Member
Joined 2003
I was thinking of this idea the other day and I am no expert at amplifier design, but I can't think of any reason why this wouldn't work. For a high power amplifier design, what if it didn't have a transformer?
What if I took the 120V straight from the wall, rectified it, filtered it, and designed an amplifier around the resulting rail voltages. The end result would be a high power amplifier that would be cheaply build due to the lack of one of the most expensive parts, and it would also be smaller and lighter for easy transportation.
Would this be a stupid idea? I just figured that there would have to be something wrong with it if nobody has built one yet.
What if I took the 120V straight from the wall, rectified it, filtered it, and designed an amplifier around the resulting rail voltages. The end result would be a high power amplifier that would be cheaply build due to the lack of one of the most expensive parts, and it would also be smaller and lighter for easy transportation.
Would this be a stupid idea? I just figured that there would have to be something wrong with it if nobody has built one yet.
SY said:
Deathtrap. Deadly, deadly dangerous. Don't even think about it.
I've heard that too, Youd have (120Vx1.414)-.6=169V DC so 85V rails. I think that would mean more signifigant power disipation on the output stage (especially at lower volumes)if im correct....
Correct me if I'm wrong that tube amps often run at higher voltages? They have a transformer ect to limit current of course.
To elaborate a bit:
In a common amplifier with an isolation transformer, if the following failure modes occur, the worst that happens is you blow a bunch of transistors or fuses:
Power lead short to ground or chassis(forgot/overlooked in wiring)
Circuit failure leads to output swinging to one power rail
power rail shorted to output terminal (don't laugh it can happen)
In the proposed power supply topology, all these lead to mains voltages AND current capabilites on either the chassis or the speaker wires (or speaker chassis)
= death to touch an innocent-looking piece of kit.
avoid.
In a common amplifier with an isolation transformer, if the following failure modes occur, the worst that happens is you blow a bunch of transistors or fuses:
Power lead short to ground or chassis(forgot/overlooked in wiring)
Circuit failure leads to output swinging to one power rail
power rail shorted to output terminal (don't laugh it can happen)
In the proposed power supply topology, all these lead to mains voltages AND current capabilites on either the chassis or the speaker wires (or speaker chassis)
= death to touch an innocent-looking piece of kit.
avoid.
If transformer-isolation is not used for the power supply, then it must be used for each signal input and each speaker output due to safety issues. So, actually, there is no advantage in supressing power supply transformer.
Furthermore, you will have to buy expensive mains isolation transformers in order to experiment with and test such an amplifier. Note that you can't connect an oscilloscope directly to live circuits (due to ground issues), and that multimeters give erratic results when measuring on high-impedance or small-signal live circuits (this happens due to unexpected capacitances from probes and multimeter body to earth).
The way to go for light weight and small size in high power amplifiers is switched mode power supplies. They allow for very small PSU transformers while still providing mains isolation and other useful features.
Furthermore, you will have to buy expensive mains isolation transformers in order to experiment with and test such an amplifier. Note that you can't connect an oscilloscope directly to live circuits (due to ground issues), and that multimeters give erratic results when measuring on high-impedance or small-signal live circuits (this happens due to unexpected capacitances from probes and multimeter body to earth).
The way to go for light weight and small size in high power amplifiers is switched mode power supplies. They allow for very small PSU transformers while still providing mains isolation and other useful features.
DcibeL said:
I still dont understand why the member count of this forum is going up, not down !
Ever considered the transformer to be a big help in keeping the rotten stuff out ?
Fools like me even use several giant isolation transformers to prevent all kinds of weird frequencies entering audio circuits.
It's not every 6 months, more like every 2, why not tell 'm to go for it next time ?
SY said:
Partypoopers
Suggestion : as from today every person asking this question will be considered a lawyer !
Eva darling,
can you tell me if it is possible to connect a 3-phase toroidal transformer to single phase 220 volts ?
(on several switchboard fuses of course, they are 5000va models)
now this may sound strange but thats a good idea that i have researched in the past and amazing found a company that has sorta done it. now most people haven't put amplifiers through hell like i have, but one particular amplifier used the line voltage to directly run the power rails. in the carver pm-1200, pm-1.5 and m-400 (prolly others but those are the ones i have mercylessy blown) in those amplifiers if you touch either output to ground you blow the power supply main triac. measuring the speaker outputs in reference to ground revealed 107 volts. and a few times we ran vaccum cleaners, box fans, track lights, and christmas lights from both an m-400 and a pm 1.5. so yes it is possible if you pwm the line with a 40 amp triac then it gains safety.
but i still don't suggest anyone tries doing it, i have and i was lucky. all i'm saying is that it's possible and it's been done. wanna do an experiment, buy a pm 1.5 from e-bay. it's dangerous and costly. i have blown up soo many amplifier circuits destroyed thousands of dollars of electronic components.
but i still don't suggest anyone tries doing it, i have and i was lucky. all i'm saying is that it's possible and it's been done. wanna do an experiment, buy a pm 1.5 from e-bay. it's dangerous and costly. i have blown up soo many amplifier circuits destroyed thousands of dollars of electronic components.
- Status
- Not open for further replies.