Hi.
I have a MusicMan amp with what seems to me to be a strange arrangement at each input. There is a pair of antiparallel 1N4148 diodes.
This (terrible) schematic shows it;
(http://members.optusnet.com.au/~jethro.dog/mypic140.jpg)
Sometimes, I'd like to drive the amp harder (there's an 12AX7 in there), but once the diodes clip it sounds bad. So I'm thinking of removing (or just destroying) the clipping diodes?
Good idea? While the LM307H is ancient, I figure it should be able to handle a bit more than +/-0.7V (tho it might not output much more than it does now - it's on a +7V/-4V supply!!).
thanks for any advice.
I'm pretty sure it's there to protect the op amp. I guess you can remove them. I would take the time to put a socket in too.
Aron's right. Have you read "What are all those parts for?" at GEO?
http://geofex.com/circuits/what_are_all_those_parts_for.htm
The diodes are there to clamp the inputs in case they try to run away from each other. They don't actually clip. Come to think of it, if you're trying to get ANY kind of non-power tube distortion or gain from a Music Man, sell it and buy another amp.
I think it's worth noting that the NE5532 has these diodes included internally. :D That makes the NE5532 a really bad candidate for use as a comparator.
Thanks fellows. :D
I didn't have my thinking cap on. Of course, in the normal scheme of things, the two inputs of an op-amp stay within a few mV of each other!!