And now I see from the ad in Stereophile that arrived today, that Levinson is offering a switchmode amplifier (as well? or is that what you were referring to?).
It is almost certainly using Gerald Stanley's interleaved topology ("class I") to get its stated (equivalent) 4MHz switching frequency.
Hi,
Well, I count 30Kto 300K as I am most concerned about SMPS Noise, you call it 10KHz - 80KHz, I think we have a great deal of overlap and I do not per se disagree with the 10KHz figure...
True tube gear, with tube rectifiers, choke input or filtered supplies and AC powered heaters has basically some of the lowest noise pollution fed back into the mains. I am not sure what you measured, how and with what gear, but IMNSHO it was not "Tube Power Supply" that you measured.
The above performance is specified without specifying load and source impedances. Am I to understand that your filter offers this performance regardless of source and load impedances and regardless of common mode and differential mode noise?
Often the reason is that they employ switched mode systems to save cost.
Implemented correctly the results of a mains regenerator can be truely astonishing. Very large Pro-Audio Amplifiers bridged may be used to provide 115V AC regenerated (one may buy them 2nd hand), very stable and low distortion sine wave generators may be build easily, giving 115V of regenerated power. The result can be WAY and I mean WAY better than any filter in measured terms.
A few killerwatt Pro Amp are surprisingly cheap these days, but it is important to make sure they use linear supplies...
Ciao T
Well, I count 30Kto 300K as I am most concerned about SMPS Noise, you call it 10KHz - 80KHz, I think we have a great deal of overlap and I do not per se disagree with the 10KHz figure...
As a tube affictionado, I suppose you'll take issue with tubes, but it's really a simple test: observe the 1...100 kHz spectrum on your scope with the tube audio off and the with on. Then discuss the problem with the oscilloscope, because the S.O.B. is transistor based.
True tube gear, with tube rectifiers, choke input or filtered supplies and AC powered heaters has basically some of the lowest noise pollution fed back into the mains. I am not sure what you measured, how and with what gear, but IMNSHO it was not "Tube Power Supply" that you measured.
The above performance is specified without specifying load and source impedances. Am I to understand that your filter offers this performance regardless of source and load impedances and regardless of common mode and differential mode noise?
Often the reason is that they employ switched mode systems to save cost.
Implemented correctly the results of a mains regenerator can be truely astonishing. Very large Pro-Audio Amplifiers bridged may be used to provide 115V AC regenerated (one may buy them 2nd hand), very stable and low distortion sine wave generators may be build easily, giving 115V of regenerated power. The result can be WAY and I mean WAY better than any filter in measured terms.
A few killerwatt Pro Amp are surprisingly cheap these days, but it is important to make sure they use linear supplies...
Ciao T
Hi,
These appear 3-Phase transformers?
It is hard to tell how transformers behave from the outside. There are many ways to winding them, layering, sequence of layers etc., the results differ greatly.
Ciao T
What if they look like this .... ?
General Purpose Transformers - Products - Quality Transformer and Electronics
These appear 3-Phase transformers?
It is hard to tell how transformers behave from the outside. There are many ways to winding them, layering, sequence of layers etc., the results differ greatly.
Ciao T
Well,if I can believe anything from Spice about the DH-120, I should remove C3, the 330p dominant pole, and install 47p from base of Q6 to emitter of Q7. Conventional Miller compensation. It makes much prettier pictures. Hmmmmm, pictures good.
I also need to adjust R19 and R20 as per the app guide. 220 and 180 worked in the sim.
I also need to adjust R19 and R20 as per the app guide. 220 and 180 worked in the sim.
And I would not trust either. CSA does a lot better job.
UL is only chartered to tell you if 1: you will get fried from electricity, and 2: You will get fried when your house burns down. I don't think they do either.
Of course, as was mentioned in another thread, in the winter those wonderful Cary triodes are 100% efficient as If I could afford them, I could turn off the heat.
Hi,
Try lead compensation instead of miller. That is cap from Vas out to negative in... May still need a touch of miller to be stable, but keep that to a minimum...
Ciao T
Try lead compensation instead of miller. That is cap from Vas out to negative in... May still need a touch of miller to be stable, but keep that to a minimum...
Ciao T
Yes .. Sorry
It's probably got switchmode supplies as well. I believe, as well, Gerald likes to do some feedforward tricks with the rail voltages talking to the pulse width modulators as well, and there's probably synchronization of the PWM and the switchmode power supply. A lot going on. And the patents are still in force, available to Levinson as both Crown and ML are Harman companies.
When I first met Gerald it was just after the acquisition of Crown. I had run across a brief description in a book on power electronics of a two-quadrant switching regulator that looked a little like Gerald's patented opposed current amplifier (which lends itself readily to interleaving, and intrinsically avoids shoot-through currents of a conventional half-bridge output). When I first saw the note in the book I was thinking that it might be a way around the Crown patents. Then Crown was acquired, and as Harman was my big client I hoped that it wasn't such a way
Stanley looked at the book and seemed slightly concerned, but then noted that the pulse width modulation scheme was different. He added that when he came up with the idea, after filing on it he presented a paper to a power electronics conference and asked if anyone in the room full of people had seen anything like it (no hands were raised).
