How long to ruin an OT running wrong impedance?

[Blacque Jacque]

Mesa/Boogie already does that w/ the warranty. Tada

But this is Marshallforum

 

[zachman]

But this is Marshallforum

The Boogie warranty is still valid, none the less.

 

[Ken]

The Boogie warranty is still valid, none the less.

Correct, and in a Mesa forum encouraging a mismatch is fine. Mesas are like Porsches: they don't break. Marshalls are more like a Lotus: when you use them correctly they are reliable, but they don't take kindly to unintended use. It's irresponsible to say a mismatch on a Marshall is okay just because Mesas have a warranty.

Ken

 

[zachman]

Correct, and in a Mesa forum encouraging a mismatch is fine. Mesas are like Porsches: they don't break. Marshalls are more like a Lotus: when you use them correctly they are reliable, but they don't take kindly to unintended use. It's irresponsible to say a mismatch on a Marshall is okay just because Mesas have a warranty.

Ken

Ken, first-- I am not 'encouraging' mismatching anything.

2nd-- I didn't say, "a mismatch on a Marshall is okay just because Mesas have a warranty".

Go back and re-read what I actually said.

Try reading slower, so as to allow for some comprehension beyond just sounding out the words. It's all there.

 

[wallythacker]

What I'm taking away from the discussion is this;

If the amp is working fine now and shows no hiccups after a prolonged high volume session at the right impedance chances are the OT is fine and not damaged in any material way.

What you do afterwards in terms of impedance matching is in your own hands.

 

[mickeydg5]

Mesa incorporate's more governor devices.
Marshall has less restrictions.
I am guessing though that you cannot hear the difference in the speeds but the engines will feel them.

No matter how the amplifier, something like 50 or 100 watt, would or could be mismatched at the output it will not blow while operating at 1 watt with a load. The problems occur when things are turned up, heated and putting out higher power. Remember some of those Marshalls can accomplish 90 watts or so from dimed 50 watt amplifier.

 

[zachman]

Mesa incorporate's more governor devices.
Marshall has less restrictions.
I am guessing though that you cannot hear the difference in the speeds but the engines will feel them.

No matter how the amplifier, something like 50 or 100 watt, would or could be mismatched at the output it will not blow while operating at 1 watt with a load. The problems occur when things are turned up, heated and putting out higher power.

Correct.

I find that the quality of modern tubes being made to much lower quality than the old mil spec GE, Sylvania, Mullard, is more of a concern re: mismatching impedances w/ 'Marshall' amps than using ex a 16 Ohm cab w/ a Head set to 8 Ohms-- being the culprit to fail and cause amp damage via a hard short of a power tube, than the EE theory re: impedance mismatch, in my example. It is BEST to match the impedance between amp and cab, because even then a hard short of a power tube can occur, and potentially cause burned grid resistors, anode and cathode, burned/melted tube sockets etc...

 

[yladrd61]

What I'm taking away from the discussion is this;

If the amp is working fine now and shows no hiccups after a prolonged high volume session at the right impedance chances are the OT is fine and not damaged in any material way.

What you do afterwards in terms of impedance matching in your own head.

It would be a good idea to replace and bias the power tubes, and also replace the electrolytic capacitors and screen resistors

 

[anitoli]

It will also partly depend on having good output bottles.

A load mismatch will cause excess power that is not delivered to the load to be reflected back into the system. Some will be dissipated in the transformer, some in the tubes themselves.

^ this right here^ especially with EL34's. Excessive electron return to the screen grid creates excessivie heat which will lead to premature tube death. There is a hefty positive potential on the screen. This was incorporated to accelerate electrons onto the plate, not soak them up.

 

[anitoli]

Ahh, i found it. This is a good explanation of mismatch:

Determining Output Transformer Reflected Loads