Is it dangerous to the output transistors or something to run a radio
without speakers?

What if the volume control is kept at the minimum?

This wouldn't be a problem with a tube set iiuc, right?, but I'm not
so sure about transistors, if, say, the volume were accidentally
turned high. (No I didn't do that, but I was wondering how much
effort I should expend just so I can turn the set on and measure some
voltages.)

If you are inclined to email me
for some reason, remove NOPSAM :-)

mm wrote:

Is it dangerous to the output transistors or something to run a radio
without speakers?

What if the volume control is kept at the minimum?

This wouldn't be a problem with a tube set iiuc, right?, but I'm not
so sure about transistors, if, say, the volume were accidentally
turned high. (No I didn't do that, but I was wondering how much
effort I should expend just so I can turn the set on and measure some
voltages.)

with tr amps its harmless, do what you like with the vol ctrl. With
most valve sets its harmless, but perhaps not all. Sometimes valve amps
were fitted with spark gaps on the output transformer HT side.


NT

It is best to run any amplifier with a matched load. If you turn up the
volume, but not to the clipping point, there should not be any damage. But,
running any amplifier with no load is not something I would recommend.

--

JANA
_____


"mm" wrote in message
...
Is it dangerous to the output transistors or something to run a radio
without speakers?

What if the volume control is kept at the minimum?

This wouldn't be a problem with a tube set iiuc, right?, but I'm not
so sure about transistors, if, say, the volume were accidentally
turned high. (No I didn't do that, but I was wondering how much
effort I should expend just so I can turn the set on and measure some
voltages.)

If you are inclined to email me
for some reason, remove NOPSAM :-)

On Tuesday 26 December 2006 09:13, wrote:

with tr amps its harmless, do what you like with the vol ctrl.

I second this. I've built and rebuilt several transistor amps, from 60W to
500W, and running without a load is not a problem. The final stage, the
current amplification, only starts pulling current when there is something to
dump it into.

Meat Plow wrote:
On Tue, 26 Dec 2006 00:13:43 -0800, meow2222 Has Frothed:
mm wrote:

Is it dangerous to the output transistors or something to run a radio
without speakers?

What if the volume control is kept at the minimum?

This wouldn't be a problem with a tube set iiuc, right?, but I'm not
so sure about transistors, if, say, the volume were accidentally
turned high. (No I didn't do that, but I was wondering how much
effort I should expend just so I can turn the set on and measure some
voltages.)

with tr amps its harmless, do what you like with the vol ctrl. With
most valve sets its harmless, but perhaps not all. Sometimes valve amps
were fitted with spark gaps on the output transformer HT side.

Some vintage valve guitar amps had a shunt prong across the 1/4" spkr
output jack when the plug wasn't in it. IIRC Marshall amps had a warning
tag that to operate the amp without a load or with a resistive attenuator
would void the warranty. I know that operating most any class AB1 valve
amp is risky to the OT.

I had an old amp that would spark across the spark gap with no load
connected. But whats the mechanism for that? No load cant take any Vs
higher than normal run voltage, unless theres some kind of LC thing
going on in the op tf, and no load means no damping.


NT

wrote:

I had an old amp that would spark across the spark gap with no load
connected. But whats the mechanism for that? No load cant take any Vs
higher than normal run voltage, unless theres some kind of LC thing
going on in the op tf, and no load means no damping.


Have you ever seen the output tubes arc over internally when there is
no load? The spikes exceed the maximum plate voltage, and you have
major problems. it an trip the power supply, damage the tubes, or cause
a complete meltdown of the tubes. Its quite a sight when a broadcast
transmitter loses its load, and the plate relays don't trip out.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

I had an old amp that would spark across the spark gap with no load
connected. But whats the mechanism for that? No load cant take any Vs
higher than normal run voltage, unless theres some kind of LC thing
going on in the op tf, and no load means no damping.




The voltage can rise to the point that the insulation in the output
transformer windings breaks down and arcs over, destroying the transformer.

"mm" wrote in message
...
Is it dangerous to the output transistors or something to run a radio
without speakers?

What if the volume control is kept at the minimum?

This wouldn't be a problem with a tube set iiuc, right?, but I'm not
so sure about transistors, if, say, the volume were accidentally
turned high. (No I didn't do that, but I was wondering how much
effort I should expend just so I can turn the set on and measure some
voltages.)

