[sdiy] sources of hum and hiss in a solid state guitar amp (LM1875) (slightly OT)

[Dave Manley]

while talking about scope's anthony wrote:
>
> Hey what does "CHOP" do? There's no "PUREE" or anything...
Some dual trace scopes have two modes: ALT and CHOP.

In ALT mode, the scope draws the channel one signal on the first 
horizontal sweep, and draws the channel two signal on the second 
horizontal sweep - it alternates between channels on alternate sweeps.  
If you turn the sweep rate way down, you can watch the scope do this - 
first it sweeps the top channel, then it sweeps the bottom channel.

In CHOP mode, the scope draws both input channels simultaneously by 
rapidly switching between (or chopping) them.

If you are using a low horizontal sweep rate CHOP works better than ALT, 
since you can see both inputs on the same sweep.  Use CHOP mode when you 
want to look at the relationship between two slowly varying signals.

-dave