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Anybody know if there is a real benefit to passives? Is the noise floor quieter? Is there a downside to running the Amp harder relative to using an active pre? Some amps do not have higher THD at higher output, I know, but most do, I believe.
Thoughts?
Follow Ups:
Memories into a journey...
Going back some fifteen years ago with limited insights into this preoccupation of ours being fueled along by my never-ending inquisitiveness, I set my sights on some gear to get closer to the musical performances.
My first purchase was a fairly efficient pair of powered Mirage OM6s and Transparent bi-cables, then I added a Plinius sa100mk3 amplifier largely due to its class a power,flexibility and great looks.
Then, onto the next I wanted something with tubes, so it came down to my source or preamp and at the time the Kora Hermes tubed dac was a steal.
The obvious choice for a preamp would be Plinius to maintain house sound.but as things stand my dealer just so happened to have a Adcom gfp 750 clean demo for 600 bucks. Done deal, now say what you will about those of you and your experiences with this class a featured design but I have had nothing but great results in my system and still have it today.
As always system matching or synergy is paramount and that being said it ran really hot with limited use of the volume in active mode, yet it possesed some of the best bass Ive heard to date, I ended up with Rothwell attenuators in active mode which allowed full use of the volume via remote controll, albeit the Rothwells were not the most transparent.
Anyhow ; I swung the Adcom into passive mode hooked up some very short siltech sq 110 interconnects from the Kora hermes to the Adcoms inputs out to the Plinius in class a mode, while the Kora has a 2volt and 5volt switch I switched it to 5volt for more drive.
Perhaps both the Plinis amplifier and Adcom preamplifier both being "direct coupled" and in ballance mode "differential" in design allowed for the beautiful music I was getting or perhaps the input and output impedances were complimenting each other all I know is it was a very beautifully warm dynamic, yet detailed sound with vocals that were in the room.
Perhaps the mosfets in the adcom along with the tubes in the dac conveyed the music who really knows. My point is it "worked"for me in this circuit.
There's many good suggestions from some very knowledgeable inmates like the Placette line or the luminous audio line from both ends of the financial spectrum, terrific inmates here with vast experiances and helpful experiances.Im pleased they're sharing with us parts of their journey.
Best wishes and good luck in yours.
Regards,
/// Tim W. ///
Great post. Thanks for the good wishes and for sharing. I'm concerned for my wallet with this journey I'm on, but must say I'm enjoying it immensely.
Find and Buy a 10k pot (stepped attenuator or not.. don't spend large as there is NO need to.. salesmens' babbles aside).
Run Short interconnects to your 'new' pot... from Source And to Amp. Then LISTEN,
If it works... as in your existing gear is impedance compatible (likely) AND up to it. Gotta be resolving enough to bother with :-)
Then you will Never want to go back to a Pre with gain.. nor should you need to.
Unless using a Turntable.. which then involves a discrete Phono Gizmo..feeding your pot.. which is a Good idea no matter what.
My Endler Audio Shotgun stepped attenuators attach directly to the power amp inputs. Eliminating one of the big problems when using passive preamps - trying to push the signal through a set of output cables and into the amp - greatly helps with transparency and dynamics.However, while I like the different sort of sound that this type of passive preamplification enables, I don't know that it sounds "better" than the sound I've gotten from the active linestages I've used.
And most passive preamps don't protect the downstream components in any way, blocking DC, etc... TVC passives do offer protection but really good TVCs are almost as expensive as good active linestages are.
Edits: 05/08/16 05/08/16
You said it might be this or that that worked for you. It was probably a combo of things. Of course the Kora having a 5V out mode is great for a passive setup. Thanks for your post
ET
I use a TVC in my system. I did compare a $4K active pre-amp in my system and it did not do anything in my system. But one thing to remember is "matching components", like others have mentioned. You have to be very careful. I would not look at speakers less than 6 Ohm load, at least 87db sensitivity, sources having at least 2V out and a high sensitivity amp (example 1.5V for full power). If I have a source that does anything less than 1.5V, the sound is anemic and lifeless. But with proper matching you will benefit from clean, transparent, honest-to-source sound. People complain about loosing the range at the audio extremes, but I do not experience that in my system. An important part, I understand from various sources, is what the "core" of the TVC is made up of.
Below is a link to a review of The Truth , putting into succinct form what the early adopters (such as myself) have known for several years now.It has no gain, but at the same time, many of the benefits of an active line stage.
Edits: 05/06/16 05/06/16
I didn't read the entire page you linked to but I have a few questions:
- Does it come with a remote* control?
