Hi calvin,
thanks a lot for that fast and pretty cool option from "under the hood" (not sure of that translation tho).
It's true that I was concern about the fact that using different amp modules using different technology would imply different power supply,(=easily more costly project) and a possible mismatch of the sonic footprints between different amps.
OK, so just to sum up, the idear will be to use a lowered power supply, in order to use one module that will output 50W into 8 ohm (seems better that 120W in the fullrange) and 300W into 4Ohm for the bass using two modules in bridge mode Right?
Things that I still have to make clearer:
using 2 modules in bridge mode is the fact to "couple" 2 modules in order to make it act as one but more powerfull - have to search the web for a practical example.
"A transformer with +-24V will give ~+-32V rails."
I have on hand a unit of that F6 universal power supply that activeXp talked about in it's home page. I have not bought a toroidal transformer yet. but the one advise was a [FONT=trebuchet ms, sans-serif]300VA Toroidal 35V - 0 -35V [/FONT]. SO I should search for a 300VA 24V-0-24V and expect a +-32V rail out of the F6 psu,
Or
I have to find the right toroidal that will allow +-24V out of the F6power supply, and those +-24V into the amp modules will give a +-32V somewhere in the amp module (bevor the transistor?)
"One big advantage of this kind of configuration is, that only one power suply is needed as all amps could be supplied from the same +-24V Transformer."
You mean that I will be able to power both the left and right channel on both the fullrange and bass drivers
Or
1 power supply for both fullrange and 1 for both bass Orone supply for one channel fullrange+bass?
Thanks a lot and best regards.
I have a lot of things to clarify ;-)
Dookie182
thanks a lot for that fast and pretty cool option from "under the hood" (not sure of that translation tho).
It's true that I was concern about the fact that using different amp modules using different technology would imply different power supply,(=easily more costly project) and a possible mismatch of the sonic footprints between different amps.
OK, so just to sum up, the idear will be to use a lowered power supply, in order to use one module that will output 50W into 8 ohm (seems better that 120W in the fullrange) and 300W into 4Ohm for the bass using two modules in bridge mode Right?
Things that I still have to make clearer:
using 2 modules in bridge mode is the fact to "couple" 2 modules in order to make it act as one but more powerfull - have to search the web for a practical example.
"A transformer with +-24V will give ~+-32V rails."
I have on hand a unit of that F6 universal power supply that activeXp talked about in it's home page. I have not bought a toroidal transformer yet. but the one advise was a [FONT=trebuchet ms, sans-serif]300VA Toroidal 35V - 0 -35V [/FONT]. SO I should search for a 300VA 24V-0-24V and expect a +-32V rail out of the F6 psu,
Or
I have to find the right toroidal that will allow +-24V out of the F6power supply, and those +-24V into the amp modules will give a +-32V somewhere in the amp module (bevor the transistor?)
"One big advantage of this kind of configuration is, that only one power suply is needed as all amps could be supplied from the same +-24V Transformer."
You mean that I will be able to power both the left and right channel on both the fullrange and bass drivers
Or
1 power supply for both fullrange and 1 for both bass Orone supply for one channel fullrange+bass?
Thanks a lot and best regards.
I have a lot of things to clarify ;-)
Dookie182
!
A bridged pair of amplifiers gives exactly the same total output as the pair of amplifier used in single mode. No extra energy is created.
A pair of 100W into 4ohms amplifiers when bridged gives 200W into 8ohms. Exactly the same as the total of 100W+100W as the two single amplifiers.
I don't know where you got ~150W @8ohms. Completely wrong !
The rule is:
A bridged pair of amplifiers delivers double the power into double the impedance compared to the single amplifier driving it's rated load.
Ok, I'm kind of lost on the impedance thing.
If I follow you, this means with a mono module giving 50w on 8ohm load, will give 100W on a 4ohm load.
But bridging two of those modules will give theoricaly 100w*2 on a 8ohm load or 2*50W into 16ohms. But my drivers in paralel are still a 4ohm loads right?
if you know of a great article on this that might enlight me, I'm ok ;-)
best regards
Dookie182
If I follow you, this means with a mono module giving 50w on 8ohm load, will give 100W on a 4ohm load.
