappointed.
All the best.
Violin, could you use a sub with a passive to deliver the needed deep bass or would that defeat the main purpose for using a passive to begin with? I noticed some integrated amps, both tube and solid state use a passive pre, seems like it could take the guess-work out of matching separates.
SMc Audio VRE-1 will make you rethink passive as non-dynamoc and wimpy.
TVAD, you have the ultimate preamp! The VRE-1 is very spendy but beautiful and one day I will own one even if I have to wait. I understand that all the years of Steve McCormack's culmative knowledge has gone into the VRE-1. Even his earlier model the TLC-1 is not chopped liver but certainly not in the same category as the VRE-1. However I never thought of the TLC-1 lacking in dynamics especially when paired with one of his amps.
Herman, thankyou sir for correcting me and pointing out this subject has been debated to death. Realistically I think that most subjects that have been put forth in the forums have been repeated over & over again. However there are some new products that have evolved that could be discussed & their attributes and possibly offer some insight to someone that is considering a passive.
Phd, I have paired the VRE-1 with Pass Labs XA-60.5 with excellent results. The Lotus Group room at CES that received rave reviews pairing the VRE-1 with Pass Labs XA-30.5 amps. I can say the VRE-1/Pass Labs XA-.5 match is optimal, IMO.
Presently, I have the VRE-1 paired with George Wright Signature AU-15 tube amps. Both the Pass XA-60.5 and AU-15 amps have low input sensitivity specifications (1.1 mV and 1 mV respectively). I'm wondering if this is relevant to the good matches..?
People that appear to have drawn conclusions about passives without considering the critical issues - the impedances & voltages involved - haven't drawn meaningful conclusions.
A well-known member here could not find any active better than his Placette Passive until he got to the $18,000 DarTZeel. I believe he tried a great many. I think at the time he had the Placette most or all other components in his system were 10-20x as expensive as it.
Both the Pass XA-60.5 and AU-15 amps have low input sensitivity specifications (1.1 mV and 1 mV respectively).
Tvad (Threads | Answers)
This was an error. The specs should be 1.1V and 1V respectively.
Probably what made a passive TVC successful in my system is that the CDP has less than 100 Zout (impedance) and doubles to 4.2V with XLR cables. Enough bass to rattle the neighbor's windows and party level SPL's (my normal listening volume) at half way.
Paul is correct. Those who dismiss them as wimpy and lacking dynamics and bass simply don't know what they are talking about. That may have been their experience with them but that isn't the fault of the passive, it is the fault of the people trying them with other components they weren't well suited for and not knowing enough about the principles involved to solve the problem. Hook up a high impedance source to a low impedance passive into a low impedance amp and you get wimpy. Do it right and you get world class sound.
Here is the ugly truth about about preamps...the volume control inside all of them, active or passive, is a passive device. It is either an inductive voltage divider like a TVC or a resistive voltage divider like a potentiometer or stepped attenuator, but they are all passive. An active preamp adds a buffer stage so it mates well with a wider variety of equipment than the voltage divider by itself. If you choose wisely as Paul states, paying close attention to the source that's driving it and the amp after it then you don't need that buffer and you get glorious results with world class dynamics and bass. In fact, it is better than an active because you've taken out an unneeded gain stage.
Active preamps are for those who can't figure out what it takes to integrate a passive into their system, their source can't drive the amp loud enough so they need more gain, or they simply are trying to use a passive with components they will never work well with. Yes, you limit your choices for other components but there are plenty out there that mate beautifully with a passive.
Like I said earlier nothing has been said here that hasn't been said before.
Active preamps are for those who can't figure out what it takes to integrate a passive into their system,...
While this statement does apply to some, I do think there are those out there that just prefer the sound/coloration of tube preamps or other active preamps for that matter. No harm, no foul. Right now I'm playing with a Berning Mico ZOTL as a preamp and do enjoy the sounds of the various 6SN7 tubes I'm rolling with it. I also enjoyed my time with a Jeff Rowland Capri. Overall, I still prefer both my passives, but I can see why some might just prefer an active circuit.
Some passives include an active buffer stage to solve potential mismatch issues. The SMc VRE-1 and Pass B1 come to mind. Both are fine preamps and an alternative for those whose systems might not be passive friendly.
Herman, I think there are plenty of people that know perfectly well how to match a passive between their source, cabling and amp, and even when getting all that right still prefer an active preamp. Obviously in the wrong system a passive preamp will stink, but we are not talking about something so gross as that. One has to wonder what it was about Albert's system that he preferred the DarTzeel to his Placette? On some level it seems to make sense, how could all that sophisticated electronics (and complexity)used to amplify the signal only to have to attentuate it yet again possibly be as pure as leaving the signal alone? Well, it seems that for some people an active will do just that, and not just with an $18,000 preamp. I still agree that with a good source voltage with low output impedance feeding a passive into a sensitive amp with high imput impedance it is pretty hard to beat a passive for SOTA sounds at a very affordable price. It is for many a very good option, but it doesn't mean others don't prefer actives to passives even under the best of circumstances. (I've had Placette, K&K, and Bent with Autoformers - all sounding wonderful, but I prefer my Joule and Atma-sphere preamps in my system). One must also consider that many may love sources and amps (and possible cables) that just won't well with a passive at all.
Herman, well put. I think another factor that hasn't been mentioned is the that highly efficient speakers could play an important role in getting sufficient gain from a system where a passive preamp is used.
I completely agree that some components demand that you use an active preamp and such systems are capable of superb performance, but I think perhaps you missed my main point. The main point of my post was that it is not the passive volume control causing the problem some experience, it is trying to use it with the wrong components.