- How much does it cost?
- Does it require the options 10-Lb weight on top to keep it from sliding around? ;-)
*I'm all for great sounding linestages, passive or otherwise, but I've come to expect a remote control in this day and age.
Hi Abe,The Truth is out there. The answers are in the review, I mean.
"- Does it come with a remote* control?"
A remote control is available, but from the review...
"Further, and related, I found the remote volume control almost completely useless because of the hyper-sensitivity of the volume control. Maybe constant practice would help, but I gave up after two evenings of frustration."
Mine doesn't have the remote, and even then, the volume control is a bit "fiddly". From "Off" to about twelve o'clock does absolutely nothing. A look inside reveals that on my Truth the LED that controls the volume doesn't emit any light until the twelve to one o'clock position.
"- How much does it cost?"
$975, sans remote, according to the review.
"- Does it require the options 10-Lb weight on top to keep it from sliding around? ;-)"
I've never had any issues with mine sliding around, because it has 3M bumper feet on the bottom of it. I can see why someone with a heavy hand, or Viagra infused interconnects might have an issue though.
After the glowing review I kidded Ed Shilling, the owner of The Horn Shoppe that if he put this thing in a $1500, half-inch thick faceplate chassis, that he could sell it for $4000 and get a A+ Stereophile rating. He says he's got a new chassis for it in the works.
It really does have a (to quote an old Corey Greenberg statement) a "Junior's first electronics project" look to it. To many, that alone would be enough to dismiss it without a fair assessment. It's noteworthy that the High-End Audio review was able to listen past The Truth's obvious visual shortcomings, and conclude, "I believe "The Truth" line stage is the most important audio component available today."
Edits: 05/08/16
I don't think I can afford it!
Dave
.., then I'd worry about miniscule distortions of that (so-called) "truth".It could be that *type of distortion* matters more than *amount of distortion*. If so, I'd probably take *best sound* over *lowest distortion* any day of the week...
Edits: 05/06/16
You call that succinct?
I tried a couple passives different times over the years- creek OBH-11 or 12 (can't remember), and a transformer based one I can't remember at all.
In all cases my system (benchmark dac, cambridge audio dacmagic, MF turntable, Transcendent Sound T8-LN OTL tube amp, Proac D-15 and Ref 3A DeCapo I speakers)
sounded tremendously better using my Transcendent Sound Grounded Grid Tube preamp instead of the passives.
I run medium length, monster cable type cables, nothing special.
But surely a ton of variables involved so YMMV.
At the risk of being tagged as the village idiot, which by the way may be more appropriate than I would wish, could one of you give a fairly simple (if that's possible) explanation/definition of "passives"? I apologize for my obvious lack of knowledge with this term, and I think I have a rough idea, but sometimes my lack of understanding things gets in the way of my ignorance of most things. TIA, I think. Dave
Everyone thinks I'm strange except my friends deep inside the earth
I really AM the village idiot. Doy.
Thanks so much to Tre', airtime & E-Stat for your simple & informative explanations. My thoughts about passives were almost in the ballpark but you guys nailed it for me. And thanks for not being condescending in your replies since I paraded my ignorance about this subject in front of God & everybody. Sometimes it's easy to be intimidated by being in the company of those who are so much more knowledgeable about these things & it's a pleasure to be enlightened, so to speak, without being talked down to, especially at the tender age of 67. Thanks again, and if anyone needs to know any mechanical tips on disassembling/overhauling & reassembling power station pumps, boilers, turbines, etc., I'm here for ya, with the guarantee of no condescension, Dave.
Everyone thinks I'm strange except my friends deep inside the earth
Tre's answer is very much to the point, but I'll add the notion of why:
When vinyl reigned, cartridges required lots of additional gain (and equalization) in order to drive a power amplifier. Preamplifiers served that purpose along with providing input switching among other things. Today, many digital sources are capable of driving an amplifier directly. All that is needed is the ability to vary the output level and balance.
I used passive attenuators between my last CDP and power amp because it had not only extremely high output - 4V - but also very low output impedance so it was well suited for that purpose.
Nothing more than a volume control between the source and the amp.
charles
A passive line stage preamp (in it's simplest form) is just a pot or stepped attenuator or a transformer volume control or a autoformer volume control in a box with input and output jacks and a input selector switch and has no active electronic circuit or power supply.Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 05/04/16
I have been using an autofomer based passive from John Chapman/Dave Slagle for the last 3 years and it is noticeably more transparent then any active I've used, tube or SS.
