What makes different amps produce different sound?

As a basic concept, different technologies and designs and parts, lead to different sonic qualities. While they all reproduce the basic musical signal, they do so with different levels of accuracy, colorations, and transparency, and also that elusive "lifelike" or "musical" quality.

There are many generalizations that are applied to certain kinds of amplifiers, but they are only generalizations, and may or may not apply as much, or at all, to a particular product being auditioned.

There are some indications that an experienced person may expect from any given amplifier design, based upon some knowledge of design/performance characteristics, but it is always better to audition the product because some designers may have done a better job than others. Also, some amps may do better with certain speakers than other amps, and the overall system environment can play a part that is generally called "synergy".

Also, individual listening tastes and preferences will play a part. This is why there is really no overall consensus about any one amp being "the best". It really amounts to what you like "best" in your system context.

I'm sure that others will offer some information on the usual characteristics that we have come to expect from certain technologies and designs. I just wanted to start the conversation out in a general kind of way.

Just for the record, there is a school of thought (and a rather well-credentialed one) that holds that competent amps operating within normal limits do NOT sound different at all. To be more specific, they would argue that if two amps sound different, it will be for one of three reasons:
1) Their levels are not matched.
2) One or both has a frequency response that seriously diverges from flat (as might happen with amps with a high output impedance driving certain loads).
3) One or both is clipping.
Of course, lots of audiophiles reject this, as is their right.

Since every amp sounds different that's probably the reason people reject that idea. There are many people who think nothing sounds different and that there is no reason to buy anything but a Bose Acoustic Wave Machine.

The same equipment in a different room sounds different.

I bought a highly regarded pair of speakers once based on a review. I sold my other speaker to facilitate this change. When the speakers arrived I hooked them up, let them break-in and then sat down to listen. I almost cried since I was a struggling music lover on a very tight budget and these speakers sounded terrible at best. At a loss to know what else to do, I rewired them with some audioquest wire I had left over from some evil experiment I had conducted on an unsuspecting victim.

I hoped for an improvement, but what I got was much more. These speakers actually sounded good. I kept them for some time before moving up to something else.

The point of all this is to say that something as seemingly inoccuous as wire can make a huge difference. When two amps with similar design use different componants they will sound very different.

Consider too, the companies that modify CD players with new caps and resistors. People swear by these mods, or was it that they swear about the mods... I can't remember.

Hi Jeff,

One design in particular, negative feedback has a rather substantial effect on sound... way back, adding massive amounts of negative feedback was a popular way to woo a consumer by drastically reducing THD or Total Harmonic Distortion... In reality, anything below 1% THD is considered (by most) to be inaudible... negative feedback seems to greatly reduce the 3D soundstage abilities of an amp... other features such as high current can sound different based on the power consumption needs of a particular pair of speakers...