I get how power amps can make really significant changes to the sound of a system. And of course speakers have an even bigger effect. And then there is the complicated relationship between the speaker and power amp. But I wonder about pre-amps.
In theory a well designed preamp should just act as a source switch and volume control. But does it add (or ruin) magic? Can a pre-amp color the sound? Alter pace and timing? Could you take a great sounding system and spoil it with the wrong preamp? Stereophile once gushed (while reviewing a preamp that cost as much as a car) that the preamp was the heart of the system, setting the tone of everything. Really? Some people don't even bother with a preamp, feeding their DACs straight into the power amp. Others favor passive devices, things without power. If one can get a perfectly good $2K preamp, why bother with 20K?
It’s about the size of the signal. The signals from sources are very small and delicate...especially from turntables. Any sins committed here are, sorry for the pun... amplified.
This is why even the quality of the attenuator is so important in a preamp. This is why sound gets colored so easily.
A good preamp is so important. It took me a good while to understand this.
I agree that the death of the preamp is inevitable. But if I had to estimate when the shift would start with significant movement it would be twenty years. That would put it where the CD player is now… a few companies stop production… the ones that are future minded, most users are not yet aware that the age is over. Most people are not aware the world has changed until long after (check out the discussions of CD vs Streamer). But analog needs to die… Don’t see that soon. So that leaves a point maybe 25 years as a good transition point. Even if I was twenty five years old, I would buy a preamp.
For just 1 added component, saya CD player, we only need 1 out So you are saying a simple DIY 44 step attenuator + some resistiors, = beats high priced pres? Yes??
Well....sorta. Mine is intended to go into volume production in products so it s a bit more complex. It was never intended to be independent from a preamp or integrated amp, and i have never used it stand-alone. Mine involves 4 inputs, 32 x 2dB steps, a bunch of relays (not cheap if you want good ones to control all this stuff and get you down from 128 to say 44 resistors) a display, a micro-controller, an IR receiver, and a TON of code. The code is a big challenge - especially controlling the IR, synchronizing actions, displaying where you are, etc. but the results, yes, are clearly superior to my monolithic ladder chip solution (also intended for volume production, in fact sooner) and that is superior to an ALPS or Nobel POT (IMO).
You will also have to design and fab some fairly complex mixed analog and digital circuit boards.
A project like this is not for the feint of heart.
There is a dutch guy selling a complete attenuator kit (two units, dual mono i believe). I think his are intended to go into an amp, but you could build a box and a power supply. No balance to the best of my knowledge (which, along with mute, is a logical nightmare BTW since both are stateful and you don’t want to swap states wrong).
For DIY i’d look at the Dutch kit. I suspect his day job is with Philips. Can’t recall his name, Google is your friend. I really wanted remote control that was as good as the best rotary pots. I suspected they could be better (even the monolithic ones) and they are. See my post way way above.
as far as volume attenuation, easily the best i’ve heard is on the battery powered darTZeel NHB-18NS; there is no potentiometer or resistor network in line with the audio, volume control being by passive attenuation governed by a dedicated processor via analogue optical couplers, offering 192 steps in increments of 0.5dB.
it is truly transparent, yet dynamically alive. alas, it does run $50k.
i've compared it with other active preamps, as well as the MSB Select II passive, and the Placette Remote Volume Control passive. so far it's my preference to any of those.
I firmly believe that for 99% of applications, a true, discrete, stepped attenuator using a minimal number of resistors, great contacts, and good (not awesome) resistors is pretty darn transparent.
~~~~~~~~~~~~~~~~~~~~~~~~ I might have to agree. My tech geek swaers by a good Acoustics (made in Italy) 44 step ateenuator,,but sadly my Jadis DPL has no room for the vol pot.. I’d bet your DIY attenuator + resistors sounds as good/better as my Jadis DPL with Mundorf + Philips caps, Takman Rey Metal resistors. Shorter path = cleaner path... Am I following you right. For just 1 added component, saya CD player, we only need 1 out So you are saying a simple DIY 44 step attenuator + some resistiors, = beats high priced pres? Yes??
A few comments on the "transformers are the answer" topic. I agree that especially when you have an impedance mismatch, particularly the wrong way (high into low), that needs **transformation** rather than gain or attenuation (fractional gain),a transformer could be very good.
