Best Preamp - NO preamp... (?)

A few hours ago I decided to experiment and bypassed my highly regarded, excellent passive preamp and hooked up my PS Audio DSD DAC directly to the power amp.
There is no going back...
Every aspect of the sound has improved so dramatically that I'm simply blown away. I'm a bit shocked, playing CD after CD and I still can't believe it.
My phono stage has gain control as well, so it seems that from now on it will be disconnecting RCAs and plugging each in turn.
Since I usually do vinyl day or cd day (or week) anyway, the trouble seems totally worth it. Letting the cable settle in for a bit is not an issue.
Am I just crazy or are any of you doing the same?
Should I be concerned about damaging  the RCAs over time?
Thanks for your thoughts and experience. :-)
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My thoughts are that there is no 1 right way.

I think it's a very good experiment to do though. :)

I have a Mytek DAC which is really kind of a mini-preamp + DAC, and I am often tempted to try that. Other living room issues have taken priority.

I've tried going directly into my amps and it was no where near as good sounding. as going through the preamp.
So, to paraphrase the NRA manta, you can have my VTL TL-6.5 preamp when you pry it out of my cold wood stereo rack!

Hi , this topic has been covered many times on this  forum and as Erik  said,  there's no right answer.  Depends totally on the listener's preferences and numerous audio system variables.  Some people go back and forth between the two choices.  There will never be universal concensus with this matter.  Just go with what sounds best to you at a given time. 
There’s no voodoo in this.
Many times people that try going direct and not liking what they hear, are using the digital domain volume control in the source at too low a level, and are lowering the resolution because they are "bit stripping" eg: 14bit 12 bit ect resolution and even lower.

To make sure that this "bit stripping" is not happening one must use the sources digital domain volume control at or above 75% of full output.
If this is too loud still,, then it should be left at or over 75% and a passive preamp used.

Cheers George
This has been discussed before . Every audiophile worth his salt should try it . It may not better your system to your liking ... then again it might  . They are so cheap its a crime not to try it .
I understand your reaction to bypassing the passive.  It appears you are not substituting anything new but rather just eliminating one link, namely, the passive preamp.  Every signal carrying device has limitations, even if it is just the RCA connecting jacks, input selector switches, and a simple attenuator, and if you can eliminate them chances are there will be a sonic improvement.  Let's also not forget you eliminated one interconnect cable as well.

In my case, I still find a very high quality active preamp best suits my system and sonic priorities.  But I use it with a single set of hardwired RCA input jacks, i.e. no selector switch, and there was a clear improvement in sound quality when I did that.
Thank you all for your thoughts.
I totally get it that it's always a personal preference, and depends on component output level, input gain, and impedance matching.
Some DACs don't even offer a variable gain output so for those it's not even an option.
My amp is a very low power Yamamoto A08S so I use the volume between 70-100% anyway, no 'lost' resolution issues.
Other than the need to match gain or impedance, I find it hard to imagine how having the passive preamp in the signal path can make things 'better'.
It makes the signal pass through additional connectors and IC cable, internal wiring, solder points, input selector, and volume control. The passive preamp I have is considered one of the best you can get at any price point, and removing it from the signal path had such a profound positive impact that I still can't believe it's even the same system. Active preamps should be worse in that regard, no matter how good they are, as the signal travels through many more components. 
I had a friend come over last night, who is very familiar with my system, and he too was shocked what a difference it made, He texted me this morning that he couldn't sleep last night after hearing my system, and is now thinking of selling his excellent gear, and getting the exact same setup as mine. I must be very lucky to find such a perfect match :-)
I still need to check how it works with my phono stage, but my TT is going for service this week. I honestly think that even if it doesn't work well, I will be looking for another phono stage that does work well, and will not even consider putting a preamp back in the system.
Highly recommended everybody - Give it a try! 
I think my point for discussion is actually better phrased this way:
Instead of looking for a best (objective) match between 3 components, source-preamp-amp, perhaps we should be looking for the best direct source-amp match, eliminating the preamp altogether. Unless you need multiple sources of course.
This should be an overall easier task as way fewer combinations are possible, and the potential benefit is much higher as the signal path is significantly shorter.
For gain / impedance matching, a simple resistor divider network can do the trick instead of a full blown preamp...
I know there are decent RCA and XLR attenuators out there for sale.
If you need the gain boost that an active preamp provides, wouldn't you be better off looking for a source with higher output, or an amp with higher gain?