With transistor amplifiers, they are all some form of emitter-followers
(common-collector) and they can run safely with no output load.

Tube amplifiers can produce voltage spikes when unloaded.

Meat Plow wrote:
On Tue, 26 Dec 2006 07:19:09 -0800, meow2222 Has Frothed:
Meat Plow wrote:
On Tue, 26 Dec 2006 00:13:43 -0800, meow2222 Has Frothed:
mm wrote:

Is it dangerous to the output transistors or something to run a radio
without speakers?

with tr amps its harmless, do what you like with the vol ctrl. With
most valve sets its harmless, but perhaps not all. Sometimes valve amps
were fitted with spark gaps on the output transformer HT side.

Some vintage valve guitar amps had a shunt prong across the 1/4" spkr
output jack when the plug wasn't in it. IIRC Marshall amps had a warning
tag that to operate the amp without a load or with a resistive attenuator
would void the warranty. I know that operating most any class AB1 valve
amp is risky to the OT.

I had an old amp that would spark across the spark gap with no load
connected. But whats the mechanism for that? No load cant take any Vs
higher than normal run voltage, unless theres some kind of LC thing
going on in the op tf, and no load means no damping.

Not sure, I just trusted the word of my elders that damage could occur.
Maybe some of the deeper thinkers in alt.guitar.amps could explain exactly
what mechanism(s) is/are involved in damaging a AB amp with no load. Now
that you've (sparked)laughs my curiosity, I'm eager to know.

I see thread has already jumped the gap to the guitar group, lets hope
it sparks someone's curiosity there too. Perhaps someone's resistance
to contributing will break down, and they'll tell us something that
resonates with us all.


NT
--
Tube e or not tube e

wrote:
Meat Plow wrote:

On Tue, 26 Dec 2006 07:19:09 -0800, meow2222 Has Frothed:

Meat Plow wrote:

On Tue, 26 Dec 2006 00:13:43 -0800, meow2222 Has Frothed:

mm wrote:


Is it dangerous to the output transistors or something to run a radio
without speakers?


with tr amps its harmless, do what you like with the vol ctrl. With
most valve sets its harmless, but perhaps not all. Sometimes valve amps
were fitted with spark gaps on the output transformer HT side.


Some vintage valve guitar amps had a shunt prong across the 1/4" spkr
output jack when the plug wasn't in it. IIRC Marshall amps had a warning
tag that to operate the amp without a load or with a resistive attenuator
would void the warranty. I know that operating most any class AB1 valve
amp is risky to the OT.


I had an old amp that would spark across the spark gap with no load
connected. But whats the mechanism for that? No load cant take any Vs
higher than normal run voltage, unless theres some kind of LC thing
going on in the op tf, and no load means no damping.


Not sure, I just trusted the word of my elders that damage could occur.
Maybe some of the deeper thinkers in alt.guitar.amps could explain exactly
what mechanism(s) is/are involved in damaging a AB amp with no load. Now
that you've (sparked)laughs my curiosity, I'm eager to know.


I see thread has already jumped the gap to the guitar group, lets hope
it sparks someone's curiosity there too. Perhaps someone's resistance
to contributing will break down, and they'll tell us something that
resonates with us all.


NT
http://www.geofex.com/tubeampfaq/taffram.htm

also:

"This varies from amp to amp. Some amps have no problem at
all with being unloaded, as long as no signal is being passed.
Others (certain Boogies, for instance) will break into oscillation
when the impedance of the feedback loop changes when the
speakers are disconnected. If your amp is wired so that a
switching jack is used to throw a short across the amp's
output when the plug is removed, then everything will be
fine. If you have a standby switch, it's always a good idea
to put the amp on standby when removing or connecting
speaker cords."

The speaker presents a “load” on an amplifier, just as a “flywheel”
presents a load on an internal combustion engine.

http://guitargeek.com/chat/showthrea...threadid=46544
"SPEAKERS & OHMS!!!! Everything you need to know about SPEAKERS & OHMS!!!

Ohms:
A value of electrical resistance. The lower the number, the less
resistance. The higher the number, the greater the resistance.


Speakers are rated at certain ohms (or impedance), most commonly, 4, 8,
and 16.

Your amplifier is also rated at a certain impedance, or has multiple
taps for speaker configurations. It is important that you match
these numbers up.