Its that "could be" part. They have many issues - several notes above, several not. And like most problems, they can be mostly solved with money, lots of money, and few have attempted it. No market maybe, or very very hard. An ideal, variable, volume-controlling transformer must be VERY expensive.
Ditto resistors. They have issues. You can buy better ones. But.... I actually think even modestly good (name brand 1% metal film) resistors are pretty transparent. And with resistors there is a mature market for VERY good ones, and while they too are expensive (like 10-50X the cost of modestly good ones), even at 10-50X they are still less than half a buck (Caddock, DALE mil-spec noise controlled, non-inductively wound, blah blah) or were the last i checked which i admit was years ago. To be clear, you need a dozen to hundreds of pairs depending on how you implement the solution. I use 11 pair. Oh, and a micro-controller to control the mess.
But look a the big picture: we are now worrying about two more resistors in the signal path, one series one shunt. There are likely dozens in your signal path already. Are you replacing all of those too? Or removing them and inserting.... what?
I firmly believe that for 99% of applications, a true, discrete, stepped attenuator using a minimal number of resistors, great contacts, and good (not awesome) resistors is pretty darn transparent. I can say for sure its revelatory compared to what nearly all of us have heard - and I can do A-B-C side by side tests since i have them all, independent of the preamp circuitry, with a switch to do the rest evaluations.
Dare I ask if it is possible to get decent sound from a home theater preamp?
sound quality is a combination of a number of things.
on this forum with it’s 2 channel focus signal path’s need to be as pure as possible (including the most pure preamp) to optimize the 2 channel media. along with rooms and acoustics which promote 2 channel listening, which is mostly diffusion. the subtle nuance is critical. the speakers are intended to work ’with’ the room.
but a dsp based multi-channel Home Theater system has a different set of rules. the room needs lots of absorption since with 11 to 15 surround speakers for performance you want direct sound not reflected sound. the challenge is still low noise but the dsp process and adding all those speakers makes it less critical (the concept of noise.....is actually signal to noise); especially if you play at the top of the dsp food-chain with 15 speakers and a Trinnov Altitude 16 or 32 processor (it's damn quiet).
but rooms are not chameleons; you have to choose......and if you combine 2 channel and serious multi-channel then one (or likely both) will be compromised. i’m talking degrees of good here, not saying both cannot still be enjoyable.....but still they both can’t be truly optimal since the room rules are different.
i have 2 separate serious rooms; one for 2 channel with mostly diffusion for the walls and one for dsp multi-channel/movies.....with 15 speakers and 3 subwoofers.....and lots of absorption.
you can get fantastic sound from a Home Theater processor, but it’s lots of effort. and if you get fantastic multi-channel sound, then playing 2 channel media will be compromised......although it’s possible you might like some sort of multi-channel effect more than just using 2 speakers for the 2 channel media from that Home Theater processor.
IMHO, The preamplifier is extremely important. I would consider it right up there with your choice of speakers. That being said, The improvements tend to be incremental, relative to price. Trust your ears and buy the best you can afford. With consideration towards future system additions.
I just ordered the Allegri Reference preamp myself. So I'll soon know the answer to the OP's question.
My Classe SSP-800 processor/DAC has been my systems preamp since 2009. It has served me very well but I've read enough from millercarbon and others to have learned that my 2 channel isn't at its best with the Classe(as great of a unit it is). My surround and digital will pass through the Allegri(until I buy an external DAC) as well to my front speakers. I don't think it will change anything sonically though.
John at Townshend told me that "there is no need at all" for additional Allegri isolation. "Save your money" he said.
Dare I ask if it is possible to get decent sound from a home theater preamp?
Not even. The problem is HT means surround means processors means noise.
Think of it this way. Some of the very best preamps out there are designed to power off the display when listening to music, because of the detrimental effect of even that tiny little bit of extra stuff running. Seriously. Stop and think about that. People can actually hear the sound degradation caused by something as seemingly minor as a function display.
Now imagine a whole big surround processor chip, about the size and power of the one in your computer. The noise and distortion that thing is generating, makes my skin crawl just to think of it. But then that is maybe partly because I know from experience, from having actually tried and compared these things. It is abysmal what they can get away with having a big screen to distract from the reality of the sonic dreck coming out of one of these things.
I certainly have never heard it. Well, I guess a $15K surround processor versus a $1.5K preamp. But no, never.
