Is a parallel amp the same as a balanced amp?
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Posted by Phil Allison on May 19, 2008, 11:44 pm
Please log in for more thread options "BobG" ** Watch out !!!! Having a "mono' switch does NOT = parallel operation of the power amps !!! Only a very few amps ( notably some Crown models ) have the ability to parallel the speaker outputs with safety. The others will BLOW UP if you dare try it. > 'Bridge'
> sticks an inverter in front of one channel so they are out of phase... ** Mostly, yes. But it only takes one resistor, connected from ch A's output to ch B's inverting input, ( virtual earth point ) to get ch A to drive ch B with equal level & reverse polarity. > never heard the term 'balanced amp' but it sort of sounds like the
> bridged definition I just tried to explain. ** The OP is a fuckwit - omitting all context from his asinine Q. ..... Phil | |||||||||||||||||||
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Posted by CampKohler on May 20, 2008, 2:53 am
Please log in for more thread options > Hello all,
> > The differences between a parallel amplifier and a balanced amplifier > is rather confusing. =A0Are they the same, or are they different? =A0Both > these circuits, and their advantages, appear to be very close to each > other, if not the same... > > Just curious, > > -Nick Parallel refers to the configuration of an amplifier's output circuit. And now for something completely different. Balanced refers to the nature of the either input or output signals. Balanced means that the two lines of the output are referenced to each other and not to ground; the input's or load's voltage is measured between two lines and voltages present on either line (as measured to ground) are typically unintentional, undesired and are to be rejected as extraneous. This is good for long runs, e.g. between a mic and an amp input, because noise is mostly referenced to ground and is so theoretically rejected. Whatever noise hits one line also hits the other and so is ideally cancelled. Unbalanced signals are measured to ground, so are limited to short runs where they won't be susceptible to noise pickup, e.g. between adjacent audio components. (The run to a speaker is typically long, but can get away with an unbalanced line by virture of a speaker's low impedance, making it much, much less susceptible to noise. If someone went crazy and designed a high-impedance speaker circuit, it would benefit from a balanced output, too. Nobody's been that crazy yet.) As you might guess, a mic input, say, that is both balanced AND low impedance, is the double-whammy for quietness. Professional mic inputs are that way. Cheapo mic inputs are high-impedance and unbalanced, the worst case, so they rely simply on short runs to avoid noise. If you have to carry signals between two buildings that use separate ground systems that may have a small difference between them (or a large one if lightning or other surges strike!), then a balanced system would be preferable so that the signals ignore the ground as much as possible. Whole books are written on signals, grounding and noise reduction tecniques. Many books. They come with magic wands. | |||||||||||||||||||
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Posted by Nick on May 20, 2008, 2:12 pm
Please log in for more thread options >
> > Hello all,
>
> > The differences between a parallelamplifierand abalancedamplifier
h
> > is rather confusing. =A0Are they the same, or are they different? =A0Bot= > > these circuits, and their advantages, appear to be very close to each
> > other, if not the same... >
> > Just curious,
>
> > -Nick
>
dmeans that the two lines of the output are referenced to each
> Parallel refers to the configuration of anamplifier'soutput circuit. > And now for something completely different. > > Balancedrefers to the nature of the either input or output signals.Balance= > other and not to ground; the input's or load's voltage is measured
> between two lines and voltages present on either line (as measured to > ground) are typically unintentional, undesired and are to be rejected > as extraneous. This is good for long runs, e.g. between a mic and an > amp input, because noise is mostly referenced to ground and is so > theoretically rejected. Whatever noise hits one line also hits the > other and so is ideally cancelled. > > Unbalanced signals are measured to ground, so are limited to short > runs where they won't be susceptible to noise pickup, e.g. between > adjacent audio components. (The run to a speaker is typically long, > but can get away with an unbalanced line by virture of a speaker's low > impedance, making it much, much less susceptible to noise. If someone > went crazy and designed a high-impedance speaker circuit, it would > benefit from abalancedoutput, too. Nobody's been that crazy yet.) > > As you might guess, a mic input, say, that is bothbalancedAND low > impedance, is the double-whammy for quietness. Professional mic inputs > are that way. Cheapo mic inputs are high-impedance and unbalanced, the > worst case, so they rely simply on short runs to avoid noise. If you > have to carry signals between two buildings that use separate ground > systems that may have a small difference between them (or a large one > if lightning or other surges strike!), then abalancedsystem would be > preferable so that the signals ignore the ground as much as possible. > Whole books are written on signals, grounding and noise reduction > tecniques. Many books. They come with magic wands. Thanks guys for the great input. The "parallel amplifiers" that I am speaking of are for HF PAs and LNAs, and are in parallel with each other and have Wilkinson dividers at their input and output. But the "balanced amplifiers" I have seen are also in parallel, but have a 90=BA hybrid power divider at their input and a 90=BA hybrid power combiner at their output. They look so darn close to each other, both circuit- wise and performance-wise, that it starts to get a bit confusing! Best, -Nick | |||||||||||||||||||
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Posted by BobG on May 20, 2008, 2:21 pm
Please log in for more thread options Who would have thought that 'amplifier' without 'rf' in front of it
meant audio? Only about 99 out of 100 I bet. Fooled me! | |||||||||||||||||||
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Posted by legg on May 20, 2008, 4:11 pm
Please log in for more thread options On Tue, 20 May 2008 11:12:04 -0700 (PDT), Nick
>>
>> > Hello all,
>>
>> > The differences between a parallelamplifierand abalancedamplifier
>> > is rather confusing. Are they the same, or are they different? Both >> > these circuits, and their advantages, appear to be very close to each >> > other, if not the same... >
> Thanks guys for the great input. The "parallel amplifiers" that I >am speaking of are for HF PAs and LNAs, and are in parallel with each >other and have Wilkinson dividers at their input and output. But the >"balanced amplifiers" I have seen are also in parallel, but have a 90º >hybrid power divider at their input and a 90º hybrid power combiner at >their output. They look so darn close to each other, both circuit- >wise and performance-wise, that it starts to get a bit confusing! > A parallel voltage amplifier can take the form of a 'compound' amplifier, where one provides the power and another provides the signal (cancelling the PA noise), whether the resulting circuit is balanced or not. An RF PA with a low frequency modulator is another form of parallel amplification, whether the resulting output is balanced or not. In fact you can't really apply voltages in parallel; they have to be isolated by identifiable impedances. Operating them in series is tricky in concept, but fairly common in practice; directly at low frequencies and magnetically coupled at higher frequencies. RL | |||||||||||||||||||
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> 'Balanced input' means it can take a differential signal on a 'cannon
> mic connector'. 'Parallel' is just a stereo-mono switch that lets one
> channel drive both amp channels in phase and in parallel.