But bridging two of those modules will give theoricaly 100w*2 on a 8ohm load or 2*50W into 16ohms. But my drivers in paralel are still a 4ohm loads right?
if you know of a great article on this that might enlight me, I'm ok ;-)
best regards
Dookie182
this does not follow. A 50W into 8ohms amplifier will not be able to drive a 4ohms speaker. You need a 4ohms rated amplifier. If you have a 4ohms rated amplifier that can do 100W into 4ohms you are likely to find it will also do ~60W into 8ohms.
you don't need a great article.
A pair of 4ohms amplifiers cannot drive a 4ohms speaker when bridged.
A 4ohms speaker will need two 2ohms rated amplifiers.
If you want 300W into your 4ohms speaker then you choose two 150W into 2ohms amplifiers.
Remember the rule is:
if you have two speakers and you "join" them together and use a bridged amplifier to drive the pair of drivers then you get exactly the same power into the speakers as the two separate amplifiers, you gain nothing
take your two 8ohms speakers join them together to create a 300W 4ohms speaker.
You can use two 8ohms amplifiers and drive the two 8ohms drivers to 150W each for a total of 300W into your dual driver speaker.
or
you can try to build two 150W into 2ohms amplifiers and bridge them to deliver 300W into your 4ohms equivalent dual driver speaker.
I know that it is far simpler to build a 150W into 8ohms amplifier than it is to build a 150W into 2ohms amplifier. It's down to current delivery into very low impedance.
All your effort to design a 2ohms capable amplifier is wasted design energies.
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Hi,
my calculation certainly is right.
In theory bridged amplifiers will supply 4 times the power into the same load impedance, as 2 times the signal-voltage over the load, times 2 times the signal current through the load calculates to 4 times the power.
This means a 50W@8Ohm amp bridged will deliver 200W@8Ohm
In praxis though its rather 3 times.
That´s the reason I wrote that a 50w@8Ohm amp could deliver ~150W into 8Ohm in bridged mode.
And of course may a amp also be able to drive a 4Ohm load in bridged mode if it is specced 2Ohm-capable.
Its just a question of output stage design and power supply capabilities.
As long as the current and power rating of the amp is not exceeded everything´s fine.
In case of paralleled basses - resulting in a 4Ohm load- though, it would mean that each of the two bridge parts ´sees´a 2Ohm load and that the current and power rating of the amps would be exceeded.
So in this regard is Andrew correct, as the amp would be prone to breakdown.
But my suggestion was to use a single amp of 50W@8Ohm for the Fullrange driver and two amps in bridged for each(!) bass driver, hence 5 amp modules per speaker.
The bridged amps would work perfectly stable into the 8Ohm load each bass driver presents.
In sum this would mean 50W + 2x ~150W into 8Ohms per speaker.
As the amp modules are so cheap, the extra costs remain quite manageable.
jauu
Calvin
my calculation certainly is right.
In theory bridged amplifiers will supply 4 times the power into the same load impedance, as 2 times the signal-voltage over the load, times 2 times the signal current through the load calculates to 4 times the power.
This means a 50W@8Ohm amp bridged will deliver 200W@8Ohm
In praxis though its rather 3 times.
That´s the reason I wrote that a 50w@8Ohm amp could deliver ~150W into 8Ohm in bridged mode.
And of course may a amp also be able to drive a 4Ohm load in bridged mode if it is specced 2Ohm-capable.
Its just a question of output stage design and power supply capabilities.
As long as the current and power rating of the amp is not exceeded everything´s fine.
In case of paralleled basses - resulting in a 4Ohm load- though, it would mean that each of the two bridge parts ´sees´a 2Ohm load and that the current and power rating of the amps would be exceeded.
So in this regard is Andrew correct, as the amp would be prone to breakdown.
But my suggestion was to use a single amp of 50W@8Ohm for the Fullrange driver and two amps in bridged for each(!) bass driver, hence 5 amp modules per speaker.
The bridged amps would work perfectly stable into the 8Ohm load each bass driver presents.
In sum this would mean 50W + 2x ~150W into 8Ohms per speaker.
As the amp modules are so cheap, the extra costs remain quite manageable.
jauu
Calvin
In praxis statement proves that your earlier statement must be wrong
A bridged amplifier delivers twice the power into twice the load impedance.