Also, I am currently enjoying a glass of Chateau Haut Bages Liberal Pauillac, 2018 while listening to my all tube system. We have our home theater upstairs… top of the line… but no match for my system down here. Life is good. I lived in Tucson for 25 years.
I have relatively recently gone down the audio rabbit hole and have had this question myself. Thank you all for your perspectives!
Dare I ask if it is possible to get decent sound from a home theater preamp?
I am very happy with the upgraded Emotiva XMC-1 I currently have, but during the lockdown I spent a lot more time listening to music and watching TV than ever......And buying used equipment, then selling it to try something else. I've had a lot of fun and discovered even with a modest budget, different components can make an obvious difference. I may be near enough the point of diminishing returns to stay put for a while, but love input for upgrade direction.
I haven't gotten into tubes yet, but I have a Cary Audio solid state that sounds great to me with Zu Druid MK IV's.
Remember that NOISE removal is the problem we face. Noise being any thing not in the original source. Since it deals with low level information, the preamp is the most likely source of noise of all sorts. Listening to a truly low noise preamp can be very "revealing" (sorry) and I believe the preamp is the most audible and critical of the power components.
Shortest signal path (not the same as least complex) is best and most efficient route to high-end sound imo. For digital sources, the future will see a well-designed preamp function with precise volume control built into primary components such as streaming DAC and amplification components as standard. We are already seeing speakers with streaming DAC, and seeing integrated amplification all with ‘everything inside’, although i would contend that such an approach as far as within the speaker enclosures is not best because of isolation from soundwaves / vibration.
The issue with transformers is loading and inter-winding capacitance.
All transformers have inter-winding capacitance. If the transformer is
not loaded correctly (usually too lightly) the capacitance may play a
role causing the frequency response to be less than flat. This
coloration can be easily heard.
Transformers are called that
because they transform impedance. It goes both ways; you're not
insulated on the input from the output. So if the output load is
reduced, so is the impedance on the input side.
What happens when
you have a transformer with multiple taps used as a volume control?
Since you are working with a variable turns ratio, to keep the
transformer linear you need to have the correct load at both the input
and output. You can't, as a designer, expect to always see the same
source impedance and you certainly don't see the same load impedance
since all power amps are different in that regard. On top of that you
have the moving target of variable turns ratio.
So you'll
need a lot of switch contacts, not just the ones to change taps but
another set with resistor to correct for the changing load impedance as
the turns ratio is varied.
This has to be done right, else the unit can introduce coloration.
It's all alchemy to me, what the great designers do. I'm glad for it though.
I disagree that the preamp’s sonic performance is always tightly correlated with the price.
Funny- I was just commenting about this on another forum. I agree the price doesn't have much to do with performance. Those that price to a formula will be less expensive generally speaking. My philosophy runs very similar to yours.
I agree that a high performance preamp is important with respect to the performance of a hi-fi system as a whole, but I disagree that the preamp’s sonic performance is always tightly correlated with the price. Sometimes you pay a lot of money for heavy cases, thick, engraved faceplates, name brand recognition, other cosmetics, etc. I prefer to spend the money on advanced circuitry, the best vintage vacuum tubes, high quality stepped resistor motorized volume attenuators, point to point wiring, dual mono power supplies, outboard power supplies, etc.
Transformers on the other hand, where resistors have problems
transformers have benefits. There is a reason after all why we use them
all over the place for isolation and power conditioning.
You solve one problem; you introduce others. Then it gets tricky.
The issue with transformers is loading and inter-winding capacitance. All transformers have inter-winding capacitance. If the transformer is not loaded correctly (usually too lightly) the capacitance may play a role causing the frequency response to be less than flat. This coloration can be easily heard.
Transformers are called that because they transform impedance. It goes both ways; you're not insulated on the input from the output. So if the output load is reduced, so is the impedance on the input side.
What happens when you have a transformer with multiple taps used as a volume control? Since you are working with a variable turns ratio, to keep the transformer linear you need to have the correct load at both the input and output. You can't, as a designer, expect to always see the same source impedance and you certainly don't see the same load impedance since all power amps are different in that regard. On top of that you have the moving target of variable turns ratio.
So you'll need a lot of switch contacts, not just the ones to change taps but another set with resistor to correct for the changing load impedance as the turns ratio is varied.
