[JRace]

When purchasing amplifiers, what specs. do you look at, and/or affect your decsion?


There is so much BS/marketing with all audio equipment, are there any specs that are meaningful any more?

 

[phyre3]

Power bandwidth

RMS power output

dynamic headroom

Power supply specs like the amount of storage/channel and rating of the transformer

Distortion (not an issue really as most are so low it doesn't matter but it is nice to note how much distortion there is at a rated power)

Damping factor is important to some people.

Power output into lower impedences


That pretty much it for me

 

[kal]

Beleive it or not, one of the specs I put the most weight on (no pun intended ) is the WEIGHT of the unit itself!


(I prefer the straight, simple brute-force/class-A approach to amp design which usually means a lot of weight).


Kal

 

[Scott B]

The power output should double or close to it when the impedence is cut from 8 ohms to 4 ohms and from 4 ohms to 2 ohms, and the signal-to-noise ratio should be very high.

 

[ClarkeBar]

I agree with all the previous posters. My favorites are:


output with all channels driven 20hz-20Khz

output with lowered impedance

weight


Also favorite gripe is impedance switches which do nothing but lower output at lower impedance. A sign that amplification may be suspect and corners likely have been rounded in the design and manufacturing.


Despite past issues, H/K for one, delivers solid power in terms of amplifiers and their ratings. And I haven't come across any impedance switches on any I've seen or owned.

 

[John F. Palacio]

1- Power output


2- Reliability (This is not technically a "spec" but is very important to me.)


3- Efficiency (Primarily heat build up) My sound gear is on 24-7


4- Noise (Acoustical from fans or transformers)


5- Build Quality


6- Looks (If somebody judges by weight. Why not?)

 

[kal]

Quote:

Originally posted by Scott B The power output should double or close to it when the impedence is cut from 8 ohms to 4 ohms and from 4 ohms to 2 ohms...

This is a good one. Very few manufacturers actually achieve this because the price of doing this is usually extremely high. You'll see this on mega-buck amps from Krell, Mark Levinson, etc.


Kal

 

[Buzz Goddard]

In solid state designs, an high (honest) S/N ratio spec can tell you quite a bit about the attention to detail in the circuit design and parts spec.

 

[Mike Matheson]

The most important spec to me is *price*.


Regarding the point of amps doubling down--even in terms of high-end amps, some designs don't approach this (Theta Citadel, for instance). I believe this can be a function of the design approach rather than a rough measure of quality/capability.


That being said, when I was last amp shopping, the ability of the amp to double-down was one of the factors I kept in mind. . .

 

[GMan4911]

This whole amp doubling down business is nothing but marketing. All amps can double down if the manufacturer specs the amp conservatively. This is not the end-all be-all indicator of a good amp, it is an indicator of good marketing because it's got a lot of you guys believing it.

 

[merc]

I'm with Mike and Buzz. I first look for a high S/N Ratio within my budget.

 

[C Clark]

I also look at the S/N and the THD.

 

[Tom_Bombadil]

Have to take issue with GMan. Ratings at lower impedences can be improved if the manufacturer specs the amp "liberally," not "conservatively." That is, if they loosen the specs into 4 ohms, they can claim better power ratings. So it is wise to check on the spec at 4 ohms to see if it is still over a full bandwidth at low distortion.


Also, not "all" amps can do this, even with very loose specs. Most notably, a lot of the amp sections in HT receivers cannot.


Another "spec" to consider is the company's warranty & access to service. I also like the suggestions on S/N ratio, build quality, and the verified output with all channels driven. This last one is where a lot of companies make outlandish claims.


Tom B.

 

[Mike Matheson]

I used to have a Kinergetics Chiro C-300 amp. It was spec'ed as "Power output: @8 ohms - 140 watts x 3; @ 3.2 ohms - 280 watts x 3; all channel drive - 280 watts x 3; THD - 0.03%".


I always got a kick out of that. It doubles down, ahh, sort of. (3.2 ohms?)


Some sharp marketing guys. . .

 

[Blade007]

I guess the most important 'spec' of an amplifier is not really a spec at all. It's how it sounds with my speakers and components. That's about it. Power ratings in most systems were talking about here don't even matter. And if you can hear the difference between 1 percent THD and .005 THD, I'd love to have your ears!!!

 

[GMan4911]

Quote:

Ratings at lower impedences can be improved if the manufacturer specs the amp "liberally," not "conservatively."

Potato, Potatoe, it depends on how you look at the specs. For example, a manufacturer specs an amp at 120wpc @ 8 ohms and 200wpc @ 4 ohms. But, he figures he can sell more amps because he thinks people like to see amps that "double-down". So he puts in his marketing literature "100wpc @ 8 ohms, 200wpc @ 4 ohms". He is being "conservative" with its 8 ohm output. "All" amps can be marketed this way, even HT receivers, which is why "doubling-down" is meaningless.

 

[Tom Rosback]

Most important spec?

A retailer who will let me do an in-home trial for a few days.

 

[Tom_Bombadil]

That's true, I forgot about a manufacturer that would downrate their amp into 8 ohms. This can be done, but it is almost never done. The reason being that the cost per watt of their amp into the most common load, that being 8 ohms, is worsened by doing this. So someone has to feel very strongly that "doubling down" is worth more than having as many 8 ohm watts as their competitors in the same price range.


All of that said, I have seen this tactic employed on expensive, high-end amps, where the cost per watt is not regarded to be as important as "doubling down." Say where a 110wpc amp is selling for $8000, but is only rated at 200wpc into 4 ohms . They might downrate the 8 ohm rating to 100 to make the amp look like higher quality - which is the primary selling point for this type of amp.


Tom B.

 

[bigwally]

Quality of design and materials, power supply, number and type of output devices per module, tested output w/all channels driven, price. Not necessarily in that order.

 

[cpc]

Specs can verify what I hear. Specs alone do not tell the whole story but they usually are representative of sound quality in some respects.