I'm not sure I understand everything a Pre-amp does... (1 Viewer)

[Dave Lyons]

I've always used receivers, and I recently took my first step towards separates by adding a Parasound 2003 amp to amplify my front sound stage (Paradigm Studio 100s and a CC450). My Denon 3200 is the "pre-amp" and amplified the surround channels.
Eventually I'd like to get another 3 channel amp for 3 rear speakers and get rid of the Denon receiver altogether. At that time I'll be in the market for a pre/pro. I was under the impression that this simply allowed me to switch between audio input sources, did video switching, and possibly had on board decoding for Dolby Digital, DTS, etc. Is this correct or does it serve another function? Other than the quality of the decoding chips for digital sound formats, is there any reason that one pre-amp should "sound better" than another?
If I wanted to spend $1500 or less and get a preamp that could decode Dolby Digital (+EX), and DTS (+ES discreet), and also had Pro-Logic II, and DTS NEO 6 and THX EX, what brands/models would I want to look at?
Thanks!!

 

[Brandon Blair]

You are pretty much right on what a Pre-amp does. However there can be quite a big difference in sound in varying pre-amps. In your price range I would highly recommend that you look at Audio Refinement. They have some great electronics at a very reasonable price. Their price is in the same range as Rotel, but they have received much better reviews in Stereophile and other similar magazines. I have heard both and prefer the Audio Refinement, however Rotel is very good as well.

 

[RAF]

Technically, you are really describing a "pre/pro" which is an abbriviation for "pre-amplifier/processor" but other than that you are right on the mark. Also, technically, a pre/pro would not be an example of true "separates" in the classical case (like in the old days) especially since some pre/pros also include tuners.

When I was starting out with separates back in the 1950's you had a pre-amplifier, a tuner and an amplifier, all in "separate" cases. Digital processing was something that wasn't even in the mix (no pun intended) at that point. Any processing that was done usually involved something like an equalizer or, a bit later, something to remove the "clicks" from records. (Anyone remember the SAE 5000 "click/pop" remover?)

Nowadays, the "separation" inferred in "separates" usually refers to separating the amplification stages from the pre-amplifying and processing stages.

The price of modern digital pre/pros is falling as new models are introduced with some very good performance for relatively little money. The Outlaw 950 ($899) is another example of something that you should consider on your short list of under $1500 units. I have one and find it to be a remarkable performer.

 

[Chip E]

RAF,

Does your Outlaw 950 hiss like others who heard it or own it describe? Just curious..

 

[Dave Lyons]

Thanks, so it sounds like I am on the right track. I'm still not sure why one might sound better than another. The Outlaw 950 and Rotel 1066 have been talked about a lot here lately, and are relatively afforable -- yet I also see pre/pros out there for $10,000+ Whats the $8000 difference?
Also is there much benefit to taking the "separates" philosophy a step further and separating the pre-amplifier and processor? I didn't think much about that until RAF mentioned it ...

 

[Tony Lai]

If you look at the 'boutique' models under a magnifying glass, you can see where the engineering goes. You might also ask the same for Ferrari automobiles.

A device from Meridian or TAG or Krell has differences from a 'basic' Outlaw 950 of which their respective websites will go into excruciating detail.

You can go one step further and get a stereo preamp like a Krell KRC3 or even a valve unit and switch it out with a 'cheap' processor like a Outlaw. That is a uniquely valid solution for the truly dedicated audiophile.

T.

 

[RichardMA]

All receivers and preamps sound different than one
another. Sometimes, the difference is subtle. Spending
the thousands a premium preamp generally gains you (from
what I've heard) detail in the mids and clarity in
the highs over lesser amps. That's just my opinion from
having owned/used a bunch of different preamps over the
years. What you have to determine is not which preamp
is the "Best" but which one provides you with the sound
function and ergonomics you will like at the lowest price.
Unless your funds are unlimited. There is a floor level
I won't go below when it comes to sound. It's hard to
price it, since there is so much variation in sound
quality from various products. If I were to try to price it, I would say I would not settle for a receiver under
$1000 or so, new. Below that, you start (strictly IMO)
to hear problems with the mids and upper frequencies and
meagre amp power does not deliver bass with the authority
I prefer. But changing speakers sometimes has an even
greater effect on sound. Just more to think about.

 

[Yee-Ming]

this is going to sound like a really dumb question, but do pre-amps actually do any amplification, e.g. the way phono requires a boost to line level before inputting it into a pre-amp or receiver that isn't equipped to deal with phono level inputs?

or put another way, if pre-amps only process digital signals (where necessary) or allow switching of sources, then if I only want to use a CD player, could I theoretically connect the CD player directly to a power amp?

 

[Larry B]

Yee-Ming:

do pre-amps actually do any amplification, e.g. the way phono requires a boost to line level before inputting it into a pre-amp or receiver that isn't equipped to deal with phono level inputs? Or put another way, if pre-amps only process digital signals (where necessary) or allow switching of sources, then if I only want to use a CD player, could I theoretically connect the CD player directly to a power amp?

Yes, preamps do amplify. This is because the signal from a CD player (for example) is too "weak" for an amplifier to deal with, so it must be "preamplified" before the amplifier can further amplify it. For this reason, a CD player cannot, in most cases, feed directly into an ampifier. However, there are a few CD players (for example, some from Wadia) that are designed to work without a preamplifier.

