Should I eliminate my preamp?

I have been using my Audio Research tube preamp and Bryston amp to drive Magnepan speakers for years. Recently I added a Oppo blue ray player to my system and connected directly to my amp using the balance cables. The reason was to eliminate the signal having to go through another piece of equipment before it hits the amp. Am I wrong or what am I missing?
This is a very smart move, unless you need any of the facilities offered by the pre amp, such as a phono input , the option to switch between multiple inputs, or tone control. But for a basic system with just a disc player and perhaps (if your Oppo alllows) an optical input for e.g. a television and/or Chromecast Audio this is fine.
I do effectively the same in my home office system: computer as source, into an ODAC usb DAC, into an Emotiva Control Freak volume control, into a Quad 405- power amplifer. It works like a treat. Adding an extra link in the chain can only degenerate the signal.
Pre amplifiers were unavoidable in the old days, because various sources had pretty divergent output levels, and in particular the turntable, that needed RIAA equalization as well. These days the 2.0 volt cd redbook output standard for rca has been adopted by quite a few other sources like many DACs. As it so happens, that is also a common input sensitivity for many power amplifiers (double this for balanced).
Since you already have the components, listen with your own ears. For me, I prefer having my Oppo 105D going into a processor or preamp and then into the amp. That sounds better to my ears but possibly not for yours.
(((This is a very smart move)))
 I strongly disagree......
((( Adding an extra link in the chain can only degenerate the signal. ))))
If your listening to a preamp with 55 cents integrated circuits you may be right
At first, it may seem cleaner with elevator music yet try it on something with
dynamics. As Mcgal suggested try it yourself and listen.
 You may have also discovered you need new tubes or different brand type installed.
 What is model pre amp it?
 Best JohnnyR
I thought using the volume control on a digital device such as the OPs UDP would degrade sound from truncating bits at lower volume settings, hence the need for a pre-amp with (presumably) quality volume control in the analog domain.
The argument about dynamics is wrong. An electrical signal comes out of the Oppo and goes into the power amp. What would be pre amp do? Change the signal?
As for digital volume control. That argument was true years ago. These days DACs have enough bit depth to avoid this problem. There is a paper by ESS somewhere but I do not have the time now to look for it.

You've done it so do you prefer the sound direct vs your preamp?  Your preamp being some 38 years old may be in need of a refresh and certainly a retube as suggested above.
Using an Oppo directly connected to Bryston amplifier can have high fidelity.  However, this combination could also sound a little sterile in a way.  Bryston amplifiers are usually very exacting and dynamic, but sometimes lack "life" - this could come across as being somewhat flat or sterile or non-engaging.  It depends on what the listener wants.  A preamp is used to help shape the sound.  The AR SP6 preamp could definitely add some life and texture to the sound.  You probably want to replace the tubes if they have not been touched since the 80's.
Assuming you don’t create a major impedance mismatch, there’s no right answer.

The goal IMHO is your personal enjoyment. Your personal enjoyment may or may not align with any particular technical measure of performance. I mean, no one wants noise, or we think we don’t, but how low is low enough, and what are you trading off for lower noise?

There are some preamps like older Conrad Johnsons, which are pretty seductive liars. I doubt technically they measure very well, but I love to listen to them. In that case, removing the preamp from my chain is not what I want. Right now, I’m using a Mytek Brooklyn through a Parasound P7. The Brooklyn is more revealing and more relaxed sounding, but for technical issues I need the P7 in the mix. Kind of depends.

I will say I have had the chance to stream video from my Oppo (older BD player) and the Mytek, and the Mytek easily beats it for sound quality, but can't do 5.1 or 7.1


@audioconnection , +1.

However, since the OP has all the tools to do the test for himself, he is best to answer his own question.

He can simply listen to his system with, and without his ARC SP6 b and decide for himself.

Trust your ears.
Thanks for all the comments.  As for the preamp, I have owned for 20 years. I purchased from a friend who was an authorized AR technician. He replaced tubes at the time I bought it. I am certain it couldn't hurt to have it tested, however I am trying to sell the SP6.
@audioconnection +2.  You need to think about the quality of the electronics involved, as well as issues like impedance matching. Use your ears, but it's extremely likely you'll prefer avec pre-amp.
You need to listen to it both ways. I have a DIY model that has bit perfect volume built in. Meaning I should be able to use the volume on my laptop and the dac continues to produce bit perfect sound to my amp. I have driven my amp with this dac as well as 2 others, but when I run the dac through my Coda preamp, Everything improves. For me the Preamp Stays
Post removed 
Ralph Karsten (Atma-Sphere) has in a few threads here lately discussed the issue of the benefits of an active pre-amp in certain system set-ups vs. the penalties. If you can find them in the Audiogon Forum, you will learn all there is to know on the subject. Ralph really covers all the trade-offs involved between the two approaches, providing all the facts necessary to help one decide which approach is better for a given system. 
In this particular case, its a bit of apples and oranges.

