Agree that's one but it has shortcomings. even a perfect amplifier will ring into a cap load due to stray inductances. Udok demonstrated that in a post with a square wave sim into 'typical' inductances.
http://www.diyaudio.com/forums/soli...b-ring-into-capacitive-loads.html#post3920281
http://www.diyaudio.com/forums/soli...b-ring-into-capacitive-loads.html#post3920281
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YO ! I made it to the other side of this planet yet one more time and lived thru it.
regarding the series output L ---- why wouldn't it be audible with some tweeters and listeners? It and the cable Ls together is not really what a dynamic tweeter wants to see. Though great for amp stability into certain loads.
Isn't there a Better way? Other topologies for amp may be better (CFA?) -- at least for low inductance dynamic tweeters.
-RNM
regarding the series output L ---- why wouldn't it be audible with some tweeters and listeners? It and the cable Ls together is not really what a dynamic tweeter wants to see. Though great for amp stability into certain loads.
Isn't there a Better way? Other topologies for amp may be better (CFA?) -- at least for low inductance dynamic tweeters.
-RNM
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As JC tirelessly reminds us, an amplifier with a common source* output stage (such as Trans-Nova, First Watt F1, etc) operates as a transconductance: a voltage controlled current source. This can be designed in such a way that it does not become unstable when you connect larger and larger capacitive loads to the output. Quite the reverse.
So if you're looking for an amplifier topology that doesn't need a series impedance (inductor) when driving a capacitive load, transconductance topologies need to be on your short list of ideas to investigate.
* or common emitter
Transconductance outputs do not have the output follower that virtually all 'op amps' have, and they actually just get slower with increased cap load, rather than ring and sometimes oscillate. IC op amps are usually protected by an external output resistor (50-100 ohms) if they are connected to outside cabling.
Remember, it is the RESISTOR that does the protecting, not the inductor. The inductor is added to keep the damping factor high in the low to mid audio frequency range. The amount of inductance depends on what frequency breakpoint you want the resistor to be fully effective in doing its job. With today's fast output power transistors or mosfets, less inductance is usually needed than in the old days, like 40 years ago.
Thanks PMA for your input. It is what I do to measure stability. I also use a low level square wave to show the tendency for ringing, and what range of capacitance to concentrate on.
As far as Julian V of NAIM is concerned, he finally told me after we had known and visited each other for years why he removed the output inductor from his amp designs. Yes, because it sounded better. BUT he thought that additional stability in his amps was unnecessary, because the lamp cord or its equivalent that he normally used in early years did the same job, effectively. When exotic cables from Japan and even Monster became popular, all H-ll broke loose, and he had to offer his own equivalent lamp cord for anxious customers.
His amps were actually better than typical, even with a primitive topology and a quasi-complementary output, because he secretly found a European bipolar NPN power transistor that was about 10 times faster, but with good safe area protection, than everybody else was using at the time.
Remember, it is the RESISTOR that does the protecting, not the inductor. The inductor is added to keep the damping factor high in the low to mid audio frequency range. The amount of inductance depends on what frequency breakpoint you want the resistor to be fully effective in doing its job. With today's fast output power transistors or mosfets, less inductance is usually needed than in the old days, like 40 years ago.
Thanks PMA for your input. It is what I do to measure stability. I also use a low level square wave to show the tendency for ringing, and what range of capacitance to concentrate on.
As far as Julian V of NAIM is concerned, he finally told me after we had known and visited each other for years why he removed the output inductor from his amp designs. Yes, because it sounded better. BUT he thought that additional stability in his amps was unnecessary, because the lamp cord or its equivalent that he normally used in early years did the same job, effectively. When exotic cables from Japan and even Monster became popular, all H-ll broke loose, and he had to offer his own equivalent lamp cord for anxious customers.
His amps were actually better than typical, even with a primitive topology and a quasi-complementary output, because he secretly found a European bipolar NPN power transistor that was about 10 times faster, but with good safe area protection, than everybody else was using at the time.
The resistor is in the middle of the coil. The magnetic field accelerates the electrons flowing through the resistor in the axial direction.
The electrons exiting the output end of the resistor therefore arrive before those travelling through the inductor* over and above the already existing time discrepancy due to the longer electron flight paths between the two routes i.e. the coil or the resistor. This additional phase discrepancy, which can be significant, causes subtractive vector summation leading to additional HF harmonics in the programme material at levels of -180 to -190 dBV (8 ohm load assumed). This is clearly audible and requires mitigation in serious audiophile level equipment.
Therefore, following extensive research at the faculty of Advanced Electrical Engineering and Research, it is recommended that the resistor be placed alongside the inductor, worst case, but preferably at 90 degrees to the coil's longitudinal axis.
*Important note: the coil winding direction is critical - clockwise for the southern hemisphere, anti-clockwise for the northern hemisphere.
More L8r
The electrons exiting the output end of the resistor therefore arrive before those travelling through the inductor* over and above the already existing time discrepancy due to the longer electron flight paths between the two routes i.e. the coil or the resistor. This additional phase discrepancy, which can be significant, causes subtractive vector summation leading to additional HF harmonics in the programme material at levels of -180 to -190 dBV (8 ohm load assumed). This is clearly audible and requires mitigation in serious audiophile level equipment.
