Hi. I'm wondering if there's such a thing as a universal paralleling 'box' you can plug two identical mono amps into to lower impedance capability. G.A.S. aka James Bongiorno did produce a bridging box called "The Bridge" for bridging their amps which was a universal circuit. TIA
Bridging actually worsens the low impedance drive capability, since the maximum output current
is not increased, but the minimum acceptable load doubles. Very different.
There would have to be series balancing resistors involved for paralleling. These days, just buying
a higher power class D amplifier is simpler.
is not increased, but the minimum acceptable load doubles. Very different.
There would have to be series balancing resistors involved for paralleling. These days, just buying
a higher power class D amplifier is simpler.
Hi Rayma. Thank you. Yes I'm aware of that. I mentioned it as a parallel(no pun intended), design philosophy. I'm also aware of the series resistor requirement for paralleling. So my question is, are they specific to the amps in question or would it be a universal circuit. I'm asking about ss. Specifically Boothroyd Stuart Meridian 105 circa 1978. I have two pairs of these and am interested in how they would perform paralleled.
Paralleling them would be worse then bridging them. This as you already mentioned need a resistor added on every output. This resistor will be higher then the internal resistance of 2 amps bridged.
How well two amps will perform paralleled is largely a function of how well their gains match over the whole frequency band. There won't be a universal box to yoke together two amps without addressing this issue.
Paralleling is asking for trouble. If you use them in biamp system with active crossover, you can achieve better results.
That has 100W per channel, do you really need even that much power? And 200W is only 3dB more.
You could bi-amp and go dsp instead of passive crossovers (not that I'm recommending that).
rayma is correct. It makes more sense to purchase a larger amplifier.
Years ago approximately 1960 or there abouts Altec Lansing published a technical paper on paralleling 70 volt amplifiers and this required a rather large resistor in edition to a 70 volt output transformer to complete the parallel process. About 30 years ago I had a box from Altec that allowed one to parallel two similar amplifiers. Back then the availability of anything above say 200 watts was unheard of but in todays world amplifiers of 1000 watts on up are common place.
To be blunt it makes no sense to parallel two amplifiers when larger stable amplifiers are available.
With respect to bridging....
As mentioned the power will increase to a factor of 4 depending on the power supply capabilities and the output stage. But as in the example I will mention the impedance at which the output is both safe and stable changes. Take for example an Altec Lansing 9440 which is rated at 200 watts @ 8 ohms, 400@ 4 ohms. When switched to bridge mode the minimum impedance for the load drops to 8 ohms and the power capability is raised to 800 watts for the ONE channel bridging comprises. Lost is the ability of the amplifier to drive 4 ohm loads in stereo mode. Despite the amplifiers rather large output stage its current capabilities are lower.
Why? To increase the maximum power output at low loads? To reduce distortion? Something else?
I believe distortion would increase. I think you would be better off selling them and purchasing a larger better sounding amplifier.
Is the speaker a relatively low impedance? Otherwise, bridging would make more sense
for increased headroom, since the voltage output doubles.
Crown did have a series of amplifiers capable by the flip of a switch to drive a low impedance load. These were available in both 70 volt and 8 ohm. This technology dates back to the 80's/90's before large amplifiers capable of driving low impedance loads were available. Also, if memory is correct the two channels in these amplifiers were very closely matched for output. Yes, they would drive low impedance loads with increased power the opposite of bridged amplifiers which require a higher impedance load.
The benefit at the time was increased power capability and the ability to drive a lower impedance load. The drawback my opinion here....they generally sounded like crap with distortion readings that didn't jive with the published specs unless the amplifier was new out of the box or didn't have much time under its belt.
Hurt them or tax them hard and they generally didn't sound right after that....again from memory.
My suggestion still remains to sell what you have and move on to a better larger amplifier with more headroom and more power.
By the way....what speakers are you using?
The benefit at the time was increased power capability and the ability to drive a lower impedance load. The drawback my opinion here....they generally sounded like crap with distortion readings that didn't jive with the published specs unless the amplifier was new out of the box or didn't have much time under its belt.
Hurt them or tax them hard and they generally didn't sound right after that....again from memory.
My suggestion still remains to sell what you have and move on to a better larger amplifier with more headroom and more power.