I know people like to torture themselves.
Diving underneath your rack and taking off one set of plugs, hooking up the other set of plugs to switch components seems insane and unnecessary.
What you're explaining indeed is you simply got rid of passive preamp in order to use active line stage of the DAC or phonostage.  Active drive is almost always better because tonal balance is easier to achieve in almost any volume setting... So my solution would be finding inexpensive active unit such as Cary AES or McCormack RLD would bring you even to higher performance level than you having with your current source units.

Thanks for your input czarivey,
Fortunately, my power amp is so gorgeous looking with it's Japanese cherry wood finish, that I have it on the top shelf of my rack (also for better heat dissipation of course :-). Therefore, changing the IC cables is very easy and convenient. I don't even have to bend.
My DAC has only one output, and all I did is disconnect it from the preamp input, and hook it up directly to the power amp, so I was using the same active line stage in both cases.
I don't understand how adding another active component in the signal path can make things better, but i'm always open to learn and experience.
I tried a few highly regarded preamps before, and my passive outperformed them all.


I am also using my PS Direct Stream sort of direct. However, I have my Direct Stream first going to the BSG QOL and then to my Pass Labs Amp.

Hi Ami, congratulations on a sound decision of running a high quality digital unit directly to your amplifier,  I've been doing this since 1996!,  of course this setup is opinionated, however,  those that believe going through another circuit board such as a active pre-amp likely does not have a truly balanced,  direct point to point wiring digital unit with a high quality volume control that has wide band specifications like 10htz to 60khtz or more,  this has extraordinary clarity and realism,  musicality, no color added that all preamplifier's  add! Cheers 
Some systems need help in getting the sound right . Speakers may be lacking in a department and the pre fills in the sonic virtue needed . Only way to tell is try . 
Hi Ami.
Since I have the same DS dac you have, perhaps I can shed some light.
First I have to give a dealer alert, since I sell the Ps line.
while the DS happens to have an extremely transparent volume, and it does sound great in my system, a top preamp will enhance your sound and enjoyment.
If one has a less than stellar pre amp, then yes the DS direct might in fact be preferable. But running the DS at less than full output (or with the -20db attenuator) is a compromise.
The preamp I’m running is a $15k all tube two box unit, but there is a stellar option at almost 1/3’rd the price.
Paul at Ps has stated that their new BHK preamp sounds much better than the DS direct.
In fact Bascom king has stated that it is the best preamp he has ever designed. And his other designs are super expensive. His hybrid design actually varies the level of tube gain as well as attenuate, so it’s a novel and very transparent approach.
While I haven’t gotten one in our system yet, having the BHK 300 Mono amps in our system, I can assure you that Bascom teamed up with Ps’s value driven aesthetic means these electronics, while not cheap, represent edge of the art sound at real world prices.
If you’re serious about building a world class system, (and you have an world class source in the DS- and one that keeps getting better with each new OS release) you need an active preamp (not a passive unit)
Also going balanced will help and means that even cheap cables can work extremely well.  
If you're ever in the NYC Area I can demo the DS direct vs. Through a great preamp.  Triode picture sound.  
It does, indeed, depend on each person's personal preference.

I have both and use both active and passive preamps, at various times, depending upon the sound I'm seeking.

I got a Creek OBH-21 Passive Preamp, primarily to use as a remote volume control.  And found the sound to be somewhat more transparent and somewhat more detailed and clear than my Parasound JC-2, and my Audio Research Ref 3.  Though, the "somewhat more" is a fairly small difference.  

I A:B'd the OBH-21 vs the Ref 3 with my wife as the judge... and... she clearly preferred the sound of the Ref 3 - called it more real and life-like sound than from the passive preamp.  Though, the passive preamp still sounded like it was a bit more detailed and clear.   

The tubes of the Ref 3, produce a deeper, more localized soundstage / image, which has more ambience - thus, the more life-like, realistic sound.  No doubt the effects of the harmonics of the tubes - "good distortion."  

The interesting thing is... the OBH-21 cost about $250, compared to the $4000-7000 of the active preamps to which I was comparing it.  So... for the money, it's hard to justify the price premium of the active preamps, when the passive preamp sounds so good and so close to the active preamps.  And... I understand... some of the custom made passives, sound even better, for a nominal increase in cost.

