Trainwreck express - negative feedback off...

[riscado]

shermock once again, there is something seriously wrong there, you can't fix squeals or howls, by reversing the leads if there is no negative feedback, reversing leads only has effect if there is a negative feedback loop...

[ODwan]

Hi Schermock

My poor old brain doesn't understand the way you get positive feeback by removing negative feedback.
i've experienced squealing when you feed a phase reversed signal in the feedback input(which i cure by reversing PT grid leads),but if you don't fed any signal in....please could you explain it to me?

Cheers

I guess he means oscillation and squealing through unwanted coupling between circuit parts.
Timo

[Shermock]

Hello

My poor old brain was too tired when I posted! Both times! I should have said the reverse. Sorry for the conufsion. I have introduced NFB into a circuit and had the amp squeal, which then led to OT lead reversal. My bad.

One other thing, though...and I'm sure all would agree, that a little bit of Golden Rule can go a long way on the Internet. Let's keep things respectful, watching out for things that may come off more harsh than intended.

Have a great day!

Shermock

[riscado]

ahh that makes more sense...

as for golden rules on the internet, I've seen some of those snowball and turn into misconceptions... that's why I usually don't trust them!

I agree with you though, the express appears to be the type of amp, that really benefits from having the NFB.