Poll - Active vs. Passive preamp

You can see my system components here:

http://cgi.audioasylum.com/systems/7245.html

I didn't take the time to add it up properly, but without including the cost of cables the system I have runs about $20k MSRP.

My preamp consists of S&B TX-102 MkI transformers implemented as a TVC and built for me by Kevin Carter at K&K Audio. This replaced a Joule Electra LA-100 MkIII in my system, a preamp which I am very fond of as it is extremely musical. I find it very hard to go back to an active preamp, although I probably will for a change of pace and to hear the differences.

Active preamp for me, ARC Ref 3. I've tried the passive route a couple times, and admit sometimes that their transparency can be initially impressive. However, I always wind up going back to the active route because I miss the body and rythmatic drive of the msuic that they can produce, especially tube preamps.

John

Active preamp. Heard my CD player through a passive, several weeks ago. No thanks (tinny, two-dimensional, no dynamics).

I'm running an "Extreme" passive. I'm using a pair of shotgun style attenuators which reside between my interconnects and the amp. That way, I can avoid having to add another pair of interconnects to my system (extra capacitance - not good with passives) and still have the volume control. I only have one source so, I don't need switching.

Active preamp (Cary SLP-05).

I have found that impedance matching becomes absolutely critical if you have a passive pre. Also, every system using a passive pre I have heard cannot reproduce big orchestra properly. I max out the volume control and still cannot get enough orchestral dynamics.

Using Red Wine Audio Sig 30 as a single input integrated amp, which makes the answer to your question - passive. I have Zu Definitions. Total MSRP irrelevant.
I tried a Legend Von Gaylord full octal tube preamp for a few days and found it to be profoundly different but not necessarily preferential. Just boxed it up to return it this morning. It was interesting but .........
In my quest for simplicity I am apt to leave well enough alone.

I'm using an active tube preamp (Audioprism Mantissa), before the Mantissa, I used a passive TVC (Bent Audio).

Different systems, same results....I'm happy.

Dave

I am firmly on the fence on this one. I am a former TVC owner and have sung it's praises here. And in the right system (especially with the right amp) it is indeed hard to beat. But after upgrading to a CJ Premier 140 I realized that it was not "passive friendly". It is indeed a better amp than my previous RM9, but really needs an active gain stage before it to realize it's potential. Not trying to be too ambiguous here, but I think a TVC or a REALLY good active linestage can be equals, but usually not in the same system. One or the other will sound better in any given situation. Don't ask me about resistor based passives, because they don't even merit discussion.

Oz

Thanks for the responses.

I should've been more specific and said "TVC" as that's what I really meant. To me, at least, resistor passives are ALWAYS unacceptable - dynamics, gone!

Of course for the TVC (or any passive) impedance matching is the key. I take that as a given - if you don't have an amp Zin/source Zout ratio of at least 50:1, and preferably better, don't even bother with a TVC. At least, don't expect it to be able to compete with state of the art tube preamps.

I current have at least 100:1 with my digital source, but don't know the Zout specifically of the graham slee phono stage - they don't publish it. But I'm sure it's low, probably way under 1K.

Paul, doesn't your supratek use a passive resistor volume control? When you turn that knob to control the volume isn't that a variable resistor? Why is that killer and what you call a passive is not?

Amfibius, your problem with dynamics had nothing to do with the fact that the preamp was passive. If the volume is all the way up and it isn't loud enough you didn't have enough overall gain for your combination of source-speakers-room. Adding an active preamp with gain solved that problem.

Here is the bottom line. Most don't understand that ALL volume controls are passive. They may be in a box with active gain stages so we call it an active preamp, but the thing that controls the volume (resistor voltage divider, TVC) is ALWAYS passive. Designing it as a unit and using an active stage to buffer the input and/or output of the control removes variables for the uninformed audiophile and they often get better results with an active stage. Not because active is superior but because they didn’t properly implement the passive control. Most actives are plug_and_play because the standard is high input and low output impedance. This is easy to achieve with active buffer circuits in the preamp but adding an active stage must also degrade the performance in other ways. Passives can’t always follow these rules so what comes before and after is critical to their performance.