One compromise... might be... to use a passive preamp and a tube buffer - which might give you the best of both passive and active preamps.  

Of course... if you must have all of the connectivity and features of a better active preamp, then most passive preamps are not an option.  

So... "to each his own."
The first time one does this it is all very exciting and new, but as aforesaid, there are combinations of gear where all things considered the pre in the chain is preferable. One simply has to try with each system. 

ami, very simple to understand in terms of simple math:

usually in dedicative active preamp the volume control is substantially better also applies to the rest of sound quality or characteristics. the minimalistic units i've mentioned may even use smaller signal preamp path than your source components believe it or not. if your source components have 'direct' option bypassing volume control, than you should at least try out active preamp for the beginning found as a loaner at your local or nearest high end electronics retailer. 
None of you have mentioned using a high quality passive pre.
Ami, you should consider this-

Thanks for all your comments!

RE: shorter path / better parts with preamp - I doubt that is the case here. The passive I was using has a $400 P&G volume pot, and the volume control of the DS DAC is a digital one AFAIK, so it introduces no additional components in the signal path.

RE: a more expensive passive or some 'magic' signal processors, I am still to be convinced that adding anything in the signal path, no matter how good, can make things better.

RE: What is "better"? that is something I can't argue with. If you like the specific distortion or the coloration that a component introduces, then by all means, go for it. I am on the search for "Hi-Fi" - transparency and not coloration. I am of the opinion that if you need to add a preamp to make up for your speaker's deficiencies, you should be looking for better speakers.

RE: PS Audio BHK, I will ask Paul in the PS audio forum again. It will be interesting to hear his answer :-)

Have a wonderful weekend all!
I typed my response that the OP should try a TVC, and then deleted it.
I would highly recommend OP to try a TVC instead of using the DAC directly. It should not be a problem because he indicates that he has enough gain in the system.
The Bespoke is a pricey TVC. He can look for something on the lines of Promitheus Reference/Signature or Audio Music AMR-S.
+ 1 🖒, I am of the opinion that if you need to add a preamp to make up for your speaker's deficiencies, you should be looking for better speakers, by ami. Amen brother 😎
Dear ami,
Hi-Fi transparency can only be relevant to and very often at the price of tonal balance and dynamics. 
RE: What is "better"? that is something I can't argue with. If you like the specific distortion or the coloration that a component introduces, then by all means, go for it. I am on the search for "Hi-Fi" - transparency and not coloration. I am of the opinion that if you need to add a preamp to make up for your speaker's deficiencies, you should be looking for better speakers.

You can't be sure unless you compare the transparency of preamp vs. your source device directly to amp. The fact that you've chosen to use your source components directly instead of passive preamp speaks for itself that you like more active drive vs. anything else posters offered.
That's where simple math kills all the science behind.

Less parts does not necessarily mean better sound. If it did we would all be using the same minimal all-in-one system.  Reproducing recorded music is more complicated than that.

However, if you enjoy  the sound of your system without a preamp, that's what's right for you.

It's been  that way 20 years ago for me and it's probably the same for many today. A DAC ( or CD player) directly into a power amp is the best route. People buying new DAC's today should look for the best one they can afford and make sure it has a simple gain attenuators on it and correct matching ( sensitivity) to your amplifier; case closed!

Agree! In theory "less parts" should equal better sound. In reality it doesn't always work out that way. Must be determined individually case by case.
An absolute "case closed" rarely if ever applies to audio/sound quality issues.
For me... bypassing the preamp has always been my "sanity check" for what the preamp is really doing, or not doing for me.  I've never heard a preamp be MORE transparent than NO preamp.... but it often adds a little something here or there that is desirable..... but of course it's still a necessary part of the system.   So you just gotta find one that has colorations that YOU like or that work in your system.   To this day.... I still have not found an AV pre/pro that I like better than my old Anthem AVM-20 for it's analog pass-through.  I've tried 4 different $2-3k pre-pros whose analog performance was terrible..... just to convince myself that i was not crazy.... I plugged my Oppo blu-ray directly into my amp.. and it sounds GREAT...... therefore.... I know for a fact that the analog pass through of the new pre-pro sucks.  My Anthem is not perfect... but it does sound very good.
Each to their own, it depends on you ears, your pre amp. Some preamps are great others disappointing. I use a number of different ones in different systems. My Yamaha c2a is an example of a good preamp. It's fast yet has a degree of warmth and solidly .  System component matching has lots to do with results too- some good components just don't get on sonically yet others  do. Cables can be another question - just be careful handling them. 
Passives of good quality are now being touted as being as good as very expensive active preamps if not better. Taking it one step further if your amp has sufficient gain, going direct can be surprisingly good but as you mentioned, you lose the ability to switch between components The best thing to do is experiment as you're doing and as suggested above, go with what sounds best to your ears
I think what you've just demonstrated is that your system has a very good gain structure. I was running my Oppo BDP105 directly into my mono blocks too for a while as it sounded better than going through the Octave Phonomudule preamp. I built a passive using Slagle autoformers and the sound is somewhat the same, maybe a touch sweeter. 
But it's all about the gain. That's why it doesn't good to go direct with most people's systems. They don't have enough gain, so they need an active pre to help the signal along. 
They don’t have enough gain, so they need an active pre to help the signal along.
If it goes loud enough for you, you have enough gain, a passive preamp will NOT compress the music if it’s up near full.