By the way....what speakers are you using?
"https://www.diyaudio.com/forums/solid-state/335337-stand-bridging-box.html"]stand alone bridging box a recent thread of yours
It seems like you still may have some misconception on how bridging works and are still confused.
The difference between Parallel and bridge I will attempt to explain.
In Bridging one channel amplifies the positive wave form and the other amplifier the negative wave form. The power factor is increased to almost 4X depending on the robustness of the power supply and there is no guarantee for example a bridged 80 watt stereo amplifier will produce 320 watts bridged into a 8 ohm load. If the power supply starts to sag the power will start to drop off.
The magic box with James sold is nothing more that a circuit that inverts the signal so that an out of phase signal can be fed into the other channel. James didn't pioneer the circuit and the circuit can be made using a simple opamp and a few parts and its nothing magic.
The parallel setup requires that the amplifiers be very closely matched in power output from a few millivolts of signal to their required signal to produce full power which if memory is correct requires some additional circuity. Any misalignment will result in increased distortion and you can surely try this and easily see what I am trying to explain by looking at your distortion analyzer and scope.
What you we looking for when we chance bridging an amplifier? Or Parallel an amplifier? Well, my opinion here again based on my stupidity in the past.
I bridged three Klipsch Heresy speakers in my home theater system because I was convinced at the time it would result in a better sound. I owned (5) Altec Lansing 9440's capable of 800 watts each in bridge mode. Why not bridge the amps and run the Heresys with 800 watt capable amps? Right? So I bridged three 9440's and ran my center, right, and left speakers with the amps. The results were interesting the bass seemed quicker and more defined and in my mind I was convinced I made the right choice that is until I removed the front covers on the speakers and noticed that the dust cap started to shift on the low frequency drivers.
So, one must consider if the outcome will justify the chance encounter with more power and are the results worth the gamble.
I did by the way finally settle for (5 mono block's) of lower power capabilities to run the theater system. I finally did away with the theater system in 2009 when we sold the house and purchased a new one.
It seems like you still may have some misconception on how bridging works and are still confused.
The difference between Parallel and bridge I will attempt to explain.
In Bridging one channel amplifies the positive wave form and the other amplifier the negative wave form. The power factor is increased to almost 4X depending on the robustness of the power supply and there is no guarantee for example a bridged 80 watt stereo amplifier will produce 320 watts bridged into a 8 ohm load. If the power supply starts to sag the power will start to drop off.
The magic box with James sold is nothing more that a circuit that inverts the signal so that an out of phase signal can be fed into the other channel. James didn't pioneer the circuit and the circuit can be made using a simple opamp and a few parts and its nothing magic.
The parallel setup requires that the amplifiers be very closely matched in power output from a few millivolts of signal to their required signal to produce full power which if memory is correct requires some additional circuity. Any misalignment will result in increased distortion and you can surely try this and easily see what I am trying to explain by looking at your distortion analyzer and scope.
What you we looking for when we chance bridging an amplifier? Or Parallel an amplifier? Well, my opinion here again based on my stupidity in the past.
I bridged three Klipsch Heresy speakers in my home theater system because I was convinced at the time it would result in a better sound. I owned (5) Altec Lansing 9440's capable of 800 watts each in bridge mode. Why not bridge the amps and run the Heresys with 800 watt capable amps? Right? So I bridged three 9440's and ran my center, right, and left speakers with the amps. The results were interesting the bass seemed quicker and more defined and in my mind I was convinced I made the right choice that is until I removed the front covers on the speakers and noticed that the dust cap started to shift on the low frequency drivers.
So, one must consider if the outcome will justify the chance encounter with more power and are the results worth the gamble.
I did by the way finally settle for (5 mono block's) of lower power capabilities to run the theater system. I finally did away with the theater system in 2009 when we sold the house and purchased a new one.
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I ran across something that maybe might explain what I was attempting to get at.
Paralleled amplifier
A paralleled amplifier configuration uses multiple amplifiers in parallel, i.e., two or more amplifiers operating in-phase into a common load.
In this mode the available output current is doubled but the output voltage remains the same. The output impedance of the pair is now halved.