This has to be done right, else the unit can introduce coloration.
smandlej-
I have the Townshend Allegri Reference (upgraded from the "standard"
Allegri). This was well reviewed by Martin Colloms of Hi-Fi Critic and
Raphael Todes of Allegri String Quartet fame, the latter uses the Bartok
and found the Reference worked far better for volume control/sound
quality. I believe both reviewers now own and use the Refernce in their
own systems. This unit requires no expensive mains lead or support
as it incorporates Max's podium style feet, but you could use one of
Max's platforms as well. From my perspective, this is the most
important element of my system, and using it is like upgrading all my
source components in one go !! It does require a substantial run-in
period and benefits from balanced interconnects between pre and power.
Martin uses solid state (Naim) whilst Rapheal uses valves - it works
well with either - see millercarbon's post above.
Good to know. It has been quite a few years since I really dug into this subject. Was really interested in improving my integrated amp which at the time one was using trim pots the other a stepped attenuator, neither one a true preamp just a volume control. The more I learned the more clear it became that transformers are the way to go.
That was a long time ago so I forget all the technical electrical reasons. But the real reason they've been forgotten is my memory tends to low prioritize the moot point. Because ultimately there will always be someone willing to throw enough time and effort and money at it to solve that part of the problem.
The one they can't solve is the seemingly simple volume control. For that they always fall back on a resistor of some sort. Trim pot, variable resistor, stepped attenuator- whatever you want to call it is just a resistor used to control volume. These things are inherently lossy and noisy and problematic.
Transformers on the other hand, where resistors have problems transformers have benefits. There is a reason after all why we use them all over the place for isolation and power conditioning.
But I gave up on transformers because a) hard (read, expensive) to find good ones and b) even harder to find one with all the taps needed to make a good volume control, and then c) you still need a lot of really high quality switches.
But yeah, like you say, eliminates an expensive power cord, can be incredibly transparent, and passive, so slight gain in not adding any field noise to the system.
I read the Colloms and Todes reviews, thanks.
In the nearly 30 years since I looked into it there must have been a hundred thousand preamp questions and discussions.
Yet I could count on my fingers the times transformers have been discussed. This kind of thing deserves a lot more mention and attention. Transformers, I mean.
Point #1: Wikipedia URL with comment "you can see its not quite that simple". Actually, it is that simple. he wikipedia article manages to make a simple topic complicated by badly explaining older dB references in the context of impedance matching. Impedance matching is, in fact, one of the key jobs of a preamp. Sometimes it’s needed, sometimes not. If only high end products adhered to some standards or conventions (they often don’t) the problem would be far simpler. In fact that article points out just how wildly out of spec most DAC outputs are today. nominal line level - under a volt rms (caveat I always thought it WAS updated to 1V rms, but no matter). Many DACs now put out 2, 3 and even 4V this means a 15V swing at the INPUT to your preamp. Are they mad? Which brings us to point #2.....
No, they are not mad. Just narrow minded (IMNSHO) or maybe lazily practical for heir own product anyway. If, as a manufacturer, you wish to offer a DAC with volume control and claim it's basically a control center for all-digital systems, you need sufficient gain (output level) to drive any amp. And they have gains that run the gamut from low to high.
So what do you do? You put out a crazy high voltage level and then attenuate it. Its a preamp. Let’s say that again, it **IS** a preamp, right there at the output of your DAC. The only question is "is it a good one"? Some are, some are not. Volume control in the digital domain is fraught with issues; so that may be compromised. With R2R DACs its largely impossible except via DSP interpolation. Next, too often the output stage (line circuitry) is an op-amp chip. Unimpressed. To be fair, some are excellent, discrete, even tubes. but most are not.
So the idea that the preamp solves the impedance matching problem, if an output stage exists (even an op-amp) is not really valid. More likely the answer to why this "simpler" chain is not in fact superior is:
it’s as simple as you might have thought
The volume control is compromised (Nice word for "sucks")
The line circuitry is compromised
They really DID simplify the signal path, by leaving out the line circuitry and placing the volume control at the output and the impedance is now high (yep seen it)
OTOH i have used high quality digital volume (done in the DAC at 32-bits resolution, with all truncation below the 18/20 bit threshold) and a decent (not all that impressive output stage - essentially what one would have with a preamp too) and it soudns very, very good.
And then there’s the elephant on the table. Most tube components ADD euphonic distortion. We like it. this is not really a bad thing - its also what a Piano’s sounding board does. but in that case technical arguments go out he window,and we pivot to music theory.
