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In Reply to: wtf just happened ?!?!?! posted by snkby on February 2, 2007 at 19:36:54:
using the headphone out i get 144.5mv on the left and 2.0mv on the right.using the line-out i get 2.0mv for both channels.
i was using the attenuator of the headphone out to drive the marchand xm-1 active xover.
the cdp has always had a nasty little --pop-- if you skip tracks or program tracks but no pop when started from beginning to end.
Follow Ups:
my wife bumped the right speaker off of its stand but i was able to catch it before it fell.i didnt bother to put it back in place as i was watching our daughter all day and wouldnt be able to do any work on the system anyway.
i gave it a quick look-over and everything seemed ok wrt wires shorting or being pulled loose.
because it is all still in the prototype stage i have it all wired with audiofool-grade alligator test leads.
its never happened to me before but........could the leads for the right subs have momentarily shorted and caused the damage to the driver ?
in the past ive accidentally shorted speaker leads and caused damage to the amp/receiver but never to a speaker.
im thinking if they shorted briefly maybe the arc was enough to separate them also ?
It is hard to connect the dots. Only so much you can do over the net. Some of the DC offsets you mention seem a little high. 10ma is bad enough but a 100ma isn't okay with me.A tube amp doesn't like to see an open ciruit to the speakers and a transistor amps doesn't like to see a short. I don't know where a digital amp stands. The speaker doesn't care as long as it is external.
When something unexplained happens, out of the blue for no good reason, I think power blink stuff. That said, a constant DC offset from a source amplified by the rest of the chain can indeed overheat and damage a voice coil. The speaker intended to do the bass is the one that isn't going to have any blocking cap and therefore most vulnerable despite having the biggest voice coil.
So I guess I'd be looking to see what DC offset I had going to the drivers. And with active (op amp) crossovers a simple power blink could possibly throw a lot of DC out.
Doubt I helped but a few things to consider.
something there.the batteries supplying the power for the xover were from my powertools and being used just for testing.
i had to rig the power leads with tape and at 1 point lost power because the tape on 1 contact got loose.
i wonder if 1 of the taped leads arced on the battery terminal ?
but then why only the right speaker and the side that has the lowest dc offset throughout ?
bought a xformer yesterday to make a real psu for the xover.
watching the kids all day so it will have to wait until tomorrow.
alligator clips, tape, power tool batteries???this sounds like a disaster... are you really surprised you're having trouble with your "prototype" system?
wrong with batteries whether powertool or not ?and who doesnt use alligator clips ?
you live and learn (hopefully) and what i learned was to not trust power connections to iffy electrical tape.
building the --real-- psu today. :)
and --prototypes-- especially first tries are usually cobbled together with whatever is at hand.
if one of your supply rails on a differential PSU fails - one that has a +, - and ground (i.e has a potential of 0v (ground potential) for what-ever reason, that will produce a large offset that will be amplified.Comfortably enough to fry a voicecoil using your normal amp.
Hope this helps
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