quad 303 bridging
Ken
anyone have any info on this or is there a website with information.
Thanks
Graham Mayor
bi-wirable speakers, there is no need to bridge the amps. Connect one
channel to the hf connector, the other to the lf connector and bridge the
input with a 'Y' connector or soldered link.
--
<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
Graham Mayor <gma...@btinternet.com>
<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
"Ken" <ke...@netcom.ca> wrote in message
news:a7vY6.38644$TW.1...@tor-nn1.netcom.ca...
Jim Lesurf
<ke...@netcom.ca> wrote:
> I've been able to get another quad 303 and would like to bridge them.
> Does anyone have any info on this or is there a website with information.
Do you mean 'bridge' or 'parallel'?
Using a pair in opposition (bridge) nominally means double the voltage
capability but leaves the current capability unchanged. The 303 means '30
Volts, 3 Amps', hence bridging may not mean you can play any louder unless
the speaker impedance is reasonably high. i.e. Being able to output up to
60 volts may not be much use if the available current is only about 3 amps.
Paralleling would nominally double the current available. This may be more
useful with speakers that have low impedance. However it more tricky to do.
Slainte,
Jim
--
Electronics http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
MMWaves http://www.st-and.ac.uk/~www_pa/Scots_Guide/MMWave/Index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html
Dave Plowman
> Using a pair in opposition (bridge) nominally means double the voltage
> capability but leaves the current capability unchanged. The 303 means
> '30 Volts, 3 Amps', hence bridging may not mean you can play any louder
> unless the speaker impedance is reasonably high. i.e. Being able to
> output up to 60 volts may not be much use if the available current is
> only about 3 amps.
Quad 'knockers' used to say the problem with the 303 was its brick wall
current and voltage limiting. So using it in bridge configuration should
get round at least one of these..
--
* I believe five out of four people have trouble with fractions. *
Dave Plowman dave....@argonet.co.uk London SW 12
RIP Acorn
Jim Lesurf
<dave....@argonet.co.uk> wrote:
> In article <4a8e832...@st-and.demon.co.uk>, Jim Lesurf
> <jc...@st-and.demon.co.uk> wrote:
> > Do you mean 'bridge' or 'parallel'?
> > Using a pair in opposition (bridge) nominally means double the voltage
> > capability but leaves the current capability unchanged.
> Quad 'knockers' used to say the problem with the 303 was its brick wall
> current and voltage limiting. So using it in bridge configuration should
> get round at least one of these..
Alas, probably the 'wrong one'. :-/ 303 implies that the optimum load for
max power output is around 10 Ohms. Bridging in opposition would mean the
optimum changes to 20 Ohms. Thus if your speaker has an impedance of 10
Ohms or less, then bridging won't really make any difference. Clearly this
depends upon the speaker, but I suspect people are more likely to be
encounting loads below 10 Ohms than above.
Stewart Pinkerton
>In article <4a8e832...@st-and.demon.co.uk>,
> Jim Lesurf <jc...@st-and.demon.co.uk> wrote:
>> Do you mean 'bridge' or 'parallel'?
>
>> Using a pair in opposition (bridge) nominally means double the voltage
>> capability but leaves the current capability unchanged. The 303 means
>> '30 Volts, 3 Amps', hence bridging may not mean you can play any louder
>> unless the speaker impedance is reasonably high. i.e. Being able to
>> output up to 60 volts may not be much use if the available current is
>> only about 3 amps.
>
> Quad 'knockers' used to say the problem with the 303 was its brick wall
>current and voltage limiting. So using it in bridge configuration should
>get round at least one of these..
Not really, since it halves the current capability! A bridged amp
'sees' half the actual speaker impedance, and the 303 is already
*very* weedy by modern standards. Bridging 303s is simply not a good
idea - indeed, the professional variant used by the BBC, the 50E, was
basically two 303 channels in parallel.
--
Stewart Pinkerton | Music is art, audio is engineering
Jim Lesurf
<pat...@popmail.dircon.co.uk> wrote:
> Dave Plowman <dave....@argonet.co.uk> writes:
> >
> > Quad 'knockers' used to say the problem with the 303 was its brick
> >wall current and voltage limiting. So using it in bridge configuration
> >should get round at least one of these..
> Not really, since it halves the current capability!
