Best interconnect against RFI

Rolox

Member
2019-10-31 8:05 am
I'm suffering a terrible RFI ingress problem with my active crossover; the RFI enters through the input RCA cable (touching it or putting ferrite clamps diminishes it)

All I have at home at the moment are VanDenHul Integration RCA interconnect (star quad configuration with shield only grounded at source end) which make the problem worse, and some professional microphone cable with the shield connected at both ends which fare a little bit better but still don't solve the problem completely.

Ferrite clamps have, in my system at least, an obvious side-effect of flattening soundstage height, microdynamics and life, and I hate them - even tho they work.

I've seen some RCA cables for sale which comprise four braided conductors, unshielded; the company advertises better noise rejection and RFI immunity than conventional shielded cables. Is that true? I'm tempted to try a pair; they are not outrageously priced - but still a waste of money if they don't work.

In parallel of this I've been trying to work internally and my next move will be to add small caps at the op-amps inputs to ground (at least on the input buffer op-amp) but that's the subject to another post of mine so... let's focus on cable :)
 
I've seen some RCA cables for sale which comprise four braided conductors, unshielded; the company advertises better noise rejection and RFI immunity than conventional shielded cables. Is that true?
Twist is far better than braid. A twisted pair of wires could possibly be better under some circumstances that a very poorly shielded coax that offers little immunity to RFI.
 
Didn't we already have this discussion?
Fluctuating high-pitch noise in op-amp circuit
IIRC ... the solution was to put the original chips back in and call it a day.


I'm suffering a terrible RFI ingress problem with my active crossover; the RFI enters through the input RCA cable (touching it or putting ferrite clamps diminishes it)

Which opamps are inside? You may want to look into RF bypassing the chips themselves. Generally with very low value capacitors connected input to ground, very close to the chip.

All I have at home at the moment are VanDenHul Integration RCA interconnect (star quad configuration with shield only grounded at source end) which make the problem worse, and some professional microphone cable with the shield connected at both ends which fare a little bit better but still don't solve the problem completely.

Crap cables... really. The ungrounded end of the cable turns the shield into an antenna. The best cables in my experience are THESE ... good old standard RCA with shielded cables.

Ferrite clamps have, in my system at least, an obvious side-effect of flattening soundstage height, microdynamics and life, and I hate them - even tho they work.

Highly unlikely. Ferrite clamps have almost no effect below several megahertz and, used on proper cables, it is beyond unlikely they would affect the sound in any way.

I've seen some RCA cables for sale which comprise four braided conductors, unshielded; the company advertises better noise rejection and RFI immunity than conventional shielded cables. Is that true? I'm tempted to try a pair; they are not outrageously priced - but still a waste of money if they don't work.

You know those cheap arsed cables that come with your gear... well there's a reason for that... they work.

In parallel of this I've been trying to work internally and my next move will be to add small caps at the op-amps inputs to ground (at least on the input buffer op-amp) but that's the subject to another post of mine so... let's focus on cable :)

You may also want to put low value caps right across the input and output connectors, at the casing... just a few pfd, maybe 47p or 100p.

The thing is that you may have to do ALL of these things to get the problem solved.


Of course the only perfect solution is to locate the source of the interference and eliminate it.... wifi routers, cell phones, etc. are common causes.
 
Last edited:
What? Again? IMG_20191219_174849.jpg
 

803370d1576766962-interconnect-rfi-img_20191219_174849-jpg


Take example (d) and lead the twisted wire pair through a shield as in (g) and it improves from 49dB by another 15dB to 64dB, by that analogy does that mean example (i) could also improve its shielding by another 15db, ie. from 79dB to 94dB?
Also, can the susceptibility improve 30dB @ f=100kHz by changing the 6 turns/foot to 18 turns/foot as in example (d) VS (i)?
 
Last edited:
RCA chassis connectors should NOT have a plastic insulator ring.
.
WONG! Having the RCA shield go in 6 directions plus grounded to the turntable platter+arm plus case on my mixer caused RF pickup and hum. Isolating the RCA jacks and connecting the rings to analog ground, not chassis, helped the hum & RF pickup a bit. That mixer, the CD player, the FM radio, the turntable, and my ST120 power amp not equipped for XLR twisted pair.
OP has still refused to put 33 pf disk caps around feedback resistor on his op amps, which have slew rate of 12 v/us.
I just tacked 33 pf on top of the feedback resistors in my RA-88a. That killed the oscillation caused by replacing 4558 with 33078. 4558 were waaay too hissy, especially at 50x gain for turntable. Oscillation was inaudible but was overheating the power amp.
 
Last edited:

Monte McGuire

Member
Paid Member
2013-07-28 2:58 am
Clamp-on ferrites can only affect common mode signals, since both signal and return are placed within the ferrite. This is especially true with a balanced cabling system where there are clearly defined signal return currents. Still, the ferrite is not just on the RCA signal, it's around the entire RCA cable, signal and shield, so it cannot alter the signal.
 
Clamp-on ferrites can only affect common mode signals, since both signal and return are placed within the ferrite. This is especially true with a balanced cabling system where there are clearly defined signal return currents. Still, the ferrite is not just on the RCA signal, it's around the entire RCA cable, signal and shield, so it cannot alter the signal.

It's amazing how many people don't seem to realize this. If it were not true, then a clamp-on ferrite would pretty much ruin HDMI, DisplayPort, and USB 3.0 SuperSpeed connections.