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Damping factor

Although very high damping factors are not a bad thing, the contrary, it was a spec "discovered" and for a while really "played up".
For most purposes, a damping factor of 50 is adequate. 200 is very good, though. :yes:
 
crooner said:
Let's not confuse amplifier instability due to oscillation with actual clipping. I believe the first Phase Linears were unstable at all signal levels and many times well below clipping. Early quasi-complementary output circuitry and low beta cutoff power transistors were responsible for this. These shortcomings were solved by the late 1970s.

That said, the higher power you have available the less likelihood you will encounter hard clipping. Also, having the treble control boosted on your preamp will certainly mean death to your tweeters if you clip the amplifier. One good reason not to use tone controls at all. I don't...

As for Power Guard, there's no clipping whatsoever when using it, a reason why McIntosh refused for many years to reintroduce tube amplifiers...
Click to expand...
Interesting, never knew that. :no: As far as a bigger amp not clipping, go get teenager, and just watch! :D
 
wineslob said:
Interesting, never knew that. :no: As far as a bigger amp not clipping, go get teenager, and just watch! :D
Click to expand...

Certainly, if you hear an amplifier with 200 wpc or more clipping continuosly, several things will happen. You will probably have damaged your speakers by then, and your hearing will also be seriously compromised. That is, if you listen to it in a normal home environment. Sound reinforcement applications are a completely different matter. Teenagers should never be allowed to handle such equipment!
 
wineslob said:
As far as a bigger amp not clipping, go get teenager, and just watch! :D
Click to expand...

This is not what I said. Read back my posts. My only point here is extra headroom, which is an advantage of a larger amp.
 
Fisher's "Z-Matic" was a damping control circuit popular in the 1950s

Here's an ad transcription describing it, plus tidbits from a 1994 interview of Len Feldman shortly before his passing. Feldman worked for Fisher at the time.

FISHER

Z-MATIC

The unusual, the choice- both are a regular and traditional product of our
engineering laboratories. But never before have we offered a technological
advance so obviously needed, so long overdue, as the exclusive FISHER Z-
Matic. Regardless of the speaker system, be it modest 8” unit or a giant
assembly, the vast acoustic improvement contributed by FISHER Z-Matic is
instantly apparent and truly astonishing. For Z-Matic has at one stroke
eliminated the energy-wasting, distortion-producing mismatch that has
prevented the complete union of speaker and amplifier ever since the advent
of electronic sound reproduction.
Z-Matic is now standard equipment on all FISHER amplifiers.

What Z-Matic Does

- Multiplies the efficiency and effective audible range of any loudspeaker
system, regardless of size.
- The continuously variable Z-Matic control permits any setting, according to
personal taste or the requirements of the speaker system.
- Eliminates need for oversize speaker enclosures and automatically corrects
inherent deficiencies in speaker or speaker housing.
- Z-Matic must not be confused with tone, equalization or loudness balance
controls.

A Word to Our Patrons

Your fisher 50-A or 70-A amplifier can be readily equipped with Z-Matic. A
complete kit of parts and easy-to-follow instructions are available at a cost
of only $ 2.50 to cover handling. Give serial number and model. “

******************************

Now read this excerpt from an interview made to the late Len Feldman
(engineer at Fisher back in the fifties) shortly before his death:

*******************************

“...There was some gimmickry, I have to admit. In about 1954, George Maerkle
came up with an amplifier circuit we dubbed Z-Matic. A little knob changed
voltage feedback to current feedback. In retrospect, it was a dumb thing to
do, because it loused up the damping factor.

“...It changed the nature of the sound. You could here a difference when you
went from one extreme to the other – in continuously varying degrees.
[laughs].

“...An he [Avery Fisher] sold slews of these amplifiers. Z-matic stayed on
the line for several years. In fact, it was an improper treatment for an
amplifier, totally improper. You wouldn’t do this today.”

Taken from “The Audio Interview with Len Feldman” by David Lander, Audio
magazine, April 1994.
 
Krell 400cx damping factor?

Does anybody know (or can find out, because I can't find it!) what the damping factor is for a Krell FPB 400cx amplifier?
 
Kegger said:
Actually I've got some pretty cheap tube amps that sound better then most solid state to.
And they do sound different then solid state even when not clipping.
Click to expand...

I didn't say tube amps did not sound different. I said I did not think they sounded better than solid state.

very high damping factor is almost always an indication that gobs of negative feedback are used in the amplifier. Not good

Negative feedback controls gain and reduces distortion. Nothing wrong with negative feedback. I don't know where that idea (that negative feedback is bad) came from, or the basis for it. Most amps have negative feedback, even many that claim they don't.
 
Negative feedback can be beneficial, but anything in excess is bad. That was my point.

Unfortunately, some designs relied exclusively on negative feedback to correct problems and instability. There's more to amplifier design than that...
 
crooner said:
Negative feedback can be beneficial, but anything in excess is bad.
Click to expand...

That's definatly true!

I wonder sometimes if the kenwood m2,m2a may have an issue with that.
It's DF is rated 1000 at 50hz, don't know what the real world spec of all
frequencies would be but 1000 at 50hz seems awfully high!
 
It's time to go beyond categorisation.