EXAMPLE --- 8 ohm cabinet---8 ohm jack on amp
EXAMPLE --- 4 ohm cabinet---4 ohm jack on amp
EXAMPLE --- 16 ohm cabinet---16 ohm jack on amp



It is typically safe to mismatch one step higher


EXAMPLE --- 8 ohm cabinet---4 ohm jack on amp.
EXAMPLE --- 16 ohm cabinet---8 ohm jack on amp.



Now for the do-not do's.




NEVER EVER hook up a cabinet with a lower ohm rating than the head.

EXAMPLE ---4 ohm cabinet---8 ohm jack on amp...THIS IS A NO-NO!!!

You will cause your output transformer to overheat, and eventually, it
will blow.


NEVER - Turn on a tube amp without a speaker load attached to it. This
can cause an output transformer to blow in a short time.

The only instance where it would be safe to turn on a tube amp without a
load would be on amps that have a standby switch (Class AB typically)
This would only be for visual diagnostics (tube heater check, bulb
check, etc) BUT, DO NOT take it off of standby. While it's in standby,
only the tube heaters are working, and will not cause damage to the
output transformer.

Also, NEVER use instrument cable to hook up a speaker cabinet. The
speaker jack can put out a high enough voltage to burn the small wire in
instrument cable, thus leaving the amp without a load, and frying the
output transformer. ALWAYS use a good heavy speaker cable.

General Speaker Info

Sensitivity - This number indicates how efficient the speaker works.
Generally, this number will be between 89 and 105. If you replace a
speaker with one of a higher sensitivity rating, you will also increase
the apparent volume.

Generally speaking, an increase of +3dB will double the overall loudness
of the amp.

Wattage - How much the speaker can handle. Smaller, combo amps usually
have a speaker rating close to the rating of the amp. If when cranked,
you don't like the sound of the speaker breaking up, then you might look
into changing it out with one of a higher wattage. Some like the way a
speaker sounds while being pushed to it's limits, and some don't. It's
all in your presonal taste.



Wiring up multiple speakers.



When wiring speakers, there are three ways to do it

SERIES: one wire from the input jack to the "+" terminal of one speaker,
from the "-" terminal of the same speaker to the "+" of the next
speaker, last wire from the "-" terminal to the input jack. When wiring
speakers in series, multiply the ohms by the number of speakers used.
Also, when one speaker blows, it will cut power to the other speaker as
well, leaving both speakers not working.

EXAMPLE: jack------"+ '8ohm' -" ----"+ '8ohm' -" ---jack=16ohms

8x2 = 16



PARALLEL: One wire from the input jack to the "+" terminals of both
speakers. Other wire from the input jack to the "-" terminals of both
speakers. When wiring speakers in parallel, divide the ohms by the
number of speakers used.
In this case, when a speaker blows, the remaining speaker will still work.

EXAMPLE:
jack----"+ '8ohm'"------------ "+'8ohm'"
jack----" - '8ohm'"-------------"- '8ohm'" = 4 ohms

8/2 = 4

This is also the way you will want to hook up multiple cabinets to an amp.

EXAMPLE: (2) 8 ohm cabinets ----4 ohm jack on amp.
EXAMPLE: (2) 16 ohm cabinets---8 ohm jack on amp.


SERIES-PARALLEL:

This is the most confusing. The total speaker load will equal the ohms
of one speaker. Most commonly used on speaker cabinets that contain 4
speakers. This theory only works with 4 speakers of the same (ohm) rating.
In this case, if a speaker blows, it will take out it's series
counterpart, leaving two speakers working, and two not working, hence
doubling the impedance.


Starting at the upper left speaker, you will run one wire from the input
jack to the "+" of that speaker, then from the same terminal to the "+"
of the speaker below it.
Then run a wire from the input jack to the "-" of the upper right
speaker, then from the same terminal to the "-" of the speaker below it.
Finally, connect the "-" of the upper left speaker to the "+" of the
upper right speaker, and the "-" of the lower left speaker to the "+" of
the lower right speaker.

Wiring Multiple Cabinets

Sometimes, it's inevitable that we need to run multiple cabs of
different impedances. Well, here's how you figure out how to solve that
problem.

EXAMPLE:

The amp has 4, 8, and 16 ohm taps.

Cabinet A = 8 ohms
Cabinet B = 16 ohms

In this case,

1/8 +1/16 = 3/16

Divide the back number by the front number to get the impedance.