A bridged amplifier does not create extra power !!!!!!
Two single amplifiers rated at 100W into 8ohms can deliver a total of 200W
Two of these 100W amplifiers when bridged can deliver 200W into 16ohms.
two 50W amplifiers can deliver 100W, they CANNOT do
In every regard to what I stated I am correct.
A pair of 50W amplifiers cannot deliver more than their rated power into their rated load.
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Bridgemode amplifiers meet specific power needs where supply voltages are limited, PA users need to mix and match amps to speakers with a flexible range of products or a manufacturer wants to reduce costs by having only a few modular amplifiers, then deploying them variously in several products.
Protecting the amplifier from overloads and accidents gets complex for this mode of operation at this high power level though. I would not suggest a beginner think about it, let alone try designing a protection circuit that will be needed, if you want your amplifier to last.
Unless you think you really need hundreds of watts, you are wasting time and money building DIY domestic amplifiers this way. It is cheaper and better to start with the correct size amplifier than to stitch 2 smaller ones together. In practical terms, the benefit of doubling 8 ohm power will be hardly noticeable and only has novelty value.
Regarding bass amplification - you don't explain but I assume you mean a 2.1 system or a subwoofer is used with your system. Subwoofers mostly are self-powered and connected only by a mono or stereo line output signal from the amplifier. Look online at any user manual for AV amplifier system diagrams. There is a dedicated bass amplifier(s) if the bass box(s) is unpowered.
Simply, you don't connect subwoofers to the main stereo amplifiers because there will be no way to independently match levels. You need either powered sub(s) or unpowered boxes with separate amplifier + control preamps.
Finally, if you want a formal description of Bridge Tied Load or bridgemode ampliers there is Google and there are several articles papers and explanations on the web worth reading if you want tutorials. Use it and search them for yourself. There is also a lot of hand-waving BS about it but I'll assume you can detect the difference.
Try the last section of this project article for a brief explanation and some design details.
Protecting the amplifier from overloads and accidents gets complex for this mode of operation at this high power level though. I would not suggest a beginner think about it, let alone try designing a protection circuit that will be needed, if you want your amplifier to last.
Unless you think you really need hundreds of watts, you are wasting time and money building DIY domestic amplifiers this way. It is cheaper and better to start with the correct size amplifier than to stitch 2 smaller ones together. In practical terms, the benefit of doubling 8 ohm power will be hardly noticeable and only has novelty value.
Regarding bass amplification - you don't explain but I assume you mean a 2.1 system or a subwoofer is used with your system. Subwoofers mostly are self-powered and connected only by a mono or stereo line output signal from the amplifier. Look online at any user manual for AV amplifier system diagrams. There is a dedicated bass amplifier(s) if the bass box(s) is unpowered.
Simply, you don't connect subwoofers to the main stereo amplifiers because there will be no way to independently match levels. You need either powered sub(s) or unpowered boxes with separate amplifier + control preamps.
Finally, if you want a formal description of Bridge Tied Load or bridgemode ampliers there is Google and there are several articles papers and explanations on the web worth reading if you want tutorials. Use it and search them for yourself. There is also a lot of hand-waving BS about it but I'll assume you can detect the difference.
Try the last section of this project article for a brief explanation and some design details.
Hi,
Andrew, just do the maths and You recognize the factor of 4 times ... its simple enough.
Double-the-voltage squared, divided by impedance, equals 4 times.
A amp specced for 50W@8Ohm will maybe good for 80-90W into 4Ohms and not 100W.
Its an modulator for the power supplied by the power supply.
Neither the power supplies nor the modulators are perfect in praxis and limit the amount of power that can be delivered into the load.
More power costs more and mostly economics enforce the compromises, not technical reasons - undersized power supplies and the current paths of the amp not beefy enough.
Which is where the factor of roundabout 3x power into the same load impedance stems from.
The same reasons why most amps are only specced for 8Ohms or higher load impedances in bridged mode.
The L12 features 4x 100W-class Output transistors.
In bridged mode 4 transistors cater for each half cycle.
150W into 8Ohms requires ~6Arms, or +-9Ap-p, hence less than 2.5A peak for each transistor
So plenty reserve from this side.
Ian has made a important point though, that the L12 comes without any Protection at all.
