Rumble filter

[Analogluvr]

Hi guys,
Been using mine beepre-for around a year now and I absolutely love it. Recently I've been messing with some Phillips full range speakers and I just added a sub.  Everything's working pretty good but I noticed my Wolfer was pumping like crazy on the phone. Need to add a capacitor to filter below 20 Hz. What size Do I use for that?? I was thinking on putting it right inside the preamp where the female RCA jacks are for the phono input.
FYI the outputs run to a solid-state kynergetics research crossover/sub amp and then go to the sub. Before the solid-state sub amp The cables are y'd and also feed the main amps.
Just need to know roughly the size of cap I should use to filter out below 20 Hz. Or any other suggestions that might be helpful!

 

[Paul Joppa]

Is it the sub-woofer (not the 8" fullrange) where you see the excess excursion? I presume so, since you call it a "woofer," but thought I should make sure. I am not at all confident I know what you mean by " pumping like crazy on the phone" - what does a telephone have to do with infrasonic disturbances?

You mentioned implementing a high-pass filter at the phono input - is the problem only with phono? If your mention of the phone means you are driving the preamp with a smartphone, I am guessing the problem is on all inputs. In that case, the best place for the filter is between the preamp and the sub amp. If it were mine, I'd put the filter inside the sub amp, since the capacitor value depends on the sub's input impedance. If you put it in the BeePre, it will only work properly with subs that have the same input impedance as the Kinergetics.

 

[Analogluvr]

Oh my god damn talk to text!  My wife was telling me to get off the phone so I didn't proofread. I don't know how the phone got into the text. The sub is pumping like crazy only on the phono input.

 

[Paul Joppa]

Does it pump when there's no record on the turntable?

 

[Analogluvr]

Not really, it trembles a bit. If you play the table then lift the stylus sometimes it keeps pumping a little bit more lightly.

 

[Paul Joppa]

The data so far suggest to me that the phono preamp may be the source of the instability. If the pumping is reduced by reducing the volume, that would support this diagnosis.

If that is the case then your idea of putting a filter at the BeePre phono input makes sense. The BeePre input impedance is not constant, so to reduce that variable I would load up the phono input with a resistance to swamp out the variation - perhaps a 10K resistor, if that is OK for the phono pre. Do you know what the phono pre minimum load impedance is?

If it can handle 10K, then a cap of about 0.8uF will do the job. Cap from phono input to resistor whose other end is grounded; take the signal from the resistor/cap junction.

 

[Analogluvr]

And if I find the bass rolled off I decrease the cap size, correct?  Also even if I don't stick with those speakers and sub I should still take care of this right?  Meaning I did not know this problem existed until I hooked up a sub but if the sub is not there to pump it is still not a good scenario right?