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I meant that a transformer with a one to one turns ratio doesn'tOn Thu, 28 Apr 2011 10:06:57 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 28, 10:35 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold" ...
Thanks Phil, is that without an output transformer? Seems like a very
wasteful way to make sound.
** My god you are a colossal fuckwit.
Gee Phil, What did I say wrong now? I don't know anything about tube
audio amps. I thought the output transformer was there to 'transform'
the relative impedances. So it doesn't make sense to compare
impedances on each side of transformer.
---
Why not?
After all, what the transformer is doing is making the tube think that
it's connected to, say, 1000 ohms and the loudspeaker to 16, so both
impedances are being matched.
---
(unless it's a one to onetransformer)
---
How do you mean?
---
George H.
--
JF
Um, let me try it... You do know that power and energy are differentOn Apr 27, 9:19 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Wed, 27 Apr 2011 08:11:13 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 10:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 27 Apr 2011 06:50:17 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce.
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Thanks Phil, These are physics people. One of the freshman physics
problems that everyone does is finding the load resistance that gives
the maximum power from a battery with some internal resistance. This
then becomes the 'model' for all impedance matching questions. I'll
try posting a gentle correction...
George H.
Point out that half the total power is lost inside the battery,
reducing available watt-hours in half... maybe worse. Batteries and
power plants shouldn't operate that way.
John- Hide quoted text -
- Show quoted text -
Yeah, I can try.
Tell them that power and energy aren't the same thing. Perhaps they heard
something to that effect somewhere back in high school physics.
I've been directed to the maximum power transfer theorem,
http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem.
Has anyone ever used this?
It's this 'd@mn' battery and resistor problem. I didn't know it got a
whole theorem named after it.
I've been directed to the maximum power transfer theorem,On Wed, 27 Apr 2011 08:11:13 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 10:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 27 Apr 2011 06:50:17 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce.
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Thanks Phil, These are physics people. One of the freshman physics
problems that everyone does is finding the load resistance that gives
the maximum power from a battery with some internal resistance. This
then becomes the 'model' for all impedance matching questions. I'll
try posting a gentle correction...
George H.
Point out that half the total power is lost inside the battery,
reducing available watt-hours in half... maybe worse. Batteries and
power plants shouldn't operate that way.
John- Hide quoted text -
- Show quoted text -
Yeah, I can try.
Tell them that power and energy aren't the same thing. Perhaps they heard
something to that effect somewhere back in high school physics.
- Show quoted text -
The impedance changes with the *square* of the turns ratio. With a 2:1 ratio,On Apr 28, 1:22 pm, John Fields <jfie...@austininstruments.com> wrote:
On Thu, 28 Apr 2011 07:27:42 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 28, 9:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Thu, 28 Apr 2011 06:20:28 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce.
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Well here is where at least some of them get their information,
http://hyperphysics.phy-astr.gsu.edu/hbase/audio/imped.html#c2
Was there ever a time in audio when 'electronic'* impedance matching
was important?
If you had an old-fashioned no-feedback class A tube amp, like in an
old radio, you'd get maximum volume, which you'd probably want, if the
amp and speaker impedances were equal.
John- Hide quoted text -
- Show quoted text -
Oh, So if I was making just a class A emmitter follower to drive the
speaker, I'd want the DC idle current equal to the max at full
volume... I'd then have equal impedances.... Still it seems wrong to
call it "impedance matching".
George H.