Let me try again. ALL systems consists of some source of an electrical signal, usually a DAC chip or a phono cartridge these days, followed by a series of active devices that eventually amplify the voltage to a level sufficient to drive the speaker. At some point in this chain of amplifiers you must include a passive volume control. To keep it simple let's concentrate on a system that only plays CDs.
The most common way to do this in a high end system is to have some amplification inside the source which amplifies the DAC chip output up to around 2V. That feeds an active preamp which may or may not amplify the voltage but contains at least a passive volume control and a buffer. That is followed by an amp that further amplifies the voltage and can supply enough current to drive the speaker. There is nothing magical about putting the volume control where it is. It could be in the CD player, it could be at the input to the amp, or if the output of the CD player is robust enough and the amp input is benign enough so the buffer isn't needed it could be put in a separate box between the CD player and the amp which we call a passive. My point is if you blame wimpy sound on a passive it means you don't understand what I stated above.
How about this? I don't have a preamp of any kind. I'm using Pure Vinyl software which controls the volume in the digital domain using 64 bit math. I modified the source so the DAC chips are connected directly to the input triode tubes of my amp through a 1:1 transformer followed by 2 more triodes. In case you are interested they also just release a version called Pure Music which doesn't include the vinyl functions.
Check it out http://www.channld.com/pure-music1.html
03-16-10: Phd TVAD, you have the ultimate preamp! The VRE-1 is very spendy but beautiful and one day I will own one even if I have to wait.
Phd if you would like a preamp that is as Mr. McCormack puts it right up there with the best might I suggest you try the McCormack TLC-1 with the Ultra upgrades from SMc. I had this upgrade done on my TLC-1 Deluxe and the difference was night and day. With the stock TLC lack of dynamics was not a concern (as far as going from quite to load passages), I had that in spades with the pair of DNA-1 mono-blocks, what did concern me was the lack of drive in the base region, it seemed like the slam was lacking when compared to the active output of my Micro Line Drive with Gold upgrades. At one point I had considered getting an ALD-1 for a comparison to see which I would prefer. The TLC Ultra completely eliminated any of these concerns. I guess this could be accounted for by the fact that to use the step attenuator that Steve builds, he has to convert the passive output to a buffered output. I had tried both the passive and buffered on the stock TLC and it wasnt quite the same. The TLC Ultra is leagues ahead of the stock TLC, so much so that you start to question what else in your system could be hindering the sound.
Anyway just a suggestion and food for thought if your interested.
Herman, any opinion on resistor attentuation versus transformer/autoformer passives? Anyone else? The consensus here seems to be TVC/AVC all the way, but that is not quite what I here when I talk to engineers....
Ig316b, I would agree with you about the TLC-1. I borrowed a CJ PF1 solid state preamp to see if this active preamp would actually sound better than the TLC-1. I gave it 24 hours of continous operation. It was a bit more dynamic but the TLC-1 sounded far better in the midrange/vocals but with a smoother (grain free) top end, also transparency was far better. Now this is the stock TLC-1, I can only imagine how good the TLC-1 would sound with the ultra upgrades. You already know that I like the McCormack products and still own one his amps as well.
I used to think the TVC/AVC designs were better. The Lightspeed Attenuator changed that thinking. Again, it probably comes down to system matching, and of course the actual design and parts used, but my system can easily work with both types.
Anthony, you know what Roger Modjeski thinks, and he seems to know a thing or two about this stuff. One of the reasons I question the TVC/AVC avalanche of opinion. When are you going to sell me your Lightspeeds:)?
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.
Ig316b, I live in Washington state which borders Canada but not sure how close we are. Yes I would love to give your Ultra a listen!
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.
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
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
Phd, Unfortunately that would be a least a three day drive for me, but I do have a buddy that lives in the Seattle area. Next time I'm out that direction I'll have to give you a shout.
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.
I am using the Sonic Euphoria PLC simply because it has beaten every 5K and under active preamp I have tried:
It is more natural and less electronic sounding than any active I have heard.
Has anyone tried Jeffrey Jackson's designs? I like the retro look. I imagine it has to sound awfully close to the BENT-TAP-x with autoformer. Sonic Euophoria is an autoformer as well, it I remember.
I think I speak for everyone and appreciate the link to Jeffrey Jackson, very interesting concept. Somewhat unconventional, definately not the prettiest looking design but isn't that the kind of gear that usually sounds good!
I had the TAP-X and although it didn't float my boat, I can see what all the fuss was about. I preferred the Sonic Euphoria because it seemed more natural, while the TAP seemed more hi-fi like.
Was your Tap-X was S&B transformer or Slagle autoformer?
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.
I would think a passive is very unlikely to ever need any support, no capacitors, no resistors, you should be grey before anything goes wrong.
IG316B, SOUNDS VERY GOOD. I still would be intersted in hearing which power amp you have paired the Ultra with.
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.
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.
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:)
I tried passive preamps and 7 volt output CD players straight into power amps on numerous occasions and with several amplifier/speaker combinations and passive never sounds as good as a high quality preamp.
I believe there is a problem with a source component being required to drive the amplifier and thereby loading the power supply of the source. Active preamps are designed to drive the power amp, not the source.
Ig31b, don't ever make the mistake I made. I sold my upgraded McCormacks. Since then it was like being adrift in a vast ocean never reaching a land mass. You have in the realm of solid state, the best possible sound.
Phd, I'm sure the McCormack gear is wonderful, but Nelson Pass and Charles Hansen have some pretty good sounding SS gear.
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.
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.
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.