Quote from Nelson Pass:
We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.
Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.
Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.
What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.
And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp.
Cheer George
I am using the Townsend Allegri Passive pre. I have used Creek and Audio Synthesis before and it is considerably better. I liked it so well that I was going to become a dealer before I got sick. It has a big lead in the Colloms sound rating on the High Fi Critic site. This is avable free if you want to look. I have been reading him since the early 70s and based many of my purchases on his reviews. Many are rare or not sold here. I got my Metrum from Europe before it was avable here. I have a very good [and expensive] active pre and I am going to give to another try when I can. [ it is very heavy and I can't lift these days] 

The bad thing about no pre is that you lose the volume control as well as the switching on most amps. Also the volume control has more effect than most think. On Audio Synthesis the different models had different volume controls. Really good volume controls are expensive. I have used my passive with CJ 350, Gamut 200, and Meridan 605s. The last are my backups and still good after all these years. Not it the class of the others of course. It has worked well with all.

I got rid of my preamp years ago (DAC straight to power amp) and never looked back. 
Here is the Colloms rating. The only one almost the same was the very top ARC and it was a very little worse.
Conrad Johnson Premier 14 39
Conrad Johnson Premier 16LS 49
Conrad Johnson Premier 18 28
Conrad Johnson Sonographe fet pre 15
Conrad Johnson 18LS 30
Conrad Johnson PV10 B 28 (line)
Creek OBH -15 MM, MC phono 35, 19
Creek OBH 22 passive (load sensitive) 39
Creek OBH 21 Headphone amp 40
Cyrus Phono (PSU) 28(35)
Edge Signature one (battery) 37
Electrocompaniet EC3 18.5 MC, 22 line
Exposure MCX 98
Halcro DM10 22 disc/26line
Jadis JP 30 (original series) 14
Klyne sk6 13.5
Krell Evolution One 120
Krell Evolution 202 70
Krell KSP pre 21
Krell KRC-2 22.5
Krell KCT 28 28
Krell KPS 28 35
Lehmann Audio Silver Cube 26
LINN Uphorik 98
Mark Levinson No 38s 33
Mark Levinson ML 26 20.5
Musical Fidelity MVX pre 12
Musical Fidelity MVT 13.5
Music First Reference Bal/SE TFR 180
Myryad MP 100 pre 15
Naim Prefix mc phono 45
Naim Superline mc phono- Hi-Cap 120
Naim Superlinemc phono Supercap, Supercap DR 145, 190
Pink Triangle PIP pre 18
Plinius Koru 15 MM/MC
Pro-ject Tube Box SE II Phono MC, MM 45,45
PS Audio GCPH 15
Roksan Platinum Phono Reference DXP SE 45
Roksan Platinum PR15B 20
Stevens and Billington transformer passive 33
Tag McLaren DPA 32 19
Thrax Dionysus 135
Thrax Orpheus 225
Townshend Allegri autotransformer 230
Townshend Glastonbury Pre 1 SE AutoTFR 195
Trichord Dino Mk2 MC phono 29 std supply, 33 NC supply
Van Den Hul Grail MC phono 65
XTC PRE II 80 (line)
YBA Pre 1 15.5
- See more at:

I do this on my analog rig... I ran my PS Audio GCPH and now my Manley Steelhead directly to my amp, as they both have volume controls.  Sounds great, wouldn't have it any other way.  I also tried using a preamp to confirm what I was hearing and couldn't get it out of the chain fast enough.
I would be interested to see (hear) what a good, active preamp could do in your system. I went preampless for a few years and thought it was great, but the got a Jeff Rowland Criterion preamp and I realized all the midrange I was missing.  Preampless is a bit too sterile for me.  My preamp is the heart and soul of my system.  
I'll add my experience here with a similar situation. I am primarily an analog listener. Vinyl is number 1 for me, but I do listen to the odd CD. It is my only digital source. Both my turntable and CD player run through an Audio Research LS17-SE, although I do have a separate phono stage between my turntable and pre-amp. My CD player is a McIntosh 301 that has the ability to run direct to my amps as it has an attenuator control for this specifically. Out of curiosity one day, I decided to give it a shot, and see what differences I could hear. For my money the quality was superior WITH the pre-amp in the circuit. I was not impressed with the direct to amp configuration. My opinion for my musical taste only folks.
I understand  your point. Keep in mind that some will say that the Criterion midrange is merely added coloration from an active preamplifier. The sterility you describe is transparency to others.
Simply having enough voltage is not the whole story.
There are so many variables (including listening preferences) that, as others here have pointed out, there really is no one answer.
In addition to having enough voltage to drive the amplifier, impedance matching is also important with a low output impedance (from the passive device) feeding a high input impedance (to the amplifier) being desirable.  The length of the IC cable between the preamp or passive device and the amplifier(s) also affects this.  
You cannot lump everything that has gain into one "preamp" basket because there are many different designs.  When folks say that preamps are no longer needed, I believe they are mostly referring to the high gain devices that were common 30 years ago.
The optimal set-up for a passive preamp is between a source with sufficient voltage output to drive the amplifier, and an amplifier with sufficiently high input impedance to not be negatively affected by the output impedance of the passive device, and finally for the connecting IC cable to be sufficiently short to not have an effect.
Even when these things seem appropriate, there are many who still prefer sending their signal through an active "preamp."
The issue is further complicated in that all "passive" devices are not the same.  Some passives are simply a volume control, including a pot or perhaps a discrete resistor type control, and others use transformers, autoformers or even LDRs (light dependent resistors).  The resistor based volume controls seem to be most affected by impedance issues.   I own two resistor-based passives, a Goldpoint single input unit and Endler attenuators which connect directly to the amp so taking the length of the IC cable out of the equation.  Both use discrete resistors and both sound very good but need careful impedance matching between the source and the amp.   I have also had the Acoustic Imagery JaySho here for an audition (this is the same design as Chapman's Bent Audio TAP unit, but repackaged) and while it may open up a wider range of equipment that will work well, IMO there are sonic trade-offs so I wouldn't necessarily say everyone would like the TAP unit better.
George posted a portion of a Nelson Pass quote previously in this thread that was taken from Pass' discussion of his DIY "buffered" preamp.  A "buffered" preamp is generally considered to be a no-gain device with an active electronic circuit that reduces the output impedance.  Here is the other half of Pass' quote;
Is impedance matching an issue? Passive volume controls do have to make a trade-off between input impedance and output impedance. If the input impedance is high, making the input to the volume control easy for the source to drive, then the output impedance is also high, possibly creating difficulty with the input impedance of the power amplifier. And vice versa: If your amplifier prefers low source impedance, then your signal source might have to look at low impedance in the volume control.

This suggests the possibility of using a high quality buffer in conjunction with a volume control. A buffer is still an active circuit using tubes or transistors, but it has no voltage gain – it only interposes itself to make a low impedance into a high impedance, or vice versa.

If you put a buffer in front of a volume control, the control’s low impedance looks like high impedance. If you put a buffer after a volume control, it makes the output impedance much lower. You can put buffers before and after a volume control if you want.

The thing here is to try to make a buffer that is very neutral. Given the simple task, it’s pretty easy to construct simple buffers with very low distortion and noise and very wide bandwidth, all without negative feedback.


Other manufacturers have also found the no-gain to low-gain approach to work well, such as Steve McCormack who originally offered no-gain or +6dB options on his highly regarded VRE-1 preamp, which is basically a very high quality buffered circuit.  The +6dB option is standard on his current version of the VRE-1 with this relatively low-level of gain resulting from high quality output transformers he uses, and not the active circuitry.   Steve has found the power supply to be very important to the quality of sound of the buffered preamps he has designed.  