16/3 = 5.33

You would want to run both cabinets from the 4 ohm taps, or daisy chain
them if (2) 4 ohms taps aren't available. Remember, it's safe to run a
slightly higher mismatch.

....And just as a reference

(2) 8 ohm cabs = 4 ohms
(2) 4 ohms cabs = 2 ohms - *typically unsafe*
(2) 16 ohms cabs = 8 ohms

(1) 8 ohm cab + (1) 4 ohm cab = 2.66 ohms - *typically unsafe*
(1) 4 ohm cab + (1) 16 ohm cab = 3.2 ohms - *somewhat unsafe*

The two above examples would typically be unsafe to run at, although,
the very bottom example would be better to run, since it's closer to 4
ohms. This would get by in a pinch on some occasions.

[disclaimer]

The information provided above is a general reference. In some
circumstances, it may not be appropriate to mismatch impedances. Use
common sense, and consult the manufacturer if possible. If you are in
doubt, the safest bet is to find a cab that has a nominal rating of that
of your amp. I am not responsible for damages caused from mismatching
impedances.

[/disclaimer]

"TD Madden" wrote in message
. ..
wrote:
Meat Plow wrote:

On Tue, 26 Dec 2006 07:19:09 -0800, meow2222 Has Frothed:

Meat Plow wrote:

On Tue, 26 Dec 2006 00:13:43 -0800, meow2222 Has Frothed:

mm wrote:


Is it dangerous to the output transistors or something to run a radio
without speakers?


with tr amps its harmless, do what you like with the vol ctrl. With
most valve sets its harmless, but perhaps not all. Sometimes valve
amps
were fitted with spark gaps on the output transformer HT side.


Some vintage valve guitar amps had a shunt prong across the 1/4" spkr
output jack when the plug wasn't in it. IIRC Marshall amps had a
warning
tag that to operate the amp without a load or with a resistive
attenuator
would void the warranty. I know that operating most any class AB1 valve
amp is risky to the OT.


I had an old amp that would spark across the spark gap with no load
connected. But what's the mechanism for that? No load cant take any Vs
higher than normal run voltage, unless there's some kind of LC thing
going on in the op tf, and no load means no damping.


Not sure, I just trusted the word of my elders that damage could occur.
Maybe some of the deeper thinkers in alt.guitar.amps could explain
exactly
what mechanism(s) is/are involved in damaging a AB amp with no load. Now
that you've (sparked)laughs my curiosity, I'm eager to know.


I see thread has already jumped the gap to the guitar group, lets hope
it sparks someone's curiosity there too. Perhaps someone's resistance
to contributing will break down, and they'll tell us something that
resonates with us all.


NT
http://www.geofex.com/tubeampfaq/taffram.htm

also:

"This varies from amp to amp. Some amps have no problem at
all with being unloaded, as long as no signal is being passed.
Others (certain Boogies, for instance) will break into oscillation
when the impedance of the feedback loop changes when the
speakers are disconnected. If your amp is wired so that a
switching jack is used to throw a short across the amp's
output when the plug is removed, then everything will be
fine. If you have a standby switch, it's always a good idea
to put the amp on standby when removing or connecting
speaker cords."

The speaker presents a “load” on an amplifier, just as a “flywheel”
presents a load on an internal combustion engine.

http://guitargeek.com/chat/showthrea...threadid=46544
"SPEAKERS & OHMS!!!! Everything you need to know about SPEAKERS & OHMS!!!

Ohms:
A value of electrical resistance. The lower the number, the less
resistance. The higher the number, the greater the resistance.


Speakers are rated at certain ohms (or impedance), most commonly, 4, 8,
and 16.

Your amplifier is also rated at a certain impedance, or has multiple taps
for speaker configurations. It is important that you match
these numbers up.


EXAMPLE --- 8 ohm cabinet---8 ohm jack on amp
EXAMPLE --- 4 ohm cabinet---4 ohm jack on amp
EXAMPLE --- 16 ohm cabinet---16 ohm jack on amp



It is typically safe to mismatch one step higher


EXAMPLE --- 8 ohm cabinet---4 ohm jack on amp.
EXAMPLE --- 16 ohm cabinet---8 ohm jack on amp.



Now for the do-not do's.




NEVER EVER hook up a cabinet with a lower ohm rating than the head.