As stated above careful attention must be paid to impedances and cabling to maximize the performance of the passive. This is exactly what the designer of an active stage does for you, but if you are knowledgeable about what is going on and you don’t need the extra gain going passive is always superior.

Herman,

That's certainly one view. But an active is providing impedance matching and buffering while a "passive" is not. Of course the VC itself is "passive"; I have a rather difficult time imagining anything else, don't you?

The "excess gain" argument has been stated ad naseaum. These days, nobody needs the gain of an active linestage - almost nobody certainly - yet they sound better in some systems, even when there would be plenty of gain without another gain stage.

Active. Tube. Battery powered. Dodd's latest.

Herman has given some feedback to think about.But think Ozzy make a reasonable argument for it being combination specific set-up that's needed. for the amount of "purity" in passive mode with good unit has't' been worth the trade off in lack of bass and dynamics.And this was born out with a same unit ($1250 Pass designed Adcom in my case).Not sure why the knock on resistor based passives since I though this is means use in a hand trimmed Vishay resistors in Placette which many regard well.Haven't experience with TVC.Others like Sonic Euphoria may use different means to same passive end but they all seem to lack drive of a good active unit.For my (cheap) money I have been thinking of looking for units which have active outputs and volume controls eve if cheap op amps in CD players and some phono's.My problem is it restricts number of units with ability that attenuate signal and would prefer those that don't thus I use an active pre.But if anybody can recommend a passive units which will work with a Aesthetix Rhea or Plinus M14 (two phono's I'd like to get) I am all ears.Just don't want to have to restrict list of cables and amp to use them with.
Chazz

I've built at least 15 passives of various kinds since giving up on a CAT SL-1 Signature with its truly horrible volume control, resistors on a rotary switch but not "true ladder", and recently built a TVC based on Stevens & Billington TX-102 transformers, a la Bent Audio. I thought I'd never improve on that, and maybe I still haven't, but I'm writing this to sing the praises of Vishay resistors, TX2352's from Texas Components, looking more "naked" than the Vishays I'd seen before. To save money, I did a shunt type, which I'd always rejected, but I realized that at fairly high attenuation levels, even -14 db, say, the "size" of the passive, Input to Output plus Output to Ground, changes little, and I certainly heard nothing bad. What I did hear was really good, and whether it beats the TVC in my system will take me a long time to decide, if indeed there's any clear verdict. Expensive with Vishays, but still miles below the cost of the S & B transformers. Anyone want details? Email me if you like.

Paul, that's not a "view," that's the way it works. You restated my point (albeit more succinctly) about buffering and all controls being passive so we evidently agree.

So why is a resistor volume control in your supratek "killer" and you dismiss them if they are in a separate box? The reason is that the designer optimized the drive and load on it. If you would do the same with a "passive" preamp you would get the same or better results.

Granted, most audiophiles don’t have the technical background or expertise to do this on their own and they therefore often get miserable results. It’s like trying to drive 85dB speakers with a 2 watt amplifier and declaring SET amps are no good. Like Amfibius they blame the passive preamp when it is actually the implementation.

Passive for delicate purity, active for dynamic realism.

Hi Herman,

Did we possibly have this conversation once before? :) I think we're arguing about semantics (if we're arguing at all).

What I stated is that the Supratek linestage itself is impressive - I'm not sure how the VC sounds on it's own. ;)

It's really two different flavors - in my system. A bit more transparency vs. a bit more body. The fact that this TVC is 'different but equal' to this near world-class active linestage is rather bloody impressive, that is for sure.

Paul, I don't consider it an argument. I think you understand what is going on. What I would argue with are statements like "Passive for delicate purity, active for dynamic realism." This shows a lack of understanding about how the volume control is integrated into the system.