You can buy Protection circuits for stereo amps and bridged amps on ebay, but those are rather simple, providing only for turn-on delay and DC-sensing.
They miss on overcurrent sensing.
The L12 has a couple of resistors on board that can be used for overcurrent sensing, which would be useful if You want to build a dedicated Protection circuit.
jauu
Calvin
Andrew, just do the maths and You recognize the factor of 4 times ... its simple enough.
Double-the-voltage squared, divided by impedance, equals 4 times.
The same reasons apply here why no practical amplifier reaches exactly double the power specs whith halfened load.
A amp specced for 50W@8Ohm will maybe good for 80-90W into 4Ohms and not 100W.
A amplifier doesn't create power at all.
Its an modulator for the power supplied by the power supply.
Neither the power supplies nor the modulators are perfect in praxis and limit the amount of power that can be delivered into the load.
More power costs more and mostly economics enforce the compromises, not technical reasons - undersized power supplies and the current paths of the amp not beefy enough.
Which is where the factor of roundabout 3x power into the same load impedance stems from.
The same reasons why most amps are only specced for 8Ohms or higher load impedances in bridged mode.
The L12 features 4x 100W-class Output transistors.
In bridged mode 4 transistors cater for each half cycle.
150W into 8Ohms requires ~6Arms, or +-9Ap-p, hence less than 2.5A peak for each transistor
So plenty reserve from this side.
Ian has made a important point though, that the L12 comes without any Protection at all.
You can buy Protection circuits for stereo amps and bridged amps on ebay, but those are rather simple, providing only for turn-on delay and DC-sensing.
They miss on overcurrent sensing.
The L12 has a couple of resistors on board that can be used for overcurrent sensing, which would be useful if You want to build a dedicated Protection circuit.
jauu
Calvin
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If the amplifier is capable of 80-90W into 4ohms,
then a pair connected in bridged mode will give double the power into double the impedance.
i.e. the 80-90W into 4ohms becomes 160-180W into 8ohms.
The rule holds true.
And
The total power in dual single mode and in bridged mode are exactly the same: 160-180W
then a pair connected in bridged mode will give double the power into double the impedance.
i.e. the 80-90W into 4ohms becomes 160-180W into 8ohms.
The rule holds true.
And
The total power in dual single mode and in bridged mode are exactly the same: 160-180W
ok,
thanks a lot guy for this pationate debat. On my side, I'm having more and more readings, but yes even if google is a good place to search, I found difficult to find sources that will make things understandable for my current level of knowledge, But I found an interesting start with lenard audio site and Eliott Sound Products articles. I understand that it might be troublesome or bothering for people that acquiered this knowledge a long time ago. Thanks for your understanding anyway.
As a beginner I for sure would like to keep things simple, doable and safe. I'm more on a WIY (Wire It Yourself) that a true DIY projetc. The all point is mostly to take time to read learn understand ask question etc with the aim of a system that will hopfully please my ears in the end.
I like the idear of calvin to tweak the module in order to output 50W>8ohms that seems safe and sufficient for the fullrange driver.
As for the bass drivers, I might have been bias by a review about a comparable OB speaker powered with a 500W amp.
In my case and after some though, I kind of think that I should keep things simpler. By using One module per speaker, i'll be keeping the matching impedance between amp and HP. with the active crossover, the bass HP will only handle the <310Hz frequency, so I guess that 120W in a 97Db@1w/1m will be sufficient, and keep the things safe, staying in the configuration it was designed for. I have neither the pretention nor the knowledge to build a protection circuit in order to keep the amp safe from overload.
For sure I also tought about using some L20D or L25D amp that would give me 250W into 4ohm. But I'm wondering If I should'nt just keep the same modules in order to prevent some different sonic prensentation that might sound ackwards. One L12-2 module for each drivers will provide sufficient power I guess. But as stated, I miss field practic and it's more just speculation for now.
In this configuration I'll have to use two power supply per side.
One for both the mono amp>bass drivers and a second that will feed the active crossover module and the 50W tweaked L12-2 modul for the fullranger.
Thanks anyway for all your insights.