And, I kid you not, i have a couple of Pianos to try out.
Do you believe it’s a point of tremendous debate that certain preamps color system sound? If so, that point of view would be surprising. One has only to look at twenty years of Audiogon preamp discussions to reach the conclusion that among many it’s not debatable, and in fact is a consideration when selecting a preamp.
@tvad
Nope- not debating that.
Or, do you rather believe it’s a point of tremendous debate that some folks like coloration that certain preamps provide?
Not debating that either.
I was talking about the endless debate between passive and active linestages.
I’m in the active camp because I can get the interconnect cables to drop out of the system equation and I can keep the distortion so low in the active linestage that coloration isn’t a thing. Not all active preamps can do that so coloration happens. Also, no passive or transformer system can do that either so you can expect coloration from them too.
To my knowledge you can either throw money at the interconnect cables in the hopes of minimizing coloration, or you can get something that was designed to minimize the coloration of cables. That latter problem was solved in the 1950s with the balanced line system (which is based on standard) but is mostly unused in high end audio. The latter part of the last statement is true because most high end audio companies either ignore the balanced standard or are ignorant of it; most high end balanced preamps I’ve seen don’t support it. The Backert is one of the few I’ve seen that does.
I am in agreement that Balanced is not always better than single ended. It's like wine , it depends on your taste.
Its not a matter of taste, its a matter of most high end products don't support the standard. If they did there would be no debate, no matter of 'taste' in this regard. IOW if you've heard a balanced setup but the standard isn't supported, you may hear colorations that cause you to prefer a single-ended setup you heard.
Essential for getting the most out of the source. Don't fall for the story of using a DAC output alone. It is lifeless and unrealistic on every DAC I've tried this with. I know, digital is digital, blah blah, but something goes wrong without a quality preamp in the chain.
I have a DAC and amp with balanced capability and the DAC has volume control. My tube pre only has single ended connections. Sometimes I run the DAC strait to the AMP via balanced. I always recognize the music a little more analytical with the balanced connections. Then I switch back and put the pre in. I always seem to settle in on having the pre in the mix for longer periods before switching back to the DAC directly connected to the amp. I am in agreement that Balanced is not always better than single ended. It's like wine , it depends on your taste.
The preamp IS the heart and soul of a system - it’s the driver in the car. The driver puts the car in gear, controls the steering and direction, and controls the throttle making the engine do what it needs to do to run the car. This is all the functions of a preamp in a sound system. It drives the system! It has to accept and manage a wide array of sources; Turntable, CD and/or BluRay player, Streamer, Cable/Satellite Box, etc., allowing you to select between all of those sources, and has to control what the amplifier does with your speakers. It’s gain, balance, treble/bass, dynamics, it controls all of those things between the sources and the amp. Without a good preamp, it would be a lot like putting a kid who just got their driver’s license behind the wheel of a race car. If you can’t manage the sources well, that’s like not knowing what gear to be in. If you can’t control what the amp is doing, it’s like not controlling the throttle, which you’re likely to blow the engine and burn the tires along with not being able to handle the steering. That’s much like not getting a good image between your speakers because you can’t control the balance and not being able to fully handle what the amp is doing to the speakers where it can sound distorted or likely blow your speakers. I hope that’s not confusing and gives you the direction you need? Good luck in your quest!
Streaming sounded like the best way to go, as I was getting my system going. I was trying to watch spending. My preamp was failing. So I connected the streamer to DAC then direct to the amp. How creative, I thought. Well, I didn't realize the digital volume was cutting bits. So with 100 dB speakers, I thought an active preamp would make my volume control run on the lower third. I currently have a tube buffer. Greatly improved vs the direct connection. The preamp is a Tubes4HiFi SP12. A solder joint and I can make it active. I think it has 5dB gain. I have not tried this version yet. Would this cause problems? I have a Pass XA25 with horn speakers(Crites).
As noted above, transformers seem key. After ten years’ pleasure from a valve phono-line stage preamp I ordered a TVC yesterday after a months trial in my system. With high efficiency loudspeakers and an SET listening to LP’s and FM radio, stripping away the many feet of wire, Audio Note caps, resistors, valves, and mains electricity of an active pre has effected greatly more clarity and presence. Omitting all that charged material, I can enjoy the effects of less noise, not least, startling delicacy of sound. Made entirely by a valve amplifier manufacturer that winds its own (copper) transformers and silver internal wiring, this unit seems very well designed (Audion. I have no connection with them). It offers very nearly the weight, huge soundstage and all the colour of sound of my valve pre. I wouldn’t go back to a powered device. It took me a month to decide. I heard it in the first half minute.
knotscott nailed it. I cannot think of any way to say it better.