IIRC The current capability nominally remains unchanged. It does not halve.
However doubling the nominal voltage capability implies that more current
may be needed when bridging, so if it isn't available then bridging may
fail to increase the available power. That said, if current limiting is the
only problem then bridging would not reduce the power. It just wouldn't
give the desired increase.
Bridging can sometimes reduce the output power capability into a moderate
load, but this is usually due to a larger fraction of the power dissipation
being in the o/p devices, causing SOA/thermal problems. (Or secondary
breakdown in a marginal bipolar design.) It also tends to double the output
impedance (reduce the damping factor). This might well be a problem bridging
the 303 as its o/p impedance is 0.3Ohms + 2000muF + 6microH in series, which
is moderately high by modern standards.
Some designs (not the 303 IIRC) have current limiters that limit to a
*lower* current at low output voltage than at high for SOA reasons. In
these cases there would be a power reduction into low loads as the current
limit would be reached at a lower total load voltage when bridging. For
that reason such designs should not be used bridged.
> Bridging 303s is simply not a good idea - indeed, the professional
> variant used by the BBC, the 50E, was basically two 303 channels in
> parallel.
Well, bridging 303's *may* be benificial, but only when the load impedance
is fairly high - e.g. noticably above 10 Ohms. Hence for speakers which are
mainly 16 Ohms or more it can help. However as you indicate, it usually
isn't worth doing, as any improvement is likely to be marginal. The
circumstances would need to be fairly carefully defined for bridging to be
worthwhile.
In principle, parallel combining 303's would be better. In practice, this
is harder to do and, again, may not be worth the effort in many cases.
In practice, if a 303 isn't loud enough it makes more sense to change
amplifier (or speakers). I quite like the 303 as part of a sensible
package, but I don't think it normally makes much sense to bridge it.
Ken
that I'm using are older B&W dm14.
"Jim Lesurf" <jc...@st-and.demon.co.uk> wrote in message
news:4a8ec27...@st-and.demon.co.uk...
Tony Sayer
and.demon.co.uk> stuck his oar in and spake
>In article <3b336dbe...@news.freeserve.net>, Stewart Pinkerton
><pat...@popmail.dircon.co.uk> wrote:
>> Dave Plowman <dave....@argonet.co.uk> writes:
>
>> >
>> > Quad 'knockers' used to say the problem with the 303 was its brick
>> >wall current and voltage limiting. So using it in bridge configuration
>> >should get round at least one of these..
>
>> Not really, since it halves the current capability!
>
>IIRC The current capability nominally remains unchanged. It does not halve.
Apart from power supply problems that may be raised, has anyone tried a
more modern replacement for the 2N3055 output devices?..
--
Tony Sayer
jim
>basically two 303 channels in parallel.
In the beeb , we had plenty 50D's - anyone know what the difference is
between these and 50E's?
jim
Stewart Pinkerton
Probably not a good idea, since modern devices with much higher GBP
could trigger instability in the circuit.
Stewart Pinkerton
I think it was the output transformer, but it was a long time
ago....... :-)
Stewart Pinkerton
>In article <3b336dbe...@news.freeserve.net>, Stewart Pinkerton
><pat...@popmail.dircon.co.uk> wrote:
>> Dave Plowman <dave....@argonet.co.uk> writes:
>
>> >
>> > Quad 'knockers' used to say the problem with the 303 was its brick
>> >wall current and voltage limiting. So using it in bridge configuration
>> >should get round at least one of these..
>
>> Not really, since it halves the current capability!
>
>IIRC The current capability nominally remains unchanged. It does not halve.
A bridged configuration 'sees' half the load impedance of a normal
connection, so the current capability is effectively halved.
Since the 303 is rated for a ten ohm load as standard, bridging rates
it for a twenty ohm load. This is fine if you know anyone with twenty
ohm speakers....................
Dave Plowman
> basically two 303 channels in parallel.
Thought it was just effectively a 303 with an output transformer to
match 100 volt lines and high impedance speakers, and with the option of a
balanced input.
--
* If horrific means to make horrible, does terrific mean to make terrible? *
Jim Lesurf
> >In article <3b336dbe...@news.freeserve.net>, Stewart Pinkerton
> ><pat...@popmail.dircon.co.uk> wrote:
> >
> >> Not really, since it halves the current capability!
