as the output impedance approaches zero ohms the DF gets bigger.
When the output impedance = zero ohms, then the DF is infinite. (this is another way of saying that DF is a useless number to quote).
When the output impedance goes beyond zero ohms, i.e becomes negative, then the DF method becomes nonsensical. "higher than infinity" is more like poking fun at a useless number (F said "irrelevant notion").
When the output impedance = zero ohms, then the DF is infinite. (this is another way of saying that DF is a useless number to quote).
When the output impedance goes beyond zero ohms, i.e becomes negative, then the DF method becomes nonsensical. "higher than infinity" is more like poking fun at a useless number (F said "irrelevant notion").
If we define DF as Re/Rgen (assuming static and ohmic resistances, Re being VC resistance), with negative Rgen DF would be negative, too. Of course we could factor in the Rgen so as to have (Re+Rgen)/0. 😱
DF (for voltage output amps) is useless once it's better than 10 or so. What is more important is whether it is load-invariant or not (because the latter is distortion).
For classifying electrical damping of bass drivers I find the only definition that makes sense is using the effective damping the driver feels from the termination. BL^2/(Re+Rgen) basically, in fact Re and especially Rgen can be complex-valued frequency dependant expressions.
The complex "Rgen" I use most often with active systems is some R+jwL, jwL kicking in above the resonance region and R ranging from about anywhere between -2/3*Re and 2*Re (but only to just below resonance, below there it goes to zero again to speed-up dynamic DC-offset recovery in case of negative Rgen). Point is to find the (large-excursion) sweet-spot of distortion depending on the driver's construction. Then reponse is EQed to whatever target.
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This might be of interest:
CARVERaudio.com CarverFest 08 pt.1 - YouTube
CARVERaudio.com CarverFest 08 pt.2 - YouTube
CARVERaudio.com CarverFest 08 pt.1 - YouTube
CARVERaudio.com CarverFest 08 pt.2 - YouTube
It may not be a global loop amplifier or the loop may have a low feedback factor and still have high damping, if one uses an EC network, like HEC for example, which uses a very high bandwidth feedback/feedforward system local to the output stage. HEC can have very high bandwidth and high damping at higher frequencies, even above the audio band. I think this helps if you intend to use the amplifier for a simple surround sound setup, where the rear speakers are connected in series at opposing phases and attached to the +out of the Rch to the +out of the Lch thus playing the difference between the R and L channels 180 degrees out. Without good damping the main speakers may effect the output node of the amp and thus the 'surround sound' signal. In my latest HEC amp, this method of creating a crystal clear sound stage works very well.😉
To generate so much hogwash on the fly is quite a feat.
You may well be right but that leaves me in a difficult situation: Who or what should I put my trust into?
On the one hand I've got a number of direct A/B comparisons friends and I have done like MC2 MC1250 (DF1000) v MC750 (DF400) and MC2 E45 v another E45 bridged etc and a guy who has designed commercially successful amps for 40 years and on the other some guy on an internet forum.
Let me think about that for a while…
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Q1. Is 1300/ch. RMS or some musical, PMPO, peak, e.t.c.?
Q2 Damping factor = 1000? looks like just a bloated figure to me.
Simple test to separate fly food from fact:
Go get that amp with a DF of 1000. ( they did not tell you what frequency now did they?) Hook up your speakers and listen. Add ONE FOOT of the same speaker wire you have and listen again. Come back and tell us what you heard. We can say all we want here, but there is no substitute for testing it yourself.
Go get that amp with a DF of 1000. ( they did not tell you what frequency now did they?) Hook up your speakers and listen. Add ONE FOOT of the same speaker wire you have and listen again. Come back and tell us what you heard. We can say all we want here, but there is no substitute for testing it yourself.
MC2 Audio state the DF at 1kHz.
The difference between the 1000 and the 400 as with the E45 with 400 and bridged with presumably 200 is quite subtle.
I doubt I could hear it if there would be an appreciable time (ie a few minutes) between switching.
Not enough for me to woory enough to buy an MC1250 as I don't need the power.
Except the subtly tighter bass they sound identical.
Bob Carvers 'Stereophile' challenge is quite telling though in various ways.
If you are not familiar with it he said he could make his $700 SS amp sound like any other high $ amp at the time.
Stereophiles J Gordon Holt and Atkinson took him up on it and came along with a $12000 Conrad Johnson tube amp.
Essentially Bob added a series resistor to his amps output and added the right types of distortion at the right amounts. After two days of fiddling the amps outputs nulled down to -70dB and after a days worth of listening neither Holt nor Atkinson could tell any difference in sound.
http://carvermk2.com/Docs/Carver Stereophile Challenge.pdf
The difference between the 1000 and the 400 as with the E45 with 400 and bridged with presumably 200 is quite subtle.
