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High Frequency Oscillation hurt resistors in Magico A5 crossovers

Hi,I am looking for help understanding how HFO could blow crossover resistors in Magico A5 speakers. Equipment playing at the time of the incident is as follows...
Magico A5 speakersHegel H30 mono blocksHegel P30 preamp (lt and rt inputs on the Aux inputs from the laptop and Dragonfly Cobalt)
Dell laptopAudioquest Dragonfly CobaltAmazon Hi-res streaming
I was listening to Amazon music at a very moderate level when the application said there was an update available.I instinctively clicked accept while music was paying. It was only off for a few seconds to update and when complete and I restarted music the A5 tweeters were not on. These happened simultaneously and there was no audible noise what so ever indicating a potential issue. After multiple source tests and tweeter test, I was certain the tweeters were fine and it was an electronic issue. The cross overs were removed and sent to Magico and that was when I was told that HFO blew the resistors.
Can anyone explain how/why this happened so I can ideally avoid it happening again?
Thank you!
128x128howaanders8
73max
46 posts
 
What kind of speaker cables are you using? Mega capacitance cables can cause high frequency oscillations with some amplifiers. Even more likely if you biwire. HF Oscillations are self-sustaining with ever increasing level once started due to the signal “reflecting” in the cable. With digital audio and high bandwidth amplifiers the chance to trigger this increases. While amplifiers  are often designed to mitigate this, I am not a fan of very high capacitance speaker cables. The effect is similar to a feedback loop you hear when a microphone picks up it’s own speaker but well above audible frequencies.
howaanders8's avatar
howaanders8 OP
22 posts
 
Wireworld Eclipse 7 Copper I believe. No bi-wires.
73max
46 posts
 
Can’t find specific capacitance per foot measurements. Not familiar with the design or layout of your cables. Generally speaking, flat layouts with “positive” and “negative” leads in close proximity increases capacitance. The greater the surface area the +/- present to each other and the closer together the greater the capacitance. The close proximity is typically used to decrease inductive losses at higher frequencies but it comes at the cost of higher capacitance.  It’s Generally accepted that this is a good thing (some might argue that) and capacitance at speaker level has minimal effect unless it gets so high that you drive the amplifier into HF oscillation.  
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