On 5/3/2008 9:46 PM Mack the Knife spake thus:

---MIKE--- wrote:

My new digital FM tuner puts out too strong a signal compared to my
other inputs (TV and CD). I want to install a dual potentiometer
between the tuner and preamp to reduce the volume. What is the best
value pot to use for this. I have ordered 50K, 100K, 250K and 500K from
Mouser (the pots are cheap - the shipping is not).

You cannot get an effective result using a simple potentiometer. You are
attempting to attenuate a signal that involves voltage, current and a
frequency range without denigrating it. It requires more that simple
series resistance. You can buy audio frequency filters that are designed
for that purpose, to correct a mismatched input, they are not expensive,
although more than just the cost of a pot. Try one of your local
hobby/electronics stores. Failing that, try to obtain a circuit diagram
for your FM tuner and try playing with the front-end AGC. If you don't
have an adjustable AGC, then that is the part of the circuit that would
be more suited to adding a pot, or preferably and tunable RC network.

With all due respect, you're just plain wrong, and this is from
empirical evidence (I've done exactly what the OP is asking about,
between the line-out output from one receiver into the line-in input to
another, and it works just fine).

Besides, just look at the circuit diagram for a receiver, and you'll see
exactly what's been suggested--a simple potentiometer--between
preamplifier stages.


--
The best argument against democracy is a five-minute
conversation with the average voter.

- Attributed to Winston Churchill