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Old 10-04-2012, 05:33 PM   #21
Captaincranky
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Quote:
Originally Posted by AcousticMirror
too high an impedance will damage a tube amp.
And that depends on what you call "too high"? I seen to recall output transformers that had different taps for different impedance loudspeakers.
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Old 10-04-2012, 05:38 PM   #22
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dawg if you plug a cab into the tap it was meant for then it's by definition not too high. it is just right.
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Old 10-04-2012, 05:45 PM   #23
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Originally Posted by AcousticMirror
dawg if you plug a cab into the tap it was meant for then it's by definition not too high. it is just right.
And then it won't damage the amp, now will it?
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Old 10-04-2012, 05:47 PM   #24
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no of course not plugging the right cab into the right tap will not damage the amp.

going too high will.

is this hard to understand.
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Old 10-04-2012, 05:50 PM   #25
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Originally Posted by Captaincranky
Say WUT?

Yeah, higher impedance reduces current flow, which reduces heat. However, too low impedance simply put, is a "short circuit".

I didn't realize I had to explain what too high impedance causes, which is much reduced power output. But, speaker impedance which is, "too high", won't damage a tube or a transistor amp.

The reason you hear a "click" a few seconds after you turn a home entertainment receiver, is because it disconnects the output transistors from the speaker circuit, and only connects the speakers after the PSU caps are charged.

This is done to prevent "current inrush", caused the caps charging, from damaging the output transistors...


Quote:
Originally Posted by Captaincranky
No, solid states amps DON'T have output transformers, and that makes impedance matching MORE critical.




Make up your mind...

The simple fact is that SS amps have a minimum impedance, but not a maximum. Tube amps have both, although there are of course design criteria that allow a certain degree of mismatch, but it's nowhere near the order of what can be done with a SS amp.

Being wrong, and then trying to cover it up by saying 'I didn't know I had to explain THAT part' is childish.
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Old 10-04-2012, 06:00 PM   #26
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Originally Posted by Arby911
Make up your mind...

The simple fact is that SS amps have a minimum impedance, but not a maximum. Tube amps have both, although there are of course design criteria that allow a certain degree of mismatch, but it's nowhere near the order of what can be done with a SS amp.
Being wrong, and then trying to cover it up by saying 'I didn't know I had to explain THAT part' is childish.
No, too little current won't cause heating, too high current will. High current comes from low impedance. I really didn't think I had to explain that. In your case, I was wrong.
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Old 10-04-2012, 06:05 PM   #27
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It is especially critical with solid state amps, to match the impedance of the cabinets, to the amp's optimum impedance. Otherwise, she dun gonna blow....!


Those are your exact words. What other way should someone take that then to mean any mismatch will cause the amp damage?
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Old 10-04-2012, 06:10 PM   #28
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Quote:
Originally Posted by Captaincranky
No, too little current won't cause heating, too high current will. High current comes from low impedance. I really didn't think I had to explain that. In your case, I was wrong.


Yes, because I'm the one that's been wrong repeatedly above....

You are priceless!

There are a fair few folks here that know more about electricity and electronics than I do, but you don't appear to be one of them.

And in all fairness, perhaps you do know a good bit, but it's pretty clear you don't know as much as you think you do. (Or if you do, you really suck at presentation...)
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Old 10-04-2012, 06:20 PM   #29
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Originally Posted by Arby911

There are a fair few folks here that know more about electricity and electronics than I do, but you don't appear to be one of them.


OK, lets deal with specs. Since you are more knowledgeable than most folks here, well start with series and parallel resistance,

Two four ohm speakers in parallel present 2 ohms of impedance. With a SS amp rated @ 8 ohms, that likely would damage the amp. It could even hurt an amp rated a 4 ohms minimum.

Two 8 ohm speakers wired in series would present 16 ohms to a amp. I'm reasonably sure a tube amp rated @ 8 ohms, would tolerate that much mismatch. Nor would a single 4 ohm speaker likely damage the same a tube amp either.

Within the confines of those limits, I suggest a tube amp is less vulnerable to damage than a SS amp.

But yeah, the transistor amp is only at risk to the low side. Too high an impedance across its output transistors, by and large, just shuts it off.

Last edited by Captaincranky : 10-04-2012 at 06:24 PM.
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Old 10-04-2012, 06:27 PM   #30
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Quote:
Originally Posted by Captaincranky
OK, lets deal with specs. Since you are more knowledgeable than most folks here, well start with series an parallel resistance,

Two four ohm speakers in parallel present 2 ohms of impedance. With a SS amp rated @ 8 ohms, that likely would damage the amp. It could even hurt an amp rated a 4 ohms minimum.

Two 8 ohm speakers wired in series would present 16 ohms to a amp. I'm reasonably sure a tube amp rated @ 8 ohms, would tolerate that much mismatch. Nor would a single 4 ohm speaker likely damage the same a tube amp either.

Within the confines of those limits, I suggest a tube amp is less vulnerable than a SS amp.

But yeah, the transistor amp is only at risk to the low side. Too high an impedance across its output transistors, by and large, just shuts it off.


It's amusing that you've artificially set the question, and then determined the answer to your preconception based on arbitrary values of your own making.

Look, I've taken a gander at several of your other postings as well as the circumstances of your warning, and from what I can see you take great pleasure in stirring up controversy (as often as not by posting marginal or outright false information).

That won't go over well in this particular forum.