---
You're missing the point, which is that if you have a tube-based
amplifier with, say, a 250VPP swing in plate voltage and an 8 ohm
loudspeaker as a load being driven at 10 watts, then the current in
the speaker would be:
P 10W
I = sqrt --- = sqrt ----- = 1.25 amperes, RMS
R 8R
Theoretically, the best efficiency you can get out of a class "A"
amplifier is 50%, so if the tube is dissipating 10 watts when it's
driving 10 watts into the load, then the plate resistance of the tube
must be:
VRMS˛
Rp = ------
P
Then, since:
(VPP/2) 125V
VRMS = --------- = ------ ~ 89.3V,
sqrt(2) 1.4
The plate resistance must be:
89.3V˛
Rp = ------- ~ 800 ohms
10W
We're now stuck with the problem of how to transfer 10 watts from an
800 ohm source into an 8 ohm load, and to solve it we'll do impedance
matching by using a transformer with an 800 ohm primary connected
between the tube's plate and its supply, and its 8 ohm secondary
connected across the loudspeaker.
--
JF- Hide quoted text -
- Show quoted text -
Thanks for the nice explanation John, You use the turns ratio of the
transformer to match the impedances.
Not for this calculation. See above.Do you need to specify the
resistance of the load/source too?
Never touch them.I'm pretty much an idiot when it
comes to tube amps. (If you couldn't tell.)
Gee Phil, What did I say wrong now?Thanks Phil, is that without an output transformer? Seems like a very
wasteful way to make sound.
** My god you are a colossal fuckwit.
** Or anything else.I don't know anything about tube audio amps.
The problem with using the maximum power transfer theorem with your amplifier andOn Apr 27, 9:19 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Wed, 27 Apr 2011 08:11:13 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 10:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 27 Apr 2011 06:50:17 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison"<phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce.
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Thanks Phil, These are physics people. One of the freshman physics
problems that everyone does is finding the load resistance that gives
the maximum power from a battery with some internal resistance. This
then becomes the 'model' for all impedance matching questions. I'll
try posting a gentle correction...
George H.
Point out that half the total power is lost inside the battery,
reducing available watt-hours in half... maybe worse. Batteries and
power plants shouldn't operate that way.
John- Hide quoted text -
- Show quoted text -
Yeah, I can try.
Tell them that power and energy aren't the same thing. Perhaps they heard
something to that effect somewhere back in high school physics.
I've been directed to the maximum power transfer theorem,
http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem.
Has anyone ever used this?
It's this 'd@mn' battery and resistor problem. I didn't know it got a
whole theorem named after it.
Thanks, I know all this.... It's trying to explain it to some phyiscsOn Thu, 28 Apr 2011 18:57:58 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:19 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Wed, 27 Apr 2011 08:11:13 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 10:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 27 Apr 2011 06:50:17 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce..
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Thanks Phil, These are physics people. One of the freshman physics
problems that everyone does is finding the load resistance that gives
the maximum power from a battery with some internal resistance. This
then becomes the 'model' for all impedance matching questions. I'll
try posting a gentle correction...
George H.
Point out that half the total power is lost inside the battery,
reducing available watt-hours in half... maybe worse. Batteries and
power plants shouldn't operate that way.
John- Hide quoted text -
- Show quoted text -
Yeah, I can try.
Tell them that power and energy aren't the same thing. Perhaps they heard
something to that effect somewhere back in high school physics.
I've been directed to the maximum power transfer theorem,
http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem.
Has anyone ever used this?
It's this 'd@mn' battery and resistor problem. I didn't know it got a
whole theorem named after it.
Um, let me try it... You do know that power and energy are different
quantities?
The maximum power will be delivered to a load with the same resistance as the
battery's internal resistance but that only gives you 1/2 the energy to the
load. The other half is dissipated by the battery. If the load is infinite
the power delivered is zero but all of the energy gets dissipated by the load.
;-)
Now, do you want the maximum power or the maximum energy. ...or something
else? - Hide quoted text -
- Show quoted text -
Yeah, I did a bit of this back in the 90's. I designed a 20 MHz RfOn Thu, 28 Apr 2011 18:38:47 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 28, 1:22 pm, John Fields <jfie...@austininstruments.com> wrote:
On Thu, 28 Apr 2011 07:27:42 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 28, 9:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Thu, 28 Apr 2011 06:20:28 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce..