My system is not perfect but I can't imagine a system more dynamic. It's not because I do or don't use a passive, it is because what I do have is well implemented. I tried a passive with 10K Zin and it sucked the life out of my system because my phono stage has a relatively high Zout. Most active stages would sound much better because they have a much higher Zin, and many would conclude that active stages are better based on this very limited sample, but when I inserted a 100K passive it was magical.

A poorly designed active stage will not be dynamic just like a passive one won't work well if used in the wrong way. Since all volume controls are passive the whole discussion is kind of silly anyway.

Herman, you discount my admittedly overly simplification, then you make an example of your system where you corroborate my statement.

Some active preamps are poorly designed and should be routed around. That should go without saying. I have heard a Wadia CDP, and a APL run the amps themselves, acquitting themselves quite nicely. At the time I was using a Pass Aleph preamp. It could be used passively, or actively. Both options added little to the mix positively or negatively. I would say then go with passive if you need the switching or get a CDP with volume control.

My present very rare active preamp is a powerful argument for active preamps. It adds tremendously to the final product.

TVC - DIY

However, the rest of the system is selected for my sonic tastes and compatability. Go balanced or go away. Sorry if that sounds rude but it is vital to get the voltage out of the source and input impedance of the amp. With the proper setup, there is no loss in dynamics. Neither is there exageration and euphonics. The same applies to RVC's. Essentially, through a passive, the source drives the amp directly, although a TVC includes galvanic isolation.

This argument is getting tiresome but a passive can't be just plugged into any system and be expected to perform. There has to be planning.

Talk Thunder 3.1b - $4500 (4.2V XLR/2.1V RCA/ <100 ohms)
TVC - $600 in parts from "Gentleman" John Chapman.
Dual bridged Plinius SA-100 mk3 - $4500 each. (over 30 dB/ 47KOhms)
Genesis 350's - $30K, including 1600W bass amp. (20Hz flat/ 91dB/4 Ohms)
Various cables, room acoustics and electrical.
LP's not currently in use because of wood floor. Even the CDP will skip on bass notes when I crank it.
I listen to Blues, Jazz, Jump/Swing, 70's/80's Rock and even some Cajun.

Mural, I'm not sure how I corroborated it since my system uses a passive and is very dynamic. I discounted your statement because there are many systems with active stages that are delicately pure and many systems with passives that are very dynamic. I believe mine is both.

I've tried various active pres and some TVC based passive units (the Bent TAP and a Bent Silver NOH). I agree with Ngjockey - John Chapman is one of the best people I have ever had the pleasure to do business with. He defines integrity, and is sympathetic to the "hobbyist" in all of us. He makes a great product and I wish him the very best.

In the end though, I have been blown away by the Gill Audio Alana (much more expensive than the TAP). To me, only the copper TVC BENT TAP was close. There is definitely some sort of magic with the Alana.

You can check my virtual system for my other bits of gear.

I have enjoyed both (recent actives CAT SL1, Lamm LL2, and Placette Active). I tried the Placette Passive and it was remarkably good and competed with the CAT and Lamm - a great deal for the price - dead silent and transparent. I then tried the Placette Active - no gain, but buffered - an it was clearly superior to the passive, at least to my ears. I then decided to get back to tubes (Joule 150 MKII). The Placette Active is a great linestage, but I guess I just crave the sound of tubes in the pre, perhaps not as transparent, quiet, etc, as the Placettes, but with my speakers and very neutral CAT JL2s, the active tubes seem necessary for me. I did want to try the Bent passive, which I have heard very good things about. In the end, I enjoyed my system with all these pres, and difficult to think in terms of which is "best". No easy answers. You have to try and see how you repsond to the equipment in your system, with your music.

i started with actives; the Levinson #38S and #32. then after buying the Tenor OTL monoblocks with integrated resistive based passive and hearing it in comparison to the #32....i went with the Placette resistive based passive RVC to get remote control. i had very short interconnects from the Placette to my Tenors and over a three year period tried 'many' actives and passives; the Bent TVC 'Silver, an autoformer based passive, the Silver Rock, the Lamm LL2, CTC Blowtorch and others. while every one of those preamps was very good to excellent; the Placette was equal or better than any to my ears in my system.

finally; 18 months ago i came across the darTZeel NHB-18NS battery powered active preamp; which was clearly superior to the Placette in every way.....even in areas of noise floor and transparency.

to my ears; a battery powered active pre has the best of active combined with the strengths of passive. it does not add warmth but it does sound sweet and full bodied.

