gjphw@ihuxm.UUCP (11/01/83)
This is a request for opinions and suggestions about amplifier performance
required by CD players.
Recently, I read an article in the Chicago Tribune (notice how low I've sunk)
that treated CD players in a cursory fashion. Among other items, the article
mentioned that CD players require more or better performance from an amplifier
or amplifier section of a receiver than analog players.
My question concerns what does that mean. What is a suitable minimum power
for an amplifier (or amplifier section of a receiver) to adequately handle
CDs? Are there other parameters of the amplifier performance that are also
important when contemplating attaching a CD player (e.g., frequency response,
rise time/slew rate, etc.)
Suggestions and opinions can be expressed by mail, and I will summarize.
Or, this might serve as a general topic for discussion.
Thank you in advance.
--
Patrick Wyant
AT&T Bell Laboratories (Naperville, IL)
*!ihuxm!gjphwcbf@allegra.UUCP (11/01/83)
>From what I understand, one of the most important attributes that
enable an amplifier to do justice to a CD player is its "dynamic
headroom". The higher it is, the better the amplifier can reproduce
those loud transient passages that are generally not found on analog
records. Supposedly, the new line of Denon receivers and amplifiers
have some of the highest dynamic headroom in the industry. They are
also among the very few "lower-than-high-end" amplifiers that can drive
2-ohm speaker loads.
Any comments from the experts?
--C.B.Francois (decvax!allegra!cbf)wjm@whuxk.UUCP (MITCHELL) (11/03/83)
The key thing when choosing an amp for an audio system that includes a CD player is to remember that CD's have 90db of dynamic range (and less noise which may inspire some users to crank up the volume). This will tend to stress the PEAK requirements of the amp. One should place particular emphasis on the dynamic headroom requirements of the amp since this is the ratio of peak power to continuous power (which is what is listed in the spec sheets, per Federal Law). The new Denon amps have excellent dynamic headroom, as do Hafler's models. How much power do you need? This depends upon the size of the room, the efficiency of your speakers (Klipshorn owners could probably get away with 20 watts or so), and the type of CD's you listen to. Classical recordings especially showpieces like the 1812 or the Firebird, massed choral works like Mahlers 8th Symphony, or organ music, have more of the peaks that require the high power than do popular works (although the AVERAGE power required to listen to rock music at disco levels is certainly higher). In general, I'd recommend about 100 w/ch into 8 ohms with a 2 dB dynamic headroom for most classical CD listening with typical bookshelf speakers in your typical 12' x 20' living room. If your room is larger, your speakers less efficient, or you have a lot of overstuffed furniture - you'll need more power. On the other hand, in a smaller room or one that is acoustically "bright" 50 w/ch might be plenty. Bill Mitchell Bell Laboratories Whippany, NJ (whuxk!wjm) The usual disclaimer that the preceeding message is my personal opinion and not that of my employer applies.
jj@rabbit.UUCP (11/04/83)
To elaborate slightly on Bill Mitchell's article: Amplifiers that have a lower dynamic headroom rating, but a higher power rating, may be just as good, since (for example) take: Amp 1.. 50 watts Continuous Power. (RMS power, foo!) Headroom of 3 dB --> 100 Watts peak, for short periods Amp 2.. 100 Watts FTC continuous power Headroom of 0dB --> 100 Watts peak, for short periods. The only differences between these two power amplifiers (in circuit terms) are likely to be: 1) Larger filter capacitors(stiffer power supply) 2) Bigger heat sinks (and thus more thermal stability) Given the better power supply and the bigger heat sinks, I would always take the bigger amplifier, with the lower headroom rating <assuming that the respective peaks are the same>, given that other performance considerations are the same. The more heavily built amplifier is likely to have several durability advantages. I also tend to disagree somewhat with the idea that organ music has huge peaks (compared to its average power.) With a few exceptional organs, this is true, but with most (either classical, romantic(ecch), or baroque) organs, the dynamic range isn't that big. None the less, the accoustic power (and hence the maximum output power required, both of amp and speakers) is *T*R*E*M*E*N*D*O*U*S*. A lot of disc recordings of pipe organs deliberately filter out the lowest rank of pipes (32 foot, yes I know that there are a FEW 64 foot ranks, but...) and compress the remainder to make the record cutting easier. (It is quite difficult, because of the de-emphasis involved, to record VERY low bass, at high energy levels. Most "rock" doesn't come close, since the bass guitar gets to 44Hz(at best), and even 16 foot pipes (open ended, not stopped) reach 32 Hz. )This leads, in many cases, to really boring recordings. <That will not nuke the average speaker, incidentally.> Down with compression! -- o O from the pyrolagnic keyboard of ~ rabbit!jj -v-v- \^_^/
caf@cdi.UUCP (caf) (11/07/83)
If you don't think pipe organs have dynamic range, chuck out "the Digital Fox" series on DBX records. Warning: these records CAN nuke your speakers. In general, DBX records have a bass end that closely approximates CD. -- Chuck Forsberg WA7KGX CDI Portland OR (503)-646-1599 cdi!caf