GC damaging speakers?

[drfrink24]

Refering to my other thread here:

Clipping GC?

I found that the mid/high distortion was a result of my mids being blown on a pair of speakers I've been using as rear channels, not clipping or a lack of Zobel or whatever...

Well, I hooked up some crappy pioneer speakers (8 ohms 40w max) speakers that I had sitting in the basement from an old "stereo in a box" from the mid 90s. Crappy as the sound was, they played nice and loud, I think I got then up to 100db peaks without much fuss.

I was listening to them in the mid 80db range a while yesterday, and now this morning, without much volume, I can get them to audibly distort.

Now I'm really starting to get concerned that I might be destroying whatever speakers that I audition with this.

The thing is, its not like it sounds bad, I just turn them up a bit to get some nice "realistic" volumes, and then pretty soon the crackling appears...

I don't have a scope, but I do have a digital multi-meter, is there anything I can do to test the output and see if something in my CG is tearing up these speakers?

Maybe its just a huge coincedence, but, sure doesn't seem like it.

[homer09]

i did not read your other thread, but basic no scope needed test is DC offset. did you check how much your GC is spitting out?

[drfrink24]

No, I haven't checked it. From what I've read, you need a tone generator, dummy loads, etc...

How would one go about doing this?

[tiroth]

No, just set your multimeter to DC and measure across the binding posts. There should be no signal at input when performing this test, although I would leave the preamp or source connected, since some people have grounding/DC blocking issues that only show up when the system is assembled.

[homer09]

oh no no, nothing so complicated. You simply need to measure the voltage across your speaker terminals of your GC while its on playing.

check out this:

http://www.decdun.fsnet.co.uk/gaincloneFAQ.html

towards the bottom, there is a scetion on what to check before connecting your speakers, Nuuk talks about DC offset.

If you dont have dummy resistors (ie. something in the range of 8 ohms with at least 2W rating), use some dispensable speakers

[drfrink24]

Ok, just got done, don't know what this means, or if its good/bad.. This is with input connected, but, no signal.


Multimeter set to 2v (.000), red lead to red on speaker term, black to black.

Left channel is -.064, right channel is -.067

[homer09]

your DC offset is good and within acceptable range.

[drfrink24]

Alright, thats good. Anything else to test?

This is specifically going to be powering tweeters, and, so far, I've heard 4 speakers in this setup, all of which very quickly developed some pretty bad distortion at higher levels. This distortion now is present with another commercial integrated amplifier, using the same speakers...

[homer09]

maybe you are overpowering you're speakers beyond their rated wattage?

also, check dc offset at every position of your volume control, and with every source you use.

[PMA]

HF oscillations above certain output level?