[ARC5] Utility Amp Driving Advice.

[David Ross]

On 3/20/2011 10:12 AM, David Stinson wrote:
> I want to protect the input so I don't blow-up the driver.
> If I calculated correctly, 10 milliwatts in 50 ohms should
> be 1.414 Volts PTP.  If so, a simple set of four
> "up" and "down" ( or "left-n-right"  ;-)  silicon diodes-
> each leg with two in series to  to ground, which
> will forward bias at 1.4 volts and limit the input
> to 20 milliwatts, should do the trick.
> At lower drive levels, they should be "invisible."
> At high levels, they'll clip and distort.
> And when I screw-up and pop 40 watts into it,
> they should short and save my amp.
>
> First- did I get the math right?
> Second- what blatantly obvious thing am I missing?
>
> Thanks, Dave S.  AB5s

Is there a possibility of the diodes generating some intermod products?  
Not 'blatantly obvious' and probably not a problem at all, but it is the 
first thing that occurred to me.

Even without Dave's protection diodes, I would bet that the Motorola amp 
has some sort of 'internal gain control' that limits it's output to a 
safe number.

73, good luck
Dave Ross    N7EPI