Currently using a passive - specifically a Sonic Euphoria PLC... (TVC for the uninitiated).

I think all this back and forth on passive vs. active (even subjects such as bass reflex vs. sealed, floorstanders vs monitors, etc) are all based on really 2 major issues:

1. Product Quality/System match
2. Subjective taste

Well, ok, also relative cost...

I've noticed on my system since the switch to passive is not only the famed "purity" or "transparency" offered but I noted a fuller, closer to "3-dimensional" effect of the images - especially in the midranges (even in my inadequate room).

I have heard excellent active and passive; I don't think there is a clear winner and it's up to a "try then buy" technique for this (and frankly for all things audio)...

Not to hi-jack this thread, but has anyone noted this "thicker, more accurate 3D body" effect in TVCs? Is this only for TVC passives or is it reflected in resistive passives as well? What about unity gain actives?

Just curious...

Audio Agnostically yours,
DeeCee

I'm waiting for my Promitheus TVC to come, so far one other TVC was not so impressive, now listening to a passive (diy from a friend until Promitheus arrival) though it's good it lacks dynamics. I think the matching is the "KEY" to this hobby. But something tells me that next year I should get the active preamp which was meant to be with my amp, unless Promitheus meet my expectations! (?)

I'm currently all passive, alternating between a Bent TVC and a Placette passive. I'll have a hard time going back to active.

I recently added a Sonic Euphoria transformer-based passive, and have noticed no lack of dynamics or gain. Clarity and transparency to the source are what I hear and enjoy. Have had fair active pres before (BAT VK 30 w/six-pac upgrade), and I am now hearing my system the best it has been. Using upgraded Marantz DV 8300, Genesis Digital Time Lens, Musical Fidelity A3/24 DAC, Aragon 3002 (300wpc) amp, driving Dynaudio
Contour 5.4 speakers. All electronic components upgraded by David Schulte. From what I'm hearing, I wonder why more people don't use passive pres. Mine is here to stay. Thanks, Dan

Passive (TVC) and, occasionally, active. Passive is in the system.
My cdp & phono output stages are quite powerful even though the amps are an average load, and I don't suffer from

...A bit more transparency vs. a bit more body.

as Paulfolbrecht notes above.
But then, I bi-amp my speakers -- maybe that makes a difference.

What is the downside, if any, to adding a buffer stage to an passive attneuator? A buffered passive preamp? And along those lines between a tube buffer and SS buffer? Between a buffer and a trandformer or autoformer passive?

Active: dynamics ++, bigger soundstage, better bass, more warm and involving sound (due to better midbass and lower midrange).
Passive: dynamics -, smaller soundstage, leaner bass, less warm, less involving sound. But there is greater transparency and slightly better resolution of detail.
Don't ask me why, but these are my findings.

Chris

Depends. I've used both with success over the years. If I had to fall off the fence, I'd lean towards active.

Does buffering the "passive" address the issues of soundstage and dynamics? I would think with no need for gain, that they typical passive "flaws" are due to impedance mismatches between source and amp - or is there something else going here with power reserves that act like torgue in better driving the signal?

You should direct your questions to John Chapman on the AudioCircle/BentAudio forum or look at the older DIYAudio site. He will probably say that a buffer isn't necessary for most systems.

If you could hear my system with a passive, there wouldn't be any question about dynamics and bass. However, I'm still dreaming about replacing the DAC/output section of my CDP with a discrete JFET Borbely buffer, imagining one ohm output impedance.

John does indicate the new Bent TAP has buffered input settings, but one should rarely find them to sound better than the non-buffered setting since most sources used today will have enough output voltage to drive the passive.