I doubt I could hear it if there would be an appreciable time (ie a few minutes) between switching.
Not enough for me to woory enough to buy an MC1250 as I don't need the power.
Except the subtly tighter bass they sound identical.
Bob Carvers 'Stereophile' challenge is quite telling though in various ways.
If you are not familiar with it he said he could make his $700 SS amp sound like any other high $ amp at the time.
Stereophiles J Gordon Holt and Atkinson took him up on it and came along with a $12000 Conrad Johnson tube amp.
Essentially Bob added a series resistor to his amps output and added the right types of distortion at the right amounts. After two days of fiddling the amps outputs nulled down to -70dB and after a days worth of listening neither Holt nor Atkinson could tell any difference in sound.
http://carvermk2.com/Docs/Carver Stereophile Challenge.pdf
It is interesting that in RF we want to match the transmitter (or receiver) impedance to that of the antenna so that you have a low Standing Wave Ratio or as little reflection and as much radiation as possible.
Interestingly a valve amplifier uses an impedance transformer to match the amplifier output with that of the speaker system.
Why is it that SS audio the theory is very different and virtually no physical law applies, only abstract, unexplained and the subjective applies. It is can be said to be a religion, you are a believer or you are a scientist.
Interestingly a valve amplifier uses an impedance transformer to match the amplifier output with that of the speaker system.
Why is it that SS audio the theory is very different and virtually no physical law applies, only abstract, unexplained and the subjective applies. It is can be said to be a religion, you are a believer or you are a scientist.
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Not quite, I think. It's only the case with amps that strive for maximum efficiency (eg guitar and RF amps). Triode amps, especially when with cathode feedback and/or some global feedback, are more like normal voltage output amps.
Actually what you write about RF is a bit too simple. Normally you match the antenna impedance to the cable impedance and have an output filter in the transmitter that transforms the impedance of the cable and antenna to whatever impedance allows the transmitter output stage to deliver maximum power. Under large-signal conditions that is not necessarily the same as the (complex conjugate of) the output stage impedance.
The same holds for a valve amplifier. The optimal load for a pentode output stage is only equal to the pentode internal resistance under small-signal conditions. Because you are normally interested in large-signal conditions, the transformed load impedance is usually chosen very different (much smaller actually) from the pentode internal resistance. In fact it is chosen close to the maximum voltage the pentode output stage can deliver without clipping divided by the maximum current it can deliver.
With feedback you can manipulate the output impedance as much as you like, but it doesn't change the kind of load impedance you need to get the maximum output power before clipping or breakdown.
I've also tried the opposite and added a ton of global negative feedback to a tube amp and afterward it sounded very similar to my SS amps. Damping factor is probably the largest factor in sound of an amp, but more is not always better.
????
the Damping Factor is simply a way of describing the output impedance of the amplifier. As seen in most of the posts above, the speaker "sound" does change with source impedance.
But, I will contest the idea that the amplifier sound changes when the output impedance changes.
Simply add a resistor to the output cable of the amplifier to demonstrate the effect on speaker sound. That added output resistor has in no way changed the amplifier sound !!!!
But an amp only makes sound through its interactions with a speaker unless you count transformer hum and DF does have an effect on those interactions.
Hi,
the example with RF amp and antenna can not be exact, we want that the antenna has a narrow resonance, then adapt the impedance on the resonant frequency, and we obtain the maximum transfer.
in the woofer, we want a flat response within a range with a small change in impedance (in theory).
At this point, what exactly is the difference played on an amplifier with DF 40 and one 1000?
the difference is on the dampening of the sounds.
it is wrong to see the difference, only in the direction of the impedance.
Amp with a DF 40, can not play the same as an amp with DF1000 (reduced to 40 by a resistor).
Not know a company that have DF4000 and reduce it to 400 by a resistor. change current output then change all on transient output (loses efficiency also) , then market is able to say, high DF value is better...as huge nfb. i'm curious know, better what? as psu..it's better unregulated.
Regards
the example with RF amp and antenna can not be exact, we want that the antenna has a narrow resonance, then adapt the impedance on the resonant frequency, and we obtain the maximum transfer.
in the woofer, we want a flat response within a range with a small change in impedance (in theory).
At this point, what exactly is the difference played on an amplifier with DF 40 and one 1000?
the difference is on the dampening of the sounds.
it is wrong to see the difference, only in the direction of the impedance.
Amp with a DF 40, can not play the same as an amp with DF1000 (reduced to 40 by a resistor).
Not know a company that have DF4000 and reduce it to 400 by a resistor. change current output then change all on transient output (loses efficiency also) , then market is able to say, high DF value is better...as huge nfb. i'm curious know, better what? as psu..it's better unregulated.
Regards
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