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Well here is where at least some of them get their information,
http://hyperphysics.phy-astr.gsu.edu/hbase/audio/imped.html#c2
Was there ever a time in audio when 'electronic'* impedance matching
was important?
If you had an old-fashioned no-feedback class A tube amp, like in an
old radio, you'd get maximum volume, which you'd probably want, if the
amp and speaker impedances were equal.
John- Hide quoted text -
- Show quoted text -
Oh, So if I was making just a class A emmitter follower to drive the
speaker, I'd want the DC idle current equal to the max at full
volume... I'd then have equal impedances.... Still it seems wrong to
call it "impedance matching".
George H.
---
You're missing the point, which is that if you have a tube-based
amplifier with, say, a 250VPP swing in plate voltage and an 8 ohm
loudspeaker as a load being driven at 10 watts, then the current in
the speaker would be:
P 10W
I = sqrt --- = sqrt ----- = 1.25 amperes, RMS
R 8R
Theoretically, the best efficiency you can get out of a class "A"
amplifier is 50%, so if the tube is dissipating 10 watts when it's
driving 10 watts into the load, then the plate resistance of the tube
must be:
VRMS˛
Rp = ------
P
Then, since:
(VPP/2) 125V
VRMS = --------- = ------ ~ 89.3V,
sqrt(2) 1.4
The plate resistance must be:
89.3V˛
Rp = ------- ~ 800 ohms
10W
We're now stuck with the problem of how to transfer 10 watts from an
800 ohm source into an 8 ohm load, and to solve it we'll do impedance
matching by using a transformer with an 800 ohm primary connected
between the tube's plate and its supply, and its 8 ohm secondary
connected across the loudspeaker.
--
JF- Hide quoted text -
- Show quoted text -
Thanks for the nice explanation John, You use the turns ratio of the
transformer to match the impedances.
The impedance changes with the *square* of the turns ratio. With a 2:1 ratio,
the voltage doubles, but current halves. 2/.5 = 4.
Do you need to specify the
resistance of the load/source too?
Not for this calculation. See above.
I'm pretty much an idiot when it
comes to tube amps. (If you couldn't tell.)
Never touch them.- Hide quoted text -
- Show quoted text -
Even EEs...On Apr 28, 11:55 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Thu, 28 Apr 2011 18:57:58 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:19 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Wed, 27 Apr 2011 08:11:13 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 10:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 27 Apr 2011 06:50:17 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce.
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Thanks Phil, These are physics people. One of the freshman physics
problems that everyone does is finding the load resistance that gives
the maximum power from a battery with some internal resistance. This
then becomes the 'model' for all impedance matching questions. I'll
try posting a gentle correction...
George H.
Point out that half the total power is lost inside the battery,
reducing available watt-hours in half... maybe worse. Batteries and
power plants shouldn't operate that way.
John- Hide quoted text -
- Show quoted text -
Yeah, I can try.
Tell them that power and energy aren't the same thing. Perhaps they heard
something to that effect somewhere back in high school physics.
I've been directed to the maximum power transfer theorem,
http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem.
Has anyone ever used this?
It's this 'd@mn' battery and resistor problem. I didn't know it got a
whole theorem named after it.
Um, let me try it... You do know that power and energy are different
quantities?
The maximum power will be delivered to a load with the same resistance as the
battery's internal resistance but that only gives you 1/2 the energy to the
load. The other half is dissipated by the battery. If the load is infinite
the power delivered is zero but all of the energy gets dissipated by the load.
;-)
Now, do you want the maximum power or the maximum energy. ...or something
else? - Hide quoted text -
- Show quoted text -
Thanks, I know all this.... It's trying to explain it to some phyiscs
people that's hard.
George H.
---George Herold a écrit :
On Apr 28, 11:55 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Thu, 28 Apr 2011 18:57:58 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:19 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Wed, 27 Apr 2011 08:11:13 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 10:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 27 Apr 2011 06:50:17 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce.
