Franco understands.
I suspect he understands because he is prepared to read what I have posted.
Pano & Tony are wrong.
I suspect that both do not understand because they refuse to read what I have posted.
Pano posted a link to support the view of increased power from bridged amplifiers.
I have shown (although there is one mistake I made that I must correct) that the QSC clearly shows that the double power into twice the load impedance holds true.
and the same data also shows that the 4times power is never true.
Tony,
Pano,
Now back to my mistake.
For some reason the QSC RMX850 has data pairs that do not fit the doubled rule exactly.
The QSC RMX 1450, QSC RMX 1850HD & QSC RMX 2450 all have three sets of data pairs that do support the doubled rule exactly.
I suspect he understands because he is prepared to read what I have posted.
Pano & Tony are wrong.
I suspect that both do not understand because they refuse to read what I have posted.
Pano posted a link to support the view of increased power from bridged amplifiers.
I have shown (although there is one mistake I made that I must correct) that the QSC clearly shows that the double power into twice the load impedance holds true.
and the same data also shows that the 4times power is never true.
Tony,
This reply shows you have not read post75.
Pano,
this reply shows you too have not read post75.
and this dicourteous reply shows you have not read anything I have posted. How could you even think I have confused volts with amperes?
Now back to my mistake.
I did not notice that two of the data pairs did not exactly show double power. I should have said 10 of the 12 data pairs, not 11.
For some reason the QSC RMX850 has data pairs that do not fit the doubled rule exactly.
The QSC RMX 1450, QSC RMX 1850HD & QSC RMX 2450 all have three sets of data pairs that do support the doubled rule exactly.
Pano, Tony, as I understand it, thats not the case. just bridging 2 amps does not magically change the load impedance, the load stays the same, however effectively only half the impedance is seen by each amplifier. remember the output impedance of a bridged amp is doubled also
I understand it as Andrew writes it, the limitation is the amplifier itself, halving a load does not half the losses as well, or double the capability of output devices. you have double the amplifier, not 4 x the amplifier. I have expressed my confusion at this belief before and actually coincidentally emailed Andrew to confirm that I wasnt crazy
I understand it as Andrew writes it, the limitation is the amplifier itself, halving a load does not half the losses as well, or double the capability of output devices. you have double the amplifier, not 4 x the amplifier. I have expressed my confusion at this belief before and actually coincidentally emailed Andrew to confirm that I wasnt crazy
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I don't know what Tony has read, but if I hadn't read your posts, how else would I know that you're wrong?
It shows nothing of the sort.
I read it, understood what you said and took issue with it. Isn't that what a discussion is about?
I suspect you well know the difference, but in your posts you seem to be ignoring the difference. That's why I pointed it out.
No amp can supply infinite power. All amps are limited by their power supply, their heat-sinks, their output devices. Most amps designed to drive a nominal 4 to 8 ohm load in non-bridged mode can not supply 4X that power in bridged mode. The limitation is not the bridge, it's the other stuff.
So I do agree that an amp which is normally not bridged will not output 4X the power in bridged mode - its power supply, output devices and heat-sink are unlikely to be up to the task. That's pretty common and why we often see them rated for about 3X the power.
However (again) that is not a limitation on the BTL mode, but of other things.
If the amp were designed from the beginning with a PSU, output devices, heat-sinks, fans, etc to supply all the power the BTL mode allows, they could supply that much power. And there are amps like that.
We are talking about two different things. About how BTL works, and about the physical limitations of real world amps not designed to take full advantage of the BTL.
See?
Hi,
God this thread is dull, stating the bleeding obvious. So more of the same :
If you bridge a stereo amplifier into a given load you will get twice
the amplifiers rated power per channel into half that load per channel.
That is the real rule, that rules, not "twice the power into twice the load",
the result can be anything from no more power to near 4 times power.
Bridging into 8ohms requires each amplifier to have more output into
4 ohms than 8 ohms. Bridging into 4 ohms requires each amplifier to
have more output into 2 ohms than 4 ohms, otherwise pointless.
Best example nowadays is BTL class T amplifiers, clearly 4 amplifiers
wired as two stereo, and clearly each amp is designed for 2 ohm
loading for 4 ohm bridge loading. All to make the best of the
limited supply voltage - 12V - for in car. In these cases you
would find near 4 times for BTL, but clearly never actually 4.
rgds, sreten.
God this thread is dull, stating the bleeding obvious. So more of the same :
If you bridge a stereo amplifier into a given load you will get twice
the amplifiers rated power per channel into half that load per channel.
That is the real rule, that rules, not "twice the power into twice the load",
the result can be anything from no more power to near 4 times power.
Bridging into 8ohms requires each amplifier to have more output into
4 ohms than 8 ohms. Bridging into 4 ohms requires each amplifier to
have more output into 2 ohms than 4 ohms, otherwise pointless.