EXAMPLE ---4 ohm cabinet---8 ohm jack on amp...THIS IS A NO-NO!!!

You will cause your output transformer to overheat, and eventually, it
will blow.


NEVER - Turn on a tube amp without a speaker load attached to it. This can
cause an output transformer to blow in a short time.

The only instance where it would be safe to turn on a tube amp without a
load would be on amps that have a standby switch (Class AB typically) This
would only be for visual diagnostics (tube heater check, bulb check, etc)
BUT, DO NOT take it off of standby. While it's in standby, only the tube
heaters are working, and will not cause damage to the output transformer.

Also, NEVER use instrument cable to hook up a speaker cabinet. The speaker
jack can put out a high enough voltage to burn the small wire in
instrument cable, thus leaving the amp without a load, and frying the
output transformer. ALWAYS use a good heavy speaker cable.

General Speaker Info

Sensitivity - This number indicates how efficient the speaker works.
Generally, this number will be between 89 and 105. If you replace a
speaker with one of a higher sensitivity rating, you will also increase
the apparent volume.

Generally speaking, an increase of +3dB will double the overall loudness
of the amp.

Wattage - How much the speaker can handle. Smaller, combo amps usually
have a speaker rating close to the rating of the amp. If when cranked, you
don't like the sound of the speaker breaking up, then you might look into
changing it out with one of a higher wattage. Some like the way a speaker
sounds while being pushed to it's limits, and some don't. It's all in your
personal taste.



Wiring up multiple speakers.



When wiring speakers, there are three ways to do it

SERIES: one wire from the input jack to the "+" terminal of one speaker,
from the "-" terminal of the same speaker to the "+" of the next speaker,
last wire from the "-" terminal to the input jack. When wiring speakers in
series, multiply the ohms by the number of speakers used.
Also, when one speaker blows, it will cut power to the other speaker as
well, leaving both speakers not working.

EXAMPLE: jack------"+ '8ohm' -" ----"+ '8ohm' -" ---jack=16ohms

8x2 = 16



PARALLEL: One wire from the input jack to the "+" terminals of both
speakers. Other wire from the input jack to the "-" terminals of both
speakers. When wiring speakers in parallel, divide the ohms by the number
of speakers used.
In this case, when a speaker blows, the remaining speaker will still work.

EXAMPLE:
jack----"+ '8ohm'"------------ "+'8ohm'"
jack----" - '8ohm'"-------------"- '8ohm'" = 4 ohms

8/2 = 4

This is also the way you will want to hook up multiple cabinets to an amp.

EXAMPLE: (2) 8 ohm cabinets ----4 ohm jack on amp.
EXAMPLE: (2) 16 ohm cabinets---8 ohm jack on amp.


SERIES-PARALLEL:

This is the most confusing. The total speaker load will equal the ohms of
one speaker. Most commonly used on speaker cabinets that contain 4
speakers. This theory only works with 4 speakers of the same (ohm) rating.
In this case, if a speaker blows, it will take out it's series
counterpart, leaving two speakers working, and two not working, hence
doubling the impedance.


Starting at the upper left speaker, you will run one wire from the input
jack to the "+" of that speaker, then from the same terminal to the "+" of
the speaker below it.
Then run a wire from the input jack to the "-" of the upper right speaker,
then from the same terminal to the "-" of the speaker below it.
Finally, connect the "-" of the upper left speaker to the "+" of the upper
right speaker, and the "-" of the lower left speaker to the "+" of the
lower right speaker.

Wiring Multiple Cabinets

Sometimes, it's inevitable that we need to run multiple cabs of different
impedances. Well, here's how you figure out how to solve that problem.

EXAMPLE:

The amp has 4, 8, and 16 ohm taps.

Cabinet A = 8 ohms
Cabinet B = 16 ohms

In this case,

1/8 +1/16 = 3/16

Divide the back number by the front number to get the impedance.

16/3 = 5.33

You would want to run both cabinets from the 4 ohm taps, or daisy chain
them if (2) 4 ohms taps aren't available. Remember, it's safe to run a
slightly higher mismatch.

...And just as a reference

(2) 8 ohm cabs = 4 ohms
(2) 4 ohms cabs = 2 ohms - *typically unsafe*
(2) 16 ohms cabs = 8 ohms

(1) 8 ohm cab + (1) 4 ohm cab = 2.66 ohms - *typically unsafe*
(1) 4 ohm cab + (1) 16 ohm cab = 3.2 ohms - *somewhat unsafe*

The two above examples would typically be unsafe to run at, although, the
very bottom example would be better to run, since it's closer to 4 ohms.
This would get by in a pinch on some occasions.