Harman is not a client anymore, but as well it turns out the two-quadrants of the example in the book were a switchmode means of sourcing and sinking current efficiently, not the bipolar voltage output that I'd hoped it might be. And once you patched the book example together with an inverted copy of itself (as it were) you got Gerald's topology
Hi,
Given the antiquity of PWM and related miscellanea I suspect that there both various ways around the patent, including money and a sufficiently motivated law-firm.
That said, while I can see many cost advantages in switched mode amplifiers, even the truly astonishing 4MHz claimed for the ML switching amp fall about 3 orders of magnitude short of what is needed for 20KHz bandwidth 16 bit audio without noise shaping...
I'd rather have 50W class AB than 500W switched mode one... The best I heard where quite wretched (as is expected, as most power amp's playing music tend to have a modulation index in the region of -20dB or more...).
I have not heard ML's version, but I have heard Crown's efforts. I'll take a DC-300 instead, thank you very much.
Ciao T
Given the antiquity of PWM and related miscellanea I suspect that there both various ways around the patent, including money and a sufficiently motivated law-firm.
That said, while I can see many cost advantages in switched mode amplifiers, even the truly astonishing 4MHz claimed for the ML switching amp fall about 3 orders of magnitude short of what is needed for 20KHz bandwidth 16 bit audio without noise shaping...
I'd rather have 50W class AB than 500W switched mode one... The best I heard where quite wretched (as is expected, as most power amp's playing music tend to have a modulation index in the region of -20dB or more...).
I have not heard ML's version, but I have heard Crown's efforts. I'll take a DC-300 instead, thank you very much.
Ciao T
I was going to agree...and explain my understanding of the why of that last bit, in my mind, but I'm in the middle of correcting the faults inherent in the design of these puppies, so I'll have to remain neutral.
Everything I've done in the world of audio was and is aimed toward fixing the issues that this type of design exaggerates so splendiferously.... thus my acquired skill set is coming in quite handy.
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Hi,
Quel dommage. The DC-300 is a complete lemon. It's only saving grace was that the designer had been thoughtful enough to provide the handles needed to throw it as far as Newtons law allows.
Ciao T
Quel dommage. The DC-300 is a complete lemon. It's only saving grace was that the designer had been thoughtful enough to provide the handles needed to throw it as far as Newtons law allows.
Ciao T
I'll play with that. You have commented before not to care for Miller; Self and Cordell really don't like the pole on the VAS output and the sim confirms that. Changing any of the other four compensation caps had negative effects in transient response. One more vote for the old guy and a slip stick. Right now, my eyes are blurry as I have been at it all day.
Sure is sensitive to input impedance. R1 at 100 helps. My "new" preamp should be here in a day or two. 60 Ohm output. Guess I am convinced about passive preamps.
Makes really abstract pictures when the sim is not stable. I have not run Monte Carlo or played with the cap values to plot how much margin it has. It is supposed to have a text based pole and zero function, but I have not read that far. If it was nothing else, it is a better drawing package than I had. Decent days wasted work. I guess I would say "Miller time" but I can't stand the stuff. Anchor for me.
Hi,
Unsurprising. EB worked then with real gear, circuit sim's if they existed at all where by far primitive than now...
Remember, a sim is limited math model of reality.
Reality, well, it's real...
Ciao T
Unsurprising. EB worked then with real gear, circuit sim's if they existed at all where by far primitive than now...
Remember, a sim is limited math model of reality.
Reality, well, it's real...
Ciao T
I continue to be baffled by people who proclaim the sonic advantages of switchmode amplification. And at that, I was affiliated, not long ago, with a startup, and inherited a class D design using the IR driver chip and their teeny low-inductance DMOS parts, and wrung considerably more performance out of it than IR had managed. And it sounded decent driving some pretty nice speakers. This all came to an end when four of us, the entire technical team and one marketing guy, realized that the head of the company was a few condiments short of a burger bar, and quit simultaneously.
When Tripath was still squandering other people's money, some of their executives claimed that their amps just sounded incredibly better. At other meetings I would hear the presenter say that his company's "digital" amp sounded "tube-like" (with the implication that this was prima facie to be desired); I barked out that surely some of this was due to the high impedance of the output filter interacting with the load and producing frequency response anomalies. As usual, a spoilsport.
When Tripath was still squandering other people's money, some of their executives claimed that their amps just sounded incredibly better. At other meetings I would hear the presenter say that his company's "digital" amp sounded "tube-like" (with the implication that this was prima facie to be desired); I barked out that surely some of this was due to the high impedance of the output filter interacting with the load and producing frequency response anomalies. As usual, a spoilsport.
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