In my limited experience, going from a decent AVR to a similarly priced stereo amp made a clear and present difference—for the better. Just have everything in balance.
For example parasound jc2 preamplifier is considered by few to be an endgame preamp. There's really no thrills with this preamp it does three things well the bass the treble and the mids with very little coloration. Everything about this preamplifier says quality build from a good designer. However take the top off and take a peek inside and you'll be amazed at just how little you see. With today's high-end portable headphone streamers and music players the competition is getting very Savvy with building high quality HiFi Sound in small boxes. Today's dacs with preamplifier sections in them are catching up to our large box Hi-Fi home preamplifiers very quickly.
I’ve never had good results running direct from CD or DAC to power amps. Others do and so obviously I haven’t made the correct equipment choices in that regard. The only good experience I’ve had with eliminating an active preamp is with utilizing a Manley Steelhead’s variable output. I found that to be excellent. I use an expensive tube preamp and can honestly say that there’s only a marginal improvement in areas of tone and transparency when compared to the Steelhead’s vari-out. But these small improvements are worth it to me, for the time being. I think there’s a higher cost threshold that one must pass through with an active preamp for there to be an overall improvement in system performance. Cheaper preamps (with lower quality parts) always seem to add coloration and remove transparency in my limited experience.
After trying numerous preamps in my system (solid state, tubes, fully balanced, newer, older...) I realized how important a preamp is and how much difference it can make your system sound. I ended up buying a McIntosh C2300 and it's going to stay here for the long run.
I went from a Parasound JC-2 solid state to a Cary SLP-05. Wow what a difference. System is really musical, never harsh. The tube preamp made all the difference.
I have the Townshend Allegri Reference (upgraded from the "standard" Allegri). This was well reviewed by Martin Colloms of Hi-Fi Critic and Raphael Todes of Allegri String Quartet fame, the latter uses the Bartok and found the Reference worked far better for volume control/sound quality. I believe both reviewers now own and use the Refernce in their own systems. This unit requires no expensive mains lead or support as it incorporates Max's podium style feet, but you could use one of Max's platforms as well. From my perspective, this is the most important element of my system, and using it is like upgrading all my source components in one go !! It does require a substantial run-in period and benefits from balanced interconnects between pre and power. Martin uses solid state (Naim) whilst Rapheal uses valves - it works well with either - see millercarbon's post above.
First i owned Sonic Frontiers Line 1, then Burmester 011 and then the gorgeous Dartzeel NHB 18NS, until I finally tested the MFA Baby Reference Preamplifier!!! I bought it and the topic “preamplifier”, has finished for me for ever. So simple.
The ultimate preamp is a transformer. This is the only way to avoid potentiometers of one form or another. The problem with transformers has always been they are difficult to implement with suitably fine steps. Townshend has done this with their Allegri preamps, and maybe others have as well.
So I’ve ran both. My PS Audio DirectStream DAC Sr. Direct into a pair of PS Audio M700’s. An excellent pairing making me wonder why would I need a preamp for anyways. Then I got an BAT VK50-SE and ran Orchard Audio Gen1 StarKimson Amps on the Mids/Tweets/Upper Bass and a class D ICE Amp on the Lower Bass drivers. Traded the PS Audio Amps for the BAT Preamp.
There will always be two camps. Straight Wire with gain and input switching. The other Camp is the reverse (my camp as well) where the preamp provides the “color” and the Amplifier is a gain block.
I took out my Ayre KX-5 Twenty a few times to test if the cost is justified. I immediately put it back in with a dCS Bartok & Lumin T2 (demo) going to an Ayre VX-5 Twenty. My experiment to omit the preamp backfired as I ended up buying an Ayre KX-R Twenty once I experienced the importance of a good preamp. It doesn't matter that the Bartok has a 6v balanced output. I wouldn't consider running raw dog unless I had a MSB Select II like @mikelavigne.
