[Roger Jones]

On Jun 23, 7:38*pm, Patrick Turner wrote:
On Jun 20, 5:40*am, Roger Jones wrote:

Hi, Vacuumlanders,
This is pretty obvious but often overlooked...

(snip)

Also, if it's a mono tuner and you use
an RCA audio cable Y-adapter to feed the L+R inputs together, the load
on the tuner output is as low as 24Kohms.
For the low end -3dB point, Xc equals Rin (plus CF o/p impedance but,
at about 500 ohms, you can ignore this.) Thus, 10^6/(2.pi.F(Hz).C
(uF)) = 24000. Substituting C=0.05 uF and solving for F gives 133 Hz.

(snip)

Its easy to remember 0.1uF and 100k give a LF pole at 16 Hz.
so 50k gives 32Hz, and 50k + 0.05uF gives 64Hz.

So how come you got 133Hz?

(snip)

Patrick Turner.

CF output impedance 500 ohms (you had 600, about the same.)
S/S amplifier input resistance 47Kohms per channel, or 23500 if
paralleled for mono (my tuner.)
Thus, total load 24Kohms, round number.
Then, f(-3dB) = 10^6/(2.pi.0.05.24000) = 132.69Hz, i.e. 133 Hz.
Or, using your reference point, i.e. 0.1 uF and 100K gives 16 Hz:
Reduce the 100K to 25K, gives 64Hz
Reduce 0.1 uf to 0,05 uF gives 128 Hz.
About the same as the 133 Hz (for 24Kohms.)
I agree that 1 uF coupling is too large with 50K input resistance, not
good for feeding a s/s unit.
Cheers,
Roger