Nelson Pass said:
With all the irregularities that an amplifier must overcome, I had the thought that an amplifier might perform better with an even load impedance--one less obstacle.
Thanks for your thoughts, Nelson.
BTW, If you happen to catch this, would you care to comment on the difference between choke loading a power amplifier vs. a pre-amplifier? It seems that a pre-amplifier requires a choke with greater inductance.
say that you choose resistor as load for your tiny jfet stage
say that that resistor is ........ 5K
say that you're nutz and wanna use choke instead
say that choke have decreasing impedance with frequency
say that you wanna decent bass
say that you choose 20Hz as corner for your decent bass
say that you think that is nice to have choke -acting as 5K resistor, even on 20Hz
say that you gonna abuse and molest google, chasing....what else than choke -having 5K impedance at 20 Hz
say that internet is full with places where you can find nice xls for calculating how much H you need for 5K at 20 Hz , even if ya don't know that simple it is : L= Z/(2 x Pi x F) ........so - 5K/(2Pix20)=39H
say that I didn't wrote anything ......... and that you conclude it by your self
say that that resistor is ........ 5K
say that you're nutz and wanna use choke instead
say that choke have decreasing impedance with frequency
say that you wanna decent bass
say that you choose 20Hz as corner for your decent bass
say that you think that is nice to have choke -acting as 5K resistor, even on 20Hz
say that you gonna abuse and molest google, chasing....what else than choke -having 5K impedance at 20 Hz
say that internet is full with places where you can find nice xls for calculating how much H you need for 5K at 20 Hz , even if ya don't know that simple it is : L= Z/(2 x Pi x F) ........so - 5K/(2Pix20)=39H
say that I didn't wrote anything ......... and that you conclude it by your self
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carpenter said:
Darn, I guess I'm not first
It is not just the imeadance of the inductor at the -3db point that we need to be concerned with. When I was working on the choke loaded ZV9 idea and testing with square waves I had a "tilt" to the square tops of the wave. This was due to my 120mH choke load and it can be caused by capacitance also. Hmmm... Whenever you try to use a cap or an inductor you are going to experience phase shift
Just like in a capacitance caused rolloff, if the -3db point is 20Hz, there are still capacitance effects happening as much as 3-4 octives higher (160-320Hz). This is why you commonly see coupling cap values set for about 2.5Hz -3db point. 3 octives higher is still only 20Hz. So the phase shift and other capacitance non linearities and whatnot, are just begining to effect the sound at the very bottom of the required passband and below.
Bigger(to a point) is better in this case. A Henry is a pretty big thing if you want output current levels through it. Nelson's 1H is 10 times the value I was working with in the inductor loaded ZV9 idea. Henry's are a much more managable value if your only working with a few milliamps
Zen Mod said:
flg said:
Darn, I guess I'm not first
Excellent information, guys. Choky, I've been playing around with the xls inductance program--what an education that's turning out to be. These ideas seem somewhat hidden in my mind and it's refreshing to pull them forward for examination.
My little F4 is a treble amp, so this explains why I've been getting away with various inductor sizes and not noticing a variance. I'm planning to operate the amp without an electronic x-over, run bass sine waves, and put it on the 'scope.
As always, many thanks. Guys like me need guys like you.....
Thanks, but I really could have been much more explanitory towards the phase shift biz. I'm not sure I can... I'm not Nelsoncarpenter said:
carpenter said:...My little F4 is a treble amp, so this explains why I've been getting away with various inductor sizes and not noticing a variance. I'm planning to operate the amp without an electronic x-over, run bass sine waves, and put it on the 'scope...
Well, square waves rely on a sine wave fundamental and sucsessively smaller level odd harmonics, in phase, all added together. They all add to be a square wave. With phase shifting from the inductive or capacitive component, the square will be distorted into something not square. Ussually a tilted looking thing...
You need to design in these components to be a very small portion of the voltage drop, or developing voltage component if it's in the signal path...
DaveM said:
Right
If you have a big enough cap or inductor, the square wave test should show something close to "square waves" in the frequency of interest. If designed for lower frequency, you might say you are wasting money(these components are $$$), or space(good Caps and most inductors are big. But, when Xc is at a level where signal can be measured across the cap, (Inductors are ussually the oposite function I think) they may also be contibuting to unwanted distortion and phase...
That may be so, but to my ear, there's not much difference in sonics between a 150mH leg and a 4mH leg above 500hz--regardless of the square wave. But, then again, I'm not the golden ears of the family.
Unless I'm feeling anal, and that's generally a temporary condition.
That is, unless I'm getting paid by a customer for remodeling his house, of course!
Unless I'm feeling anal, and that's generally a temporary condition.
That is, unless I'm getting paid by a customer for remodeling his house, of course!
carpenter said:That may be so, but to my ear, there's not much difference in sonics between a 150mH leg and a 4mH leg above 500hz--regardless of the square wave. But, then again, I'm not the golden ears of the family.
Unless I'm feeling anal, and that's generally a temporary condition.
That is, unless I'm getting paid by a customer for remodeling his house, of course!
80mH * 2 inductors does the trick for feeding a FE166e. If you feel you have a need to go deeper than approx 40hz, you may need more, but I have not seen any need for this for full range drivers anyway.
Magura
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