> >
> >IIRC The current capability nominally remains unchanged. It does not
> >halve.
> A bridged configuration 'sees' half the load impedance of a normal
> connection, so the current capability is effectively halved.
No. The current capability nominally remains unchanged. It is not halved.
For a 303 it remains 3 amps. It does not fall to 1.5 amps. (Nominal values.)
The apparent load seen by an individual amplifier is changed, but that is
not the same statement as claiming that the current capability halves. What
may reduce is the maximum *voltage* the individual amplifier channel can
apply to a low load since, as you say, it 'sees' a lower load, so reaches
exactly the same limiting current as before at a lower single-channel o/p
*voltage*.
The result is that, for a low load, the maximum current and voltage that
can be applied to the load remains nominally unchanged by bridging. Neither
the total load voltage nor current should reduce. This means bridging may
be a waste of effort.
> Since the 303 is rated for a ten ohm load as standard, bridging rates it
> for a twenty ohm load. This is fine if you know anyone with twenty ohm
> speakers....................
What you are saying that *is* correct is that bridging potentially makes
twice the peak voltage available, so twice the current would be desired to
make effective use of this into an unchanged, low, load impedance. The
optimum load for maximum power output will double as you say.
Hence if the problem is a current limitiation, bridging does not help.
However it does not "halve the current capability".
When driving a given low load, a bridged amp nominally has precisely the
same current capability (and hence power output) as an unbridged one. The
provisos were outlined in my earlier posting.
As you indicate, if someone has a load whose impedance is above 10 Ohms,
bridging *may* raise the maximum nominal power available, but you would not
get the full benefit until the impedance was around 20 ohms or more. Thus
in practice, bridging won't usually produce any significant increase in
power capability. However this is quite different to claiming that "it
halves the current capability", which incorrectly implies a reduction in
output capability.
Don Pearce
No, the current capability isn't halved - the current requirement is
doubled. Same effect in the end though - not enough current.
The speaker impedance problem is "easily" solved with a 1.414:1 step
down transformer. At least the technology matches the vintage of the
amp.
I have to say, though - I would be hard-pressed to go to the bother of
bridging a pair of 303s these days. And there is still the question of
providing a balanced input. The output of the 33 (assuming that is
what he has) will need to go through either a transformer or a couple
of op-amps to provide the balanced differential drive. Too much effort
for too little return IMHO.
d
Telecommunications consultant
http://www.pearce.uk.com
Stewart Pinkerton
>In article <3b343da4...@news.freeserve.net>, Stewart Pinkerton
><pat...@popmail.dircon.co.uk> wrote:
>> Jim Lesurf <jc...@st-and.demon.co.uk> writes:
>
>> >In article <3b336dbe...@news.freeserve.net>, Stewart Pinkerton
>> ><pat...@popmail.dircon.co.uk> wrote:
>
>> >
>> >> Not really, since it halves the current capability!
>> >
>> >IIRC The current capability nominally remains unchanged. It does not
>> >halve.
>
>> A bridged configuration 'sees' half the load impedance of a normal
>> connection, so the current capability is effectively halved.
>
>No. The current capability nominally remains unchanged. It is not halved.
>For a 303 it remains 3 amps. It does not fall to 1.5 amps. (Nominal values.)
Which part of 'effectively halved' did you fail to understand? 3 amps
into a 4 ohm load is half the current capability of 3 amps into an 8
ohm load.
Stewart Pinkerton
>On Sat, 23 Jun 2001 07:00:52 GMT, pat...@popmail.dircon.co.uk
>(Stewart Pinkerton) wrote:
>
>>Jim Lesurf <jc...@st-and.demon.co.uk> writes:
>>
>>>In article <3b336dbe...@news.freeserve.net>, Stewart Pinkerton
>>><pat...@popmail.dircon.co.uk> wrote:
>>>> Dave Plowman <dave....@argonet.co.uk> writes:
>>>
>>>> >
>>>> > Quad 'knockers' used to say the problem with the 303 was its brick
>>>> >wall current and voltage limiting. So using it in bridge configuration
>>>> >should get round at least one of these..
>>>
>>>> Not really, since it halves the current capability!
>>>
>>>IIRC The current capability nominally remains unchanged. It does not halve.
>>
>>A bridged configuration 'sees' half the load impedance of a normal
>>connection, so the current capability is effectively halved.