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Thanks Phil, These are physics people. One of the freshman physics
problems that everyone does is finding the load resistance that gives
the maximum power from a battery with some internal resistance. This
then becomes the 'model' for all impedance matching questions. I'll
try posting a gentle correction...
George H.
Point out that half the total power is lost inside the battery,
reducing available watt-hours in half... maybe worse. Batteries and
power plants shouldn't operate that way.
John- Hide quoted text -
- Show quoted text -
Yeah, I can try.
Tell them that power and energy aren't the same thing. Perhaps they heard
something to that effect somewhere back in high school physics.
I've been directed to the maximum power transfer theorem,
http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem.
Has anyone ever used this?
It's this 'd@mn' battery and resistor problem. I didn't know it got a
whole theorem named after it.
Um, let me try it... You do know that power and energy are different
quantities?
The maximum power will be delivered to a load with the same resistance as the
battery's internal resistance but that only gives you 1/2 the energy to the
load. The other half is dissipated by the battery. If the load is infinite
the power delivered is zero but all of the energy gets dissipated by the load.
;-)
Now, do you want the maximum power or the maximum energy. ...or something
else? - Hide quoted text -
- Show quoted text -
Thanks, I know all this.... It's trying to explain it to some phyiscs
people that's hard.
George H.
Even EEs...
I just received a request for a 27MHz power amplifier design with >70%
efficiency and an output SWR=1.1
OK, now I'm confused. You asked if anyone had used the "maximum powerOn Apr 28, 11:55 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Thu, 28 Apr 2011 18:57:58 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:19 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Wed, 27 Apr 2011 08:11:13 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 10:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 27 Apr 2011 06:50:17 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce.
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Thanks Phil, These are physics people. One of the freshman physics
problems that everyone does is finding the load resistance that gives
the maximum power from a battery with some internal resistance. This
then becomes the 'model' for all impedance matching questions. I'll
try posting a gentle correction...
George H.
Point out that half the total power is lost inside the battery,
reducing available watt-hours in half... maybe worse. Batteries and
power plants shouldn't operate that way.
John- Hide quoted text -
- Show quoted text -
Yeah, I can try.
Tell them that power and energy aren't the same thing. Perhaps they heard
something to that effect somewhere back in high school physics.
I've been directed to the maximum power transfer theorem,
http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem.
Has anyone ever used this?
It's this 'd@mn' battery and resistor problem. I didn't know it got a
whole theorem named after it.
Um, let me try it... You do know that power and energy are different
quantities?
The maximum power will be delivered to a load with the same resistance as the
battery's internal resistance but that only gives you 1/2 the energy to the
load. The other half is dissipated by the battery. If the load is infinite
the power delivered is zero but all of the energy gets dissipated by the load.
;-)
Now, do you want the maximum power or the maximum energy. ...or something
else? - Hide quoted text -
- Show quoted text -
Thanks, I know all this.... It's trying to explain it to some phyiscs
people that's hard.
even touch on the subject in college. The profs took them out of the syllabusOn Apr 28, 11:59 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Thu, 28 Apr 2011 18:38:47 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 28, 1:22 pm, John Fields <jfie...@austininstruments.com> wrote:
On Thu, 28 Apr 2011 07:27:42 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 28, 9:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Thu, 28 Apr 2011 06:20:28 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce.
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Well here is where at least some of them get their information,
http://hyperphysics.phy-astr.gsu.edu/hbase/audio/imped.html#c2
Was there ever a time in audio when 'electronic'* impedance matching
was important?
If you had an old-fashioned no-feedback class A tube amp, like in an
old radio, you'd get maximum volume, which you'd probably want, if the
amp and speaker impedances were equal.
John- Hide quoted text -
- Show quoted text -
Oh, So if I was making just a class A emmitter follower to drive the
speaker, I'd want the DC idle current equal to the max at full
volume... I'd then have equal impedances.... Still it seems wrong to
call it "impedance matching".