Best example nowadays is BTL class T amplifiers, clearly 4 amplifiers
wired as two stereo, and clearly each amp is designed for 2 ohm
loading for 4 ohm bridge loading. All to make the best of the
limited supply voltage - 12V - for in car. In these cases you
would find near 4 times for BTL, but clearly never actually 4.
rgds, sreten.
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Hi,
Noting the error in the above post. Bridging an amplifier is pointless
if output halves with load halving, i.e. its current limited. If 4 ohm
and 8 ohm outputs are identical (often are) then you get twice
the power into 8 ohm.
For the latter case output doubles for the same 8 ohm loading,
but as AT states it would also double for a high 16 ohm loading.
rgds, sreten.
Noting the error in the above post. Bridging an amplifier is pointless
if output halves with load halving, i.e. its current limited. If 4 ohm
and 8 ohm outputs are identical (often are) then you get twice
the power into 8 ohm.
For the latter case output doubles for the same 8 ohm loading,
but as AT states it would also double for a high 16 ohm loading.
rgds, sreten.
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Answering the OP's question, I'm going to throw a spanner in the works here and say that he will probably get away with 26V on a bridged setup. But I'd also go along with a suggestion above not to do a bridged amp if you want to keep enjoying the hobby.
There is a very good reason for this, which is that, in practice, you rarely ever push the amp as hard as you think. While you imagine you are doubling the current, you are actually not.
The reason for this is that the output spl from a speaker is determined by the current, not the voltage - from F=BIL. So, when you have a bridged amp playing at the same volume as its single amp equivalent, each amp is of necessity seeing the same amount of current as it would as a single amp.
This is how amps like the NAP500 manage to drive a 4 ohm load quite easily, they are not actually pushed that much harder than they otherwise would be but now they have a lot more headroom. (In this example I guess the 500 can manage continuous full output; at least I'd hope so.)
Dissipation is the key to whether this works or not. You certainly won't be able to get away with anything small, and once temperature gets above a threshold you might be stuffed. But, and this is my get out clause, this is a pretty weedy transformer so you will have plenty of sag if you push it hard. And that will mean you get back inside your SOA.
Not the most conservative approach, I grant you, but I think it should fly.
There is a very good reason for this, which is that, in practice, you rarely ever push the amp as hard as you think. While you imagine you are doubling the current, you are actually not.
The reason for this is that the output spl from a speaker is determined by the current, not the voltage - from F=BIL. So, when you have a bridged amp playing at the same volume as its single amp equivalent, each amp is of necessity seeing the same amount of current as it would as a single amp.
This is how amps like the NAP500 manage to drive a 4 ohm load quite easily, they are not actually pushed that much harder than they otherwise would be but now they have a lot more headroom. (In this example I guess the 500 can manage continuous full output; at least I'd hope so.)
Dissipation is the key to whether this works or not. You certainly won't be able to get away with anything small, and once temperature gets above a threshold you might be stuffed. But, and this is my get out clause, this is a pretty weedy transformer so you will have plenty of sag if you push it hard. And that will mean you get back inside your SOA.
Not the most conservative approach, I grant you, but I think it should fly.
Bridging 2 similar amps will certainly produce 4 times more power into a load than what an individual amp produce into the same load seperately...! The term "4 times more power" must be seen only as the ratio what a load get when connected in bridge to what it get when conncted single endedly. Dont compare the total power of two single ended load to one bridged load. However, the fact stand true only if ;-
1.The power supply is capable to maintain its rail voltage at increased (double) current demand.
2.The output stage of each amp in the bridge is designed to handle half of the nominal single ended impedance.
1.The power supply is capable to maintain its rail voltage at increased (double) current demand.
2.The output stage of each amp in the bridge is designed to handle half of the nominal single ended impedance.
I can't follow stevensoosai2527's argument too well until items 1 & 2 which, as a X2 power person, I agree with. But such an amp must be rare. It would be capable of operating safely, without distortion or risk of smoke at double the spec on the label.
Consider the replies if someone posted on this forum the following question.
"I have a 100w RMS MAXIMUM amp - into 4 ohm MINIMUM load. Can I get 200w RMS by using a 2 ohm speaker ?"
Or muse over this. A 100w/4 ohm amp could be considered to be a 100w, 20v rms ac generator. But if you had two 120v ac, 1Kw petrol generators and connected them in series (and synchronize them appropriately) would you have a 240v 4Kw generator ?
Does not common sense tell you the answers ? It's a case of not seeing the wood for the trees methinks when bridged mode comes on the scene.
If I've understood it correctly, Earlier in the thread it was suggested that a bigger transformer might help an amp reach X4 power. In my, admittedly limited experience, amplifier output transistors/chips are the most critical, vulnerable components.
Finally, an apology for resurrecting an old thread but I read all 91 posts with interest. A thread which started with a quote from Wikipedia which had it right to start with.....Well I would say that wouldn't I...I wrote it
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