>>
>>Since the 303 is rated for a ten ohm load as standard, bridging rates
>>it for a twenty ohm load. This is fine if you know anyone with twenty
>>ohm speakers....................
>
>No, the current capability isn't halved - the current requirement is
>doubled. Same effect in the end though - not enough current.
Quite so - same thing, you are arguing semantics, not reality.
>The speaker impedance problem is "easily" solved with a 1.414:1 step
>down transformer.
Which reduces the voltage output, hence making bridging
pointless.............
BTW, you need 2:1. not 1.414:1.
> At least the technology matches the vintage of the amp.
>I have to say, though - I would be hard-pressed to go to the bother of
>bridging a pair of 303s these days. And there is still the question of
>providing a balanced input. The output of the 33 (assuming that is
>what he has) will need to go through either a transformer or a couple
>of op-amps to provide the balanced differential drive. Too much effort
>for too little return IMHO.
Not a great amp in the first place (yes, I owned a 33/303, like most
older Brit audiophiles), so certainly a pointless exercise. The only
possible excuse for using the geriatric 303 is to build a 'vintage'
system, so modifying the 303 instantly destroys the authenticity!
Stewart Pinkerton
>In article <3b336dbe...@news.freeserve.net>,
> Stewart Pinkerton <pat...@popmail.dircon.co.uk> wrote:
>> indeed, the professional variant used by the BBC, the 50E, was
>> basically two 303 channels in parallel.
>
> Thought it was just effectively a 303 with an output transformer to
>match 100 volt lines and high impedance speakers, and with the option of a
>balanced input.
Monobloc, doubled up current capacity.
Don Pearce
(Stewart Pinkerton) wrote:
>donald.wi...@pearce.uk.com (Don Pearce) writes:
>
>>On Sat, 23 Jun 2001 07:00:52 GMT, pat...@popmail.dircon.co.uk
>>(Stewart Pinkerton) wrote:
>>
>>>Jim Lesurf <jc...@st-and.demon.co.uk> writes:
>>>
>>>>In article <3b336dbe...@news.freeserve.net>, Stewart Pinkerton
>>>><pat...@popmail.dircon.co.uk> wrote:
>>>>> Dave Plowman <dave....@argonet.co.uk> writes:
>>>>
>>>>> >
>>>>> > Quad 'knockers' used to say the problem with the 303 was its brick
>>>>> >wall current and voltage limiting. So using it in bridge configuration
>>>>> >should get round at least one of these..
>>>>
>>>>> Not really, since it halves the current capability!
>>>>
>>>>IIRC The current capability nominally remains unchanged. It does not halve.
>>>
>>>A bridged configuration 'sees' half the load impedance of a normal
>>>connection, so the current capability is effectively halved.
>>>
>>>Since the 303 is rated for a ten ohm load as standard, bridging rates
>>>it for a twenty ohm load. This is fine if you know anyone with twenty
>>>ohm speakers....................
>>
>>No, the current capability isn't halved - the current requirement is
>>doubled. Same effect in the end though - not enough current.
>
>Quite so - same thing, you are arguing semantics, not reality.
>
The effect may be the same, but it isn't the same thing. To hold two
pints of beer, you need a two-pint glass, while to hold one pint of
beer, a single pinter will do. I don't suppose for one moment you
would call those two the same thing. Calling that a semantic argument
would leave you thirsty.
>
>>The speaker impedance problem is "easily" solved with a 1.414:1 step
>>down transformer.
>
>Which reduces the voltage output, hence making bridging
>pointless.............
>
>BTW, you need 2:1. not 1.414:1.
>
No. To get a 2:1 impedance transformation, you need a 1.414:1
transformer - I'm talking turns ratio as is usual with transformers.
>
>
>> At least the technology matches the vintage of the amp.
>>I have to say, though - I would be hard-pressed to go to the bother of
>>bridging a pair of 303s these days. And there is still the question of
>>providing a balanced input. The output of the 33 (assuming that is
>>what he has) will need to go through either a transformer or a couple
>>of op-amps to provide the balanced differential drive. Too much effort
>>for too little return IMHO.
>
>Not a great amp in the first place (yes, I owned a 33/303, like most
>older Brit audiophiles), so certainly a pointless exercise. The only
>possible excuse for using the geriatric 303 is to build a 'vintage'
>system, so modifying the 303 instantly destroys the authenticity!
