Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics.

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Re: What Do You Guys Think Of This?

Posted by tomservo (M) on April 23, 2007 at 15:11:35

In Reply to: What Do You Guys Think Of This? posted by thetubeguy1954 on April 23, 2007 at 07:40:54:

Hi Tubeguy

Well a couple of the others hit the nail.
Amplifiers (open loop) are normally limited in bw by a first order slope (-90 degrees), this insures that at no frequency is there more than 90 degrees phase when gain is greater than one. This is usually an RC filter which has a lower corner than all the other corners which the various other R’s L’s and C’s in the amplifier parts cause.
What the ad copy writer may not be aware this is called “Bode criteria” which defines unconditional stability. Having positive gain AND 180 degrees phase shift is an oscillator.

This device is not “in” the feedback loop, it is tied to the output between the amp and load.
The only thing that could “improve” feedback stability (from the outside) would be to lessen the load at high frequencies (via a series L).
This (if large enough) would be audible as it rolls the hf off.
To the listener, a speaker which is flat sounds very bright even brittle. People like a rolled off high end and an inductor is about the only part small enough to have an effect and fit in the package.

Tell you what, I am curious now about your RCA’s and what you would think of them if they were dialed in.
If I remember, you didn’t have any drivers for them.
It’s spring here, my measurement tower is up and running in the back, if you send me one of the boxes empty in a re-usable box, I’ll figure out some drivers and crossover and ship you an empty box back and a list of stuff.
I re-did an A-7 driver / crossover a few years ago that turned out very nice but it required some internal bracing (which even shows up on the TEF haha) so it would make sense to do this before the boxes are nicely finished etc.
If interested, write me off list.
Best,

Tom

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