Best regards.
thanks a lot guy for this pationate debat. On my side, I'm having more and more readings, but yes even if google is a good place to search, I found difficult to find sources that will make things understandable for my current level of knowledge, But I found an interesting start with lenard audio site and Eliott Sound Products articles. I understand that it might be troublesome or bothering for people that acquiered this knowledge a long time ago. Thanks for your understanding anyway.
As a beginner I for sure would like to keep things simple, doable and safe. I'm more on a WIY (Wire It Yourself) that a true DIY projetc. The all point is mostly to take time to read learn understand ask question etc with the aim of a system that will hopfully please my ears in the end.
I like the idear of calvin to tweak the module in order to output 50W>8ohms that seems safe and sufficient for the fullrange driver.
As for the bass drivers, I might have been bias by a review about a comparable OB speaker powered with a 500W amp.
In my case and after some though, I kind of think that I should keep things simpler. By using One module per speaker, i'll be keeping the matching impedance between amp and HP. with the active crossover, the bass HP will only handle the <310Hz frequency, so I guess that 120W in a 97Db@1w/1m will be sufficient, and keep the things safe, staying in the configuration it was designed for. I have neither the pretention nor the knowledge to build a protection circuit in order to keep the amp safe from overload.
For sure I also tought about using some L20D or L25D amp that would give me 250W into 4ohm. But I'm wondering If I should'nt just keep the same modules in order to prevent some different sonic prensentation that might sound ackwards. One L12-2 module for each drivers will provide sufficient power I guess. But as stated, I miss field practic and it's more just speculation for now.
In this configuration I'll have to use two power supply per side.
One for both the mono amp>bass drivers and a second that will feed the active crossover module and the 50W tweaked L12-2 modul for the fullranger.
Thanks anyway for all your insights.
Best regards.
Hi,
It depends simply on the power capabilities of the amplifier.
If the amplifier´s power supply and current paths are designed to cope with the increased power levels of bridging nothing blows up.
Say You want to drive a 4 Ohm load in bridged mode, each of the two amp legs ´sees´ a 2Ohm load.
If the amps are now specced to be 2Ohm or lower capable, nothing blows up at all.
It´ll only deliver between 3-4 times the power into the load.
If the amps are rated for 4Ohms load only, they will still be fine at lower levels, below their designed-in power and current limitations, but not up to full power levels that exceed the designed-in limits.
Then either their current limiter will be activated or they may indeed blow up.
Understand, that the warning of possible blowup into low impedances is a maybe- not a must-condition.
It is just a hint of the manufacturer, telling You something about the restrictions of his design, no more no less.
Let´s for example stick with the L12 and 50W@8Ohm, 100W@4Ohm requirement.
Into a 8Ohm load the limit will be the supply voltage --> voltage clipping.
Into a 4Ohm load the limit will be the allowed maximum current of the transistors --> current clipping.
For all loads below 4Ohm the limit will also be current.
And though the L12 is not explicitly specced for 2Ohm loads, it can drive 2Ohms till it runs into current clipping.
LJM specs the L12-2 for 120W into 4Ohms load with +-24V supplies.
This indicates a current capability of at least +-7.75App.
This then calculates to 60W into 2Ohms.
So bridged mode operation into 4 Ohms is possible up to 180W-240W into a 4Ohm load.
So my guess of 150W@4Ohms is already conservative.
jauu
Calvin
That claim may hold true in many cases, but is not allways right.
It depends simply on the power capabilities of the amplifier.
If the amplifier´s power supply and current paths are designed to cope with the increased power levels of bridging nothing blows up.
Say You want to drive a 4 Ohm load in bridged mode, each of the two amp legs ´sees´ a 2Ohm load.
If the amps are now specced to be 2Ohm or lower capable, nothing blows up at all.
It´ll only deliver between 3-4 times the power into the load.
If the amps are rated for 4Ohms load only, they will still be fine at lower levels, below their designed-in power and current limitations, but not up to full power levels that exceed the designed-in limits.
Then either their current limiter will be activated or they may indeed blow up.
Understand, that the warning of possible blowup into low impedances is a maybe- not a must-condition.
It is just a hint of the manufacturer, telling You something about the restrictions of his design, no more no less.
Let´s for example stick with the L12 and 50W@8Ohm, 100W@4Ohm requirement.
Into a 8Ohm load the limit will be the supply voltage --> voltage clipping.
