info on amplifier damping factor

[dayveshome]

I am doing research for an amplifier that I hope to eventually build. What I have noticed is something called, "damping factor" in specs of some amps. Is there something somewhere that is written that explains: what it is, what is a good #, bad #, and especially, what in the amp determines damping factors, and how do design this into my amp. Any help would be greatly appreciated. Thanks!

[gromanswe]

Damping factor is something I never
understood either.
A welldesigned amplifier doesn't have to worry
about damp factor.
As most expressions is this a "market slogan"
mostly used to get you into A BUY!

This is the conclusion I, Groman, and Torseten Loesch
agreed upon, when discussing this
uninteresting subject at AudioAsylum,
before the people at AA,
got afraid of me
telling "that the meperor was naked"
and BANNED me PERMANANTLY.

regards
Groman doesn't need to be damped
neither should you need to be

[gromanswe]

Here you can reach Torsten Loesch.
And share the "know how" of a man who
knows about loudspeakers and amplifiers.

http://thunderstoneaudio.nav.to/

Groman selects his associates
someones are not selected

[sianturi]

Damping factor is a ratio between loudspeaker impedance and amplifier output impedance, ie:

DF = Z loudspeaker/ Z ampli-out

Ideally, DF should be as high as possible, so that Z ampli-out is as low as possible (an ideal voltage source). With a low Z ampli-out, your ampli becomes more independent of your Z loudspeaker (Z variation in loudspeaker has little effect on the voltage across you loudspeaker).

But some say that this is not so important. You could read Douglas Self or Randy Slone book about this jargon, and the explanation on why DF is not so important.

Typical tube amp has low DF, while solid state amp has high DF. Speaking which one is the best, depends on your loudspeaker. Lynn Olson said that Ariel works best with low DF amp, while Linkwitz said his Phoenix speaker works best with high DF amp.

Cheers,

[phase_accurate]

Hi dayveshome

Sianturi was a little quicker than me (so I had to erase some part I've already written) but I can generally agree to what he wrote.

An amplifier should ideally represent a voltage source* i.e. it's output voltage should be independant of the load connected to it. IMO one could live with a damping factor of 50 which can be reached easily by almost any carefully designed SS amplifier. I personally don't see any reason to have damping factors up to 10'000 because this is easily reduced by the resistance of speaker cable, contact resistance, crossover network etc. Some might argument that such an amplifier would achieve tighter control over the cone motion (i.e. damping) and would have much punchier bass . The damping argument can easily be destroyed by the fact that the voice-coil DC-resistance is the dominating part when it comes to cone-control (and this one is some orders of magnitude larger than the output impedance of an amp with a damping factor of 10000 !).
To achieve a low output impedance somebody has to use either a circuit that has an inherently low output impedance (e.g. class A) or use a large amount of feedback or any combination of both. When you have two amplifiers with the same damping factor (which is just a static measurement into a resistive load) usually the more generously dimensioned amplifier (i.e. class A, large PSU) will have the better bass control and a more consistent damping factor over it's operational frequency range.
Some tube amplifiers achieve only very low damping factors (often lower than 10) which can cause irregularities in the frequency response since the amplifier's output impedance and the speaker's impedance act as a frequency-dependant voltage divider. But tube fanatics (or me as well who only listens to tubes occasionally) can even live with that since it is perfectly possible to correct the speaker's impedance.

Regards

Charles


* P.S. this is of course different when the speakers are current-driven rather than voltage-driven, but thats another story

[jan.didden]

Originally posted by gromanswe
Damping factor is something I never
understood either.
A welldesigned amplifier doesn't have to worry
about damp factor.
As most expressions is this a "market slogan"
mostly used to get you into A BUY!

This is the conclusion I, Groman, and Torseten Loesch
agreed upon, when discussing this
uninteresting subject at AudioAsylum,
before the people at AA,
got afraid of me
telling "that the meperor was naked"
and BANNED me PERMANANTLY.

regards
Groman doesn't need to be damped
neither should you need to be

No offense meant, but you seem to have a strong opinion on something you don't understand, as you state yourself....

Cheers, Jan Didden

[sonnya]

Groman go read about damping factor!!!!

A loadspeaker with cabinet and anything around it can be showed as a model the same way as an amp.

In this model you will find the output impedance of the amplifier!! Which divided with the speaker impedance gives the damping factor...

Even if you like it or not you will be able to hear the difference on a amp with a high damping factor or low damping factor. Mostly you bass response gets weaker!! This is both Theory and reallife!!
Go try ad a series resistor to you speaker.. Lets say 1 Ohm.. Try it!!
I do not like the sound of a amp with a to low damping factor..

Regarding strong opinion on things you do not know of... In the AudioAsylum .. John Curl ...Should i say more?

Sonny

[gromanswe]

Cat Stevens, in song Can't Keep It In:
"Say what you mean, Mean what you think
and Think anything! Why Not?"

I think I have seen others here pointing out
that damping factor of different magnitude
are easily to live with.

There are a lot more important factors
both in Amplifier and Loodspeaker
that call for more attention.
That influence the result more.

A amplifier is just an adaptor
A device between an input and output.

When construction an amplifier you see
'whatinput is, and what is to be driven.
Then you make your adaptor.

If you can not reach a good solution,
then you must modify the source, input.
Or modify the device at output so you can
reach satisfying result.

Maybe put a preamplifier before drive amplifier.

Maybe see to that loudspeaker behavior
is good regarding resistance and impedance.

You cannot build an amplifier suiting all
devices there are.
An adaptor should be adjusted to the environment
it is supposed to serve.

Anything else have to be a compromiss
and a compromiss is only ideal
in a few cases.
In most cases not optimal.

Groman
who says what he means
and think his thoughts
although they cant suit everyone,
else they would have to be compromisses.

[sonnya]

Be Carefull with strong opinions and how you express them.... That is what i was trying to say to you...

1)There is all kinds of people in this forum from very yound people to very old people .. Not everyone likes the "here i am" attitude

2)If you have an opinion on a subject which have something to do with design... Then you opinion should be backed up by some good evidence.. A lot of people around here try to designs thing the right way by learning from other peoples knowledge.
I do not say that you have a big knowledge, but you have be carefull on expressing your opinion on things like damping factor... When you are not in the position to answer the question Like :

"Damping factor is something I never
understood either." - Then you should stop your opinion here!

"A welldesigned amplifier doesn't have to worry
about damp factor." - This is nonsense!

"As most expressions is this a "market slogan"
mostly used to get you into A BUY!" - I do not think that a engineer thinks that way when he wrote the spec.sheet.

;O) But if i am to hard on you? tell me!

Sonny

[gromanswe]

Sonnya!

some people are
Negativism radiators"

That is not something most people can
be happy about at this forum.

they look for fault in others
Never encurage others statements
with any appreciation.

Just out to make themselves appear
as the perfect way to be.

Can not accept other opinions then their own.
never trying to set themselves into the other man's
thinking.

There is an expression: "See me in my good eye"
That means try to see the good sides of a person,
instead of trying to look in his bad eye.
Surely I have one bad eye,
but the one with no faults may throw first stone...

Groman
avoids trowing stones