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Kilowatt 2nd January 2002 02:02 AM

Help! distortion problem
 
For now, I have a system that I have rigged up until I have my Leach amps done, and the distortion levels are through the roof! I can hear it as clear as day, the upper frequencies are filled with intolerable buzzing and scratching sounds especially when certain notes hit.

It's all set up something like this:
[IMG]C:\My Documents\mysystm.bmp[/IMG]

I can unplug the little CD player and play from my computer, or disconnect my computer with the switch and play from the CD player or other source, it sounds bad either way. It sounds slightly better with the EQ bipassed, but still pretty bad, and the spectrum analyzer on the stereo says I'm not clipping. I don't know what the problem is. What do you think could be wrong?

AudioFreak 2nd January 2002 02:13 AM

your graphic is not appearing.

Kilowatt 2nd January 2002 02:34 AM

2 Attachment(s)
Here it is:

AudioFreak 2nd January 2002 02:36 AM

I'd say this is almost certainly a ground loop problem.

Kilowatt 2nd January 2002 02:44 AM

Keep in mind that it's not just noise, but rather distortion. It sounds good enough when nothing is playing, no matter how high I crank it. If it is a ground loop problem, do you have any idea where the source of the problem could be?

AudioFreak 2nd January 2002 02:56 AM

ok, here's another suggestion... it is possible that something in the signal path is clipping not necessarily that amp but possibly something earlier in the chain this would be consistent with the distortion you are experiencing and wont always show on the meter.

Kilowatt 2nd January 2002 03:26 AM

I don't think the EQ is clipping, because even with the volume control at it's input set very low, the problem still exists. Is it at all possible that the distortion originates from the input volume control? Or maybe there is a problem in the EQ, causing it to clip or something. I had a similar, but not as bad, problem with the EQ in place before I introduced the volume control, but that could have been the EQ clipping because I had little control over the input signal it saw, except from my computer, which I usually keep at the same volume level. I had not used the seperate CD player before I put the input volume control in, I came up with that slightly afterward. I suspect the volume control is responsible for the problem, I don't see what else it could be. What can I do?

By the way, the trimpots are 25kohms.

JBL 2nd January 2002 04:13 AM

In those case it might be better to try to find where is the problem. You should try to disconect anything and just use the amp with the speaker no xover.

One other thing is that xplod sub are extremly bad for amp stability. I saw those destroy a panasonic amp by some sort of stange oscillation.

It does not seem to be that but it can.

Kilowatt 2nd January 2002 04:51 AM

Xplods are bad for stability? I didn't know. They must have a killer phase shift, or maybe Sony and Panasonic just don't like each other:) . Anyway, do you think they will hurt my Leach amps? Is this problem made worse when two Xplods are in series? That's how I have them right now, but my distortion problem is above the xover freq., not below.

By the way, I can't just take out the crossover, besides, there is no passive crossover. The Panasonic SA-AK24 is a bi-amped stereo unit. There must be a passive crossover for the mid/high speakers, but they are built in to unopenable speaker boxes that came with it. Anyway, I will try to track down the problem.

AudioFreak 2nd January 2002 05:05 AM

because of the particular resistance/inductance/capacitance combination that certain speakers (particularly sub) present to the amp it can require the amp to produce current that is 45degrees out of phase with voltage and this is not a easy thing for an amp to do ...


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