Based on experience, I found that any preamp, regardless of quality, degrades sound reproduction compared to a direct connection. My power amp has a passive source selector and passive precision stepped atteuator, allowing me to enjoy life without a preamp. Until now. I had to move my sources away from the power amp, behind my listening sofa, and the number of sources has increased. The need for switching between sources, and to drive a long interconnect (9m) from the back to the front of the listeing room forces me to re-visit preamps. Too bad for me.
So how does one evaluate a preamp? I just purchased two units to audition. Since I already know it is impossible to "improve" and only alter the signal from the source, I want to begin by assessing the extent to which a preamp damages the sound compared to no preamp at all. How much transparency is lost by inserting the unit in the system? If all is not lost at this point, I want to assess "how" the unit alters the signal. I don't understand the usual reviewer approach that analyzes individual facets of sound, i.e. deep bass, mid-bass, mid-range, hf, micro dynamics, macro dynamics, etc. Rather I hear different genres of music reproduction that I call "synthetic sound", "euphonic sound" and "natural sound". These are complicated to explain, but the names communicate an idea of the meaning.
Synthetic sound is typical contemporary high-end sound. My reaction to synthetic sound is "this is (or is not, as the case may be) the most amazing sounding stereo system". Synthetic sound excels at resolving detail like the number of cymbal shimmers, background sounds, fingers working frets and keys, breathing, recording session editing, etc. I can hear individual parts, but synthetic systems tend to fail at synthesizing and integrating the parts in to the whole. Or they simply distract from the holistic experience of reproduced music. Euphonic sound is just that - very pleasing to the ears. Music sounds beautifully enhanced on euphonic systems. They may or may not also be resolving and accurate - I've heard both. When I listen to euphonic systems, the experience is look viewing through a golden-tinted lens. It can be pleasurable, but over the long term not my cup of tea. Natural sound is typically unspectacular and unimpressive at first listen because nothing jumps out. No earth-shaking bass, ultra-sonic "air", or microscopic resolution. I guess they error in being subtractive rather than additive. Over time, they become extraordinary for not imparting electronic artifacts or artificial additives. To me, this is the correct approach.
An observation on the "absolute sound", comparison to live music. This is a very silly concept. First, no audio system compares to a live event. Yes, I listen to a lot of live music. Yes, I play instruments (piano now, alto sax and clarinet in the past). Yes, I have listened to some very expensive SOA systems. None of these remotely compares to a live experience. None. But what is intereting are systems that elicit reactions similar to the reactions we experience while attending exceptional live music events. In other words, an exceptional system is one that is able to re-create reactions in the listener that the listener might experience during a live musical event - not trying to re-create the sound of a live musical event, because that is an exercise in futility.
So what does this have to do with evaluating preamps (finally! get to the point!)... To my way of thinking, synthetic sounding preamps are doomed from the beginning. The perceived resolution they render is distracting and has no contribution to recreating the emotive experience of live music. Ask yourself this: when was the last time you were at the symphony or a Stones concert and thought, "I can hear the sound of Mick Jagger's heavy boots when he is strutting across the stage" or "listen to the breathing of the third chair viola in the second row". Who cares? On the other hand, on a euphonic system I listened to some of the most heart-achingly beautiful classical music (Michelangeli on the second movement of Ravel's concerto in G), and on the same system listened to Dereck and the Dominos play "Why does love got to be so sad" recorded live. Clapton's guitar was more beautiful than ever! It was a little weird hearing rock sound so beautiful, but not entirely objectionable.
So, how do you evaluate a preamp? I'm seeking one that allows me to switch sources and control volume, while minimizing corruption to the input signal, and imparting a natural sound.
The only way I know of to accurately evaluate any components insertion into an existing system is to have references (recordings) which are an intregal part of your musical memory and represent instruments, including voice, which replicate your impression of their sound live, or as close to live in the most important aspects of that sound that can be recorded.