[disclaimer]

The information provided above is a general reference. In some
circumstances, it may not be appropriate to mismatch impedances. Use
common sense, and consult the manufacturer if possible. If you are in
doubt, the safest bet is to find a cab that has a nominal rating of that
of your amp. I am not responsible for damages caused from mismatching
impedances.

[/disclaimer]

Very interesting FYI Thanks.

On Tue, 26 Dec 2006 17:35:26 -0500, "Charles Schuler"
wrote:


"mm" wrote in message
.. .
Is it dangerous to the output transistors or something to run a radio
without speakers?

What if the volume control is kept at the minimum?

This wouldn't be a problem with a tube set iiuc, right?, but I'm not
so sure about transistors, if, say, the volume were accidentally
turned high. (No I didn't do that, but I was wondering how much
effort I should expend just so I can turn the set on and measure some
voltages.)

With transistor amplifiers, they are all some form of emitter-followers
(common-collector) and they can run safely with no output load.

Tube amplifiers can produce voltage spikes when unloaded.

So it looks like I almost had it backwards, and tube amps need more
care about running without speakers. But iireadc, transistor amps can
also have problems under some circumstances. So I will keep to my
cautious ways at all times, unless there is an overwhelming reason not
to.

Thanks to everyone. (I still have to finish reading thios thread
too!)

If you are inclined to email me
for some reason, remove NOPSAM :-)

"Warren Weber" wrote in message
...

"TD Madden" wrote in message
....
[/disclaimer]

Very interesting FYI Thanks.

Jeebus, folks, trim your frickin' replies.

"Mee too bye!"
__
Steve
..

mm wrote:

So it looks like I almost had it backwards, and tube amps need more
care about running without speakers. But iireadc, transistor amps can
also have problems under some circumstances. So I will keep to my
cautious ways at all times, unless there is an overwhelming reason not
to.

A tr audio amp isn't going to have a problem with no speaker load,
ever. And thats regardless of whether its low z output, as nearly all
are, or current drive, as a very few are.


NT

TD Madden wrote:

"This varies from amp to amp. Some amps have no problem at
all with being unloaded, as long as no signal is being passed.
Others (certain Boogies, for instance) will break into oscillation
when the impedance of the feedback loop changes when the
speakers are disconnected.

It looks at first sight like an explanation, but I'm not sure it really
is. Here's why. Whether an amp is driving max output or oscillating
with no load, in either case the output pentodes can only deliver so
much V swing to the output iron. The v limit is the same in either
case. So why would one cause arcing and the other not? Why does
oscillation create more primary V swing than audio?

I can think of 2 perhapses. One may be that due to valve impedance the
pentode can produce more v swing when not loaded than when loaded. But
still it takes around 300v to arc across a small gap in air, and I've
seen quite a small amp arc across an air gap when unloaded, and while I
dont know for sure, I wouldnt expect B+ to be over 300v on that one,
more like 250.

2ndly there might be an LC resonance within the output iron, possibly
in combination with some other capacitance, causing a voltage
magnification. The frequency of that will pull the closed loop whole
amp resonant frequency to it, and if the 2 are close enough one could
get ac voltage above B+ on the output tfs.

Is there any truth in either of these 2?


NT

On Tue, 26 Dec 2006 18:36:18 -0500, TD Madden
wrote:

It is typically safe to mismatch one step higher


EXAMPLE --- 8 ohm cabinet---4 ohm jack on amp.
EXAMPLE --- 16 ohm cabinet---8 ohm jack on amp.

It is typically safer to mismatch one step *lower* on a tube amp.

EXAMPLE --- 8 ohm jack on amp---4 ohm cabinet.


-Dave

mm wrote:
Is it dangerous to the output transistors or something to run a radio
without speakers?

Why the **** would you want to run a radio without speakers?

What if the volume control is kept at the minimum?

What if you use a condom when you **** Magic Johnson?

This wouldn't be a problem with a tube set iiuc, right?,
If you want to watch something glow then turn on a toaster, or better
yet, get a ****ing life.

but I'm not so sure about transistors, if, say, the volume were accidentally
turned high. (No I didn't do that, but I was wondering how much
effort I should expend just so I can turn the set on and measure some
voltages.)

