MAINS... simple, old style amplifier, plugged into mains electrical outlet (110) - diyAudio
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Old 15th June 2008, 02:00 PM   #1
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Default MAINS... simple, old style amplifier, plugged into mains electrical outlet (110)


I had the idea to plug it into the mains...the circuit topologie is old...already know, nothing special.

I have created this amplifier, the one i gave the name MAINS
because it is plugged into the 110 AC volts mains outlet....yes... dangerous!

Of course, a full wave rectification and filtering will be needed
… then we may have something around 150 volts DC.

A positive series pass regulator is used into the positive line,
to divide a the DC voltage by a ratio of 2… then 75 Volts
Will feed the amplifier.

Current was calculated not to allow “young brazilian powerholic
guys” to install 2 ohms impedances into the output…. It is rated
as 60, 70 and 80 watts, to 8, 6 and 4 ohms loads… this way will
not burn the output units because of maximum dissipation beeing
reached…. Suggested speaker impedance will be 8 ohms

The input stages are all class A… only the output is biased into
class AB….less than 1 miliampere goes crossing the output
transistors…all them NPN to be easier to local folks to find
transistors without worry with the long search of good matched
complementary output units.

The circuit topologie and idea is very old, down the sixties and seventies.
but has a disadvantage that can be an advantage, the output condenser, as
It will block DC if something result damaged (not difficult here to produce
long term shorts into the output)

Minus 3dB points goes to 20 hertz and around 100 Kilohertz, and this,
of course will depend (the high end) on your transistor selection. and
the low end will depend on the output condenser capacitance

The idea is to allow folks to use burned PC supplies, the input has good
rectifiers and some filters…. The capacitance multiplier effect will
hold (that’s what I imagine…not absolutelly sure, I have to build) the
dc pulsating filtering… I hope so.

The idea is to make simple, reasonable sonics (not special those kind of
circuits in my point of view), allowing Brazilian boys to build without
have to buy expensive and heavy transformers (mail costs)… this way,
a small box can be the heatsink, some fan can be helpful and the idea
is to plug it into the mains.

Dangerous?…. Yes, it is dangerous, i am thinking to provide this circuit
into a board…. together the amplifier or into a separate board…but
could not imagine, till now, the way to protect those folks against
Electrocution…. This is the main problem in my mind.

Showing you, to see if this seems interesting, to listen some opinnions…
make a lot of sense to Brasil…because of many reasons…. But for
strangers this may be not a good idea…..but even this way I would like to know
How bad is this idea in your mind.

Brazilian young folks do not perceive differences in quality.... a bad amplifier can became good if has power to move woofer... the average is 30 watts each channel, and used into automobile amplifiers, 4 channels.... they use to plug those things into their homes and to build enormous speakers... exponential style cases... and to produce noise.... the majority do not know how to wire transformers and have small knowledge/experience to build things... they want cheap, fast, small and with some power.

I do not believe they can perceive differences in quality if you do not offer them a controled A to B testing, with something bad and something really good.... them they will perceive...so... the main focus is price, easy of construction, size and some power (more than 30 watts RMS.

Panzer is ready for pcboards production.. (local guys will do them)..... NAD style amplifier is stopped for a while.... Maximus is sounding no good (today evaluation..tomorrow will be another day)... and doing this one.

Carlos
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File Type: pdf mains.pdf (9.0 KB, 70 views)
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Old 15th June 2008, 02:27 PM   #2
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Location: Recife - Brasil Northeast
Default 30 to 40 years ago those amplifiers, using mains voltage


were used.

They had the mains rectified and filtered to the tube's plates.

To the heaters they used special tubes with high voltage heaters, and some of them were wired in series.

The idea is not new.... of course abandoned because the early transistor voltage ratios....now a days...we have transistors that can hold the 110 mains rectified and filtered.

regards,

Carlos
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Old 15th June 2008, 02:31 PM   #3
SY is offline SY  United States
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Dangerous? INSANELY dangerous, and just as likely to kill someone innocent.

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