It's too hot today outside, so I relocated from my barn to a living room.
The space between tube unit and a power supply will be occupied by a control unit that will contain own PS, 3 electromagnetic relays: for transistor PS power control, and for speaker protection, and as well servos and speaker protection networks.
The space between tube unit and a power supply will be occupied by a control unit that will contain own PS, 3 electromagnetic relays: for transistor PS power control, and for speaker protection, and as well servos and speaker protection networks.
Let's check.
A first, let me repeat for the beginning, the servo output does not trigger protection. A voltage on integrator's inverting input triggers it. In the normal mode this voltage is always close to zero, and changes abruptly only and only when the integrator's output sticks to one of rails, i.e. when the integrator clips a voltage on it's inverting input changes enough to open one of diodes biased by 22 MOhm/750K voltage dividers from 12V sources, i.e. each of diodes is under-biased by 0.39 Volts on each.
In a normal mode the servo works as an integrator, but when something wrong happens an output voltage abruptly goes to +50 or -50. An integrator clips and a voltage on it's inverting input goes up.
Let's check time of the reaction.
1 mOhm, 50V means 50 microam current that in the normal mode goes to an input of an integrator. Time to clip from zero volt to one of opamp's rails would be 12V * 10^-6 F / 50 *10^-6 amp = 12/50 seconds, i.e. 0.24 second. When it clips it is no longer an integrator, and a voltage on it's inverting input starts going up, and 1V shift (let's assume that we need 1V to open a diode and trigger the comparator) happens during 1/50 seconds.
That means, we allow 1/4 seconds for servo to react (it's a cannon fire in Glinka's 1812), and 1/50 seconds only when servo can't correct the situation (it's no longer a cannon fire).
Is it too much?
A first, let me repeat for the beginning, the servo output does not trigger protection. A voltage on integrator's inverting input triggers it. In the normal mode this voltage is always close to zero, and changes abruptly only and only when the integrator's output sticks to one of rails, i.e. when the integrator clips a voltage on it's inverting input changes enough to open one of diodes biased by 22 MOhm/750K voltage dividers from 12V sources, i.e. each of diodes is under-biased by 0.39 Volts on each.
In a normal mode the servo works as an integrator, but when something wrong happens an output voltage abruptly goes to +50 or -50. An integrator clips and a voltage on it's inverting input goes up.
Let's check time of the reaction.
1 mOhm, 50V means 50 microam current that in the normal mode goes to an input of an integrator. Time to clip from zero volt to one of opamp's rails would be 12V * 10^-6 F / 50 *10^-6 amp = 12/50 seconds, i.e. 0.24 second. When it clips it is no longer an integrator, and a voltage on it's inverting input starts going up, and 1V shift (let's assume that we need 1V to open a diode and trigger the comparator) happens during 1/50 seconds.
That means, we allow 1/4 seconds for servo to react (it's a cannon fire in Glinka's 1812), and 1/50 seconds only when servo can't correct the situation (it's no longer a cannon fire).
Is it too much?
Now I know why I took a time off... Nelson Pass reported today that he started shipping a production with Silicone Carbide output JFETs. I did not know before now that they were already available: http://www.semisouth.com/products/uploads/DS_SJEP120R063_rev1.3.1.pdf
Anyway, it will not be hard to switch from silicone MOSFETs to silicone carbide JFETs; that will mean almost the same design, but with much better sound quality.
Anyway, it will not be hard to switch from silicone MOSFETs to silicone carbide JFETs; that will mean almost the same design, but with much better sound quality.
Going to order http://www.j-tron.com/product/2_lb._FeCl_Etchant_Powder.html -- mine exausted...
Meanwhile, making wooden body, to match speakers. The same palm tree grill, the same hardwood look...
Meanwhile, making wooden body, to match speakers. The same palm tree grill, the same hardwood look...
Thermal properties of the material that means less of factors of variability of parameters on working temperatures. Dirty currents, effective geometry modulations were significant factors that drove switch from Germanium to Silicon. The same leap means switching from Silicon to Silicon Carbide; the next leap may be switching to Diamonds. Can you imagine devices with 100 GHz Ft, 1,000W dissipation, 100 Amperes/Volt transconductance, and 1 picoampere of dirty currents, in an 1/4 inch bolt screwed into a threaded hole in a heatsink?
Would they actually need a normal sized heatsink? I can imagine them glowing intensely at 600C and not giving up the spirit if pure diamond.
Yes, I dream of such devices inside of tube cathodes, such a powerful hybrid tube would not need any additional heater supply.
Can you imagine a single tube power amp, very powerful one? Something like zero dB input, 500W output.
To a brave new audio world.
