Is a parallel amp the same as a balanced amp?

[Nick]

Hello all,

The differences between a parallel amplifier and a balanced amplifier
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...

Just curious,

-Nick

 

[Eeyore]

Nick wrote:

Hello all,

The differences between a parallel amplifier and a balanced amplifier
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...

Is this what you mean ?
http://en.wikipedia.org/wiki/Bridged_and_paralleled_amplifiers

Graham

 

[John Popelish]

Nick wrote:

Hello all,

The differences between a parallel amplifier and a balanced amplifier
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...

I'm not sure where you found a parallel amp, but it can
hardly be the same as a balanced amplifier because the two
outputs of a balanced (bridged amplifier) are in series,
with the load between them. This increases the total
voltage applied to the load.

I can only assume that paralleled amplifiers are just
connected in parallel (to raise the total output current
capability) with the load connected between that node and
the signal common (ground).

So if you need more voltage for the load, use a balanced
configuration. If you need more current for the load, use
the parallel configuration.

--
Regards,

John Popelish

 

[BobG]

'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. 'Bridge'
sticks an inverter in front of one channel so they are out of phase...
one red wire is going positive and the other one is going negative....
hook the speakers up to the two red terminals for more ooomph. I've
never heard the term 'balanced amp' but it sort of sounds like the
bridged definition I just tried to explain. Hope it helped.

 

[CampKohler]

On May 19, 5:41 pm, Nick <nick.adam...@yahoo.com> wrote:

Hello all,

The differences between a parallel amplifier and a balanced amplifier
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...

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.

 

[legg]

On Tue, 20 May 2008 11:12:04 -0700 (PDT), Nick
<nick.adams95@yahoo.com> wrote:

On May 19, 11:53 pm, CampKohler <lug...@hotmail.com> wrote:
On May 19, 5:41 pm, Nick <nick.adam...@yahoo.com> wrote:

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 90ş
hybrid power divider at their input and a 90ş 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

 

[Nick]

On May 19, 11:53 pm, CampKohler <lug...@hotmail.com> wrote:

On May 19, 5:41 pm, Nick <nick.adam...@yahoo.com> wrote:

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...

Just curious,

-Nick

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.Balancedmeans 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 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 90ş
hybrid power divider at their input and a 90ş 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

 

[BobG]

Who would have thought that 'amplifier' without 'rf' in front of it
meant audio? Only about 99 out of 100 I bet. Fooled me!

 

[Eeyore]

BobG wrote:

Who would have thought that 'amplifier' without 'rf' in front of it
meant audio? Only about 99 out of 100 I bet. Fooled me!

Well, it didn't fool me which is why I asked "is this what you mean ?".

Nevertheless, a classic example of why it's best to provide more rather
than less info when asking such a question.

Graham

 

[Frank Raffaeli]

On May 20, 1:12 pm, Nick <nick.adam...@yahoo.com> wrote:

On May 19, 11:53 pm, CampKohler <lug...@hotmail.com> wrote:



On May 19, 5:41 pm, Nick <nick.adam...@yahoo.com> wrote:

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...

Just curious,

-Nick

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.Balancedmeans 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 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 90ş
hybrid power divider at their input and a 90ş 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

Sounds like a continuation from the other thread ...
An RF balanced amplifier usually refers to a 180-degree phase split,
not 90. The main reason to use a balanced amp is to suppress the 2nd
(and other even order) harmonics.

The main reason to use a 90-degree split is to match the amplifier
over a broader bandwidth, and to realize a good match at the optimum
noise figure (Zopt).

So ... you still didn't answer the question: what linearity do you
need?

Frank

 

[Nick]

On May 21, 7:02 am, "Steve" <sNodots.bu...@Nodots.jomega.com> wrote:

"Nick" <nick.adam...@yahoo.com> wrote in message

news:30acee9a-6448-46ab-bbbd-57809a53254c@k1g2000prb.googlegroups.com...
On May 19, 11:53 pm, CampKohler <lug...@hotmail.com> wrote:





On May 19, 5:41 pm, Nick <nick.adam...@yahoo.com> wrote:

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...

Just curious,

-Nick

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.Balancedmeans 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 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 90ş
hybrid power divider at their input and a 90ş 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

In this context, the balanced amp is usually used to cancel second order
harmonics and second order intermod products. By careful matching of the
phase shifts, you can get around 40 dB improvements in IP2, sometimes more,
along with the 3 dB additional gain of the fundamental. Usually seen when
the band is more than an octave wide, because second order intermods
generated by 2 signals at the low end will be in-band near the top of the
band.

Steve- Hide quoted text -

- Show quoted text -

Thanks for all the clarifying answers guys. Now it's finally clear!
(Frank, linearity is not an issue for me, since I was just trying to
fill in one of the many gaps in my electronics knowledge, and not
actually trying to build either a parallel or balanced amplifier).

Best regards,

-Nick