George H.
---
You're missing the point, which is that if you have a tube-based
amplifier with, say, a 250VPP swing in plate voltage and an 8 ohm
loudspeaker as a load being driven at 10 watts, then the current in
the speaker would be:
P 10W
I = sqrt --- = sqrt ----- = 1.25 amperes, RMS
R 8R
Theoretically, the best efficiency you can get out of a class "A"
amplifier is 50%, so if the tube is dissipating 10 watts when it's
driving 10 watts into the load, then the plate resistance of the tube
must be:
VRMS˛
Rp = ------
P
Then, since:
(VPP/2) 125V
VRMS = --------- = ------ ~ 89.3V,
sqrt(2) 1.4
The plate resistance must be:
89.3V˛
Rp = ------- ~ 800 ohms
10W
We're now stuck with the problem of how to transfer 10 watts from an
800 ohm source into an 8 ohm load, and to solve it we'll do impedance
matching by using a transformer with an 800 ohm primary connected
between the tube's plate and its supply, and its 8 ohm secondary
connected across the loudspeaker.
--
JF- Hide quoted text -
- Show quoted text -
Thanks for the nice explanation John, You use the turns ratio of the
transformer to match the impedances.
The impedance changes with the *square* of the turns ratio. With a 2:1 ratio,
the voltage doubles, but current halves. 2/.5 = 4.
Do you need to specify the
resistance of the load/source too?
Not for this calculation. See above.
I'm pretty much an idiot when it
comes to tube amps. (If you couldn't tell.)
Never touch them.- Hide quoted text -
- Show quoted text -
Yeah, I did a bit of this back in the 90's. I designed a 20 MHz Rf
amp. Three stages with several watts at the output.. Driving coils to
do NMR. The design approach was to calculate the power gain of each
stage, and the input and output impedances and then insert the proper
transformers to make it all work.... (And then f around to get it to
turn on fast and not ring... )
The only tube I've used was in a ham rig back in high school[*]. They didn't
Should have read SWR<1.1 Not that the difference matters...On Fri, 29 Apr 2011 20:02:24 +0200, Fred Bartoli <" "> wrote:
George Herold a écrit :
On Apr 28, 11:55 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Thu, 28 Apr 2011 18:57:58 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:19 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Wed, 27 Apr 2011 08:11:13 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 10:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 27 Apr 2011 06:50:17 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce.
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Thanks Phil, These are physics people. One of the freshman physics
problems that everyone does is finding the load resistance that gives
the maximum power from a battery with some internal resistance. This
then becomes the 'model' for all impedance matching questions. I'll
try posting a gentle correction...
George H.
Point out that half the total power is lost inside the battery,
reducing available watt-hours in half... maybe worse. Batteries and
power plants shouldn't operate that way.
John- Hide quoted text -
- Show quoted text -
Yeah, I can try.
Tell them that power and energy aren't the same thing. Perhaps they heard
something to that effect somewhere back in high school physics.
I've been directed to the maximum power transfer theorem,
http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem.
Has anyone ever used this?
It's this 'd@mn' battery and resistor problem. I didn't know it got a
whole theorem named after it.
Um, let me try it... You do know that power and energy are different
quantities?
The maximum power will be delivered to a load with the same resistance as the
battery's internal resistance but that only gives you 1/2 the energy to the
load. The other half is dissipated by the battery. If the load is infinite
the power delivered is zero but all of the energy gets dissipated by the load.
;-)
Now, do you want the maximum power or the maximum energy. ...or something
else? - Hide quoted text -
- Show quoted text -
Thanks, I know all this.... It's trying to explain it to some phyiscs
people that's hard.
George H.
Even EEs...
I just received a request for a 27MHz power amplifier design with >70%
efficiency and an output SWR=1.1
50W, but power has nothing to do in the non sense requirement.---
How much power?
