#1
For anyone who really gets negative feedback- how does it work? I know that you can get the most gain out of a triode with the emitter/cathode grounded, and that there's less gain when you've got a resistor there. What I don't get is how that resistor actually limits the gain. Also, how does an emitter/cathode cap affect the tone? Thanks to anyone who can help.
#3
Yeah, I don't really get that. I haven't had any education in electronics other than the pedals I've built and modded, but I do understand the basics. This is one of my weak points, though. The resistor I'm talking about is attached from the emitter or cathode of the triode, to ground. Like in this schematic: http://www.euthymia.org/DIY/VJstock.jpg the resistor would be the 2.2K on the cathode of the preamp tube triodes.
#4
a good example of negative feedback is in a simple op-amp voltage amplifier (i love those things!)

http://en.wikipedia.org/wiki/Negative_feedback

pretty accurate tbh

in summary, negative feedback is the feeding back of the output signal into the input terminal to control the gain (by gain, i mean amount of amplification)
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Last edited by mcw00t at Sep 21, 2007,
#5
^ Well, I know what negative feedback is, per se, but I really want to know how it works in an amplifying device like a tube triode. Basically, why does that cathode resistor decrease gain?
#6
it quite hard to explain WHY it does it, but put basically, it limits the amplification potential of the device, otherwise, it would just amplify with the open loop gain (as you don't seem like an idiot, i won't explain this term) which in an ideal amplifier would be infinity, the negative feedback set up by the resistors, would the limit this open loop gain to a gain that would be manageable as opposed to driving the output into saturation on any signal that isn't 0.

I'm sorry I can't be of any more help

EDIT; i can be of more help! but it's VERY hard for me to explain without doing drawings etc
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God & Founder of UG Electronics


Electronics God of the Laney Cult

My Gear:

Ibanez RG370DX
Laney VC30-212
Dunlop Crybaby
Boss CS-3
Ibanez TS9DX
Last edited by mcw00t at Sep 23, 2007,