I believe the new Pass B1 has buffered outputs and addresses what I think is a more important issue with the ability of the passive to drive the amp, primarily due to component and/or cable impedance mismatching. It's my belief that any lack of bass or drive from a passive is primarily due to these issues. If a buffered output solves this then perhaps we're on to something. IIRC Burson makes a buffer stage that has been very well received, but unlike the Pass I do not beileve it offers a volume control.

As to whether a tube buffer or solid state buffer works best, I really can't venture to say since I've tried neither. I'm also not aware of a tube buffer with a volume control.

I think an early version of the Music Fidelity had tube buffer with volume control. This is something Roger Modjeski is looking into, and it sounds like Ralph K. is as well - should be interesting as the theory makes sense. I'll say the active Placette which is essentially a volume control with a very robust buffer stage sounded much better to me than the "nude" RVC. What I don't understand is the technical difference between using a buffer for impedance matching and the use of a transformer/autoformer.

No loss of bass or dynamics here with only a stepped attenuator as a pre. The only thing I lost was coloration.

Doesn't seem to be a problem if impedances, output voltages, amp sensitivity, and cable capacitance are right. But they do have to be right and often are not, so gain and buffering usually necessary - I would like do without the complexity of gain, but think buffering will help. Though I hear you, Roger Modjeski has been using an attentuator (Poit-in-a-Box) with his amps for the past 15 years or so.

If your source has enough potential voltage output to drive your amp to it's max wattage: You will lose nothing but coloration. If that's the case: You need nothing but attenuation. That's providing we are discussing a very transparent passive, like the Placette. Source material varies widely though, with regards to recording level. When I had my Placette Linestage, there were some recordings that just did not give me the SPLs that I crave(live levels- Jazz/Blues). Then too: There are many out there that just enjoy the colorations that most pre-amps add to the signal.

Voltage does not seem to be the issue with passives (I always got plenty of volume), but current, the ability to drive low impedance and thereby maintain bass drive and dynamics. A buffer seems to address that issue. So is there any justifcation at all for gain other than to step phoni signals? If not, are we not better off without gain devices in our preamps if buffered to handle impedance matching? You may be right though, there may be colorations that are appealing with every active providing some flavor or favourably sounding distortions to the source signal - and nothing wrong with that [?].

Some systems require gain, some don't. Below unity gain, active and passive, are both an attenuator?

Other features aside, and if you only require attenuation of the signal....you have nothing to "gain" by spending a lot more money for an active preamp.

Dave

There are already a few active/passive threads here on the 'gon. But I think this is the only poll so far...

In my system I have speakers that are 97 db. Depending on the material that I play, I would not have a hope of having enough gain without an active line section (MP-1 Mk.III), at least not if I want to play the final act of Wagner's Götterdämmerung at anything near the right volume!

That is undoubtedly true with vinyl, but why would that be true with a 3V digital source? Now the active argument seems to be volume, but I get plenty of volume with passives, though not ideal with the M-60s with their sensitivty. But assume a 1V sensitivity on the amp (like my other amp)and a 3V digital source (like my Accustic Arts)why would any gain be of any benefit? Now the need for active buffering is another issue, and I assume it always helps to make the load easy and consistent for the source through the cables to the amp. Why pay for gain? And isn't any gain device less perfect than straight wire to the buffer?

Pubul57, if you don't need the gain then that is all there is to that and I would not add any more!

There is a classic set of tradeoffs between gain, bandwidth and distortion. The rule is that you don't get all three. We traded off distortion for less gain in our amps so it takes a bit more to drive them. At least in the case of our preamps, that makes for only 4 stages of gain total between the phono cartridge and the loudspeaker.

I prefer a lower output in digital gear as the analog section will have less gain and should sound better, all other things being equal...

Never had a problem running my vinyl rig through a passive. At the time I was using a K&K SE phono stage (65db) and Dynavector 20XL with my K&K TVC. However, I do see where vinyl could present an issue.