There are no speakers connected so you shouldn't have to worry about
your hearing.


If you are inclined to email me
for some reason, remove NOPSAM :-)

Why would I want to email somebody who tries to listen to the radio
without any speakers connected?

Meat Plow wrote:

Not sure, I just trusted the word of my elders that damage could occur.
Maybe some of the deeper thinkers in alt.guitar.amps could explain exactly
what mechanism(s) is/are involved in damaging a AB amp with no load. Now
that you've (sparked)laughs my curiosity, I'm eager to know.

No deep thinking required. The mechanism is inductive kickback in the
primary of the output transformer.

Think of it this way. If there is no load on the map, then the
secondary of the output transformer can't conduct any current. If it
never conducts, then for purposes of mental exercise, it isn't even
there. You could (in your mind) physically remove the secondary without
changing the situation in question.

At that point, you are left with a pair of push-pull output tubes
connected to the ends of an inductor - the output transformer primary.
The inductor has a center tap which is connected to a power supply.
When one of the tubes turns on, current begins to flow in it's half of
the primary. The current builds up at a rate determined by the
inductance of the primary. Once current is flowing, what happens if the
tube suddenly drops out of conduction? (Think of an audio transient like
a drum-snap). The result is that the current can't continue to flow,
but the energy stored in the inductor's magnetic field has nowhere to
go. The magnetic field collapses and produces a very high counter-emf
(i.e., voltage spike).

This is the same mechanism that generates the high-voltage spark in a
car ignition or a television flyback - allow current to flow, then
suddenly cut it off.

By the way, this can happen in ANY amplifier, tube or solid-state, that
uses an output transformer. In most practical cases, though, tube-based
amps use an output transformer because tubes are high-impedance devices
that have to be matched to the low-impedance load (the speakers).
Transistor-based amps have an inherently low output impedance, and so do
not require a matching transformer.

Bill

Malissa Baldwin wrote:


mm wrote:
Is it dangerous to the output transistors or something to run a radio
without speakers?

Why the **** would you want to run a radio without speakers?


Simple:
a) Take load from the rest of the system to check for instability in the PSU
b) Maybe a Radio has tons of other functions that are desireable (RDS et.
al. )
c) maybe the speakers are in one part of the chassis, the electronics in the
other, and for maintenance you got to open it?


What if the volume control is kept at the minimum?

What if you use a condom when you **** Magic Johnson?


Simple, too:
You won't get Aids or any other funny disease.

This wouldn't be a problem with a tube set iiuc, right?,
If you want to watch something glow then turn on a toaster, or better
yet, get a ****ing life.

Best stuff to look at glowing is either sunrise or sundown, or the coal in a
grill whilst doing barbecue-grilling.


but I'm not so sure about transistors, if, say, the volume were
accidentally
turned high. (No I didn't do that, but I was wondering how much
effort I should expend just so I can turn the set on and measure some
voltages.)

There are no speakers connected so you shouldn't have to worry about
your hearing.


Unless he's an extraterrestrial he cannot hear electronic signals inside
some circuits, but he might be toasting the transistors depending on the
design. And that would



If you are inclined to email me
for some reason, remove NOPSAM :-)

Why would I want to email somebody who tries to listen to the radio
without any speakers connected?

Oh my - why I am trying to explain obvious things to a fern that
accidentally dropped on it's users keyboard?
Oh, no. Was preteen-schoolkid on daddy's computer, right?

Malissa: Plonk
--
Sincerely

Ruediger

On Thursday 28 December 2006 10:49, Rüdiger wrote:

Oh my - why I am trying to explain obvious things to a fern that
accidentally dropped on it's users keyboard?
Oh, no. Was preteen-schoolkid on daddy's computer, right?

Malissa: Plonk

Best way to treat people like this, it to give em the silent treatment,
otherwise they'll come back for more. So, no more replies on this
sub-thread

If you are inclined to email me
for some reason, remove NOPSAM :-)

Why would I want to email somebody who tries to listen to the radio
without any speakers connected?


Why do you keep posting useless posts? Quit Trolling and go away.

Michael Kennedy wrote:

Why would I want to email somebody who tries to listen to the radio
without any speakers connected?

Why do you keep posting useless posts? Quit Trolling and go away.

dont treed the folls.

NT