My personal preamp is a no-gain, buffered unit that was custom built by Steve McCormack and is very similar to his early VRE-1 preamp.  It works well with every amplifier I have used and sounds better than the over-20 highly regarded preamps that have paraded through my system over the years. Below is an excerpt from a 1995 interview with Steve where he was discussing his thoughts at the time on passives and buffering.  A link to the full article follows.

The sonic performance of the finished product, called the Line Drive, fulfilled all of the original design goals. It was characterized by the exceptional transparency and natural musicality which are now recognized as classic passive features when the preamplifier is properly designed and manufactured, yet rarely heard from other types of components.

With further experimentation, I discovered that the very best performance of my design came from running it with a high input impedance (20 kOhm or higher), high gain power amplifier. This too is characteristic of all passive units. The amplifier's high input impedance prevents loading effects while the high gain assures ample capability to drive loudspeakers to an appropriate volume level. Only extremely low loudspeaker sensitivity combined with low gain amplifiers present a problem for attaining high volume levels. Again, this combination of factors is rarely present in the real world.

While investigating early reports of "insufficient" volume, I found that people simply were not turning the volume control far enough to achieve the levels they wanted. Following the lessons they had learned about not turning up the volume of active preamplifiers too much as a precaution against system damage, these individuals were setting their controls too low. Since passive line-level preamplifiers have unity gain (1X), there is no reason not to turn the volume all the way up if that is required.

Please understand that I have nothing against active circuits, and I assume the same is true of other creators of passive designs. I build active units for applications where they are appropriate, such as phono preamplification. However, I prefer the passive path in some other applications because of the exceptional transparency and natural musicality possible through this approach.

During the latter years of the original Line Drive's seven year tenure, I worked with design refinements in preparation for releasing its successor. These experiments confirmed most of my earlier conclusions, but they also led me to appreciate the advantages of offering a buffered output in addition to the passive output. I had resisted that option for a while because the buffer circuits I knew had a negative effect on sonic performance. It was during the development of the Active Line Drive ALD-1 preamplifier that I designed a special buffer circuit that was based on a simple complimentary FET pair, but which required a very high quality power supply to make it work properly.

This was the first electronic circuit I had worked with that complimented the passive circuit and did not compromise sound quality. It allows the use of any length of cable between the preamplifier and power amplifier. Adding the buffered circuit brings the opportunity to enjoy the sonic benefits of minimalist preamplification to all systems.


The purpose of taking the time for this post is to provide information showing why I believe there is no one answer or product that is going to work well for everyone and to respond to the OP as to why simply taking things out of the signal path is not always a recipe for success.
Mitch2, thank you for taking the time to explain in detail the other variables involved and pointing out the genius behind Steve McCormacks designs which I believe are top notch!
Thanks for the detailed post Mitch.
I totally agree with you that if your source and amp gain and/or impedance are mismatched, an active unit may improve the overall result.
What i'm questioning is the common approach on how to solve this mismatch.
My suggestion is that you might be better off trying to find a better matched source-amp combination than introducing an active pre-amp to make them work well together. 
If you invest the money you save on the preamp, and get an upgraded and better matched source or amp, the overall result may be much better than having to introduce a preamp as a 'match maker' for a 'given' source and amp.

I would like to add a quote from Ted Smith that addresses cable capacitance as well, which was posted on the PS Audio forum regarding the DS DAC direct to amp approach. The key sentence here IMHO is
  • "We don’t always build our systems from whole cloth where we might have the opportunity to find a set of components with no interface issues: a preamp is a good thing to have on hand for the cases where other factors like gain mismatch or cable length or… get in the way of a well balanced system." - 
So why not strive for a well balanced, preamp-less system to begin with?

Here is the full quote:

“There are two issues that come to mind: gain (which has already been mentioned) and the other is cable capacitance.