The image shows two identical amplifiers A1 and A2 connected in parallel configuration. This configuration is often used when a single amplifier is incapable of being operated into a low impedance load or dissipation per amplifier is to be reduced without increasing the load impedance or reducing power delivered to the load. For example, if two identical amplifiers (each rated for operation into 4 ohm) are paralleled into a 4 ohm load, each amplifier sees an equivalent of 8 ohm since the output current is now shared by both amplifiers — each amplifier supplies half the load current, and the dissipation per amplifier is halved. This configuration (ideally or theoretically) requires each amplifier to be exactly identical to the other(s), or they will appear as loads to each other. Practically, each amplifier must satisfy the following:
Each amplifier must have as little output DC offset as possible (ideally zero offset) at no signal, otherwise the amplifier with the higher offset will try to drive current into the one with lesser offset thereby increasing dissipation. Equal offsets are also not acceptable since this will cause unwanted current (and dissipation) in the load. These are taken care of by adding an offset nulling circuit to each amplifier.
The gains of the amplifiers must be as closely matched as possible so that the outputs don't try to drive each other when signal is present. A simple and robust solution is to use paralleled voltage followers, which by design have exactly unity gain, driven by a common voltage amplification stage.
In addition, small resistors (much less than the load impedance, not shown in the schematic) are added in series with each amplifier's output to enable proper current sharing between the amplifiers. These resistances are necessary because the output impedance of the two amplifiers will not, due to manufacturing variation, be perfectly identical. Introduction of output resistors isolates this imbalance and prevents problematic interactions between the two amplifiers.
Another method of paralleling amplifiers is to use current drive. With this approach the close matching and resistances are not needed.
Paralleled amplifier
A paralleled amplifier configuration uses multiple amplifiers in parallel, i.e., two or more amplifiers operating in-phase into a common load.
In this mode the available output current is doubled but the output voltage remains the same. The output impedance of the pair is now halved.
The image shows two identical amplifiers A1 and A2 connected in parallel configuration. This configuration is often used when a single amplifier is incapable of being operated into a low impedance load or dissipation per amplifier is to be reduced without increasing the load impedance or reducing power delivered to the load. For example, if two identical amplifiers (each rated for operation into 4 ohm) are paralleled into a 4 ohm load, each amplifier sees an equivalent of 8 ohm since the output current is now shared by both amplifiers — each amplifier supplies half the load current, and the dissipation per amplifier is halved. This configuration (ideally or theoretically) requires each amplifier to be exactly identical to the other(s), or they will appear as loads to each other. Practically, each amplifier must satisfy the following:
Each amplifier must have as little output DC offset as possible (ideally zero offset) at no signal, otherwise the amplifier with the higher offset will try to drive current into the one with lesser offset thereby increasing dissipation. Equal offsets are also not acceptable since this will cause unwanted current (and dissipation) in the load. These are taken care of by adding an offset nulling circuit to each amplifier.
The gains of the amplifiers must be as closely matched as possible so that the outputs don't try to drive each other when signal is present. A simple and robust solution is to use paralleled voltage followers, which by design have exactly unity gain, driven by a common voltage amplification stage.
In addition, small resistors (much less than the load impedance, not shown in the schematic) are added in series with each amplifier's output to enable proper current sharing between the amplifiers. These resistances are necessary because the output impedance of the two amplifiers will not, due to manufacturing variation, be perfectly identical. Introduction of output resistors isolates this imbalance and prevents problematic interactions between the two amplifiers.
Another method of paralleling amplifiers is to use current drive. With this approach the close matching and resistances are not needed.
Paralleled amplifier
Attached is a simple diagram of a paralleled amplifier
Attached is a simple diagram of a paralleled amplifier
Attachments
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You see the LM3886 x3 Paralleled amps all the time giving output over 120wpc . Never really thought that it was a relative "downgrade" at the expense of more power.
But I also always thought it would be best just to add amps to each driver (Bi-Amp - Tri-Amp)...
And just to add to my own confusion - this "downgrade" does not apply to adding paralleled output devices on an amp module (ie - Pass Aleph Mini to Aleph 5, etc)... or is it?
But I also always thought it would be best just to add amps to each driver (Bi-Amp - Tri-Amp)...
And just to add to my own confusion - this "downgrade" does not apply to adding paralleled output devices on an amp module (ie - Pass Aleph Mini to Aleph 5, etc)... or is it?