Quote:
Originally Posted by Piggie
This does beg an idea or though to you Don. Take a CM7777, it already has 2 switches on it. One for combined or separate and one to add or remove the FM trap filter.
I wonder if it would not be a good idea, since a switch is more reliable than a pot to add a switch to something of the gain and low noise of a CM7777 that drops the gain in half, if and only if that drop also gives an increase in the dynamic range of the amplifier.
The reason I add that last constraint is if you look at holl_and's evaluations of amps, even though the CM7778 has 10 db or so less gain than the CM7777, it apparently has no better dynamic range. |
That's what I took away from his chart, too -- dynamic range doesn't necessarily have an inverse relationship to gain, so this capability must be due to something else in pre-amp design. What that might be, I can't say: I only roomed with an EE in college, I didn't major in it!
Unless you were thinking out loud here, I see little advantage to having a switch for selectable gain if it wouldn't also mean greater dynamic range. The only benefit I can imagine is that a switch might bail the buyer out in situations where a higher setting causes amp or tuner overload, but the lower setting doesn't. That's a pretty narrow circumstance that can be avoided through careful pre-amp selection.
I read a post not so long ago from a knowledgeable source asserting that a) most people who think they need an amp need a better antenna instead and b) of the few who do need a pre-amp, almost none of them need look any further than the high-input Winegard HDP-269, because its 12
dB gain was all just about any household within roughly 50 miles of the transmitters and with fewer than five TVs really needed. (He wasn't a Winegard shill,
AFAIK.)
A CM 7777 makes sense in the deep fringe because its noise figure is 1
dB lower than that of the HDP-269. It's not really due to the high gain at all. That lonely little
dB becomes crucial in weak-signal areas that are close to the noise floor in the first place.
