[andyr]

The specified output impedance of my amp is 40 milliohms.  

I'm interested to know how this compares to other power amps ... is it "really low" or just "average"??  Can you post what your amp is (ask the mfr, as I did, if it's not in the spec-sheet)??

My understanding is that having a low output impedance amp is good for a current-hungry speaker (like a Maggie!).  

Regards,

Andy

[denverdoc]

Andy,

If I recall correctly, the damping factor is equal to the input impedance of the loudspeaker divided by the output impedance of the amp. For a nominal 8 ohm load

 df: 8/.04=200

which is a fine, but not heroic figure.  500 to 1000 would be benchmark, but overkill unless driving some ungodly low impedance loads. Really, with any decent ss amp, this is for the most part a non-issue. The loudspeaker cabling and internal wiring should also be accounted for, hence the recommendation that heavy gauge wire be used, esp for long runs. Has nothing to do with resistive heating.

Now the interesting thing I believe about all of this is that the q of the bass driver alignment is affected be all this--if the bass sounds too thin, it can be fattened up by adding to the source impedance, which is of course what tube amps do in the extreme. This increases the driver Qts. The calculation is basic arithmetic, but to see the effects on the system as a whole requires unibox or equivalent software.
John

[andyr]

Andy,

If I recall correctly, the damping factor is equal to the input impedance of the loudspeaker divided by the output impedance of the amp. For a nominal 8 ohm load

 df: 8/.04=200

which is a fine, but not heroic figure.  500 to 1000 would be benchmark, but overkill unless driving some ungodly low impedance loads. Really, with any decent ss amp, this is for the most part a non-issue. The loudspeaker cabling and internal wiring should also be accounted for, hence the recommendation that heavy gau ...

Hi, John,

I think you're being a bit too "techernical".  I'm not interested in "damping factor" or any other "factor" of anyone's amp except the specified output impedance.

You probably want to know why I want to know this ... it's because someone told me that an amp with a very low output impedance is good for current-hungry speakers (like Maggies).

My amp (with output impedance of 40 milliohms) sounds pretty damn good with my Maggies so I was wondering whether its 40 milliohms output impedance was "good and low" or just "average"??  

Regards,

Andy

[denverdoc]

Andy,

As I mentioned this is an average to good figure.
DF is just another way of experessing the same thing.
 10 miliohms would be stellar.

But there are considerably more important variables that determine how much current an amp can deliver.  For your Maggies, I would want an amp that is happy playing into 4 ohm loads (note some receivers and amps explicitly do not recommend playing into loads under 4 ohms or sometimes 6 ohms. These are to be avoided as you will stress the output transistors and things will likely go into thermal shutdown--besides even at moderate volumes such a product would likely not do full justice to the maggies.)

If I were you instead of worrying about a single specification that is almost irrelevant below a certain level of performance, say 100 milliohms, ask the question in broader terms in the 2 channel forum. Or if there is a Maggie forum on the net which I bet there is, go there and you will get much more complete advice.
Enjoy,
John

[andyr]

Andy,

As I mentioned this is an average to good figure.
DF is just another way of experessing the same thing.
 10 miliohms would be stellar.

But there are considerably more important variables that determine how much current an amp can deliver.  For your Maggies, I would want an amp that is happy playing into 4 ohm loads (note some receivers and amps explicitly do not recommend playing into loads under 4 ohms or sometimes 6 ohms. These are to be avoided as you will stress the ou ...

Thanks, John.

My amps are quite happy driving down to a 3 ohm load and, to my ears, sound great.  However, there has been talk on the Maggie Forum about how Maggie only really sounds her best when driven by a "high-current amp", and I understood low output impedance is one factor of a "high-current" amp.  So I was interested to know how my 40 milliohms stacked up.

Regards,

Andy

[doug s.]

Thanks, John.

My amps are quite happy driving down to a 3 ohm load and, to my ears, sound great.  However, there has been talk on the Maggie Forum about how Maggie only really sounds her best when driven by a "high-current amp", and I understood low output impedance is one factor of a "high-current" amp.  So I was interested to know how my 40 milliohms stacked up.

Regards,

Andy

if yure wanting to explore different amps, electrocompaniet amps are stable to below 0.5 ohms, & have some of the highest current output ratings per watts, of any amps made.  ie: the aw220's, 70wpc amps, have output current ratings >60a.  while i prefer tubes, i think the ec amps are about as good as it gets for s/s amplification.  

if yure interested strictly in damping factor, check out the crown k-series pro-audio amps, w/damping factor >3000 from 10hz-400hz.

qsc's best amps are rated at >500 damping factor, except for their one top model, which is rated at >2000 damping factor (below 1khz).

doug s.

[denverdoc]

Andy,

Exactly right: "one factor." Try to think of it this way: the output impedance is akin to the diameter of a garden hose. You could make a hose 6 inches in diameter but w/o enough water, aint gonna help you put out a fire or water the lawn any faster. The amount of water (current) is a function of basically two things: 1) the power supply composed of the big transformer--usually in the shape of a big doughnut--and capacitors (large upright cylinders that can be the size of a soda can but usually aren't). You can't help but notice these if you take the top off. These will determine the amount of energy stored in the system and how rapidly it can be replenished from the ac line.  The second thing are the output transistors--the switches of sorts that actually conduct the juice to the speaker.  You need to have lots of them to conduct a lot of juice or they will burn up trying.

At this point, if you are happy, stay that way, and know that your amp is good enough. If you are curious about what could be, well then take a trip to the high end shop of your choice and borrow a loaner for the weeekend or Sunday--whatever their policy permits. Try to pick something generally considered near state of the art, and give it a listen. You may come away with the knowledge that what you got is plenty good, or .............
Hope this wasn't too techy,
John

[andyr]

Andy,

... take a trip to the high end shop of your choice and borrow a loaner for the weeekend or Sunday--whatever their policy permits. ...

Hi, John,

Very good suggestion ... it had not occurred to me to do this!  Exactly ... that will decide the matter!

Regards,

Andy