For me piano, solo horns, and voice reproduction is critical and very revealing. I'm familar with their sound live and proper replication is very important to me. I do not use large group performances or electronic music to judge - one's not capapable of reproduction on any approximation of live, and the other is too variable as to be identifiable to anyone except the person with the gear. IMHO.
Once you have recordings which from past experience you know to represent the best reproduction of the sources in your extant system its easy to judge the capabilities of an inserted component, in your case a pre-amp. You do have to listen to the sound segmented. Unless you are a musical savant its incredibly difficult to in any reasonable period of time to identify minute differences in high quality components.
For me distortions of high frequencies and upper mid frequencies are far more important than lower mids and bass which in real life are too variable depending on the recording environment. Then I listen carefully to the the segemented sound for sounds most linear and clear/transparent, consequently natural. I probably am listening to an octave at a time.
If you want to insert a pre-amp into an existing system and you want to minimize the differences it can introduce you are going to have to insure that it has the capability to drive long cable runs without creating impedence issues, noise issues, and plain old sonic issues. This is both pre-amp and IC related. You will also need to insure that it has SOTA volume control. Bewarned, even with the greatest dilligence, and the best (read SOTA) pre-amps you will not be able to replicate what you have now, so it will be seeking out the lesser of evils (to you).
I hope that makes a bit of sense to you and helps.
Maybe for a controlled experiment connect a headphone amp and set of phones you are familiar with and run it through the preamp outputs. The relative differences should be clear (warm, detailed, up-front, whatever...). Use a known pair of interconnects for this.
A SOTA d/a converter does less damage to a signal than most passive volume controls. Long story short, during our "passive" years we found that one Vishay 201 resistor in the line with a pot shunted to ground, was about as good as it gets, being only slightly bettered by having one Vishay in each position - depending on the quality of the switch used. We made these for years and took on all challengers. Then we discovered digital room correction. With it the sound is much less confused (more intelligible) and more natural sounding (less distorted). I store response curves in memory and tweak them to compensate for different sources and program material. So my advice is IMPROVE your system with a digital pre-amp with room correction. I use one made by Tact, but others may work as well.
I have a modded passive "pre". I have tried just for kicks on occasion, connecting my Benz phono pre unit directly into my amp, effectively running the amp full out with no volume control. Since I do this with a pair of very inefficient loudspeakers, the volume is not crazy loud. This arrangement gives me just a little bit more of everything, but I think it actually sounds better with the passive "pre" in between as it 'softens' the sound just a tad on very detailed treble passages (case in point Steely Dan's Aja on MFSL). For an active pre, check out Klyne series 7. They have the reputation of the type of sonic presentation you prefer, I think.
Scott; your musings on this issue have a familiar ring to me. 6 years ago i purchased a pair of Tenor OTL monoblocks with integrated resistor based passive volume controls and input selectors. at that time i owned the Levinson #32 preamp and loved it. the Tenors and #32 seemed to work well together....i was happy.
inevitably one day i bypassed the #32 and ran straight into the Tenors. it made the #32 sound very broken. the $16k #32 was cloudy, congested, and closed in. the #32 lacked micro-dynamics and immediacy.
next i needed a remote volume control as dual manual volume knobs were not going to work for me long term. i had known about the Placette passives so i found a used balanced RVC on Audiogon. i then added it in front of the Tenors while still using the Tenor passive volume control. i could not 'hear' the Placette in the signal path......which kinda defines transparent. later; i traded my integrated Tenors for Tenors without the passive volume control. these Tenors had true balanced circutry and were a little more transparent than the integrated ones.
for the next 4 years i tried maybe 15 mostly very spendy both active and passive preamps in my system......only a couple were on par (with trade-offs) with the Placette passive......the rest were not as good.
i had 10 or 15 recordings that i used to compare the preamps; all types of music and my first priority was transparency and lack of signature. my system was natural sounding with passive and anything that added a signature distracted me from the musical event. i also was after natural transients and microdynamics......and any pre that blunted or added crispness to transients was not for me. i desired an open but texturally rich mid-range.....not bleached or golden. i wanted clarity but not color one way of the other.
