Something smells fishy. 300W in 8ohm is 70V peak. The electrolytics in the photo are 63V.
300w could be peak power, that is 150W sine. This, I'm buying, it matches the transformer sizes, the electrolytic voltage and the number of output pairs (two each channel, apparently) and the cooling system physical size (apparently forced air).
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Yes. It deserves more consideration and coverage complete with T&M data.
A lot more useful perhaps than going over and over the same issues with a microscope.
THx-RNMarsh
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Hi Richard,
Well, I think just the fact that this is a standard construction method for high end T&M should carry a little weight. I think a lot of us are familiar with the concepts, and then there are those that should be asking questions. Not about data points. It's the entire concept that bears discussion.
This is a subject that the design by ear crowd just won't get.
-Chris
Well, I think just the fact that this is a standard construction method for high end T&M should carry a little weight. I think a lot of us are familiar with the concepts, and then there are those that should be asking questions. Not about data points. It's the entire concept that bears discussion.
This is a subject that the design by ear crowd just won't get.
-Chris
Waly, 8 outputs on each bridged channel PCB (16 amps actually present in the box), 63 V caps are just fine. All together 64 outputs mounted in the SAE amp. 😎
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Hi David,
What, the shielded coax? I haven't looked in years / decades. Have a look at Belden and the other usual suspects. It might be classified as a military wire these days.
-Chris
What, the shielded coax? I haven't looked in years / decades. Have a look at Belden and the other usual suspects. It might be classified as a military wire these days.
-Chris
Are you saying that there are 16 amplifiers each rated @ 150W into 4ohms and that these are bridged to give 8 outputs rated @ 300W into 8ohms?
Yes. According to the brochure it can also deliver 8 x 450 Wrms/4 Ohm. Quite a beast, fully differential, pure balanced, as they say. 😇
I hate the way the word "pure" is used in audio discussions. Also, it is a "pure" A-B amplifier I suppose.
Anyway, using terms like pure in describing anything usually is trying to convey some positive attribute before any judgement has been done by the other party. Sometimes the situation is more like "Pure class C", as in RF amplifier use (obviously an exaggeration).
-Chris
Anyway, using terms like pure in describing anything usually is trying to convey some positive attribute before any judgement has been done by the other party. Sometimes the situation is more like "Pure class C", as in RF amplifier use (obviously an exaggeration).
-Chris
You may be right (I see two output coils on each board) but then 16x150W simultaneously requires 4kW of transformers. Those two transformers in the photo are max. 1kW each. Not to mention that the cooling, even forced air as it appears to be, doesn't cut it for almost 1kW of power dissipation (worst case at 4ohm).
Embarrassingly, all three Vbe spreaders for the output stages of the first silicon on the AD524 oscillated at 27MHz. Simply integrating the two diodes in the same tub fixed it. Diode connected transistors that is, the gain was much lower than your arrangement because it was simply a small "cheater" resistor to remove a few tens of mV from the Vbe of one of them.
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Two conventional single-ended amplifiers bridged to make a pair of opposite-polarity outputs to double the power is not a true balanced design. The guts of the amplifiers in such a case are just single-ended.
Cheers,
Bob
My mentor in IC design used to say "If it works on first silicon, you weren't aggressive enough." God almighty that was a fun place to work.
But he said that in the days before wafer steppers and $100K mask sets {which now cost north of $5M for nosebleed digital}
@ Mark
How much PM does does a current source need. Is it not enough just to get them stable?
How much PM does does a current source need. Is it not enough just to get them stable?
Agree about that, since sch is not published we don't know, maybe they connected both amps differential inputs as per second pic in post #7613, where each diff pin is not floating but referenced to gnd via 25 k impedance (SAE specs), which is quite common practice in professional equipment, even if opamps are used as the input stage.
Hi David,
It is just class C, my comment was on the audiophile use of the word "pure" placed in front of anything they want to push.
-Chris
It is just class C, my comment was on the audiophile use of the word "pure" placed in front of anything they want to push.
-Chris
Yes I know Chris.
Class C is RF use and in RF there are no buzz words like
We are better because we use 'pure' Class C.
It just wouldn't have any meaning.