Yeah, when I was in school (late 60s) the EE department had. They didn't
even touch on the subject in college. The profs took them out of the syllabus
in the '60s.
[*] The 750V plate supply literally hurt! Haven't touched them since. ;-)
In the 37 years since I graduated, I've run into the need to use a tubeOn Fri, 29 Apr 2011 19:31:19 -0500, "krw@att.bizzzzzzzzzzzz"
krw@att.bizzzzzzzzzzzz> wrote:
The only tube I've used was in a ham rig back in high school[*]. They didn't
even touch on the subject in college. The profs took them out of the syllabus
in the '60s.
[*] The 750V plate supply literally hurt! Haven't touched them since. ;-)
Yeah, when I was in school (late 60s) the EE department had
already ditched tubes... but curiously they were still part
of the ME curriculum. When I mentioned this to one of the
EE profs he was pretty dismissive, equal parts "why would
you want to know about that old stuff" and "it's easy enough
to just figure out yourself". (Ha!) I was a bit miffed...
not only were we missing out on a fundamental topic (and it
was still pretty important then), but also those danged MEs
were getting it and we weren't!
Sorry for the confusion. So the "maximum power transfer theorem" isOn Fri, 29 Apr 2011 06:28:44 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 28, 11:55 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Thu, 28 Apr 2011 18:57:58 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:19 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Wed, 27 Apr 2011 08:11:13 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 10:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 27 Apr 2011 06:50:17 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce.
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Thanks Phil, These are physics people. One of the freshman physics
problems that everyone does is finding the load resistance that gives
the maximum power from a battery with some internal resistance. This
then becomes the 'model' for all impedance matching questions. I'll
try posting a gentle correction...
George H.
Point out that half the total power is lost inside the battery,
reducing available watt-hours in half... maybe worse. Batteries and
power plants shouldn't operate that way.
John- Hide quoted text -
- Show quoted text -
Yeah, I can try.
Tell them that power and energy aren't the same thing. Perhaps they heard
something to that effect somewhere back in high school physics.
I've been directed to the maximum power transfer theorem,
http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem.
Has anyone ever used this?
It's this 'd@mn' battery and resistor problem. I didn't know it got a
whole theorem named after it.
Um, let me try it... You do know that power and energy are different
quantities?
The maximum power will be delivered to a load with the same resistance as the
battery's internal resistance but that only gives you 1/2 the energy to the
load. The other half is dissipated by the battery. If the load is infinite
the power delivered is zero but all of the energy gets dissipated by the load.
;-)
Now, do you want the maximum power or the maximum energy. ...or something
else? - Hide quoted text -
- Show quoted text -
Thanks, I know all this.... It's trying to explain it to some phyiscs
people that's hard.
OK, now I'm confused. You asked if anyone had used the "maximum power
transfer theorem". Sure, I've used it but it's silly in the context of a
battery since the goal is rarely to transfer the maximum power from a battery
to the load. Solar cell, sure. A battery? *Rarely*.- Hide quoted text -
- Show quoted text -
Got me, but the physics is there. The purpose, is to maximize power transfer,On Apr 29, 8:26 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Fri, 29 Apr 2011 06:28:44 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 28, 11:55 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Thu, 28 Apr 2011 18:57:58 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:19 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Wed, 27 Apr 2011 08:11:13 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 10:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 27 Apr 2011 06:50:17 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce.
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Thanks Phil, These are physics people. One of the freshman physics
problems that everyone does is finding the load resistance that gives
the maximum power from a battery with some internal resistance. This
then becomes the 'model' for all impedance matching questions. I'll
try posting a gentle correction...
George H.
Point out that half the total power is lost inside the battery,
reducing available watt-hours in half... maybe worse. Batteries and
power plants shouldn't operate that way.
John- Hide quoted text -
- Show quoted text -
Yeah, I can try.