Interesting discussion. One topic I haven't seen mentioned is how the "Line Level" of a DAC or preamp output affects the equation. When I was young, I was taught that the main purpose of a preamp, assuming you don't want to color the sound, is to receive an input signal and output an uncolored signal to the power amp at "Line Level". So, in theory, if you have a good DAC (with a good volume control and analog output section) which provides an analog output at the same Line Level as a given preamp, how could the preamp do anything BUT add coloration? But, if you look up Line Level on wikipedia (https://en.wikipedia.org/wiki/Line_level), you'll see it's not quite that simple.
To use a specific example I'm familiar with, the Gustard x26-Pro is reputed to be a pretty good DAC, and some of the posts on this site have said that it's analog output section is a good one. Yet others will say that feeding its output directly into a high quality amp provides noticeably poorer sound than using it with a good, uncolored SS preamp, such as a Benchmark HPA4. Why would that be? I don't know the answer, but I'd bet it has something to do with the DAC's analog output being unable to match the Line Level of the output of the HPA4. This doesn't make sense to me if the DAC truly does have a good output section, but I trust the people who tell me it matters to them. If anyone would like to weigh in on this, I'd love to learn more.
The preamp is very important. I just purchased a new preamp and it has completely changed my listening experience. I thought I had a bad match between my speakers and amplier but the problem was the preamp. I found this out my accident. I only purchased the preamp because I was on a buying frenzy. I wasn't expecting a change in the sound signature at at all. If you are not happy with the sound of your speakers try a new preamp.
Used integrated amps for ages, till i got my firstwatt SIT-3. At first connected to dac direct, rockna wavedream dac has some digital volume control. Loved the amp enough to decide to get a pass XP-22. The preamp arrived and i got mind blown! There is "drive" even at lower volumes. Sound stage expanded in all directions and everything within it separated beautifully. More details which is counter intuitive! Supposed to be the opposite, but it was not. Even tone and timber improved. I highly recommend a decent preamp. Its not just a volume control, I'm a believer now
The preamp is the electrical buffer between yourpower amp and line stage components, volume control, and switch between components. The separation of the preamp from the amplifier made theoretical sense when they contained phono sections for low output cartridges that needed separation electrical fields from the amplifier output. Adding another another supply, chassis, and cables increases the cost and complexity. Well designed integrated amps are plentiful, and popular. Concerning dacs, be sure that there is a true volume attenuators in the output stage, and not just truncated digital paths
I wont add too much redundancy to what has been said here. MillerCarbon made me chuckle.
But an overlooked fact is that in the majority of cases the volume and balance controls (essentially two sequential attenuators, so the distortions are doubled keep in mind) are one of the most non-linear and distorting parts of the preamp. Most are in fact pretty bad.
In fact, my current design project is a preamp that eliminates traditional volume potentiometers and replaces them with one of two technologies at different price-points, both are substantially better, and both lend themselves to very nice remote control.
Let’s put aside volume control in the digital domain which has an entire raft of issues, but under the right circumstances can be very good. 99.999% of people have never heard those right circumstances.
Your basic volume (or balance) control is a carbon powder strip with a wiper. It is noisy, prone to dust and moisture, and does not track evenly left to right.
The next step up are Noble/ALPS style, which are still carbon powder, but in a plastic carrier. They are smoother, largely sealed and less prone to issues. They are expensive and in doing so track better left to right. They are still very imperfect.
At the top of the food chain are pairs of discrete, precision, metal-film, low noise resistors. You switch in two matched pairs of these for each volume level - maybe 64 pairs. A smaller number suffice for the balance. Stepped attenuators can cost a HUGE amount due to the labor and the 128 position switches, and are large in size, don’t play well with remote control. BUT computers and relays can come save the day ( as i am doing).
In the middle are what boil down to chips with 128 pairs of resistors that can be switched in and out. They are chips resistors, so imperfect, but i speculated that they are better than the lousy alternative. They can be, but if you use them normally or per the data sheet they are truly awful. It took me many weeks to figure out how to us them correctly. (and a really great chip engineer at the fab firm that made me his fun project). These are a little complex but overall can be cost effective in somewhat reasonably priced designs - the biggest cost being yet another very quiet power supply (or else.....).
So, the little things are way more complicated than you might imagine. Now that i have prototypes floating around, i can’t go back.
By the way, switches have their own issues, and a preamp does have an amplification stage. If its a Phono (RIAA) it has a very complicated amplifier with up to 2,000X amplification which makes noise a (expletive omitted) nightmare.
So yea, all you need to do is be perfect and it works great.
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