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Old 17th April 2003, 07:40 AM   #1
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Default From two amps stereo to single amp balanced?

Hi!

I am using a single LCAudio The End Millenium Board as a mono subwoofer amp, via normal cinch input.

Now I also have a second LC EM board lying around , and I thought about using that one to increase the output power of my amp, but without the side effects of bridging (being forced to use a load of 8 ohms, or lower voltage).

So I thought about if it was possible to use just one board for the positive signal, and the other board for the negative signal, thus resulting in twice the output power...???

I think that could easily be implemented via a balanced input, am I right?

Since I can program my DSP in a way, simply using a normal signla for one side of the amp, and a phase reversed for the other wouldn't do the trick, would it? Since each part of the amp would still get the complimentary signal (+ / -). Maybe I could use my OPA134 lying around...???

Is that possible at all, or does it require changing the layout of the amps?

Thanks for suggestions,


Arndt
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Old 17th April 2003, 08:42 AM   #2
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Off the top of my head and without seeing a schematic, i'd say that this will probably require some pretty major changes to the circuit.
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Old 17th April 2003, 01:17 PM   #3
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Default Re: From two amps stereo to single amp balanced?

Quote:
Originally posted by Cradle22

Now I also have a second LC EM board lying around , and I thought about using that one to increase the output power of my amp, but without the side effects of bridging (being forced to use a load of 8 ohms, or lower voltage).

So I thought about if it was possible to use just one board for the positive signal, and the other board for the negative signal, thus resulting in twice the output power...???

I think that could easily be implemented via a balanced input, am I right?
But that is bridging!

What you do when you bridge is invert the phase of one amp so you float the speaker from ground.

As most amps are positive phase, bridging is achieved by inverting the phase of one amp and connecting the speaker from both outputs.

If the amp were totally balanced, from input to output, you wouldn't need the inverting stage.

The limits in power and load are mostly due to small power supplies, few or weak output transistors and small heatsinks.

That's why voltage is lowered.

Do you know the minimum impedance of you speaker?


Carlos
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Old 17th April 2003, 02:04 PM   #4
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carlmart,

What cradle22 has tried to describe is not really bridging because only the +ve output will be driven. The way I read it, he essentially wants the following:

*Only +ve output terminal driven

*One of the amplifiers only sees the +ve 1/2 of the signal and the other amplifier only sees the -ve 1/2 of the signal.

In effect, you would end up with one amplifier (the one that handles the +ve 1/2 of the signal) having it's dc output level referenced to it's Vdd and the other amplifier (the one that handles the -ve 1/2 of the signal) having it's dc output level referenced to it's Vcc. So if each board uses say +/- 25V, you'd end with one amplifier running off +50V/0V and the other amplifier running off 0V/-50V. You'd then have each side of each transformer handle 1/2 of the signal seen by that amplifier or 1/4 of the total signal. In other words, you'd get 3 crossover points in the output waveform. This kinda of topology is doable but you probably wouldnt have much left of the original amplifier if you wanted to modify a normal amp to function in this fashion.
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Old 17th April 2003, 05:16 PM   #5
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Hi!

Quote:
Originally posted by AudioFreak
carlmart,

What cradle22 has tried to describe is not really bridging because only the +ve output will be driven. The way I read it, he essentially wants the following:

*Only +ve output terminal driven

*One of the amplifiers only sees the +ve 1/2 of the signal and the other amplifier only sees the -ve 1/2 of the signal.

In effect, you would end up with one amplifier (the one that handles the +ve 1/2 of the signal) having it's dc output level referenced to it's Vdd and the other amplifier (the one that handles the -ve 1/2 of the signal) having it's dc output level referenced to it's Vcc. So if each board uses say +/- 25V, you'd end with one amplifier running off +50V/0V and the other amplifier running off 0V/-50V. You'd then have each side of each transformer handle 1/2 of the signal seen by that amplifier or 1/4 of the total signal. In other words, you'd get 3 crossover points in the output waveform. This kinda of topology is doable but you probably wouldnt have much left of the original amplifier if you wanted to modify a normal amp to function in this fashion.

Yeah, I would say that what you describe is exactly what I would like to do (or would have liked to be doing )...

Btw., of course I meant BB DRV134 as balancing OP, not OPA134...

But I also got deeper into (Assembler) DSP programming today, and I also could achieve the balancing of the signal inside of the DSP (comparatively easy to do...)

If I understand you right, it would require modifying both mono amps so that each of them puts the full available voltage to the signal part it receives (either + or -), and not just exactly half of it...??

Yeah, at least with the LCAudio amps that would be overkill... (very complex circuit and SMD)...

But with other, not so complex circuits, like P3A from R. Elliot, or his 300W Subwoofer amp, maybe a modification would not be nearly impossible...?

Who knows... I'm having enough to build right now, but later this year...


Thanks anyway,


Arndt
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