Tell them that power and energy aren't the same thing. Perhaps they heard
something to that effect somewhere back in high school physics.
I've been directed to the maximum power transfer theorem,
http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem.
Has anyone ever used this?
It's this 'd@mn' battery and resistor problem. I didn't know it got a
whole theorem named after it.
Um, let me try it... You do know that power and energy are different
quantities?
The maximum power will be delivered to a load with the same resistance as the
battery's internal resistance but that only gives you 1/2 the energy to the
load. The other half is dissipated by the battery. If the load is infinite
the power delivered is zero but all of the energy gets dissipated by the load.
;-)
Now, do you want the maximum power or the maximum energy. ...or something
else? - Hide quoted text -
- Show quoted text -
Thanks, I know all this.... It's trying to explain it to some phyiscs
people that's hard.
OK, now I'm confused. You asked if anyone had used the "maximum power
transfer theorem". Sure, I've used it but it's silly in the context of a
battery since the goal is rarely to transfer the maximum power from a battery
to the load. Solar cell, sure. A battery? *Rarely*.- Hide quoted text -
- Show quoted text -
Sorry for the confusion. So the "maximum power transfer theorem" is
used in solar cell design?
This is one case where maximum power transfer from a fixed source is the goal.Obvioulsy we want the maximum power from a
solar cell, is there a balancing of impedances?
Everything real has some impedance. Superconductors have no resistance, butOn May 2, 6:37 pm, "k...@att.bizzzzzzzzzzzz" <k...@att.bizzzzzzzzzzzz
wrote:
On Mon, 2 May 2011 07:56:35 -0700 (PDT), George Herold <gher...@teachspin.com
wrote:
On Apr 29, 8:26 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Fri, 29 Apr 2011 06:28:44 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 28, 11:55 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Thu, 28 Apr 2011 18:57:58 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:19 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Wed, 27 Apr 2011 08:11:13 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 10:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 27 Apr 2011 06:50:17 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce.
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Thanks Phil, These are physics people. One of the freshman physics
problems that everyone does is finding the load resistance that gives
the maximum power from a battery with some internal resistance. This
then becomes the 'model' for all impedance matching questions. I'll
try posting a gentle correction...
George H.
Point out that half the total power is lost inside the battery,
reducing available watt-hours in half... maybe worse. Batteries and
power plants shouldn't operate that way.
John- Hide quoted text -
- Show quoted text -
Yeah, I can try.
Tell them that power and energy aren't the same thing. Perhaps they heard
something to that effect somewhere back in high school physics.
I've been directed to the maximum power transfer theorem,
http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem.
Has anyone ever used this?
It's this 'd@mn' battery and resistor problem. I didn't know it got a
whole theorem named after it.
Um, let me try it... You do know that power and energy are different
quantities?
The maximum power will be delivered to a load with the same resistance as the
battery's internal resistance but that only gives you 1/2 the energy to the
load. The other half is dissipated by the battery. If the load is infinite
the power delivered is zero but all of the energy gets dissipated by the load.
;-)
Now, do you want the maximum power or the maximum energy. ...or something
else? - Hide quoted text -
- Show quoted text -
Thanks, I know all this.... It's trying to explain it to some phyiscs
people that's hard.
OK, now I'm confused. You asked if anyone had used the "maximum power
transfer theorem". Sure, I've used it but it's silly in the context of a
battery since the goal is rarely to transfer the maximum power from a battery
to the load. Solar cell, sure. A battery? *Rarely*.- Hide quoted text -
- Show quoted text -
Sorry for the confusion. So the "maximum power transfer theorem" is
used in solar cell design?
Got me, but the physics is there. The purpose, is to maximize power transfer,
though the source isn't a simple linear Thevinin-ish source.
Obvioulsy we want the maximum power from a
solar cell, is there a balancing of impedances?
This is one case where maximum power transfer from a fixed source is the goal.
It rarely is.
