Please explain amplifier output impedance

One more thing. Sometimes i'm simply debating something based on the technical merits of the subject at hand. I do this from an educational standpoint, and to be honest, because i like to debate. There's nothing wrong with discussing opposing points of view, having some fun and possibly learning something along the way. : )

As i've said many times in the past, i only know what i do because others have taken the time to share their knowledge and try to educate me. I'm trying to do the same thing. Sometimes, my methods may not be the best or most "friendly", but then again, i've never claimed to be "PC" or a "teacher" by trade. I'm simply a big-mouth sharing my point of view, so take it for what it's worth : )

Having said that, my pointing out what "I" consider to be technical flaws in a product does not mean that one can't like / listen to / enjoy a product that i have attributed these specific "negative" connotations too. As i've said before, one should buy / use / listen to / enjoy what brings them closer to the music and their system goals. The owner of the system is the only one that has to be pleased with the end result, negating most any other comment that i or anyone else could ever make about a given product or installation.

As a case in point, i typically tend to like the sound of Cary tubed amps, even though i don't own any of them. I know that they are quite coloured and less than linear into most loudspeaker loads, primarily due to their high output impedances and some other factors. Like some of the products mentioned above, these items fall into the "specialty" products category and i treat them as such. They can require very careful attention to detail in terms of selection of mating components to say the least.

Having said that, the end result of installing one of these amps ( or something similar ) into a system can be a very luxurious and smooth sound with great spatial characteristics. While i know that i'm NOT listening to strictly what was on the record and am hearing quite a bit of "system artifacts", it doesn't make it any less enjoyable.

I just wanted to put things into perspective, as i know that some will be upset with my post above for various reasons. If it upsets you, blow it off and consider the source : ) Sean
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Well let's see how long this thread lasts. I'm betting on late Sunday afternoon and I have no dog in this fight.

10-15-06: Audiofeil
Well let's see how long this thread lasts. I'm betting on late Sunday afternoon and I have no dog in this fight.

If so, it'll be too bad. This thread has more useful discussion and debate than any in a long time, IMO.

Sean & Dave,

Thanks for talking this discussion even further.

There are quite different design philosophies behind the conflicting views on output impedance;

One philosophy is that the amplifier and cables should have a minimum affect on the speaker response - i.e. the speaker is designed for SS amps of many types and the speaker impedance variation with frequency is NOT intended to affect system frequency response. (provided the amp has enough power to drive the load this philosophy leads to consistent results => the flat speaker response will be maintained provided it is coupled with a low output impedance SS amp.)

The other philosophy is that amplifier and cables should be chosen in order to augment/adjust speaker response by behaving as a kind of "equalizer" or a tuned system; in this case, system response will vary as a function of speaker impedance. (amp ouput impedance - cable - speaker load act together as a filter/equalizer on the sound => this leads to a system which can be tuned to taste, according to the preferences of the user and the selected high output impedance amp)

It is the differing philosophy that leads to different views on amplifier output impedance. There are advantages to both. One is consistent and accurate; but you get what you get. The other approach offers greater flexibility for tweaking to taste.

This is why I qualified my earlier comments in this thread by saying they were generalizations for SS amps an not for tubes. Tubes seem to be desirable to those that like a certain flavor to the sound...a certain warmth or punch to the bass. (and there is nothing wrong with that. Doug Sax, one of the industry leading professional Mastering Engineers, uses tubes for mastering for this very reason. Indeed, most people seem to prefer an equalization curve with a boosted bass and a rolled off treble.

Apparently my point was missed about the subject of speaker damping. The point that I was making concerned the subject of optimum damping in response to a transient waveform. Music is made up mostly of transients whereby many frequencies are present at once and transient attacks are part of the normal program source. Stereophile frequency flatness measurements represent a different type of measurement and do not address the transient properties of the speaker-amplifier. I repeat, a low output amplifier impedance does not guarantee proper speaker damping. It often actually overdamps the speaker. The subject of overdamping, critical damping and underdamping is a well-studied topic in engineering. No one interested in this subject would ever assume that the most is the best without verifying with measurements. I have done this and I described the apparatus that I developed for these measurements in my previous post.

Oh by the way, Berning amplifiers have a nominal output impedance of less than two ohms, but the user can increase this in the ZH270 by setting the feedback switch to MED or LOW to best optimize system transient response and user preference.