With respect to gain, there’s a “best” sensitivity of amp to use with the DS direct: you need enough headroom to have dynamic music (even on your louder tracks) but also enough sensitivity that you aren’t using the volume control far from 100 a lot of the time. Obviously if your music collection has tracks that are significantly different in loudness or dynamic range or if the amp isn’t sensitive enough or is way too sensitive you’ll probably want a preamp.
With cables that have too high of a capacitance there are FR response issues with almost any source. With most sources high capacitance implies a high frequency rolloff, but at times the transformer output of the DS can interact with cable capacitance to add a little high frequency boost. In an already existent system that already has high capacitance cables but is otherwise balanced changing from some other DAC to a DS may make quite a difference in the very top of the audio band. Either a rolloff or a boost of the highs could be beneficial in some setups, but in general, average to lower capacitance cables will be better with the DS or you’ll need a preamp to drive/buffer a higher capacitance or long run cables after the DS.
My counter argument to the minimalist point of view is that “Why should you expect a $6000 preamp in a $6000 DAC for free?” We don’t always build our systems from whole cloth where we might have the opportunity to find a set of components with no interface issues: a preamp is a good thing to have on hand for the cases where other factors like gain mismatch or cable length or… get in the way of a well balanced system.
Given a particular amp the DS could be designed so that you probably wouldn’t want a preamp – and similarly given the DS an amp could be designed so you probably don’t want a preamp, but in real life, as all things in audiophile land, you’ll need to listen for yourself to different setups and make up your own mind.”

If your source has sufficient output voltage, there are a couple of DACs that offer volume control solutions that maybe superior to even properly implemented passives, and may approach the sonic quality of very good active preamps.  These are implemented by changing the reference voltage of the dacs, which does not affect the "bits."

Steve Nugent's Empirical Audio Overdrive SE and SX offer this type of on-board volume control method as does Metrum's new Adagio.  I am currently enjoying Metrum's Pavane (which does not offer volume control) but I am very curious to try the Adagio, which is said to offer other sonic improvements over the already very good Pavane, in addition to the volume control option.

I have no clear idea how PS Audio's DirectStream DAC controls volume although it is said to be in the "digital domain."  It was surprising to me that Art Dudley didn't even try the direct-to-amp approach in  Stereophile's first review of the DirectStream DAC.  He brushed it off by saying;
Given the choice, I always prefer the sound of my system with an active preamplifier—the passive approach seems to me sorely lacking in drive by comparison—so I didn't try using the DirectStream to directly drive any of my amps.
Robert Deutsch did try it direct and had this to say in his 2015 follow-up;
Since the DS's analog output is variable, it can be used to drive an amplifier directly rather than running the signal through a preamp. Like most people who've compared a high-quality active preamp with a passive controller, I've found active preamps to be superior, particularly in dynamics. But the DS is different: its output level is controlled in the digital, not the analog domain, and Ted Smith, lead designer of the DS, claims that using the DS's variable output to drive an amp directly results in no loss of resolution. In fact, this is what PSA recommends for optimal sound quality.

Listening at matched levels through my Convergent Audio Technology SL-1 Renaissance preamp vs direct connection, I went back and forth at least a half-dozen times, trying to decide which was better—which should give you an idea of how close the sounds were. The sound through the CAT was a bit warmer, which was welcome with voices. The direct connection to the MC275LE resulted in even more finely defined detail, but perhaps veered slightly in the "clinical" direction. Overall, I preferred the connection through the preamp, but it was a close thing. The CAT is one of the best preamps around; pitted against a lesser preamp, the direct connection would likely be the winner.

He seemed to observe the "more detailed but thinner, dryer, less full, etc." perception that others report when running DACs direct to amplifiers, or when using passives, compared to using active preamps.  In fairness to PS Audio, AudioStream also preferred having an Ayre preamp in the signal path when compared to running the Empirical Audio Overdrive SE direct to their Ayre amplifiers.
Here is a part of the review from 6 Moons for the new Gryphon Antileon Evo poweramp, driving Wilson Alexia’s
What was used first as the preamp was his Supratek Reference DHT, and yes this quote of part of the review is pushing my product, but it goes to show at least to this reviewer what a passive can do.
And if his source (AMR CD-77.1) had a volume control of it’s own, it would have sounded even better to him direct.
That’s the quintessential description for the sound of the Antileon EVO, too. There’s a sense of weight, power, dominance and uncompromising authority to music when played via this amplifier. And it’s not just about the bass either. It’s about overall dynamics that approach reality (yes, rest of gear permitting…) with explosive contrasts. This last came through even more outwardly when I connected George Stantscheff’s Lightspeed Attenuator quad-matched LDR passive. The Lightspeed does no harm. It’s as clear a conduit to the musical content from your source as you’re going to get, provided all impedance parameters are optimal, and without hindering dynamic expression in any way, shape or form.
Cheers George
Hi George,
I'm very impressed with your candor:
And if his source (AMR CD-77.1) had a volume control of it’s own, it would have sounded even better to him direct.
Wow... coming from the manufacturer of the product, that is rare.
If I ever consider a passive again, (for this system or another one) your Lightspeed attenuator will be the first one I'll try.
ami OP
Hi George,
I'm very impressed with your candor:
Thanks ami, just telling it like it is.
On a side note, there is just too much voodoo and shilling that goes unmoderated in these forums, maybe I'm just getting crotchety in my mature age.