overall bass performance, macrodynamcis, and soundstaging were down my list since those things only matter after the other issues are handled. the Placette was always excellent in these areas; but for me the other issues are what connect me to the emotion of the music.....i want to hear into the music and be effected by it first and foremost. maybe others want to focus on tone and bloom......or soundstage depth or height.
does the system escape the speakers and connect me?.....the Placette did.
about 2 years ago i was introduced to the darTZeel amp.....which i really liked but was not as good a match with the passive as my Tenor hybrids.....i think an impedence issue when the dart was used with the DC compensation turned off. it still sounded good but not 'perfect'. then the battery powered dart pre was introduced.
for the first time; here was a preamp that easily bettered the Placette in every way......even at the things that the Placette had always bettered all the other pre's......low noise floor, transparent, and amazing micro-dynamics. it added a sweetness and dynamic range that was singular. in battery mode; the dart was special. and it also bettered my long term phono stage reference; the Lamm LP2.
sorry i got a bit wordy; but to me pre's are very easy to compare (and i have done lots of pre comparisons).....since the differences jump out much more than amps or sources......especially when you are comparing different topologies. if you have clear reference recordings it should be easy.
the only caution is with the synergy issue with amps. my Tenors loved passive......my dart was good with passive but is other-worldly with the dart pre (it also uses a unique 50ohm proprietary cable between the dart amp and pre).
Before one "evaluates" it's good to check the EFFECTS a pre will have. Since yr amp has a volume control and you have piano and winds music and knowledge, insert the pre into the system and compare (you can also do this with white noise fm a radio):
*normal connection (i.e. output) *tape out or any other connection bypassing the pre's active circuit.
You'll know what effects the pre's circuit has
Then compare these findings with yr present connection standard -- direct to amp.
As Mike above intimates, you'll need an outstanding active pre to better the "no pre" option!
Concur with the above. Although counterintuitive, a top notch active pre will always better no pre. While my Wadia direct sounds pretty good (and it's modded including improvements to that section in particular), it just can't compete with the ML 326S; it's not even close.
Interesting comment about the ML 32 pre. I used it with an Accuphase DP75V CD player for a long time and one day connected the DP75V directly to my Edge NL12 amp and, yes, it made the ML 32 sound broken (veiled and blurred). (Yes, the DP75V has a level control.)
Gethe; i've spoken to Guy at Placette regarding the passive verses the active. when a system is optimized for passive then the passive is 'as good, but different' than the active. the problem is that most systems are not optimized for passive.
you cannot generalize on active verses passive. or even resistive based passive verses transformer based passive....or autoformer based passive.....or battery based active.....i have tried them all in my system.
at the top performance level of each topology it becomes all a matter of context. i have heard many people say that the active Placette is better IN THEIR SYSTEM than the passive...and i believe it.
i would say that until you compare a properly implimented battery powered preamp (combined with an impedence matched amp) with the Placette active (with that same amp) you won't know what preamp is truely transparent to the source.
Hi, just checked the thread this morning. I should have written my original post more clearly. I really am not asking HOW to evaluate preamps. I have my ideas and methods that work well for me, outlined in my original post. I was interested in how OTHERS conduct their preamp assessments. The original post was intended to stimulate thought and exchange of ideas, not as a personal inquiry. Sorry for the confusion.
For me piano, solo horns, and voice reproduction is critical and very revealing. I'm familar with their sound live and proper replication is very important to me.
Agree with you that certain instruments are especially difficult to reproduce convincingly. For me, those instruments are piano, voice, violins and violas.
You will also need to insure that it has SOTA volume control.
ABSOLUTELY agree with you on this Newbee. The volume control has tremendous potential to damage the signal. Nothing less than a precision device with matched discrete components is adequate. I am currently auditioning a pre with TVC.
This leads to the biggest challenge for any preamp, totally transparent volume control.
The best preamp would be one that has no sound of it's own. It should be completely transparent.