Agree entirely.
Jim Lesurf
> >In article <3b343da4...@news.freeserve.net>, Stewart Pinkerton
> ><pat...@popmail.dircon.co.uk> wrote:
> >> Jim Lesurf <jc...@st-and.demon.co.uk> writes:
> >
> >> >In article <3b336dbe...@news.freeserve.net>, Stewart Pinkerton
> >> ><pat...@popmail.dircon.co.uk> wrote:
> >
> >> >
> >> >> Not really, since it halves the current capability!
> >> >
> >> >IIRC The current capability nominally remains unchanged. It does not
> >> >halve.
> >
> >> A bridged configuration 'sees' half the load impedance of a normal
> >> connection, so the current capability is effectively halved.
> >
> >No. The current capability nominally remains unchanged. It is not
> >halved. For a 303 it remains 3 amps. It does not fall to 1.5 amps.
> >(Nominal values.)
> Which part of 'effectively halved' did you fail to understand? 3 amps
> into a 4 ohm load is half the current capability of 3 amps into an 8 ohm
> load.
I am afraid that it is you who seem to be having difficulty with the
English language here. Your sarcasm is noted, but I am afraid that it is a
poor substitute for your thinking about what you are writing.
In what way does "effectively halved" mean a quantity remains unchanged? I
can only make sense of the phrase in the context you are using it if I
assume that by "essentially" you mean "not really". :-)
It is simply nonsense to claim as you do that "3 amps into a 4 ohm load is
half the *current* capability of 3 amps into an 8 ohm load." 3 amps
remains 3 amps. An ammeter is not going to care about the load impedance,
it will read 3 amps in each case. The current capability remains at 3 amps.
Consider removing the word "effectively" from your claim. Would you then
still assert that the *current* is halved? If not, then you may perhaps
then realise that some other quantities may change, but the current does
not, and your statements are being muddled by the use of the word
"effectively". Or are you genuinely asserting that the current reduces from
3 amps to 1.5 amps? If so, this is incorrect.
I apologise if I have not made the point clear. If you do not follow what I
am saying then perhaps I should not labour the point.
Stewart Pinkerton
Not really, since a bridged amp leaves three guys standing behind you
grabbing those pints as they are served.................. :-)
>>>The speaker impedance problem is "easily" solved with a 1.414:1 step
>>>down transformer.
>>
>>Which reduces the voltage output, hence making bridging
>>pointless.............
>>
>>BTW, you need 2:1. not 1.414:1.
>>
>No. To get a 2:1 impedance transformation, you need a 1.414:1
>transformer - I'm talking turns ratio as is usual with transformers.
Unfortunately, voltage capacity in a bridged amp is doubled, i.e. 2:1
ratio, which also halves available current............ :-)
Stewart Pinkerton
It's clear to me that current *capability* involves the ability to
drive a specific load. If this statement has another meaning to you,
then there's no more to be said. Whatever, I guess that most readers
will understand that bridging a Quad 303 is a very bad idea, which was
the point of the thread.
Don Pearce
(Stewart Pinkerton) wrote:
What? The whole idea of bridging is to double the power - i.e. the
full rated power from each amp is summed. You double the voltage, but
leave the current the same (V x I = P) and get double the power. If
you double the voltage and halve the current, you get no more power
than from a single amp.
If you used a 2:1 ratio transformer the voltage would be back down
where you were with a single amp, but the current capability would
double, so you would need a speaker with half the normal impedance.
With a 1.414:1 transformer, the voltage is 1.414 times that of a
single amp, and so is the current. Into the original load impedance
this doubles the power (1.414 x 1.414 = 2).
Bridging the outputs of amplifiers has no impact on their current
capability whatever.
Don Pearce
No, the current capability is the capability to supply current. It is
measured in amps, not ohms. It says nothing about loads. The current
capability of a bridged amplifier is identical to that of a single
amplifier.
Stewart Pinkerton
A bridged amplifier is however limited to driving loads of twice the
impedance of the unbridged amplifier, which is the *relevant* measure.
As noted, a bridged 303 would be suitable only for speakers with an
impedance of twenty ohms or more. Know any?
