Tube Preamps

I was wondering opinions on whether or not a tube preamp might fix or reduce my overly bright sounding system. I am currently sourced by a Rotel RCD_1520 with Rotel RB-1582 2x200 watt amp, Rotel RC-1580 preamp with B&W CM7 speakers. I know the speakers are a tad bright, but when I disconnect the Rotel amp/pre and reconnect my old NAD c317 integrated, it sound great. I like the warm sound and deep bass of the NAD. Isn't the amplifier just amplifying what it receives from the preamp? Is it possible for an amp to be bright?
Only trying a tube pre will tell. Time to visit a dealer and get a loaner. As you have done, only putting something in your chain will tell. Try to get two different loaner's, that way you can hear if it is 'tube' you are hearing as opposed to a just a single unit.
Yes, your speakers are a tad bright and it's very possible for an amp to sound bright too... and pretty likely if it's solid-state. Some sound brighter than others. Yes, flat response is the goal, but you probably wouldn't like it if you heard it anyway.

A tube preamp could help if mellow-sounding tubes are used, but the bass will be less deep and distinct. I'm sure the tone controls on the NAD amp help out... if it has a preamp output maybe you could try the preamp output into the Rotel amp's inputs. That way you could simply turn down the treble. Do you have a nice padded rug on the floor???

Good Luck
Yes, in general a tube preamp, or tubes somewhere in the chain will reduce brightness or glare. At least that has been my experience. Something else I do that tames my speakers is I cut some felt to place around the it sort of looks like a bagel with nothing touching the dome itself......I can't expalin why, but that helps eliminate some of the edge in my room....I don't have an extremely expensive set up, but it is comparable to yours. Good luck. The felt makes my system less aggresive without a significant side effect.
I don't mean to ask the obvious but if you like the sound of your NAD integrated why not stick with that or go foe NAD's separates?
Plato said, "Yes, flat response is the goal, but you probably wouldn't like it if you heard it anyway."

An audiophile paradox from the philosopher Plato.

So if the goal is a flat freq response, why then would it not be what we want.

Ya,stick with the NAD like Cmalak says..I second that.

I always thought the rotels had more grain and are bright..

A good tube integrated might be what you would like???

IMO,I think a lot of people cant name what there looking for in HIFI.

I think it's tone,the tone had to be right,not alot of hifi has good tone...

I have found tube amps to have superior tone by a mile.

With that said,the solid state amps that I found to have good tone are Accuphase,Forte 4,threshold,some early NAD's.
Arcams OK. I know there are more....

"Isn't the amplifier just amplifying what it receives from the preamp?"

Yes,and some amps do it much much better than others.

I now run Quicksilver's,
American made, hand made, tube amps,mono blocks

they have outstanding tone(natuaral tone),low level detail,depth,musical up the yinyang.
The cost me a measily $800 off eBay too.
So,super duper sounds dont have to cost a small fortune...

Keep posting question and learning!!

Good luck!
I have hardwoods with a huge area rug centered in the room. I have thought about NAD separates, and may go that route. I'm just trying to research all my options. I can't afford to replace everything right now so I've made the decision to keep the Rotel slot loading CD player and the speakers. I found someone who would like to purchase my Rotel preamp so hopefully that's gone this week. I heard a Bryston B100SST yesterday and I really thought it sounded excellent, although a tad pricey for me right now. It does carry a 20 year warranty which blows my mind. I like the sound of NAD gear, but would really like to move up one notch. I thought the Bryston did a good job, and I'm wondering what else I should try to hear, even if it's tubes. I like that liquid sound, I don't mind colorization as opposed to up front and bright.
You might want to try angling your speakers inward so the tweeters cross slightly in front of you.
You can get a bigger improvement in sound by changing your speakers. B&W have a reputation for being bright.

Keep your NAD sell the B&Ws and Rotel pre and amp and get a better pair of speakers.
Tube DAC, another option. If your listening is CD, a tube DAC can help tame the SS to SS to SS. There are choices on the market. You might look at Scott Nixon.
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This abstruse hobby of audio cannot be logically explained. Much of "high-end" audio is based on psycho-acoustics. If the the soound is liked, stick with it. In the late '90's I opted for tubes in the form of a Melos Sha-Gold. It sounded great at the time. At present, I listen to Sennheiser HD-580's via an aged Adcom GCD-700 and Creek OBH-11. It also sounds great. It's all subjective.
DON'T CHANGE ANYTHING! Get a powerline conditioner first. If you do not currently have one, borrow one. It may solve the problem.
I really have to say cables and powerline conditioners are the audiophiles only tone controls anymore. The powerline conditioner would smooth out your top end. (it may do some stuff you don't want, but the right pwer conditioner will do pretty much want you want.)
I use somewhere in my system: Monster AV2000, Monster 7000SS, Adcom AC (I have THREE of these) A Rotel AC in a box, a 50' extension cord conditioner, various homemade AC cords, some aftermarket AC cords.. Various Ferrite clamps..
And plan on buying an AC regenerator soon.
I second Rwwear's suggestion of experimenting with various toe-in angles, and I suggest that you do that as thoroughly as possible, trying many angles. Here's my reasoning:

Bob made an excellent find with the S&V frequency response plots. Here is a direct link, which provides additional information:

As you'll see there, the plot reflects an average over a +/-30 degree listening angle, with double-weight given to 30 degrees (presumably corresponding to a typical listening angle with the speakers aimed straight ahead). The corresponding plot (the green line in the figure) is basically a roller-coaster in the upper mid-range, swinging nearly 10db peak-to-peak.

As Atmasphere (Ralph K.) has pointed out in other threads here, it is common for certain amplifier distortion products to create the subjective perception of brightness. My suspicion is that the reason for the different behavior with the two amplifiers is that with the Rotel the predominant distortion products happen to fall at the peaks of the roller-coaster with the music you tend to listen to, while with the NAD they are happening to fall into the trough.

But regardless of whether that theory is true, it seems to me that the roller-coaster frequency response curve, that occurs right in the problem area you are describing, is likely to be the root cause of the problem. And hopefully it can be improved by simply re-aiming the speakers. Many of the other suggestions that have been offered may subsequently help further, but without first addressing that frequency response roller-coaster they strike me as using a band-aid when a tourniquet is required.

-- Al
Wow!! Great responses from everyone and they are greatly appreciated. I will try the different toe ins first, being they are the easiest and least expesnsive. I will post my findings.
Try solid core copper speaker cable.Lighting cable can work very well in damping bright speakers and costs very little and outperforms most dedicated speaker cable.Many muti strand cables sound tinny by comparison.
I see you can buy that cable at Walmart. What did you terminate on the end?
Agree with Bob - upgrade your speakers and keep your Rotel electronics. There's many speakers that outperform B&W's CM range. I'd seriously take a look at Vanns and find a pair of the Energy RC-70 brand new for just over $1k. They originally retailed for $2k/pair and sound more natural and non-fatiguing than the CM7s and CM8s I've heard. Or if you want even better (but much pricier) performance, check out Dynaudio.
easy fix for that. add some .1 bypass caps to your pre amp main filter caps.
"I really have to say cables and powerline conditioners are the audiophiles only tone controls anymore."
If your using these as tone controls mabey you should reevaluate your equipment choices