Yes, agree with you. From personal experience I know that most volume controls are horrible, and just become adequate when moving up to precision matched devices like those used by Guy Hammel (Placette) and Emanuel Go (First Sound).
When defining what exactly a preamp is and what it does, as a bare minimum, it's a volume controller.
Sorry, this is not correct. Preamp literally means pre-amplifier. By definition a preamp MUST include an active gain stage (the definition of amplifier). We may be getting entangled in semantics, but the phrase "passive preamp" is technically incorrect, and misleading.
For me, transparency is not as important as musicality (coloration). I find I enjoy a preamp that adds some color to the system because the result is a sound that approaches the sound of real music, in my opinion. It's my personal preference.
Adding colorations to enhance pleasure is what I describe as "euphonic sound" in my original post. Intellectually, I have reservations about adding colorations. Emotionally, I have really enjoyed some euphonic systems.
inevitably one day i bypassed the #32 and ran straight into the Tenors. it made the #32 sound very broken. the $16k #32 was cloudy, congested, and closed in. the #32 lacked micro-dynamics and immediacy.
Yes, your experience is similar to mine, comparing Lamm L2 and Lamm L1 to direct connection. There is just no comparison in terms of transparency. By transparency I mean compared to nothing. It is surprising and disheartening the extent to which even expensive preamps change the signal, compared to direct connection.
for the next 4 years i tried maybe 15 mostly very spendy both active and passive preamps in my system......only a couple were on par (with trade-offs) with the Placette passive......the rest were not as good.
The Placette has a precision matched value volume control and uses Vishay resistors which are very transparent in this application. I think this is the reason so many Placette users remark on the success they have compared to other units.
about 2 years ago i was introduced to the darTZeel amp.....for the first time; here was a preamp that easily bettered the Placette in every way......even at the things that the Placette had always bettered all the other pre's......low noise floor, transparent, and amazing micro-dynamics. it added a sweetness and dynamic range that was singular. in battery mode; the dart was special. and it also bettered my long term phono stage reference; the Lamm LP2.
Mike you know me, I'm one of those idiosyncratic horns and tubes guys. I totally agree with you about the ss Dartzeel preamp, based on listening to yours. It is very, very good. To my ears, it is one of the best "natural sound" preamps I heard, with an added touch of beauty. And yes, it also has that killer phono stage. Someday I need to get one to audition in my system.
Ok guys, who has hands-on experience using TVCs for volume control in the preamp? Sorry, no TVC passives. I'm listening to one now. First impression: the TVC is comparable to precision discrete resistor based unit.
Your response about the definition of preamp doesn't make sense to me.
You start off with a good point, as far as semantics go, in pointing out that the term "preamp" does refer to an active/amplified unit.
Then your logic seems to go astray when you try to put a totally passive pre into some sort of category, being that you seem to have concluded that it somehow can't, by definition, be classified as a preamp.
My take, and I believe the take of the entire audio industry, is that a passive preamp, does count as a preamp, even though it doesn't amplify anything.
Just think of it as one of the many oxymorons in our twisted vernacular. kinda like "jumbo shrimp".
IMHO, if your logic were to be played out in the above example, a jumbo shrimp couldn't classified as being in the shrimp category. It would have to have a separate classification.
Oops, I just noticed I made a mistake in saying your source unit was pulling double duty as a passive preamp.
In your case, it's not the variable output on the source unit, but your quasi-integrated amp, that's pulling double duty as a passive preamp volume controller. My apologies.
I have a very simple method of evaluating preamps____by ear and what sounds good to me with the associated gear. Unfortunately no home electronics can come close to live as Skushino mentioned. Even with the preamp removed you still are dealing with what negative effect the electronics in the source and power amp are having on the audio signal, not to mention the CD is processed by a recording engineer as to what he thinks will sound good, not all CDs are created equal. The addition of a quality active preamp will detract from transparency to some degree but will add impact & realism imparting a more Live sound in my opinion. Whatever preamp you choose, pay attention to its design & capatability, the shortest signal path & quality engineering will always bring you closer to your music. This should apply to your other components as well.
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