[Occam]

Hi Steve,

I've just spent some time looking at the Synergistic and Tara websites tying to understand biased interconnect implementations. Its not something I've followed, and my exposure has been limited to an early 90s article in HiFi World where the bias was applied to the signal leg and then removed via caps. From a commercial product perspective, applying the bias to a telescoped shield certainly make more sense than applying the bias to the signal conductor.
But as someone with more enthusiasm than common sense, I've never let practicality stand in my way. As a method of actually testing biased interconnects, using the offset of the preamp should be straightforward. My own CF output preamp has about +60vdc on its output prior to the coupling cap. A Squeezebox has about +4.5v and if you bypass the opamp stage, about +2.5vdc.
If one were to attempt this experiment, a standard coax like Belden 89259, or better yet, Audience Au24 would be appropriate. This would also make DB happy in that the ground would be a solid low resistance shielded connection.
I read the url you provided, but am unsure as to what voltage is appropriate for such a biasing experiment. Suggestions? Explanations?
My rational for entering this fray is that regardless of my off hand reaction, IMO, its allways makes sense to actually empirically verify with a straightforward experiment.
I don't have a Squeezebox, but I do have a few spare yards of 89259.

Regards,
Paul

[Steve]

Hi Steve,

I've just spent some time looking at the Synergistic and Tara websites tying to understand biased interconnect implementations. Its not something I've followed, and my exposure has been limited to an early 90s article in HiFi World where the bias was applied to the signal leg and then removed via caps."

Hi Occam. I have limited exposure as well. I wonder if the additional caps may do more sonic harm because of the added caps than good that biasing might provide. I guess that is why we experiment though.

As a method of actually testing biased interconnects, using the offset of the preamp should be straightforward. My own CF output preamp has about +60vdc on its output prior to the coupling cap."

Although dangerous, yes, "removing" the output coupling cap and introducing the cap at the input of the amplifier would provide bias for the IC and the voltage would certainly be quite high.
(For the newbies reading this, I would be very careful cause 60 volts can kill!)

I read the url you provided, but am unsure as to what voltage is appropriate for such a biasing experiment. Suggestions? Explanations?"

I am not an expert in chemistry, but these two comments are interesting.

"When a capacitor is discharged across a load the polarized dipoles thermally relax in a statistical manner, exhibiting a time decay, observed as a tailing decay of residual current as complete discharge is approached."

"can orient electronically, with less mechanical change in the polymer structure."

I do not know if biasing helps enough to notice a sonic difference, but if it does, 60 volts sounds plenty high to begin with. Below that, I would only be guessing where the point of diminishing returns would be. Maybe 3 or 4 times the highest maximum signal voltage?? 

I think that since nothing is perfect, i.e. there are problems with inductors (none linear losses indicated by the hysteresis loop), that similar losses and distortions might occur with capacitors and dielectric materials in ICs. Especially as the caps swings through 0?? Good luck on the experiment.

[mgalusha]

The voltage seems quite high to me for the purpose intended. The reasoning for this kind of cable design is considered in the article below. It is based on capacitors, but the issue is pertinent with cables.
http://www.audience-av.com/on_capacitor_dielectric_material.htm

What voltage are you referring to?

Hi Occam,

     I was basing my comment on MGs comment.

"Hell, it might work OK but I shudder at the thought of say 150V on the center pin of an RCA plug."

I just made up the number Steve, as you well know the DC present on the output of a tube line stage can cover quite a range. I just picked a high value and called it go. My CF line stage has about 75V at the coupling capacitor, so the 150V I used was just a thin air number.

mike

[mgalusha]

Oh my; another possible grounding issue? Just exactly how many times do I get to write about this? If these active cables are any benefit at all it will have nothing to do with the voltage on the wire but Isolating the DC ground potential with the caps.
In any case I suggested to Mike awhile back to use his Jensen Isolator to Isolate the Squeezebox from the rest of his system. The Jensen is not just for 60 Hz ground loops as I have demonstrated to many folks in the past. I have inserted the Jensen Isolator between the CD player and the rest of the system on a number of occasions and have been met with reduced noise and the shock of the user as to just how decent their "crappy" Sony player managed to sound. That probably sounds like heresy to most of you but  I'm still convinced that over 50% of consumer audio electronics issues are grounding related.

Dan,

In this case I wasn't talking about a grounding issue. As you know, my current source is a much hacked Squeezebox 2. It doesn't have any connections to earth ground other than the power supply safety ground. The power supply outputs are not referenced to earth ground. It only has it's own internal circuit ground, which could probably be better but I don't seem to be having any problem with leakage or ground currents. I do own a Jensen ISO-MAX and have tried it with my SB and there is virtually no change. I have tried all the various configurations of the grounding switches and it's very quiet no matter which configuration I use. I say virtually no change as the bass changes very slightly with the ISO-MAX in the circuit.

I agree that many problems are caused by ground current/ground loops and that's why I own the Jensen, I've had need for it in the past. In my current setup it's not needed, at least not to my ears. If I have time I'll build a test jig to measure the ground current and try it between my SB and the crossover. Now there is a place which might benefit, between the Marchand XO and the amplifiers. I may give the ISO-MAX a try there as well.

The thought that crossed my mind was that since earth ground is primarily related to safety and not to noise that perhaps if the ground had HF noise on it that having a separate shield that was grounded via a LP filter (inductor) *might* help. It may not, it was just a thought. Since I have the materials on hand I thought an experiment might be fun and won't cost me squat.

mike