(I'll google and see what I find.)- Hide quoted text -
- Show quoted text -- Hide quoted text -
- Show quoted text -
Oh, so all power generators have an 'impedance',
Do you want maximum power transferred or do you want maximum efficiency?(though I've never
heard it refered to as such.) an optimium load that they would 'like'
to see. (I'm picturing some human powered generator, a variable
transformer, and a load.)
No. Why would you want to do that? If you're measuring voltage, youAren't all transducers involved with some sort of impedance matching?
(For maximum power transfer)
Oh, so all power generators have an 'impedance', (though I've neverOn Mon, 2 May 2011 07:56:35 -0700 (PDT), George Herold <gher...@teachspin..com
wrote:
On Apr 29, 8:26 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Fri, 29 Apr 2011 06:28:44 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 28, 11:55 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Thu, 28 Apr 2011 18:57:58 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:19 pm, "k...@att.bizzzzzzzzzzzz"
k...@att.bizzzzzzzzzzzz> wrote:
On Wed, 27 Apr 2011 08:11:13 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 10:46 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 27 Apr 2011 06:50:17 -0700 (PDT), George Herold
gher...@teachspin.com> wrote:
On Apr 27, 9:18 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"George Herold"
There was a question about speaker impedances (8 Ohms vs.. 4 Ohms.).
On a list server that I follow. Several reponders mumbled about
matching of the speaker impedance to the amplifier impedance.
To me this sounded like a lot of hooey. I assume modern audio amps
have very low output impedance. And that the 4 or 8 ohms is more
about the maximum voltage and current that the amp can produce.
** Fact:
Matching an amp's RATED load impedance to a speaker's NOMINAL impedance
is what is meant.
Only the dumbest of jerks confuse * actual source impedance* with the
former.
The two are simply NOT RELATED in value at all.
.... Phil
Thanks Phil, These are physics people. One of the freshman physics
problems that everyone does is finding the load resistance that gives
the maximum power from a battery with some internal resistance. This
then becomes the 'model' for all impedance matching questions. I'll
try posting a gentle correction...
George H.
Point out that half the total power is lost inside the battery,
reducing available watt-hours in half... maybe worse. Batteries and
power plants shouldn't operate that way.
John- Hide quoted text -
- Show quoted text -
Yeah, I can try.
Tell them that power and energy aren't the same thing. Perhaps they heard
something to that effect somewhere back in high school physics.
I've been directed to the maximum power transfer theorem,
http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem.
Has anyone ever used this?
It's this 'd@mn' battery and resistor problem. I didn't know it got a
whole theorem named after it.
Um, let me try it... You do know that power and energy are different
quantities?
The maximum power will be delivered to a load with the same resistance as the
battery's internal resistance but that only gives you 1/2 the energy to the
load. The other half is dissipated by the battery. If the load is infinite
the power delivered is zero but all of the energy gets dissipated by the load.
;-)
Now, do you want the maximum power or the maximum energy. ...or something
else? - Hide quoted text -
- Show quoted text -
Thanks, I know all this.... It's trying to explain it to some phyiscs
people that's hard.
OK, now I'm confused. You asked if anyone had used the "maximum power
transfer theorem". Sure, I've used it but it's silly in the context of a
battery since the goal is rarely to transfer the maximum power from a battery
to the load. Solar cell, sure. A battery? *Rarely*.- Hide quoted text -
- Show quoted text -
Sorry for the confusion. So the "maximum power transfer theorem" is
used in solar cell design?
Got me, but the physics is there. The purpose, is to maximize power transfer,
though the source isn't a simple linear Thevinin-ish source.
Obvioulsy we want the maximum power from a
solar cell, is there a balancing of impedances?
This is one case where maximum power transfer from a fixed source is the goal.
It rarely is.
(I'll google and see what I find.)- Hide quoted text -
- Show quoted text -- Hide quoted text -
- Show quoted text -