Tubes(not tube amps but tubes themselves)are reported to have a built in neg feedback.
The open-loop perfomance of a circuit design is the most important factor.What's done after with neg feedback is less important than what happened before neg feedback was applied.
Amplifiers are extremely interesting,and I'm certain that we are still in the dark ages(not referring to digital amps)with regard to amp design.It hasn't been 100 years yet,a lot more to be learned. :yes:
 
Kegger said:
That's definatly true!

I wonder sometimes if the kenwood m2,m2a may have an issue with that.
It's DF is rated 1000 at 50hz, don't know what the real world spec of all
frequencies would be but 1000 at 50hz seems awfully high!
Click to expand...

At another forum we discussed high DF and most of the people there agreed that these high DF amps tend to sound too restrained or lifeless.
 
The SX-1980 has a damping factor of 40. The power amp section was designed to reduce TIM by employing reasonable amounts of negative feedback. I believe this DF is in the ballpark for satisfactory performance.
 
More generalisation.

I can guarantee that in my system the high damping factor of the Kenwood M2 sounds anything but lifeless and stifled.
I haven't another spare amp of equal power output to substitute for the M2 as my Bass amp,however the stunning quality of discrimination of tonal colour,variety,nuance,the ability to convey artistic technique,intent etc leave me in no doubt that the high damping factor of the M2 in no way disqualifies it musically. :thmbsp:
All this in a pair of speakers whose drivers were designed before transistors became a market force. :yes:
The sins laid at the feet of damping factor probably come down to choices made by the designers(ie the taste of the designers reflected in the final product).
 
The Kenwood uses a totally different approach with the sigma drive system. I am sure it sounds fantastic!

theophile said:
I can guarantee that in my system the high damping factor of the Kenwood M2 sounds anything but lifeless and stifled.
I haven't another spare amp of equal power output to substitute for the M2 as my Bass amp,however the stunning quality of discrimination of tonal colour,variety,nuance,the ability to convey artistic technique,intent etc leave me in no doubt that the high damping factor of the M2 in no way disqualifies it musically. :thmbsp:
All this in a pair of speakers whose drivers were designed before transistors became a market force. :yes:
The sins laid at the feet of damping factor probably come down to choices made by the designers(ie the taste of the designers reflected in the final product).
Click to expand...
 
Crooner,
The technicalities of Sigma Drive escape me,I just understand that it extends the reach of the neg feedback loop to the speaker terminals.
I also have the non Sigma M2A which is nice,but the M2 has the subtlety.
Kenwood used a technique with both amps which coupled two different amps together.A great sounding small signal amp with a bigger one for OOMPH.They called this"DLD"Dynamic Linear Drive.
Gawd the Japanese liked to invent really stoopid sounding names.
Someone said that the voltage rails for the power supply have two different voltages(of course this might be for the meter voltages).
 
With Sigma Drive you are sort of biwiring with the extra set of wires working as a feedback loop to the amplifier. The circuit would self correct with the actual speaker load connected to it. Quite advanced for its time.


theophile said:
Crooner,
The technicalities of Sigma Drive escape me,I just understand that it extends the reach of the neg feedback loop to the speaker terminals.
I also have the non Sigma M2A which is nice,but the M2 has the subtlety.
Kenwood used a technique with both amps which coupled two different amps together.A great sounding small signal amp with a bigger one for OOMPH.They called this"DLD"Dynamic Linear Drive.
Gawd the Japanese liked to invent really stoopid sounding names.
Someone said that the voltage rails for the power supply have two different voltages(of course this might be for the meter voltages).
Click to expand...
 
Last edited:
Theo just so didn't think I was knocking the Kenwood amps I actually feel pretty
strongly about how good they are but was wondering about that DF being so high
if it might have some possable hinderence.

Lately mine only do bass or sub duty (As I went the way of tubes) but when I did use
mine for stereo playback with large ported speakers it was tough to outdo the Kenny's!

I realy like the sound of sealed bass speakers and tubes so luckely for me there a good
match on paper and in the real world. (But the Kenny's aint goin nowhere)
 
Kegger said:
Theo just so didn't think I was knocking the Kenwood amps I actually feel pretty
strongly about how good they are but was wondering about that DF being so high
if it might have some possable hinderence.
Lately mine only do bass or sub duty (As I went the way of tubes) but when I did use
mine for stereo playback with large ported speakers it was tough to outdo the Kenny's!

I realy like the sound of sealed bass speakers and tubes so luckely for me there a good
match on paper and in the real world. (But the Kenny's aint goin nowhere)
Click to expand...

On the above mentioned forum (apogee owners) with Ap's the high DF will show up as a sterile quality (lack of "warmth").
 
Never any offence taken.

Kegger,

Relax totally,I understand perfectly that some low damping factors match perfectly with certain speakers and I'm no advocate per se of high damping factors.
My thrust has been that notions of negative effects being laid at the door of either neg feedback(high or low) or high damping factors overlooks the fact that when someone or a team designs an amp inevitably the final result reflects the goals,biases,taste,preconcieved judgements,budget and a million other things which influence how the final result turns out.
Mostly it's not what's done in an amp,rather it's how it's done.
 
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