The ARC is single-ended, but the Oppo has balanced capability as does the amp.

The simple fact is that balanced often sounds better because of improved cable immunity, and that the amp might sound better driven by a balanced source.

The ARC OTOH is getting a bit long in the tooth- and is certainly old enough to have filter caps failing as well as tubes.

In this case, I'd be all about dumping the preamp until its serviced out, but that is not to say that an active balanced preamp would not be able to help. Right now there are a few too many variables to be scientific about it.
This is exactly what I recently did. I bought an Oppo Sonica DAC and asked myself "what do I need a preamp for?" Like you, I have an ARC pre-amp (SP-6B) but since I no longer listing to vinyl, I was just using it as a volume control. The Sonica DAC has a perfectly good digital volume control which sounds fine to me. Plus, the Sonica DAC has balanced XLR outputs, and my Rane AC22B crossover has balanced inputs. I noticed a marked improvement in quiet when getting rid of the SP6B and it's single-ended interconnects, and moving the the DAC/Crossover/balanced XLR setup. How could an extra piece of gear in the signal path improve anything?

My SP-6B recently came back from service at ARC, and I'm am wondering if I should sell it. There are a lot of new vinyl fans out there who might want it (along with my SOTA Sapphire turntable, Linn ITOK II tonearm, and the Dynavector Karat 23R cartridge).
No doubt, you have to listen to your system with and without and decide which sounds better...and in my own system, no doubt at all, much better with the preamp than Oppo direct to the power the mean time, just for fun, check out this video...
However, since the OP has all the tools to do the test for himself, he is best to answer his own question.
I have always found that if you have enough gain for the loudness level you want or need, then going direct (with no preamp) has always been the most transparent, dynamic, least coloured way of listening to the source.
So long as the source is not a tube output, which can be high impedance, then you may get a impedance mismatch to your amp.

Nelson Pass made a preamp he loved called the Aleph L, which is passive until the volume control get’s to 3 o’clock, after which an active stage come in if you need more level, but as he says at a detriment.

Nelson Pass: " At the 3 o’clock volume control position, the Aleph L offers a direct path from input to output.
The only component in the signal path is wire and switch contacts.
At positions below 3 o’clock, the volume control functions as a precision passive attenuator using discrete resistor ladders.
Above 3 o’clock, active gain is added to the output signal in 2 decibel increments, for amaximum of 10 dB.
As a result, you suffer the effects of active circuitry only when additional gain is necessary."

Also a Nelson Pass quote:
" 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."

Cheers George

I’m confused. As you have listened to the system both ways surely you are best placed to know the answer?   It's like asking "I have a Californian and a French red wine, both of which I have tasted before.  Which tastes better?"
I just travelled this road.  The direct from DAC was clean, extended, with great dynamics from lower mids down.  Things like Neil Young at the Cellar Door sounded live, and bombastic things like Emerson Lake and Palmer sounded bombastic.  No listening fatigue.

Then Karma stepped in.  A friend sent an email saying he was downsizing and selling his system.  Amid the pieces was his totally rebuilt Audio Research SP3.  I tried it and was amazed at the difference. Voices were illuminated and compelling. Joni shimmered.  Percussion sounded like wood and membranes instead of thuds. Performers I thought I knew sounded more three-dimensional and nuanced.  The difference in soundscape from album to album was surprising.  I was entranced by what I heard, whereas the direct link presentation was far less captivating.

But I lost "bombastic" and the lower frequencies were softened on the SP3, probably because there was insufficient room for larger caps in the rebuild, and that rebuild was done quite awhile ago.

I was so convinced that I searched for the right linestage.  I could find nothing but praise for ARC REF 3 linestage, so I'm spending a lot of money I didn't intend to.

My schooling and career was about logic, and logically the direct link should be best, and that added piece shouldn't be able to add something that wasn't there before, but this is about experience and emotions, and logic only takes you so far.