Stewart Pinkerton
>On Sat, 23 Jun 2001 23:15:35 GMT, pat...@popmail.dircon.co.uk
>(Stewart Pinkerton) wrote:
>
>>donald.wi...@pearce.uk.com (Don Pearce) writes:
>>>>>The speaker impedance problem is "easily" solved with a 1.414:1 step
>>>>>down transformer.
>>>>
>>>>Which reduces the voltage output, hence making bridging
>>>>pointless.............
>>>>
>>>>BTW, you need 2:1. not 1.414:1.
>>>>
>>>No. To get a 2:1 impedance transformation, you need a 1.414:1
>>>transformer - I'm talking turns ratio as is usual with transformers.
>>
>>Unfortunately, voltage capacity in a bridged amp is doubled, i.e. 2:1
>>ratio, which also halves available current............ :-)
>What? The whole idea of bridging is to double the power - i.e. the
>full rated power from each amp is summed. You double the voltage, but
>leave the current the same (V x I = P) and get double the power. If
>you double the voltage and halve the current, you get no more power
>than from a single amp.
You seem to be completely unaware of how power amplifiers operate.
They are constant voltage devices, i.e. they attempt to maintain the
required output voltage, regardless of the load. Hence, a bridged amp
should give *four* times the output power of the original amplifier,
not double.
There is of course a limit to how low an impedance any amplifier can
drive, and many amps have current limiting to protect the amp from
excessively low loads. The Quad 303 interpretation of 'excessively
low' is less than ten ohms, so it runs out of current at 3 amps. This
limits the maximum output of a bridged 303 to 60 volts at 3 amps,
which is the *same* power into the same ten ohm load, no power
advantage whatever.
>If you used a 2:1 ratio transformer the voltage would be back down
>where you were with a single amp, but the current capability would
>double, so you would need a speaker with half the normal impedance.
>With a 1.414:1 transformer, the voltage is 1.414 times that of a
>single amp, and so is the current. Into the original load impedance
>this doubles the power (1.414 x 1.414 = 2).
I see what you're getting at, you're adopting the tube amp philosohy
of regarding the 303 as a 90 watt amplifier requiring matching to the
intended speaker load, but you're still stuck with a weedy amp which
is incapable of driving a load of less than ten ohms! At least the 2:1
transformer would allow a more realistic (if still marginal) minimum
load of 5 ohms at full output.
>Bridging the outputs of amplifiers has no impact on their current
>capability whatever.
As noted, that depends on how you interpret 'current capability'. Nuff
said, this thread is done to death.........
Mike Coatham
"Stewart Pinkerton" <pat...@popmail.dircon.co.uk> wrote in message
news:3b359255...@news.freeserve.net...
> donald.wi...@pearce.uk.com (Don Pearce) writes:
>
>
> >Bridging the outputs of amplifiers has no impact on their current
> >capability whatever.
>
> As noted, that depends on how you interpret 'current capability'. Nuff
> said, this thread is done to death.........
>
> --
>
> Stewart Pinkerton | Music is art, audio is engineering
.........................but if you really want to see how to completely
"audiophool-ise" a couple of 303's then take a look at this offering:
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1249140190
Jim Lesurf
The "current capability" will be one factor that may determine the limit on
the ability to drive a specific load. So it is reasonably to use the word
"involves". However a relationship is not an identity.
To me "current capability" in this context means "how much current the
amplifier is able to supply into a load". When driving low loads, bridging
nominally leaves this value unchanged, it is not halved. If your definition
differs from mine then I suspect your definition is perhaps in need of
reconsideration. If you mean that some quantity *other* than the current
changes then it would clarify things if you noted that the term you use is
misleading.
> Whatever, I guess that most readers will understand that bridging a Quad
> 303 is a very bad idea, which was the point of the thread.
In most cases bridging 303's is likely to be a waste of effort. However it
may not always be 'bad'. That would depend upon the context in which the
amp was to be employed. Since bridging leaves the available maximum current
unchanged it does not nominally diminish the maximum power available into
low loads. Where a load exceeds 10 Ohms it may permit higher power
delivery. As a result, in practice there is unlikely to be any benefit (or
at most only a marginal one) in most cases. I would not recommend it.
However where someone is using speakers that have an impedance of 16
Ohms, it may well permit higher powers. These days, however, high impedance
speakers are probably rarer than when Quad produced the 303.