Don't go away mad, just go away. Or learn to play well with others.
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Old 10-04-2012, 06:35 PM   #31
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Originally Posted by Arby911
It's amusing that you've artificially set the question, and then determined the answer to your preconception based on arbitrary values of your own making.
Are those values realistic or not? They're not really, "values of my own making", nor are they "arbitrary". They're simply factors of 1/2 or 2 times the typical load impedance of typical SS or tube amplifiers. So, what is the likely effect of a 1/2X or 2X impedance mismatch on either type of amp?
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Old 10-04-2012, 06:38 PM   #32
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Quote:
Originally Posted by Captaincranky
OK, lets deal with specs. Since you are more knowledgeable than most folks here, well start with series and parallel resistance,

Two four ohm speakers in parallel present 2 ohms of impedance. With a SS amp rated @ 8 ohms, that likely would damage the amp. It could even hurt an amp rated a 4 ohms minimum.

Two 8 ohm speakers wired in series would present 16 ohms to a amp. I'm reasonably sure a tube amp rated @ 8 ohms, would tolerate that much mismatch. Nor would a single 4 ohm speaker likely damage the same a tube amp either.

Within the confines of those limits, I suggest a tube amp is less vulnerable to damage than a SS amp.

But yeah, the transistor amp is only at risk to the low side. Too high an impedance across its output transistors, by and large, just shuts it off.


I don't agree with the 4 ohm load on an 8 ohm tube amp. I've done that before, to a MESA of all amps which are DESIGNED to handle that and it ended up red plating the output tubes in no time. Mesa brand tubes as well. Yes, it didn't destroy the amp, but MESAs are purposely over spec'd to handle this mismatch, in general most tube amps aren't.

In general mismatching the load ohms over the output ohms is safe for all amps, but it will be some strain on the output tubes of a tube amp. As for an SS amp, if anything it'll be less strain. Your assertion that tube amps can handle more of a mismatch is too general for one thing, not backed up by any evidence, and, in the end, generally not true.
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Old 10-04-2012, 06:51 PM   #33
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Originally Posted by Kevin Saale
I don't agree with the 4 ohm load on an 8 ohm tube amp. I've done that before, to a MESA of all amps which are DESIGNED to handle that and it ended up red plating the output tubes in no time. Mesa brand tubes as well. Yes, it didn't destroy the amp, but MESAs are purposely over spec'd to handle this mismatch, in general most tube amps aren't.
Part of problem of even entertaining this entire discussion in relation to musical instrument amps, is that they undergo quite a lot of abuse. Low impedance causes high current flow, on that we agree. If we used these amps in a sensible manner, who knows what the disposition would be..

However, overdrives, distortion pedals, and whatnot, add really deviant signal waveforms and bandwidth to the equation. Amp clipping is notoriously deadly for speakers. To much signal delivered to the output stage isn't good for any amp.

Suppose we abandon this altogether, and suggest to the OP, "just make certain the impedance of the cabinet you choose, is matched to the amp's output impedance, or you may have problems".

On that note, I suggest the TS pick out the amp first, then the cabinet last.

That shouldn't be too contentious, but who knows.
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Old 10-04-2012, 07:18 PM   #34
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Originally Posted by Captaincranky
Part of problem of even entertaining this entire discussion in relation to musical instrument amps, is that they undergo quite a lot of abuse. Low impedance causes high current flow, on that we agree. If we used these amps in a sensible manner, who knows what the disposition would be..

However, overdrives, distortion pedals, and whatnot, add really deviant signal waveforms and bandwidth to the equation. Amp clipping is notoriously deadly for speakers. To much signal delivered to the output stage isn't good for any amp.

Suppose we abandon this altogether, and suggest to the OP, "just make certain the impedance of the cabinet you choose, is matched to the amp's output impedance, or you may have problems".

On that note, I suggest the TS pick out the amp first, then the cabinet last.

That shouldn't be too contentious, but who knows.


That IS what the first posters said. Then you come out of left field with bullshit, get called on it then back pedal into a debate. Just sayin.
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Old 10-04-2012, 07:43 PM   #35
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Originally Posted by Captaincranky
, "just make certain the impedance of the cabinet you choose, is matched to the amp's output impedance, or you may have problems".
.


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Old 10-05-2012, 04:06 AM   #36
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this is so confusing, what with all the posturing

tube amp -> match impedance (cab impedance should match the speakers out).

solid state -> use a speaker that is >= amp's min impedance.

...and i thought i was long winded.

cab's power handling needs to be rated at the amp's output or greater.
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Old 10-05-2012, 10:42 AM   #37
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I didn't realize when I started this thread, I would have commenced this great debate over something that I am now EXTREMELY confused on . So I will just check back when the fact checking has been done and a winner has been chosen.
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Old 10-05-2012, 10:49 AM   #38
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Originally Posted by Kevin Saale
That IS what the first posters said. Then you come out of left field with bullshit, get called on it then back pedal into a debate. Just sayin.

I'm just sayin' too.
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Old 10-05-2012, 10:53 AM   #39
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Originally Posted by FenderBender72
I didn't realize when I started this thread, I would have commenced this great debate over something that I am now EXTREMELY confused on . So I will just check back when the fact checking has been done and a winner has been chosen.


Don't be confused, the first line of post #2 is correct and was all you needed.

Ignore the rest.
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Old 10-05-2012, 10:58 AM   #40
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Dude, don't be confused. On a tube amp, match the impedance. period. It is generally a good idea to get a cab that is at bare minimum rated for the wattage of your amp, and many folks would suggest a cab rated over the output of the amp, but that is getting into another debate about different speakers being rated more conservatively than others.

This thread kinda turned silly, but that is what happens when you have a person arguing for the sake of arguing, who isn't even particularly good at presenting their argument.
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