question about amplifier push|pull

[AndrewT]

I now understand.
Sy is referring to the use of +(positive) or -(negative) as close to incorrect.

[cihtog]

Originally Posted by AndrewT

I now understand.
Sy is referring to the use of +(positive) or -(negative) as close to incorrect.

That's the way I understood it - the OP was looking at it as though one was push, and the other pull (from a somewhat DC perspective), not one being both push and pull, and the other being the middle (from an AC perspective).

When in fact, polarity doesn't even matter, unless there is a phase relationship with another speaker involved. In any case the amp couldn't care less which way 'round you hooked it up.

[currentflow]

Originally Posted by cihtog

That's the way I understood it - the OP was looking at it as though one was push, and the other pull (from a somewhat DC perspective), not one being both push and pull, and the other being the middle (from an AC perspective).

I agree and as I confirmed in post #12, taken in context (explanation of an instantaneous positive half-cycle condition ONLY, described as a "push" by the OP), I can see no reason why the description I gave using a polarity designation might be considered incorrect. For the positive half-cycle, the red-coloured terminal becomes positive with respect to the negative terminal. Had the question been centered around complete cycles, i.e. AC, then the polarity factor would have been relatively meaningless other than for ensuring loudspeaker phase matching.

[AndrewT]

I still don't accept the push pull explanation.
The output terminal at the back of the amplifier is the Hot terminal. It provides the Push.
The Ground or return terminal on the back of the amplifier is effectively passive or Neutral. It has no push.

When the load is connected the Hot terminal provides the EMF that sends current around the circuit that ends up back at the Return terminal.

It makes no difference whether that circuit passes DC current due to a DC emf or is AC current due to an AC emf.

The only bit that Sy pointed out, that I now agree was wrong, was the reference to "positive & negative"

[Boscoe]

Originally Posted by anwaypasible

amperage = watts / volts

okay

10 watts / 550 volts = 0.0181818181818182 amps

if the resistor can handle 550 volts at that many amps..
anybody know how to adjust that to the amperage limit for 6 volts?

**edit**

22 watts / 6 volts = 3.666666666666667 amps

550 / 6 = 91.66666666666667

so then i should be taking 0.0181818181818182 x 91.66666666666667 = 1.666666666666668 amps for 6 volts

i am basically 2 amps over the limit right?

no worries,
i wont go 'pointless' by wiring up each resistor to eachother trying to get the wattage to double.
no sense confusing the radio, not knowing if it should flow through the resistors or through the coil.



oh gawd
ohms law says voltage / resistance = current (amps)

6 volts / 2 ohms (splashing into the resistor only here) = 3 amps

550 volts / 2 ohms = 275 amps

makes me think i am 272 amps shy of blowing the resistor.
if that is the case, then the thing shouldnt be warm to the touch at all.


who thinks one way is right and who thinks the other way is right?

I'm not going to try to give an answer to all posts I don't have time!

550V is the max the resistor can handle it doesn't dictate to current capability. Current through the resistor can be calculated by...

Total lowest impedance from the resistor and driver will be about 4ohm. your amplifier is capable of 22W into 4ohm (I could be wrong I haven't read everything that deeply) to achieve 22Wrms into 4ohm requires about 9.38Wrms.

22/9.38 gives 2.35A going through the resistor which is fine. half the power will be spilt most of the time between the resistor and driver so if you had 22Wrms of sine running through it you will have 11W dumped in each.

I suggest you forget about amplifiers and speakers for a couple of years go an learn the basics and I mean very basic basics then come back and things will make sense.

[Boscoe]

Originally Posted by AndrewT

I still don't accept the push pull explanation.
The output terminal at the back of the amplifier is the Hot terminal. It provides the Push.
The Ground or return terminal on the back of the amplifier is effectively passive or Neutral. It has no push.

When the load is connected the Hot terminal provides the EMF that sends current around the circuit that ends up back at the Return terminal.

It makes no difference whether that circuit passes DC current due to a DC emf or is AC current due to an AC emf.

The only bit that Sy pointed out, that I now agree was wrong, was the reference to "positive & negative"

Does a push/pull amp just not source current from V+ through the output transistor through the driver to ground? Then sink current from ground through the driver through the output transistor to V-?

The red terminal is providing all the grunt/volts whether they are positive or negative and source/sink current to ground.

[sreten]

Hi,

Assuming black is neutral or earth then red is the "hot" terminal.
For AC red must push or source current and pull or sink current.
Black being neutral therefore sinks pushed/sourced current and
sources pulled/sinked current, all driven by the red voltage.

Related to the original question : yes you can put a 2R resistor in series
with a 2R driver, it will do horrible things to the bass Q of the driver.
Doesn't matter if it is before or after the driver. that gives 4 ohms.
22W into 4 ohms = ~ 11W to the speaker.

By putting a 2R resistor in both leads you have effectively added 4R
and made the bass drivers Q even worse and have a load of 6 ohms.
22W into 4 ohms = ~ 15W into 6 ohms = ~ 5W into the speaker.

rgds, sreten.