I have had the same experiences as electro slacker.  There are times when a certain preamp will add a magic to the sound that isn’t there with the DAC/source.  Just like I mentioned above, a preamp is a tool that can be used to help shape/tune the sound.
My dac digital  section is no slouch, but the last McIntosh  preamplifier brought magic to my system. Wihout it the sound was thinner, narrower..
This discussion reminds me of the time Bob Carver made his non-audiophile solid-state amplifier sound exactly like a Stereophile Class A Conrad Johnson tube amp by adding distortion. 
After several demo sessions,I found, ARC and Bryston to mate perfectly.
Consider moving up to a newer ARC pre-amp and you will be musically rewarded.
Happy Listening!
This appears to be a perennial question and is asked on a regular basis. Lots of threads with great discussions but no conclusive answer. It boils down to taste. For me, For the types of music I listen, I love the "color/distortion" that a tube preamplifier adds to the texture of the music and my brain translates that into musicality, life, and can paint a more realistic soundstage in my head. I could care less if it is not completely accurate but on the other hand this color sounds more like live music to me.  
No way. We all consider this at some point. A great preamp always preferable in my opinion. Give each a weeks listen then decide. 
A high quality (and usually higher priced) pre will only enhance the listening experience. Most people who say no preamp speak on theory or have just never used a good enough pre to hear the difference themselves.
The theory is correct. Any preamp will add frequency response anomalies and distortion. You may prefer that sound to the unmodified signal, but it is good to be honest (as most of the posters in this thread have been) about what is actually going on. Sometimes I enjoy the listening to different DSP settings in my Yamaha A/V receiver  :-)
Any preamp will add frequency response anomalies and distortion
Quite so. But with the best preamps, those levels are far below the threshold of audibility.

Any DAC or digital front end I've ever used as volume control simply,and I've owned some expensive ones,doesn't have the rich fullness of a top tier tube pre amp.
Although I've been rationally inclined towards simplifying a system as much as possible for the "purest" sound, personal experience has shown me that inserting a GOOD preamp between a source (w/volume control) and the amp often resulted in better sound. 
Since I listen to music instead of theory, measurements or specs, I keep the preamp in the system.

Any preamp will add frequency response anomalies and distortion. You may prefer that sound to the unmodified signal, but it is good to be honest (as most of the posters in this thread have been) about what is actually going on.
One of the most misunderstood tasks of any good preamp line section is to control the interconnect cable. This reduces coloration, which is often heard as an overall thinness and loss of bass impact.

Passive controls often have the issue of effectively raising the impedance of the source by putting a resistance in series with that source. This can often have the effect of acting as if a smaller coupling cap is used in that source, causing a loss of bass impact.

A buffer for the volume control (at the very least) is required; that buffer also has to control the interconnect cable, so in practice many preamps reduce the colorations described in several previous posts, with a much smaller coloration introduced by the line stage- a net improvement overall.
The OP was asking about getting rid of the preamp in the case when the DAC has a volume control. In that case, there is no downstream volume control, and no need to provide a low impedance buffer for the interconnect, as the amplifier will take care of that.
The OP was asking about getting rid of the preamp in the case when the DAC has a volume control. In that case, there is no downstream volume control, and no need to provide a low impedance buffer for the interconnect, as the amplifier will take care of that.
This is correct, and the source having a digital domain VC it will have a low impedance output, probably lower than many preamps especially tube ones, and it will drive any interconnect just as well if not better.
Besides, driving interconnects with a 10kohm passive is not an issue either, unless the interconnects are"low quality high capacitance" and are 3mt or more long. I can give you the maths if you want. 

Cheers George
"I can give you the maths if you want."

An offer that is hard to refuse, if not too complicated for my pay grade... 

I like 10kohm pots as passives, as the can be driven by just about any solid state source, just some high impedance tube sources have trouble, and being 10kohm as a voltage divider passive they have the lowest output impedance at worst (mid possition) around 2.5kohm.

With 2mt of poor quality interconnect with high capacitance at (100pf picofarad per ft) that 2mt is approx 650pf total

6.28 (2 pie) x 2500ohms (2.5k) x 650 (650pF) ee to the -12 1/x = gives a very respectable -3db point at 98khz! and this is the worst interconnect at 2mt at the worst mid volume setting.

So as you can see driving the capacitance of poor quality 2mt interconnects with a 10kohm passive at worst volume mid position of 2.5kohm Z is not an issue at all as we are at only -3db at a still very high 98khz!

With one meter of that same interconnect, it becomes -3db at 196khz!!

With one meter of better quality interconnect which has only 50pf per foot then the -3db is at 392khz!!!!   

Cheers George
"I can give you the maths if you want."

An offer that is hard to refuse, if not too complicated for my pay grade...
Here is some additional math:

With a 10K pot in series with the output coupling cap, a timing constant is introduced.

The formula for a timing constant is this:
1,000,000/Resistance x capacitance x 6.28 = F

Resistance is in ohms, capacitance in microfarads, F is frequency in Hertz and 6.28 is Pi x 2.

If you have a solid state source like a CD player, quite often it has a coupling cap at its output (probably an electrolytic capacitor). Depending on the designer's expectations, the cap is probably between 1uf and 10uf. But without knowing that, if we do know the amplifier's input impedance which has to be included, we have enough information to draw some conclusions.

If the amplifier input impedance is 10K (worst case scenario) we can see that the timing constant is raised an octave if the volume is all the way up. Depending on the design, this can introduce phase shift in the lower frequencies, which is perceived as reduced impact.

