A friend of mine accidently connected a solid-state power amp(switched on) and a pair of tube power amp(switched off) to the same speaker through speaker cables. As soon as the solid-state amp was switched on there was some sharp noice from the tweeters and the amp was immediately switched off but the damage was done. There was smoke from the tweeters and smoke, and later inspection and testing showed that the tweeters were burnt and a diaphragm of one mid compression driver was damaged, and the speaker crossovers(resistors, caps and inductors) went bad as well. There was damage in the non-playing tube power amps as well. And when the solid-state power amp was checked later, there were no issues found it it.
Now, the question is: how did so much damage happen, what could have caused it, especially when the tube amp was switched off. Somebody suggested that since the tube amps were switched off, it would have no effect whatsoever.
Can someone with technical know-how throw some light on the cause of the incident, was it some kind of interaction between the amplifiers or some grounding issues or oscillation in the solid-state power amp?
Now, the question is: how did so much damage happen, what could have caused it, especially when the tube amp was switched off. Somebody suggested that since the tube amps were switched off, it would have no effect whatsoever.
Can someone with technical know-how throw some light on the cause of the incident, was it some kind of interaction between the amplifiers or some grounding issues or oscillation in the solid-state power amp?
Did the amplifiers have the inputs connected to some common source?
Either the solid state amp reacted poorly with some resonance on the tube amp output transformer or there was a signal path through the inputs that caused a bad oscillation.
Anyway, this sort of thing can easily happen when two amplifiers have their outputs connected.
Either the solid state amp reacted poorly with some resonance on the tube amp output transformer or there was a signal path through the inputs that caused a bad oscillation.
Anyway, this sort of thing can easily happen when two amplifiers have their outputs connected.
My guess is when the solid state power Amp turned on, it see a very low lmpedance load (speaker paralleled to the tube amps output transformer secondary windings), it overload the SS Amp and caused clipping. If the clipping signal is high enough, it will fried the speaker high/mid drivers. If the tube amps output transformer can't handle the high current produced by the SS Amp, it will be fried as well.
I'm guessing the solid state amp oscillated due to the reactive load of the output transformer in the tube amp. A high-frequency, rail-to-rail oscillation will kill tweeters and mids pretty quick.
If the solid state amp is reasonably powerful it would generate quite a bit of voltage across the primary of the output transformer in the tube amp. That could fry some things. Do you know what fried in the tube amp?
Tom
If the solid state amp is reasonably powerful it would generate quite a bit of voltage across the primary of the output transformer in the tube amp. That could fry some things. Do you know what fried in the tube amp?
Tom
The tube amp was a dht gm70 amp. It was not connected to any source, and apparently it did not suffer much damage, just the resistors were burnt in the heater part. The solid-state amp was Quad 606 mk2.
@Galu, @daqvin_carter, @chrisng, @tomchr
A clarification, first a Schiit Aegir was connected in the same way with the tube amp, and it played fine and no adverse effects happened. Then the Quad was connected which caused the damage. Is it possible that the 2 solid-state amps can react differently due to different topology, power ratings, etc. The Quad has been running without issues for several years, and was found to be working and measuring perfectly in later technical check-up.
A clarification, first a Schiit Aegir was connected in the same way with the tube amp, and it played fine and no adverse effects happened. Then the Quad was connected which caused the damage. Is it possible that the 2 solid-state amps can react differently due to different topology, power ratings, etc. The Quad has been running without issues for several years, and was found to be working and measuring perfectly in later technical check-up.
Absolutely. How an amp reacts to a reactive load depends on its topology and how it's compensated internally. How much damage it'll cause when it goes unstable depends on the power rating of the power amp.
I don't either. Unless, maybe, they're cathode resistors in a DHT type circuit.
Tom
Absolutely, the high reactance of the tube output transformer sent the SS amp into oscillation. An almost guaranteed way to kill tweeters. [B]Anike[/B]t you say there is no damage to the SS amp. Check again there will a zobel network across the outputs, small cap and resistor in series. Its job it to protect against oscillation from long speaker leads etc. Good chance you have taken those out as well, the amp will still play but it won't have protection.