[cihtog]

Originally Posted by currentflow

Your first statement is correct. Current flows from the red (positive) wire, through the voice coil and back to the black (negative) terminal.

Originally Posted by SY

I think this is confusing and close to incorrect. The + and - (or red and black) are arbitrary designations. It's important to keep them the same between channels, but just as much current flows out (or in) of red as it does with black. + or red isn't "positive," - or black isn't "negative" in the sense of current flow.

What part of the second reply is incorrect? Aside from the fact that he is quoting part of currentflow's reply, but in reading further up in flow's post...

Originally Posted by currentflow

Two 'groups' of transistors are arranged such that each group generates one half-cycle of the audio signal feeding the loudspeaker.

...it's quite obvious that both parties understand the true function of the terminals.

-----------------------------------------------------------------------

AndrewT - Which push/pull explanation do you not accept? please quote ;-)

I'd be more apt to scratch my head at the following combination of statements...

Originally Posted by currentflow

Audio amplifiers normally have a designed frequency response, for example from 10Hz to 25KHz. This means that the amplifier will not allow DC to reach the voice coil. The voice coil current will change in sympathy with the audio signal (hopefully very accurately) and only pass the frequencies of interest in the audible range.

...as one has nothing to do with the other.

Attached is an image from melab-bd that I keep on my phone, to show customers when trying to explain how their amp works - in fact, the whole site may be of benefit to the OP.

[anwaypasible]

Originally Posted by Arty

Let me.. ask if i managed to understand correctly:
You would like to know if it is safe to connect a 2 ohm speaker to a cd player that requires 4 ohm load, via a 10 watt 2 ohm resistor.
Yes, it is safe.
But it is inefficient.
Sugested solution was to use 2 speakers in series.
otherwise you loose half of amplifier power wasted as heat.

hi.
i know of the power being wasted to the resistor.
but
look at what i am looking at.
it cost me $10 for those speakers at the junkyard, and the regular OEM speakers are said to be 15 watts RMS at 4 ohms.

yes they are the right resistance, and maybe they are louder.
but
1. they will distort and|or blow
2. they dont have a seperate tweeter
3. i doubt their timing will play as nice with the front speakers.

To the OP - resistors are not speakers, and should not be used in any way to modify their impedance - it won't work, and could e dangerous.

$10 at the junkard got me the tweeters on the speakers i wanted, and it was also cheaper than the $40 used speakers on ebay.
if i had the extra money, i would of jst got an amplifier and maybe some peerless drivers with at least a 2-way crossover for the front, and a 3-way crossover with cutouts in the rear doors for the woofer with the midrange and tweeter in the rear deck.

i hear what you are saying about could be dangerous.
nobody needs to be using a resistor on only one speaker terminal.
it makes the amp lop sided and that stress is dumb to say the least.

i didnt agree with the person that said the electricity wouldnt be poised to stay in the voice coil rather than make its way down to another 2 ohms of resistance.
but
it was said that the voice coil gap doesnt offer any place of lesser resistance, which is really jst saying the impedance is a constant.

i still believe the electricity would shy away from going further forward to the other speaker terminal.

amplifiers are for the most part basic, until the equation of the pieces are looked at.
for example..
one amplifier has a rail that pushes the speaker cone from neutral to outwards, with the ability to slowly bring the cone back to neutral without the need of the other rail.
the same amplifier will use the other rail to pull the cone from neutral and slowly move the cone back to neutral.

while another amplifier uses one rail to go forward and the other rail to go backwards regardless of whether the cone position is positive above the neutral spot or negative under the neutral spot.

i figure the only way to make each speaker wire do something for a simple sine wave is to allow each side to output something at the same exact time.
doesnt appear immediately possible without both rails being fully bipolar.
i get that the rail needs to be polarized for the sake of push or pull.
i was trying to get some speaking about each side being bipolar.

perhaps under-utilized.. perhaps under-supported.

[anwaypasible]

Originally Posted by sreten

Hi,

Assuming black is neutral or earth then red is the "hot" terminal.
For AC red must push or source current and pull or sink current.
Black being neutral therefore sinks pushed/sourced current and
sources pulled/sinked current, all driven by the red voltage.

see.. this is the THIRD type of amplifier design.
where it was specifically said.. one terminal outputs the full bias while the other terminal simply adds a sink.

the FOURTH type that i was talking about is kinda like this one, except the sink is biased in relation to the other side, thus creating the clamp.

going by the third amp design, i would use a resistor on the positive speaker terminal and not worry about the amplifier seeing something with 2 ohms on one side and 4 ohms on the other rail.

but
with the fourth type, i would need a resistor on both sides again since each side has an input and and output.
(the third amplifier type basically says the red is input and the black is always output.. while the fourth says the red is input as the black is output, but both the red and black terminals are biased for input and output to create the clamp i was talking about)

see..
i knew it made sense that i thought it might ever be possible for 11 watts RMS to be combining from each side to create the full stride of 22 watts.