At volume control settings at less than full volume, a series resistance is introduced by the control. This effectively raises the output impedance of the source as far as the amplifier is concerned. To reduce the volume by 6 db, the control is at mid position, with 5K driving the output and 5K to ground. The series resistance thus introduced with such a low impedance load of 10K at the input of the amplifier can be audible as a reduction of dynamic punch at all frequencies.

Now the reason I mentioned the formula is that with different controls, the timing constants are different. Sometimes it works out well and sometimes it does not. But in all cases the interconnect cable is uncontrolled by such a high output impedance so its artifacts will be much more audible than if driven by a lower source impedance.

So audition is important- and its important to remember that while it might sound alright with a passive, it could well sound better (less colored for the reasons stated above) with an active. If you spent some money on the amps and speakers, it seems a shame to me to not get the most out of them.

This is an example of you get what you pay for. 
Yes, but the OP asked about using a DAC with volume control as a low impedance source to drive the interconnect to the amplifier. There is no passive attenuator in this scenario, and from an engineering standpoint no need for the preamp. The people arguing for retaining a preamp are arguing that they prefer the sound of the preamp. That may well be, but it is not more electrically accurate. The preamp is providing a subtle distortion that sounds pleasing to them. 
If you have a solid state source like a CD player, quite often it has a coupling cap at its output

What Ralph mentioned about coupling caps above is not relevant these days, as nearly all solid state sources have been direct-coupled for years, only tubed sources may have this problem as they have a caps on the output.
But below tubed preamps have this problem at the other end of the system with some of today's low input impedance amps.  

All is not good a match with 99% of tube preamps with  low input impedance amps these days, many Class-D's, some First Watt's, some Pass Lab's and many others.

The coupling cap that's needed on the output of 99% of tube preamps can be too small for these amps I mentioned, which can be as low as 10kohm input impedance. 

This is not a good match and will roll off the bass very early, to the point of owners saying this "tube pre has little or no bass".
To fix this one can change the cap for a much larger uF one which can be a fitting issue in itself or revert to a not so good sounding bi-polar electrolytic cap which will be small

Cheers George 
Willemj- how do you know what an album is supposed to sound like? Are you telling me by bypassing a preamp you are closer to the master? If you like vinyl these guys will tell you their master is more realistic. 
There are many reasons to go thru a preamp:
1) if your dac/cd player is solid state, you might want to go thru a tube preamp that front end solid state amps
2) you might want to upgrade to an external dac, add a tuner, turntable phono preamp, etc...

Bring home a couple of good preamps and compare them to your direct connect setup
You may think at first that you're hearing a more transparent signal but a preamp properly matches the impedance between stages and provides more muscle (better dynamics) in the long run if it's a fairly good pre which it sounds like you have. You will get more dynamics and you won't be as susceptible to roll-off of high frequencies. The pre-amp is more than just a handy switching device, it provides an easy load for whatever you plug into it and outputs a lower impedance which will make the amplifier happier than if you just plug in a source device.
The first truly high end piece of gear I bought was a pre-amp. I couldn’t believe that change it made in my system. Without changing my midfi CD player or power amp, I was hearing a 3 dimensional sound stage for the first time, and a less brittle, much warmer and rounder sound. It excited me so much I rushed to purchase a high end power amp. It added bass authority and an even rounder more musical sound, but the soundstage magic was still a product of the preamp. I’ve been a preamp believer ever since, and would not consider using only a DAC with a volume control. That’s my limited experience. 
I most certanly prefer my Audio Research LS27 to no preamplifier by far.  In fact if I play my 35 year old or so Stax headphone system thru the record out of mt LS27 instead of the audio source directly in the audio reproduction is extremely better thru the tube LS27.  It is not just a minor improvement in sound quality.  Whatever audio source is used, say even my OPPO 205 as well as 105, the addition of a fairly recent Audio Research tube preamp will be the best choice.  By doing so a quality close to40 year old Stax headphone system can actually compete favorably to some of the recent expensive planer magnetic headphones of today.  For a fraction of the cost.  That is what a true quality tube preampkifier can do for an audio system.  It is simply someting one has to try out for themself.  Recently Paul McGowan of PS Audio said the same on his own current top audio systems.
As a long time (>20 year) user of and believer in passive line stages / removing active line stages, the answer is a big "it depends."   I.e., it depends on the output impedance of your source, the overall quality of the output stage (including both volume control mechanism and current delivery) of your source, the capacitance of your interconnects, the input impedance and sensitivity of your amplifier, and (of lesser importance) the sensitivity of your speakers.  Beyond that, I don't see enough information about your components and system to give a more definite recommendation.  I own an older Oppo (BDP-83se), but don't believe it has output volume control; however, my general impression is that I don't think the output stage is of the quality that I would necessarily prefer a direct drive sound.  By contrast, some of the aftermarket Oppos that significantly upgrade the output stage are suitable candidates for direct drive to the amplifier.