The signal from a phono cartridge is even weaker than that from a CD player, so it needs an extra "boost" which is provided a phono-stage preamp, which then feeds into the "conventional" preamp (the correct name of which is "line stage" preamp).

BTW, when you speak of the processing of digital signals by a preamplifier, you are actually referring (as someone mentioned above) to a preamp-processor. A traditional preamplifier (i.e., a stereo preamplifier) cannot process digital signals, so all digital-to-analogue processing must take place prior to the preamp. This would occur either in the CD player, or in a separate digital processor (which would be fed by a transport). (A transport is essentially a CD player without a processor. Therefore, they can output only digital signals.)

I hope that (a) makes sense, and (b) helps.

Larry

P.S. That was not a stupid question at all, and please don't ever hesitate to ask questions.

 

[Andrew Pratt]

Actually if you plug your CD player directly into your amp you'll quickly find out that your volume is very loud. Really what your pre amp does is turn down the volume from the strenght it comes in at and sends that off to the amps. Now in most cases your pre amp will be lowering the signal strenght going to the amps but if you turn it up really loud you might get to the point where it has to boost the signal but thats usually going to be very loud (ie louder then if you plugged your CD player directly into the amp) Its this fact that allows you to use passive pre amps in place of pre/pro's since they only have the ability to turn down the volume ie no power = no signal boost. Many people will tell you quality passive pre's are where its at for the best sound possible

 

[Larry B]

Andrew:
I stand corrected.
Larry
Edit: Why then are all preamps not passive? Is it because of the impedance matching?
Edit No. 2: It appears that one can get away without amplification only if one has very efficient speakers. See
http://www.uhfmag.com/Issue54/Passive54.html

 

[Andrew Pratt]

Larry doing passive right isn't cheap either esp if you want remote volume control and since most pre's are also processors they have a power supply to tap into anyway. At least that's my take on it.

 

[John Royster]

As an aside I ran my Adcom GCD700 cdplayer directly into an amplfier and didn't have a pre-amp for 7 years. The CD player had a pair of variable outputs controlled by the remote.

Maybe I got lucky, I thought sometimes you can run into input impedance problems this way?

 

[Philip Hamm]

Dave,

Another important function of a preamp is volume attenuation.

If I wanted to spend $1500 or less and get a preamp that could decode Dolby Digital (+EX), and DTS (+ES discreet), and also had Pro-Logic II, and DTS NEO 6 and THX EX, what brands/models would I want to look at?

If you're not in a hurry I'd recommend waiting to see what Sherwood has to offer in the fall. They're coming out with a new pre/pro and with the comments I've read about bassmanagement on their new top of the line receiver I think that the bm on the new pre/pro should be perfect.

 

[Mike Bledsoe]

Dear Dave
The closest thing I can think of is an Adcom for 1,200
that does everything except dd ex. There may be others also. The other function of a per-amp is to control the volume. Yes also the more expensive pieces cost more because of better parts (and covering their bottom lines)
Mike Bledsoe

 

[Dave Lyons]

Thanks everyone, this has been an informative thread -- I'm glad Yee-Ming added his question, it helped draw out some of the information I was seeking.
I'm not in a hurry to buy anything just yet, I still need three more channels of amplification first, so I may check out what Sherwood offers in the Fall ... thanks Philip.

 

[RAF]

Does your Outlaw 950 hiss like others who heard it or own it describe? Just curious..

Chip,
If I turn the volume up to MAXIMUM and I press my ear against the speaker I hear a very slight hiss. The minute I move ONE INCH away from the speaker grille the hiss becomes inaudible.
In other words, this is a NON-ISSUE as far as I'm concerned. I have no hiss in practical terms.
(Note: I'm not trying to make light of a couple of people who are experiencing some hiss in their units. However, in some cases they might have faulty units or in other cases something else is causing the hiss, not the 950. For someone with a hiss, this is a serious matter, but it's just not a general problem with the majority of 950s that I've heard about.)
BTW, If I drop my 950 from a 50 story building several times it begins to behave sporadically so maybe I have a gravitational problem with my 950? (Just kidding!)

Take care.

 

[Yee-Ming]

Gentlemen:

many thanks for clearing all that up.

 

[Sankar]

BTW, If I drop my 950 from a 50 story building several times it begins to behave sporadically so maybe I have a gravitational problem with my 950? (Just kidding!)

Precisely!! I suspect that it may have to do with the rapid deceleration. By symmetry rapid acceleration should also cause a similar effect (unless it somehow cures the problems of rapid deceleration). The equivalence of acceleration and a strong gravitational field thus suggests that the repeated inclusions/removals of massive objects into/from the vicinity of a 950 could cause unpredictable effects. Which is exactly why one should be careful when you put/remove amps from the shelf next to the 950!

 

[Chris Tsutsui]

I plugged a portable CD player into my Rotel 2ch power amp to see what it sounded like.

What I got was completely horrid "multimedia" quality sound through my mains. The volume was adjustable since portable CD players have knobs so I wasn't hearing it full blast.

I tried different portable CD players to see if I could see a difference in them. Surprisingly when the player is amplified the differences between them arn't as subtle.

I guess it could be the 1 bit DAC that could be setting them back. Oh well, I'm not a huge fan of portable music anyways because i'm too embarrassed when I wear my bulky sennheiser headphones in public.