That's about where it should be around 10% of mains ,do fuse each transformer as it is a circuit too, That's how I got my nick name smoking stuff,lol I use circuit breakers and fuses, I had a SWTP Tiger.01 built 2 of them ,they would turn on oscilate and blow fuses everyone in school laughed at my system blowing fuses ,BUT they did gather around to listen,lol.
Cheers!
That's about where it should be around 10% of mains ,do fuse each transformer as it is a circuit too, That's how I got my nick name smoking stuff,lol I use circuit breakers and fuses, I had a SWTP Tiger.01 built 2 of them ,they would turn on oscilate and blow fuses everyone in school laughed at my system blowing fuses ,BUT they did gather around to listen,lol.
Cheers!
A pair of 800VA transformer will suffer repeated and frequent nuisance blowing of close rated fuses.
Fuses rated to start a transformer would normally be about 3 times the value of close rated fuses.
800VA / 115Vac * 3 = 20.8A.
A T20A fuse would be expected to start a single 800VA toroid transformer without suffering nuisance blowing on start up, or later.
Adopt a soft start circuit and close rate the fusing for each transformer.
You should find that a T8A fuse will work reliably. You may find that a T6.3A works in the long term if you select appropriate values in the soft start circuit.
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I am building 2- V3 Turbo's. After studying Mr. Pass's article on power supplies, (http://www.passdiy.com/pdf/powersupply.pdf). It seems you need about 1500va transformer per 100 watts. 2- 800va in parallel looked like the cheapest way to go. Anybody have any idea how hot the diodes are going to get? They going to need a big heat sink or are we just looking for thermal stability? I have all the parts in hand and Teabag has mailed the boards. Any timeline on the Matched outputs Buzzforb?
Most ClassA power amplifiers draw sufficient continuous current through the rectifiers that the rectifiers dissipate considerable heat.
They generally need heatsinking.
Each diode drops ~700mV.
You can calculate the dissipation of each diode from it's duty cycle (usually 50%) and the current passing times that 700mV.
From there it is an easy stage to select a suitable heatsink.
They generally need heatsinking.
Each diode drops ~700mV.
You can calculate the dissipation of each diode from it's duty cycle (usually 50%) and the current passing times that 700mV.
From there it is an easy stage to select a suitable heatsink.
minimum 2X the powerdraw.
so minimum around 500VA pr ch for your V3
i'm going for 600VA pr monoblock. at +/42V rails and bias at around 2.4A
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2times does not seem right.
Prior to F5 I saw pass recommendations varying from 6times to 10times maximum ClassA output power for the transformer in a ClassA amplifier.
The F5 is a 27W ClassA amplifier and the minimum transformer rating I have seen recommended was 180VA. That is a ratio of 6.7times.
That fits within the previous PASS recommendation range. The F5 is no different in this respect from other ClassA amplifiers.
Why should the F5t be any different?
Prior to F5 I saw pass recommendations varying from 6times to 10times maximum ClassA output power for the transformer in a ClassA amplifier.
The F5 is a 27W ClassA amplifier and the minimum transformer rating I have seen recommended was 180VA. That is a ratio of 6.7times.
That fits within the previous PASS recommendation range. The F5 is no different in this respect from other ClassA amplifiers.
Why should the F5t be any different?
Sorry, I was thinking about the ones on the circuit board that Mr. Nelson is using for/instead of source resistors. I have seen bridge rectifiers get very hot and definitely plan to heat sink those..
"If the stereo amplifier is rated 200 watts per channel pure Class A, it will
draw about 1000 watts all the time, meaning that about 3000 watts of
power transformer is called for, no less." Nelson Pass on Power supplies 2001.
"If the stereo amplifier is rated 200 watts per channel pure Class A, it will
draw about 1000 watts all the time, meaning that about 3000 watts of
power transformer is called for, no less." Nelson Pass on Power supplies 2001.
Since the Op is in the states, a 20.8A fuse option would be a waste of time unless he had a dedicated 30A power drop equal to the task to allow the fuse to actually blow.
Most power outlets in the states are 15A fuse/circuit breaker protected. Perhaps a run or two at 20A in the kitchen or laundry, but, it is not normal practice.
Maybe that is a potential solution in lieu of a soft start circuit.
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