IMHO, the MAIN advantage of a passive is transparency and possibly lower noise but many SS linestages are extremely quiet these days.
That being said, there can be disadvantages to passives. You have to be much more careful in choosing the other components to be used in a passive setup. You might gain transparency but I've heard some passive setups sound dynamically dull, sterile, and thin.
Basically you want a source with a robust signal output and higher than normal voltage swing can be very beneficial. As an example, the Cary CDP that used I in my passive setup provided 3vrms output which is higher than typical. My amp didn't require a lot of drive to reach full output power, and my speakers were somewhat sensitive.
So in the end, I was able to achieve excellent transparency, maintain great dynamics, and the sound wasn't sterile, thin, or anemic. I was also able to keep the passive about midway in it's range so it wasn't turned all the way up or nearly all the up. I still had plenty of room in both directions.
These critical component matching issues are key to a great sounding passive setup, and not nearly as critical when using an active linestage.
The Best Sounding Passive Setup I Ever Had
Placette Passive with a network of relay switched discrete precision resistors & the Cary CDP source.
I agree with Abe, a passive volume attenuator will work best with a high output source and amplifiers having high input impedance, such as 100K ohms or higher.
I have a Goldpoint unit here as well as Endler attenuators, both of which are resistor controls.
I have also had the Chapman Bent unit here (Acoustic Imagery JaySho) and I agree there are some equipment matching advantages the TVCs have over the resistor units but, to me, the resistor units sound more "real."
However, compared to the many active preamps I have owned, all of the passives resulted in the "dynamically dull, sterile, and thin" sound Abe described, to some extent.
My nirvana came with a buffered zero gain unit constructed by Steve McCormack at SMc Audio. Being buffered, the preamp controls the cables and drives anything, and the zero gain works well with my high'ish output Metrum DAC (4V). The volume control uses Audio Note Tantalum resistors, which sound very nice.
Another preamp I really enjoyed was the 6dB gain Tom Evans Vibe with pulse, which uses a DACT attenuator with SMD resistors.
The days of needing high gain preamps are pretty much gone for those of us using digital sources since most of those have outputs of 2V minimum to as much as 6V and amplifier sensitivities are typically in the 1-1.5V +/- range for full output.
As long as you maintain a a proper impedance match there really is not much need for a traditional preamp.
Again matched properly!
If you try matching with a lower impedance amp it will be very bright and edgy. Not a nice thing. Too high and things get bloated. But that could be what you want?
charles
I feel passives that use a transformer don't have the problems that resistive passives have
Alan
Unless the transformers are VERY good, I have found TVCs to be less transparent than a resistor based passive and even many good active preamps.
The only nearly invisible volume control I have tried is a shunt volume control, which passes the signal through only 1 resistor and the pot is shunted to ground.
The Luminous Audio Axiom works really well IF your source has a really good output stage. It won't do wonders with wimpy opamp outputs.
Its hard to convince the TVC lovers other passives are worthy. Resistive types are much more dependent to proper equipment suitable for passives. Id bet a sizeable percentage of people who have tried passives dont really have the ideal gear scenario for it.
ET
I had the same Placette Passive years later in another setup and it didn't work out. tI sounded a little thin and dull.
TVCs may be less finicky with the surrounding equipment choices (I haven't tried one personally to experience it) but one of the BIG advantages of the Placette (to me anyway) is that it has a 128 step remote volume control. Maybe they exist in a TVC but I don't know of any with fairly small discrete volume steps like the 128 steps in the Placette.
Yes I have the same one and like the many steps.
ET
"...but I don't know of any with fairly small discrete volume steps like the 128 steps in the Placette."
I think you're right.
My AVC has only 25 steps, 2db each, but I have never felt like I was "caught between steps".
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Morricab hits it right with his comments in my experience.
I have been using two preamps on and off for the last decade or so. A DIY SET single stage VT137 triode preamp with stepped DACT volume pot and a Sonic Euphoria autoformer volume control (SE).
In terms of tonal balance, they are virtually identical. I think the SE is slightly more focused sounding, VERY slightly less noisy (my VT137 preamp is VERY quiet four an active, tube preamp, a requirment since I use 100db+ effiecient horns) and I never have to turn it off or on.
My active VT137 preamp sounds bigger (wider, deeper soundstage), has more "air" or a sense of room accoustics where the recording occurred, actually sounds more transparent (that always get me, how can an active preamp sound more transparent than an autoformer Which is basically a long wire?) and has better bass (deeper, bigger, more). I like both sounds.
