Hotrod Deluxe channel switching

[nickb]

So it only switches to MORE drive SOMETIMES with the footswitch. I think I'll wait till I get the 4560 in and install it.

You had to use 27k as U3-7 changed from -10.5V to -7V. If it's not working with the foot switch then Q4 is still not fully off. Just get the right part. No need (or time) to redesign it.

PS: In general you can't use an op-amp for a comparator. The reason is that op-amps are not always designed to work with big differential input voltages. It may say in the absolute max ratings that it won't fail with big swings but it doesn't mean it will work properly either.

[lowell]

Nickb. Would you be so kind as to suggest some educational materials on opamps? I have the Opamp Cookbook but there isn't much theory or explanation in there.

So does a comparator output generally go to one rail or the other? Is it a very crude comparison of the differential input voltages?

[nickb]

This should do it (from the nice people at TI for free)

Op Amps for Everyone.pdf

[christarak]

This should do it (from the nice people at TI for free)

[ATTACH]46788[/ATTACH]

Thank you nickb. That is a serious tome that offers many (many, many) hours of learning enjoyment.

[lowell]

464 pgs. Not sure it's as in-depth as I'd hoped.

[lowell]

BA4560 in place.
2n4401 in Q4.

Pin7
-13.2 drive
-13.6 more drive

Fixed. Thanks!!