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dave
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 Posted: Mon Jul 21, 2008 2:42 am Post subject: What to us for a PA dummy 300W load? |
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Looking for ideas here... I>d like test a PA amplifier rated at 300
watts into 4 ohms.
Any ideas as what I could use for an dummy load - apart from some
actual speakers (drivers) that is! I>d also like the load to be as
resistive as possible and not inductive as the drivers would be.
As I don>t have a 4 ohm 300 watt resistor in the spares box - any
ideas what could be used as a "subsitute"? |
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Bill
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| Posted: Mon Jul 21, 2008 2:42 am Post subject: Re: What to us for a PA dummy 300W load? |
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On Jul 20, 5:20 pm, "DaveM" <masondg4...@comcast99.net> wrote:
[quote]"dave" <d...@127.0.0.1> wrote in message
news:rvb784hr7086opqfqf0d4qpth9mm38u4f5@4ax.com...
Looking for ideas here... I>d like test a PA amplifier rated at 300
watts into 4 ohms.
Any ideas as what I could use for an dummy load - apart from some
actual speakers (drivers) that is! I>d also like the load to be as
resistive as possible and not inductive as the drivers would be.
As I don>t have a 4 ohm 300 watt resistor in the spares box - any
ideas what could be used as a "subsitute"?
You will probably get advice to use a string of light bulbs for this purpose,
but I have to advise caution there. The resistance of an incandescent bulb is
very low when cold, and rises significantly when current is applied. It>s not
easily predicted and can lead to blowing your amp. The bulbs can easily look
like a short to the amp when cold and kill it before you get started with a
test.
You should look for something that has less resistance change when heated..
Thinking of the heating element from a toaster, electric frying pan, electric
space heater or other household appliance. Of course, you>ll have to measure
and combine appliances as appropriate to get the right value.
Of course, the correct solution would be to spring for the resistor(s) to do
your testing.
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)
Experience: What you get when you don>t get what you want
[/quote]
Buy wire wound resistors |
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DaveM
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| Posted: Mon Jul 21, 2008 3:20 am Post subject: Re: What to us for a PA dummy 300W load? |
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"dave" <dave@127.0.0.1> wrote in message
news:rvb784hr7086opqfqf0d4qpth9mm38u4f5@4ax.com...
[quote]Looking for ideas here... I>d like test a PA amplifier rated at 300
watts into 4 ohms.
Any ideas as what I could use for an dummy load - apart from some
actual speakers (drivers) that is! I>d also like the load to be as
resistive as possible and not inductive as the drivers would be.
As I don>t have a 4 ohm 300 watt resistor in the spares box - any
ideas what could be used as a "subsitute"?
[/quote]
You will probably get advice to use a string of light bulbs for this purpose,
but I have to advise caution there. The resistance of an incandescent bulb is
very low when cold, and rises significantly when current is applied. It>s not
easily predicted and can lead to blowing your amp. The bulbs can easily look
like a short to the amp when cold and kill it before you get started with a
test.
You should look for something that has less resistance change when heated.
Thinking of the heating element from a toaster, electric frying pan, electric
space heater or other household appliance. Of course, you>ll have to measure
and combine appliances as appropriate to get the right value.
Of course, the correct solution would be to spring for the resistor(s) to do
your testing.
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)
Experience: What you get when you don>t get what you want |
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Jean-Yves
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| Posted: Mon Jul 21, 2008 7:04 am Post subject: Re: What to us for a PA dummy 300W load? |
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In article <rvb784hr7086opqfqf0d4qpth9mm38u4f5@4ax.com>,
dave <dave@127.0.0.1> wrote:
[quote]Looking for ideas here... I>d like test a PA amplifier rated at 300
watts into 4 ohms.
Any ideas as what I could use for an dummy load - apart from some
actual speakers (drivers) that is! I>d also like the load to be as
resistive as possible and not inductive as the drivers would be.
As I don>t have a 4 ohm 300 watt resistor in the spares box - any
ideas what could be used as a "subsitute"?
[/quote]
something like this :
http://www.terrydownsmusic.com/technotes/dummyload/dummy_load.htm
--
Jean-Yves. |
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RST Engineering (jw)
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| Posted: Mon Jul 21, 2008 7:04 am Post subject: Re: What to us for a PA dummy 300W load? |
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First you have to tell us what "rated" means. Is this 300 watts pure sine
wave power or the poorly defined "music power". I doubt that there are
speakers available that would take 300 watts CW.
Jim
--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle
"dave" <dave@127.0.0.1> wrote in message
news:rvb784hr7086opqfqf0d4qpth9mm38u4f5@4ax.com...