Jim Lesurf
<pat...@popmail.dircon.co.uk> wrote:
> donald.wi...@pearce.uk.com (Don Pearce) writes:
> >>
> >>Which reduces the voltage output, hence making bridging
> >>pointless.............
> >>
> >>BTW, you need 2:1. not 1.414:1.
> >>
> >No. To get a 2:1 impedance transformation, you need a 1.414:1
> >transformer - I'm talking turns ratio as is usual with transformers.
> Unfortunately, voltage capacity in a bridged amp is doubled, i.e. 2:1
> ratio, which also halves available current............ :-)
Nope. The current capacity remains at 3 amps.
Jim Lesurf
> >Jim Lesurf <jc...@st-and.demon.co.uk> writes:
> >
Agree with Don.
Don Pearce
(Stewart Pinkerton) wrote:
>donald.wi...@pearce.uk.com (Don Pearce) writes:
>
>>On Sat, 23 Jun 2001 23:15:36 GMT, pat...@popmail.dircon.co.uk
>>(Stewart Pinkerton) wrote:
>
>>>It's clear to me that current *capability* involves the ability to
>>>drive a specific load. If this statement has another meaning to you,
>>>then there's no more to be said. Whatever, I guess that most readers
>>>will understand that bridging a Quad 303 is a very bad idea, which was
>>>the point of the thread.
>
>>No, the current capability is the capability to supply current. It is
>>measured in amps, not ohms. It says nothing about loads. The current
>>capability of a bridged amplifier is identical to that of a single
>>amplifier.
>
>A bridged amplifier is however limited to driving loads of twice the
>impedance of the unbridged amplifier, which is the *relevant* measure.
>As noted, a bridged 303 would be suitable only for speakers with an
>impedance of twenty ohms or more. Know any?
This is a strange argument. You keep restating a position which says
nothing about current capacity, but you are still trying to justify
your claim that current capacity is halved on the strength of it. WHat
you say is right, but has nothing to do with the case. It is a
non-sequitur.
Jim Lesurf
Are the above statements 'right'? I have my doubts. They seem to be using
the words "limited" and "suitable" in an unclear manner, and are ambiguous
in other ways. Bridging nominally increases the available power for loads
above 10 Ohms, and nominally leaves the available power for lower loads
unchanged. You don't need to double the load, just ensure it is above 10
Ohms, to get an increase in the maximum nominal power available. 20 Ohms
would only be required if you insist that the maximum possible power must
be obtained.
The statement:
"A bridged amplifier is however limited to driving loads of twice the
impedance of the unbridged amplifier"
is potentially misleading since its meaning is unambiguous - what load
impedance value is being assumed for "the impedance of an unbridged
amplifier" in the statement? The bridged amplifier would function into,
say, 8 Ohm loads. In that sense it is not 'limited'. it is just that
bridging would give no advantage into such a load.
> It is a non-sequitur.
I thought that was the effect which arises when you are in the garden and
find that you can't prune the roses. :-)
Arny Krueger
"Jim Lesurf" <jc...@st-and.demon.co.uk> wrote in message
news:4a8fa11...@st-and.demon.co.uk...
> In article <3b35bb9...@pubnews.netcom.net.uk>, Don Pearce
> <donald.wi...@pearce.uk.com> wrote:
> > On Sun, 24 Jun 2001 07:23:45 GMT, pat...@popmail.dircon.co.uk
(Stewart
> > Pinkerton) wrote:
> > >A bridged amplifier is however limited to driving loads of twice
the
> > >impedance of the unbridged amplifier, which is the *relevant*
measure.
> > >As noted, a bridged 303 would be suitable only for speakers with
an
> > >impedance of twenty ohms or more. Know any?
> > This is a strange argument. You keep restating a position which
says
> > nothing about current capacity, but you are still trying to
justify your
> > claim that current capacity is halved on the strength of it. What
you
> > say is right, but has nothing to do with the case.
> Are the above statements 'right'? I have my doubts.
I see this as a problem of characterization. There are 4 relevant
numbers: ohms, volts, amps, and watts. However, they are related by
simple math and if you provide any two of them, it is easy to
calculate the rest.
Mr. Pinkerton's statement that " A bridged amplifier is however
limited to driving loads of twice the impedance of the unbridged
amplifier" does not imply that the current capacity is diminished in
any way since the voltage that is applied to the load is doubled.