Therefore, following extensive research at the faculty of Advanced Electrical Engineering and Research, it is recommended that the resistor be placed alongside the inductor, worst case, but preferably at 90 degrees to the coil's longitudinal axis.
*Important note: the coil winding direction is critical - clockwise for the southern hemisphere, anti-clockwise for the northern hemisphere.
More L8r
John, I don't see people abusing you for your view (at least this time around, past times I make no such assessment), inasmuch as just stating the plusses and minuses.
And, of course, the inductor is there as a LF bypass for the series resistor, and that crossover point needs to be selected in terms of the GBW of the amplifier's outer loop (primarily, at least), which is largely decided by the bandwidth of the output stage.
Also: welcome back, PMA, even if it's a short visit.
And, of course, the inductor is there as a LF bypass for the series resistor, and that crossover point needs to be selected in terms of the GBW of the amplifier's outer loop (primarily, at least), which is largely decided by the bandwidth of the output stage.
Also: welcome back, PMA, even if it's a short visit.
The resistor is in the middle of the coil. The magnetic field accelerates the electrons flowing through the resistor in the axial direction.
The electrons exiting the output end of the resistor therefore arrive before those travelling through the inductor* over and above the already existing time discrepancy due to the longer electron flight paths between the two routes i.e. the coil or the resistor. This additional phase discrepancy, which can be significant, causes subtractive vector summation leading to additional HF harmonics in the programme material at levels of -180 to -190 dBV (8 ohm load assumed). This is clearly audible and requires mitigation in serious audiophile level equipment.
Therefore, following extensive research at the faculty of Advanced Electrical Engineering and Research, it is recommended that the resistor be placed alongside the inductor, worst case, but preferably at 90 degrees to the coil's longitudinal axis.
*Important note: the coil winding direction is critical - clockwise for the southern hemisphere, anti-clockwise for the northern hemisphere.
More L8r
Sigh, so wrong.....
Lemme splain...
A resistor will have a voltage drop from end to end as a result of current. This voltage causes the electrons to accelerate axially in the bulk material. This is a straight path normal to the field gradient. When the music is smooth and clean, the electrons will continue on a smooth clean straight path, with little desire to hit the lattice which is the resistive material. On the other hand, when the music is harsh, or heavy metal for example, the electrons get all bent out of shape, and start to impact the lattice more, as well as other tangential movements.
Now here's the reaaaaaal physics part...when the lectrons stray from the path chosen them by the gradient, they begin to cross solenoidal field lines of the overwound inductor. As a consequence, the electrons will begin to spiral, much like they do in the upper atmosphere (northern lights)..aurora borealis**. remember green...
Due to the longer path of a spiral, the lectrons take a much longer time to get from one end of the resistor to the other. Because the inductor decouples at high frequencies, this spiralling effect goes away at high frequencies, but this "spiraling delay" (tm) alters the low frequency timing. Since we can't hear absolute timing, this appears to normal humans as a high frequency smear..
Explaining why Def Leppard is so harsh....
That green? I'll tell ya bout CD edge color someday...
John
ps. Bonsai, we should start a company. We could probably sell cans of air..
Sigh, so wrong.....
Lemme splain...
A resistor will have a voltage drop from end to end as a result of current. This voltage causes the electrons to accelerate axially in the bulk material. This is a straight path normal to the field gradient. When the music is smooth and clean, the electrons will continue on a smooth clean straight path, with little desire to hit the lattice which is the resistive material. On the other hand, when the music is harsh, or heavy metal for example, the electrons get all bent out of shape, and start to impact the lattice more, as well as other tangential movements.
Now here's the reaaaaaal physics part...when the lectrons stray from the path chosen them by the gradient, they begin to cross solenoidal field lines of the overwound inductor. As a consequence, the electrons will begin to spiral, much like they do in the upper atmosphere (northern lights)..aurora borealis**. remember green...
Due to the longer path of a spiral, the lectrons take a much longer time to get from one end of the resistor to the other. Because the inductor decouples at high frequencies, this spiralling effect goes away at high frequencies, but this "spiraling delay" (tm) alters the low frequency timing. Since we can't hear absolute timing, this appears to normal humans as a high frequency smear..
Explaining why Def Leppard is so harsh....
That green? I'll tell ya bout CD edge color someday...
John
ps. Bonsai, we should start a company. We could probably sell cans of air..
Damn. I thought I had it right and then a real expert shows up.
Cans of Air I think that has been done already!
www.zoro.com/dust-off-aerosol-duste...gclid=CL-S57eov88CFcmXfgodQRICoA&gclsrc=aw.ds
Canless Air O2 Hurricane
Canadians are selling cans of fresh air to China
www.zoro.com/dust-off-aerosol-duste...gclid=CL-S57eov88CFcmXfgodQRICoA&gclsrc=aw.ds
Canless Air O2 Hurricane
Canadians are selling cans of fresh air to China
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