[quote]Looking for ideas here... I>d like test a PA amplifier rated at 300
watts into 4 ohms.
Any ideas as what I could use for an dummy load - apart from some
actual speakers (drivers) that is! I>d also like the load to be as
resistive as possible and not inductive as the drivers would be.
As I don>t have a 4 ohm 300 watt resistor in the spares box - any
ideas what could be used as a "subsitute"?[/quote] |
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Eeyore
Guest
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| Posted: Mon Jul 21, 2008 10:42 pm Post subject: Re: What to us for a PA dummy 300W load? |
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dave wrote:
[quote]Looking for ideas here... I>d like test a PA amplifier rated at 300
watts into 4 ohms.
Any ideas as what I could use for an dummy load - apart from some
actual speakers (drivers) that is! I>d also like the load to be as
resistive as possible and not inductive as the drivers would be.
As I don>t have a 4 ohm 300 watt resistor in the spares box - any
ideas what could be used as a "subsitute"?
[/quote]
There are loads of options. Farnell sell ultra-large wirewound resistors
for example.
Graham |
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Eeyore
Guest
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| Posted: Mon Jul 21, 2008 10:43 pm Post subject: Re: What to us for a PA dummy 300W load? |
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"RST Engineering (jw)" wrote:
[quote]First you have to tell us what "rated" means. Is this 300 watts pure sine
wave power or the poorly defined "music power". I doubt that there are
speakers available that would take 300 watts CW.
[/quote]
I know one that takes 1200W ! It has a 6 inch voice coil though !
Graham |
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Michael Black
Guest
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| Posted: Mon Jul 21, 2008 11:28 pm Post subject: Re: What to us for a PA dummy 300W load? |
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On Sun, 20 Jul 2008, dave wrote:
[quote]Looking for ideas here... I>d like test a PA amplifier rated at 300
watts into 4 ohms.
Any ideas as what I could use for an dummy load - apart from some
actual speakers (drivers) that is! I>d also like the load to be as
resistive as possible and not inductive as the drivers would be.
As I don>t have a 4 ohm 300 watt resistor in the spares box - any
ideas what could be used as a "subsitute"?
I seem to recall reading about using a toaster, or at least the toaster>s[/quote]
heating element, as a load for an audio amplifier.
It likely helps to explain why you need the load. Once upon a time, every
amplifier needed a load, because the design required it. But most solid
state amplifiers can operate without a load, so the need for a load may
no longer be needed, depending on what you are doing.
Michael |
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Clint Sharp
Guest
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| Posted: Tue Jul 22, 2008 5:43 am Post subject: Re: What to us for a PA dummy 300W load? |
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In message <4884CA6E.9E675483@hotmail.com>, Eeyore
<rabbitsfriendsandrelations@hotmail.com> writes
[quote]There are loads of options. Farnell sell ultra-large wirewound resistors
for example.
Or plenty of smaller cheaper ones although I do have a couple of their[/quote]
250W aluminium clad ones. Couldn>t resist.
[quote]Graham
[/quote]
--
Clint Sharp |
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Jasen Betts
Guest
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| Posted: Wed Jul 23, 2008 5:08 pm Post subject: Re: What to us for a PA dummy 300W load? |
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On 2008-07-20, dave <dave@127.0.0.1> wrote:
[quote]Looking for ideas here... I>d like test a PA amplifier rated at 300
watts into 4 ohms.
Any ideas as what I could use for an dummy load - apart from some
actual speakers (drivers) that is! I>d also like the load to be as
resistive as possible and not inductive as the drivers would be.
As I don>t have a 4 ohm 300 watt resistor in the spares box - any
ideas what could be used as a "subsitute"?
[/quote]
If you can scrounge up 3600W worth of 120V heating elements from junk
equipment and wire it in parallel that>ll be 4 ohms.
Otoh you could just some of the nichrome wire from an old toaster
Bye.
Jasen |
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Stephen J. Rush
Guest
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| Posted: Thu Jul 31, 2008 7:06 am Post subject: Re: What to us for a PA dummy 300W load? |
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On Mon, 21 Jul 2008 18:43:28 +0100, Eeyore wrote:
[quote]"RST Engineering (jw)" wrote:
First you have to tell us what "rated" means. Is this 300 watts pure
sine wave power or the poorly defined "music power". I doubt that
there are speakers available that would take 300 watts CW.
I know one that takes 1200W ! It has a 6 inch voice coil though !
[/quote]
Cerwin-Vega, I>ll bet. Their slogan is "The LOUD!speaker company." They
build systems for rock concerts, motor-race tracks and other places that
need insane amounts of acoustic power. |
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