Hi Chuck -- Great questions! I'll answer them in the order presented:
1. Using larger caps would accomplish nearly the same thing as shorting them out, but since doing so gains nothing, there is no advantage to changing the cap to a larger value. Shorting the cap out looses nothing, and removes the filter completely.
2. The filter is basically a garbage filter, helping to prevent rumble, wow and flutter, and other LF noises from the mechanical sources of the day from needlessly wasting power on non-musical signals. In doing so, it prevents output stages from becoming overloaded, and also prevented the resulting IM distortion that such LF garbage might create. It also acts as an additional rumble filter of sorts -- this since so many of Fisher's pieces ended up in a console setting -- either by Fisher themselves, or by individual owners after purchase. In that setting, it helps to prevent LF feedback from the speakers to the turntable. Today however, while there are still many console junkies around (a term of affection!), most who still play vinyl typically have far superior TTs than the changers that were so often used with Fisher equipment back in the day, which greatly minimize the garbage noise from the decks and changers of old. Plus, modern sources simply don't have the garbage noise issues associated with them, so the filter is an anachronism today.
3. The reason that the filter should not be removed in a 500C or 800C receiver, is because in those units, Fisher employed their electronic Stereo/Mono switching in the FM section, which changed state based on whether an FM Stereo MPX station was being received or not. Earlier units either did not have the feature, or early units that did, employed a mechanical relay to perform the Stereo/Mono switching. It was found however that the relays were not real dependable in switching audio signals, because the micro arcing that normally occurs between the contacts in a properly sized relay doesn't happen in that setting. The result was that channel dropout happened all too frequently due to contacts that became compromised. Fisher's answer was to develop a diode matrix electronic switching circuit that is utterly dependable in operation. The only drawback to the circuit is that when the diod
Hi Chuck -- Great questions! I'll answer them in the order presented:
1. Using larger caps would accomplish nearly the same thing as shorting them out, but since doing so gains nothing, there is no advantage to changing the cap to a larger value. Shorting the cap out looses nothing, and removes the filter completely.
2. The filter is basically a garbage filter, helping to prevent rumble, wow and flutter, and other LF noises from the mechanical sources of the day from needlessly wasting power on non-musical signals. In doing so, it prevents output stages from becoming overloaded, and also prevented the resulting IM distortion that such LF garbage might create. It also acts as an additional rumble filter of sorts -- this since so many of Fisher's pieces ended up in a console setting -- either by Fisher themselves, or by individual owners after purchase. In that setting, it helps to prevent LF feedback from the speakers to the turntable. Today however, while there are still many console junkies around (a term of affection!), most who still play vinyl typically have far superior TTs than the changers that were so often used with Fisher equipment back in the day, which greatly minimize the garbage noise from the decks and changers of old. Plus, modern sources simply don't have the garbage noise issues associated with them, so the filter is an anachronism today.
3. The reason that the filter should not be removed in a 500C or 800C receiver, is because in those units, Fisher employed their electronic Stereo/Mono switching in the FM section, which changed state based on whether an FM Stereo MPX station was being received or not. Earlier units either did not have the feature, or early units that did, employed a mechanical relay to perform the Stereo/Mono switching. It was found however that the relays were not real dependable in switching audio signals, because the micro arcing that normally occurs between the contacts in a properly sized relay doesn't happen in that setting. The result was that channel dropout happened all too frequently due to contacts that became compromised. Fisher's answer was to develop a diode matrix electronic switching circuit that is utterly dependable in operation. The only drawback to the circuit is that when the diodes change state, there is a healthy pulse associated with it that overloads the line amp input stage if the filter is removed. So, in those units, the filter must stay in place to prevent momentary overload as the matrix circuit does it's thing.
4. If you do pursue replacing the jacks, just remember that some of them are mounted so as to be isolated from the chassis -- this so that the jacks can be grounded at the point of lowest noise for the circuit served.
I hope this helps!
Dave
Thinking out loud - for the 500C/800C maybe a larger cap value would be a good compromise providing some benefit - since you cannot short the cap.
es change state, there is a healthy pulse associated with it that overloads the line amp input stage if the filter is removed. So, in those units, the filter must stay in place to prevent momentary overload as the matrix circuit does it's thing.
4. If you do pursue replacing the jacks, just remember that some of them are mounted so as to be isolated from the chassis -- this so that the jacks can be grounded at the point of lowest noise for the circuit served.
I hope this helps!
Dave