Cheers George
I have tried many passive, direct dac, and active preamp,and vacuum tubes do
Sound more realistic and natural per dollar then a solid state model ,there too there are exceptions if you gave the $$.vacuum tubes give you more bang for the buck.
Active gain stage on a good quality preamp over  $3k has better detail and 
Dynamic range when the volume goes up the whole performance should stay rock steady. I have listened to transformer based passive preamps that are very good 
Like U.K based Billington and Steven's very good but over $4k.
Having the ability to operate a audio store while in Europe and play with all the options was very interesting. I have yet to hear a direct feed from digital converter
That has the slam and control as with a quality preamplifier, DCS Edgar another exception great build and sound quality but pricy.
Just to clarify.   I have heard it explained that The volume control in the Ps audio DS (I'm a dealer) is digital up until 50 - from 50 to 100 it is analog.  as Robert Deuch found it sounds fantastic and close in sound to the Cat preamp.   Well as good as the DS is - the reports from Paul at ps audio is that the BHK preamp is significantly better in all respects.   he's a straight shooter and these days won't release a product that doesn't live up to his expectations.   He spent years developing a hypex based amp with custom front end, and scraped it because there were better out there. 
audio doesn't always make sense.  One would think less parts means better sound but it doesn't always.  
Bascom king who measures electronics for a magazine once tested a ss amp from a DAC manufacturer that measured much lower in distortion than any other - but it didn't sound good.  
Paul McGowan was against using a tube input and in fact planned to offer a solid state input and and tube as well (ss on a tube socket) but once he heard the tube input he had to throw out his preconceptions and just build his new amp with tube input only.  

I prefer no preamp. MSB Analog DAC direct to Pass Labs amp. Previously i had Wadia 521 DAC direct to amp. I tried a few notable preamps which robbed the sound of pinpoint imaging and timbral purity.  The MSB volume control is better than the Wadia. With the Wadia the volume control needed to be above 67. I could adjust the output gain on the Wadia to match the amp in order to use volume control from 67 to 100.     The MSB has high resolution from very low volume. 
At the advice of my most experienced audiophile friend, I bypassed the preamp about a month ago, and I'm going directly into a power amp from my Benchmark DAC2.  It's sounding wonderful, and I don't know why I'd want to add anything else to the chain. I'm not even going to buy the preamp that goes with the amp, even though I can get a good price on it. 
@ alfa 100
Hi alfa, just letting others know that with the Wadia 521 you can change the gain setting ratio inside with switches or links, so then you can use it’s volume control above 65 with no "bit stripping". As "bit stripping" happens with any dacs digital domain volume control if their not used above 75% of full.
All sources with digital domain volume should have this feature, but sadly they don’t, that’s when a good passive pre is needed for the next possible best sound.

Quote from Wadia
We strongly recommend that you use your Wadia 521 Decoding Computer connected directly to your power amplifier. Even if you purchased your Wadia 521 Decoding Computer with the intention of connecting it to your preamplifier, we suggest that you try direct connection to your amplifier. Many listeners are surprised by the improvement in performance over even the most expensive preamplifiers.
Optimizing the Output Level Best performance is obtained when operating the Wadia Volume Control near the top of its range. If needed, the maximum output level of your Wadia 521 Decoding Computer can be adjusted to match the overall sensitivity of your system so that the critical listening will take place with the volume control operating in near the top of its range.
The maximum output level of the Wadia 521 Decoding Computer is adjustable by means of a set of internal switches. The Wadia 521 Decoding Computer is factory set to accommodate the most common range of system sensitivity. If you find that your typical volume level during critical listening is below 65 on the volume display, it will be advantageous to use a different setting. To change the output level, consult your dealer.

Wadia do know what their talking about, being the fathers of high end dacs and cdp's.
Cheers George