I have experiemented with many resistive based passives and agree that they are more transparent than my SE and probably a bit more than my VT137 pre but they always sound dryish, strangly lifeless and ultimately somewhat boring. I can run my PS PWD II dac straight into my amps without a preamp and I get that same sound as with a resistive passive preamp (the sound is detailed, transparent, fast) but ultimately somewhat fatiguing and lifeless.
With passives you are listening to more of YOUR amp. The review of music sound quality is more a reflection of your amp when it comes to passives.A good passive will use a very transparent resistor. So it will offer almost nothing to the actual signal.
Edits: 05/05/16
Nice post. I have not had this issue with my passive (Placette) I have an ideal scenario with a source that is rated 2.53 VRMS @50 ohmsand amps that require a volt with 100K input impedance. I bi-amp with my passive. I think the best case is that with your passive you must still be able to overdrive your amp or amps fairly easy. Ive seen a few passive set ups and most could not.
ET
Thanks. I have a pretty good setup for passive preamps too. PS Audio PWD II has a stout output section (is actually designed to work well without a preamp) and low output impedance, my amps have ~100k input impedance. My phono preamp also has tons of gain (~70db with SUT) but output impedance is a bit higher than it could be.
I used to have problems with just too much gain in my system, my preamp volume control was never above about 4-5 clicks. I ended up going from a highish gain 3-stage SET to a much lower 2-stage SET amp setup and that works great. I can basically use pretty much all of my volume control now and it maxes out at levels MUCH higher than I can tolerate.
Straight out of the DAC (without preamp) or using a resistive based passive preamp might be the most truthful and accurate setup but perhaps it is too revealing and I find it somewhat fatiguing in the long run, so I prefer the slightly more "euphonic" and dynamic sound I get from my active preamp or my autoformer preamp.
The impudence doesn't drop as much (at all?) when you turn up the volume, though i think you still need to be careful about getting the impedance ratio between the digital source and the amplifier, even with a TVC.
"Is there a downside to running the Amp harder relative to using an active pre?"
That doesn't follow.
If you have a input level control on your power amp and you run your source straight into it and adjust the level control to achieve your normal listening level, you will not be running the "Amp harder".
You will be running it the same.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
In my setup, if I max out the volume of the Pre (zero attenuation), the average output volume is 100dB. I can achieve this same dB at about 12:00 - 3:00 setting on my active preamp.
So...the amp is "working harder" to achieve the same volume level with the passive.
Make sense?
No it doesn't.
Your active preamp has gain, your passive preamp does not.
A 12:00 to 3:00 setting of the volume control on your preamp equals unity gain and gives the same signal voltage to the power amp and the same volume out of the speakers as your passive pre turn all the way up.
Either way the power amp is doing the same amount of work. That is made evident by the speakers outputting the same SPL into the room.
There's an easy test you can do.
Get a 60Hz test tone off the internet. Open it in a audio editor like Sound Forge. Normalize it. (That sets all the peaks and valleys of the wave form at a digital zero)
Loop it so it's a few minutes or so in length and then burn a CD of it.
Play it in your CD player and measure the output voltage of the player with a AC voltage meter (any multimeter will work).
Now do the same with the signal going through the passive pre adjusted to max. (the output voltage should be about the same)
Now do the same again with the signal going through the active pre.
Adjust the active pre so that it's output is the same as the passive pre set to max. (according to what you said that setting will be somewhere about 12:00 to 3:00)
With the active pre set to the same signal output voltage as the passive pre, the power amp receives the same amount of signal voltage from the CD player and it therefore is doing the same amount of work.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Now we're getting somewhere...
I was uncertain if my description or yours was the correct one. I had an answer from someone (don't recall which forum) that told me the description that I gave was correct. But yours makes more sense to me.
Except...My A21 has an input sensitivity of 1V. The Dac has an output of 2V. Am I getting a voltage drop of more than 1V in the 4' of cable + preamp? My blue jeans cables are 25AWG, so even at 48", that's only about 0.1ohms of resistance.
" Am I getting a voltage drop of more than 1V in the 4' of cable + preamp?"
That question is a little confusing but I'll give it a try.
No and Yes.
No. You are not losing any appreciable voltage through the cable.
Yes. You will be losing voltage through your preamp depending on where you have the volume control adjusted to.
If you are referring to your active preamp and you have the volume control adjusted to less than unity by more than 6db then that's where the loss is.
If you are referring to your passive preamp and you adjust it to more than 6db of attenuation then that's where you are losing more than 1 volt.