Into a 4Ohm load the limit will be the allowed maximum current of the transistors --> current clipping.
For all loads below 4Ohm the limit will also be current.
And though the L12 is not explicitly specced for 2Ohm loads, it can drive 2Ohms till it runs into current clipping.
LJM specs the L12-2 for 120W into 4Ohms load with +-24V supplies.
This indicates a current capability of at least +-7.75App.
This then calculates to 60W into 2Ohms.
So bridged mode operation into 4 Ohms is possible up to 180W-240W into a 4Ohm load.
So my guess of 150W@4Ohms is already conservative.
jauu
Calvin
Yes, very much so.
One must operate the equipment within the limitations of the manufacturer's specification.
Asking an 8ohms amplifier to operate with an effective 4ohms load does not improve reliability.
Similarly asking a 4ohms amplifier to operate with an effective 2ohms load does not improve reliability.
Hi,
@Sajti
Man, You´re right. I cited wrong.
LJM talks about the AC transformer voltage not the DC supply rails.
2x 24V transformer is just sufficient for 120W@4Ohms
@Andrew
LJM suggests a range of transformer voltages, depending on the load impedances.
Up to 2x 36V AC @8Ohms for 120W max.
He suggests 2x 24 @4Ohms for 120W max, already indicating a close current limit.
He could also have suggested a 2x 18V transformer for 120W into 2Ohms.
Staying within these limits and everything is fine, exceeding them, Yes, face the conseqences.
But anyway, to return to the original Q:
If supplied from a 2x24V transformer the L12-2 will be good for ~55W@8Ohm in single mode and theoretical 220W, practical 150-180W@8Ohm in bridged mode.
The three drivers only require the useage of 5 amplifier modules.
jau
Calvin
@Sajti
Man, You´re right. I cited wrong.
LJM talks about the AC transformer voltage not the DC supply rails.
2x 24V transformer is just sufficient for 120W@4Ohms
@Andrew
LJM suggests a range of transformer voltages, depending on the load impedances.
Up to 2x 36V AC @8Ohms for 120W max.
He suggests 2x 24 @4Ohms for 120W max, already indicating a close current limit.
He could also have suggested a 2x 18V transformer for 120W into 2Ohms.
Staying within these limits and everything is fine, exceeding them, Yes, face the conseqences.
But anyway, to return to the original Q:
If supplied from a 2x24V transformer the L12-2 will be good for ~55W@8Ohm in single mode and theoretical 220W, practical 150-180W@8Ohm in bridged mode.
The three drivers only require the useage of 5 amplifier modules.
jau
Calvin
A second set of drivers + 2pairs of OPs?
Hi Calvin,
If the Predrivers can drive another set of OP drivers + 2 pairs of additional OP Trs. then with an add. on pcb bracket for the new added set of add. drivers + OPS the Current & Voltage SOA is solved, thus preserving the sound signature of the main AMP modules, within all V DC ranges LJM specified as a workable options, the main Transformers power rating needs to be increased accordingly to max total power needed + the PSU caps and it can fit nicely in to the multi AMP Project here.
BRgds,
Andreas
Hi Calvin,
If the Predrivers can drive another set of OP drivers + 2 pairs of additional OP Trs. then with an add. on pcb bracket for the new added set of add. drivers + OPS the Current & Voltage SOA is solved, thus preserving the sound signature of the main AMP modules, within all V DC ranges LJM specified as a workable options, the main Transformers power rating needs to be increased accordingly to max total power needed + the PSU caps and it can fit nicely in to the multi AMP Project here.
BRgds,
Andreas
Hi,
the CFP Output stage is a bit critical regarding paralleling of output transistors, more than the traditional EF stage.
It may well be that adding output pairs results in oscillations.
The idea of bridging avoids that risc and allows for a simpler power supply design with only one single set of supplies rails and it insures the same sonic fingerprint over the full audio bandwidth.
jauu
Calvin
the CFP Output stage is a bit critical regarding paralleling of output transistors, more than the traditional EF stage.
It may well be that adding output pairs results in oscillations.
The idea of bridging avoids that risc and allows for a simpler power supply design with only one single set of supplies rails and it insures the same sonic fingerprint over the full audio bandwidth.
jauu
Calvin