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Started by teemuk, July 04, 2007, 09:40:09 PM
Quote from: R.G. on July 23, 2007, 06:31:49 PMJust curious - why didn't you just use an LM3886 for the power amp? That's what I've done when running current feedback setups. It works fine. In this iteration of the current feedback where you're using the current feedback to in effect predistort the signal into the power amp you should have even less problems than normal with it.It is very hard to come up with good reasons for making amps under 60W out of other than the LM3876 or 3886.
Quote from: teemuk on July 24, 2007, 04:32:55 AMI agree with all of you: It's a pretty complex design for only 60W but also a product of experiment. I could build a 60W (push-pull) amp with three transistors...
Quote from: LJ King on July 25, 2007, 01:38:30 PMSeems to me that there is a life-cycle that eventually affects most corporations... ...Fender is a good example, although they are now back in stagnant mode.
QuoteHow about the Sunn Concert? The earlier ones used a transformer driven "dual" totem pole in a "grounded bridge" configuration with a floating power supply for the outputs.
QuoteWhen did Mesa get credit for channel switching? I hadn't heard that one. I know Mesa had a patent on "mode switching" which isn't the same thing, and the primary cause of their suit against Acoustic.
QuoteI know engineers will tell me I need these things, but heck, I have been overdriving SS poweramps without them for over 35 years with great results - so nothing is going to convince me I need their tone defeating qualities this late in the game.
Quoteo Protection circuits are necessary for the ignorant consumer and manufacturers that cater to them. Professional level equipment do not need them.
QuoteI guess this is more of a statement than a question. But as an example, take short circuit protection. When is it really necessary? When the output is shorted. Ok, what kind of idiot would short the output? An ignorant consumer.
QuoteMost professionals follow a simple rule that makes short circuit protection totally unnecessary: "Never power on an amp without a speaker load attached."
QuoteCatering to people that ignore this rule (that pertains equally to solid state and tube amplifiers)
Quoteisn't necessary for yet another reason: output transistors are cheap. Tubes on the other hand are at least an order of magnitude more expensive, not to mention the output transformer - but I've yet to see a tube amp with "open circuit protection" which is more damaging to a tube amp than a short circuit (other than low wattage plate and screen resistors acting as fuses).
QuoteSo maybe the real question is: why use circuits designed to protect a device that is cheap to replace? Especially when they can adversely affect the sound.
QuoteMy favourite pick concerning tube tone myth would be Russell O. Hamm's famous "Tubes vs. Transistors" convention paper from 1974. Even today people like to refer to it as gosbel although most of it's content has been debunked or otherwise corrected.