Maintaining EQUAL peak current leads to the requirement for a
doubled load impedance.
Jim Lesurf
Krueger <ar...@hotpop.com> wrote:
> I see this as a problem of characterization.
We may differ there. :-) I see it as a matter of being able to use the
English language to explain the situation clearly and without ambiguity.
> There are 4 relevant numbers: ohms, volts, amps, and watts. However,
> they are related by simple math and if you provide any two of them, it
> is easy to calculate the rest.
True enough. Provided it is clear what situation is being described.
> Mr. Pinkerton's statement that " A bridged amplifier is however limited
> to driving loads of twice the impedance of the unbridged amplifier" does
> not imply that the current capacity is diminished in any way since the
> voltage that is applied to the load is doubled.
Agreed. That particular statement says nothing about current at all. My
query regarding the above statement was quite independent from my queries
regarding his statements about "the current halves". However it is not
clear what meaning is being assigned to "limited", not is the meaning of
"the impedance of the unbridged amplifier" clear. I assume he is *not*
talking about the o/p impedance of the amplifier, so what is he referring
to?
If he means "to get the maximum possible power you would wish to use double
the value of load impedance with a bridged amp than when unbridged" I would
agree. However this implicitly gives the word "limited" a rather odd
meaning in his statement.
It is perfectly possible to use, say, an 8 Ohm load with either the bridged
or unbridged 303. In each case the same nominal power, current, and
voltage, will be available for the load. In that sense it is not "limited"
to a specific load, either bridged or unbridged. It may well be a waste of
time to bridge a 303 for an 8 Ohm load, but the meanings of "waste of time"
and "limited" are not the same.
BTW By "voltage that is applied" I assume you mean "maximum voltage that
*may* be applied provided current limiting does not occur first". However
you do not say this, so I may not have interpreted you correctly.
> Maintaining EQUAL peak current leads to the requirement for a doubled
> load impedance.
Not if in each case the peak available current is 3 amps set by an inherent
limitation of the amplifier. When a 8 Ohm load is used with either a
bridged or unbridged 303, the current will nominally be limited to 3 amps
in each case. You don't need to change to 16 Ohms to get a current limit of
3 amps with the bridged arrangement.
I am now wondering if you (and perhaps Stewart) have been implicity
assuming a *high* load impedance. It would be reasonable to say that when
dealing with a load of 10 Ohms or more we find that the current is then
constraigned by the maximum *voltage* (30 volts) a 303 can apply. When we
bridge the amplifiers we could choose to raise the load impedance to double
this value and would then nominally get the same current level, again due
to *voltage* limitation. Hence your statement would be correct for loads
above 10 Ohms unbridged/20 Ohms bridged, but *not* for lower loads. However
here we are talking about the effect of *voltage* limitation into a high
load. Not the result of the amplifier having a current limitation of 3 amps
into low loads.
If the above is what you or Stewart have in mind then, again, the problem
has its root in being able to explain this clearly since the statements
made by Stewart have not been in these terms at all. This may be your
assumption. However I would be surprised if it is what Stewart was assuming
as I thought his concern stemmed from the relatively low current limit of a
303 being the reason bridging would often be a waste of effort. (A point I
have agreed with.)
TBH I suspect that Stewart (and yourself) understand what happens well
enough. My concern is that the statements he made are unclearly worded and
may therefore mislead readers who do *not* understand the topic into
thinking he is saying something that he does not intend.
Don Pearce
Caid mille failte for this Jim. I think you have summed the whole
thing up perfectly.
Depending on the design of a particular power amplifier, it may run
out of either volts or current first when hitting its limit with an 8
ohm speaker. If it still has plenty of current to spare, then bridging
can be permitted into the original 8 ohms, taking advantage of that
spare current capacity to recover rather more than double the original
power. In the case of the 303, it is already pretty marginal on
current, so nothing is to be gained by this strategy and a doubled
load impedance (probably by means of a step down transformer would be
indicated.
I think things got into a bit of a semantic stew (sorry, Stew, pun not
intended) over what did and didn't get halved or doubled. There are
just too many permutations of what you can do with a bridged setup to
go through without constructing tables - which you can't do too easily
on an ASCII news group.
d
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