Point of fact; a 2 volt signal attenuated by 6db is a 1 volt signal.
Again, with a steady tone to test with you can measure this and then you will know.
You will know things like, how much voltage gain does your active preamp have and at what setting of the volume control equals unity (input voltage = output voltage)
You will also get an idea of how much signal going into you power amp produces how much SPL from your speakers.
BTW Your DAC only outputs 2 volts when the music signal hits digital peak, not all the time.
That's why I said to make a normalized test CD with a single tone. Then you would know exactly how much signal you are working with.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Thanks. I will test it out as you suggested. Sounds like the 2V output is deceptive. The average is obviously much lower.
" Sounds like the 2V output is deceptive. The average is obviously much lower."
Exactly. But you should setup you gain structure so that the 2v peak will never place more than 1v at the input of your power amp.
That way your power amp is never over driven but instead only driven to max power at the peak of the music and never higher.
Most systems have too much gain and, if the operator is not careful, can be easily over driven.
Sometimes I think that what people don't like about passive preamps is they lose the ability to over drive their systems.
They confuse over drive distortion with dynamics. Upper order harmonic distortion can sound "exciting".
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
!
The Mind has No Firewall~ U.S. Army War College.
I found a large benefit. Zero noise floor and more transparant with a smoother more natural HF. To use a passive youll want higher output low impedance sources and a sensitive high impedance amplifier. Resistive based passives have no gain and TVC based ones often provide about 6dB gain. As to the THD thing its not an issue until you reach the maximum output of the amp (rated power) and it doesnt matter what kind of pre causes it to reach that point. If you tell us your sources and your amp folks here can tell you if your gear is a good candidate for a passive.
ET
Personally, I don't think there are any benefits to passives compared to expensive high-end active preamps. I've never owned a passive, but I have listened with my active preamp removed. All the power amplifiers I've owned over the past 30-years have had attenuators on their inputs making it very easy to connect a source component directly to the amplifier without using a preamp. I have done this on several occasions just to evaluate whether or not my preamp was degrading sound quality. I never though eliminating the preamp improved sound quality. There was always a slight difference, but I never thought the sound was necessarily better without the preamp.
Anyway, it's pretty easy to test even if you don't have attenuators on your power amplifier. It's easy to fabricate a simple resistive voltage divider so you can connect your CD player or your phono stage directly to your amplifier and listen for yourself.
Best regards,
John Elison
Just so everyone knows my prejudice, I've always equated "transparent" with "thin" and "threadbare." Sue me:-)
Whether a passive, or TVC or Autoformer preamp will flip your switch is totally system dependent, as others have pointed out.
In my system, my active preamp just has more "something" than either the TVC or Autoformer preamps I have.
The Sonic Euforia autoformer preamp I have is transparent, quiet and very well-built.
But, in my phono-based system, I keep going back to my Audible Illusions line stage.
The active preamp adds a "drive", for want of a better word, that I like.
But with either preamp, I never worry about harming anything down the chain.
While a passive can be easy to build one that does not degrade the sound is not. Especially one with a cheap pot. My high output tube pre with a cathode follower and low Z out was always used to attenuate my sources. It never provided gain. Connecting my source to my sensitive high Z input amp could easily overdrive it. An unneeded gsin stage will provide no benefit. My pre was a nice CJ with lots of tweaks like coupling caps, ps upgrade and a power cord and IEC inlet as well as nice black plate tubes.
ET
I'm using:
Parasound A21
Schiit Gungir Dac
Maggie 1.7's
I'm trying a pre, now, and can easily max out the volume. Average loudness maxed out (depending on source's recorded volume) is 100dB.
My opinion is that I like it. It sounds beautiful. But I'm not sure it's any different than the P5 I used previously, other than having much lower overall sound level capability. Basically...I can't decide, yet, if it's a good setup.
Thanks for the help.
If you go balanced XLRs I see no issues. Using RCA's not so much.
ET
The pre does not have a balanced option. I'm using 2' BlueJean RCAs, now.
Do you say this because of the difference in input impedance of the amp between these options?
Not only the amp but the DAC too. Its output doubles balanced. Im saying if you get a passive get one that is balanced. there are plenty of all types that have balanced connections (XLR) Your preamp wont be used anymore then.
ET
I read a post in a forum about the Lightspeed volume control that suggested that a balanced system would not be as good (more noise, blah blah blah)...
ahhh...that makes sense (I think). Many thanks for the help. I'll try out a balanced pre and see what happens.
You guys are great!
Yes and get it from a place that will let you return it if youre not happy with it.
ET
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