noise

[vitalstates]

Following on from the px4 thread I thought I'd start a new one about noise, PS or otherwise.

As I dont have ac mv on my DMM I thought I'd investigate with the scope. As you will guess from this question it will be obvious that I havnt got a clue what I'm doing....but at the risk of serious ridicule I'll press on.

As the thread was talking about PS noise I thought the voltage would be in the order of 50hz or close multiple. With the scope set accordingly I find nothing at the OP when connected to LS and input shorted.

what I did find however was this:
scope was set at 5mv/div and 0.2microsecs(NOT millisecs)
I have to say there is no audible noise whatsoever, I'm just curious.

Has anybody got any idea what this is....its sort of organic in as much as the trace grows and shrinks between 5 and 15 mv over a period of about 20 seconds.

oh btw this is son of rocky SE EL34

scope.JPG

[BOONDI]

It's a 5MHz triangular waveform with 5-15 mV level, as you correctly surmised. Where it comes from is anyones guess.....

The best thing to try is to follow it through from input to output, methodically testing all the signal points. You may find it is high frequency oscillation of the valve, or it may be the scope lead that you are using......

Anyone else???

[andrew ivimey]

At such a level, I can't help thinking it may be more to do with the test conditions rather than the amp itself, too.