Any limitation on the interconnect length to power amp from FPIII?

[audiblesoundwave]

Any impacts on using longer run (any limits) of the interconnect cables to power amp?

Thank you,
Milton

 

[Doc B]

The FPIII has a low output impedance and a lot of drive . Should be able to handle 50 to 100 foot runs, no problem. However at those kinds of lengths the single ended cable required may pick up noise. FWIW I've never had noise problems with quality cables and 15 foot runs. I strongly suggest shielded twisted pair cable with the shield attached to the RCA shell at the preamp end only.

 

[audiblesoundwave]

Thanks Doc!

Can I use the same type of STP wires that are being used in the Bottlehead kits to build a pair of the long running (between 10 and 15 feet) interconnects?

Milton

 

[Paul Birkeland]

You "could" use the shielded twisted pair that comes with the kits.  It is solid core wire, however, which is great for kits, but may experience some work hardening if you make interconnects out of it.  Stranded shielded twisted pair is pretty easy to find! 

Canare Canare L-4E6S is a quality inexpensive shielded cable that you can use for single ended and balanced applications.

 

[Doc B]

We just happened to do a comparison of cables made with the solid core Belden STP and the stranded version of that STP. They sound comparable to the Canare, not quite as good as our more exotic homebrew unobtanium stuff, but very good.

 

[audiblesoundwave]

Hi Paul and Doc,

May I ask a stupid question regarding Canare Canare L-4E6S cable?

I took a quick look of the cable spec and noticed there are 4 conductor wires inside of the wire.  Is the wire for (one set) two RCA connectors?  Two hot and two ground wires!  If not, how do I wire the RCA plug?

Thanks,
Milton

 

[Paul Birkeland]

Yes, I do 2 hot 2 ground, wiring the braided shield to the RCA connector that is the source (preamp if going preamp to amp, CD player if CD player to preamp). 

I use 2 colors of heatshrink to make left/right pairs of cables, then I use a 1/4" cut of the opposite color of heatshrink to mark the end with the shield connection.  I can post a photo of that if it helps.

 

[audiblesoundwave]

Thank you Paul!

That would be very helpful to me! 

Milton

 

[Paul Joppa]

The Canare is a star quad cable; it's important to connect the right pairs of wires together. Here's a .pdf from Canare:

http://www.canare.com/UploadedDocuments/Cat11_p35.pdf

 

[coca]

Milton, I have been using the Canare star quad cable for several years now, with excellent results. My interconnects are about 10ft long from my foreplay II, to my amps, which are monoblocks, and are on amp stands next to my speakers. I would advise though, not to skimp on the quality of rca's. You don't have to break the bank to purchase good ones either. Everything everyone else has said, is right "on the money."

 

[Aljaheejus]

Yes, I do 2 hot 2 ground, wiring the braided shield to the RCA connector that is the source (preamp if going preamp to amp, CD player if CD player to preamp). 

I use 2 colors of heatshrink to make left/right pairs of cables, then I use a 1/4" cut of the opposite color of heatshrink to mark the end with the shield connection.  I can post a photo of that if it helps.

Can you please confirm that the shield is connected to the ground along with the "ground" pair?  I understand this only is to connect at the end to be connected to the source.  Thanks!

 

[glowboy7]

This topic has confused me for a long time.  If you have a shielded twisted pair and connect one wire to hot on each RCA, and the other wire to ground on each end, then why does connecting the shield to only one end matter?  It is still connected to both ends though the ground wire.  I am not questioning that you guys are hearing a reduction of noise in long lengths between preamps and amps. I am wondering why?  The shield is just as connected to the amp as it is to the preamp, no matter which end is plugged into which component.

Help me Obi-Wan...

 

[Paul Joppa]

This topic has confused me for a long time.  ...

That's because it's confusing. As is almost everything having to do with shielding, grounding, hum, noise, and RF interference. I'll do my best but I'm sure I'll be wrong in some way:

The wires between two audio devices can pick up noise, in the sense of unwanted electrical current or voltage. It can come from the electric and/or magnetic environment, or from the devices themselves.

Much of the available literature deals with currents flowing in the ground connection between the devices. The common analyses talk about magnetic fields, which are caused by such things as electrical motors and transformers near the audio system. If the ground connections make a loop, such as power line ground to device 1 to device 2 back to power ground, current will be induced into that loop and will flow in the interconnect ground wire. These days it is more common for such currents to come from the devices themselves, usually capacitive coupling inside the power transformer, from the power line to the signal ground inside the device. A third cause is different grounds; typically the video cable ground is not the same point as the power line ground. In all these cases, the current flow creates a voltage difference along the ground line of the interconnect, in proportion to its resistance which is almost but not quite zero. That voltage adds to the signal. There are other solutions, but the simplest is to minimize that resistance, in which case you would connect the shield at both ends (and use heavy-duty RCA jacks and plugs).

The other way noises are introduced is electrical fields which are coupled into the wires. They typically come from radio transmitters and unshielded electrical devices - now we're talking cell phones, radio and TV stations, light dimmers, drills, RC models, etc. There are many more of these devices than there were 100 years ago when interference was first studied (for telephone applications), which is probably why these issues are less widely documented. These electrical fields are picked up by wires like an antenna. They can be drained to ground at either end; the shield intercepts these noises and prevents them from reaching the signal ground wire inside the shield. This is slightly better than having the shield itself be the ground, as in a coaxial interconnect. The current of those noises going to ground still drops a tiny voltage as it finds its way to the earth, and usually the output of a source is less sensitive to those tiny voltages than is the input of the next device, because the source impedance is much lower. So usually it is slightly better to ground that end of the shield instead of the other. But it's not universally true for all devices, all cables, or all situations.

 

[JC]

OK, I see now that Paul Joppa has posted a very detailed response, and adding my long-winded monologue to the thread would indeed run the risk of adding to the confusion of what admittedly can be a very confusing topic.

So, in the interest of avoiding that risk, I have pulled mine.

 

[dstrimbu]

It is solid core wire, however, which is great for kits, but may experience some work hardening if you make interconnects out of it.  Stranded shielded twisted pair is pretty easy to find! 

I'll second Paul's vote against solid core... tight braiding of solid core can cause great disappointment.  Imagine spending a snowy evening building a gorgeous set of 24-pair x 23 gauge speaker cables... meticulously hand-braided... even my wife thought that they were "beautiful". 

Until I pulled out my D-VOM.  Imagine my dismay... a 9.0 Megohm short across the conductors.  I should have known better...

Go with stranded. If you carefully dissect a good Cat6 plenum-rated Ethernet cable, you'll find more stranded, Teflon-jacketed wire than you can shake a finger at...  it's not Canare, but you'd be amazed at how well it works.

YMMV,

-Don

 

[ssssly]

Just to add to the try it and see what you think list. A few years ago it was suggested to me to double up the ground wires. (1 pos strand, 2 neg; 2 pos 4 neg...etc) Don't remember where it came from but I have had positive results.

Be well

 

[glowboy7]

This topic has confused me for a long time.  ...

These electrical fields are picked up by wires like an antenna. They can be drained to ground at either end; the shield intercepts these noises and prevents them from reaching the signal ground wire inside the shield. This is slightly better than having the shield itself be the ground, as in a coaxial interconnect. The current of those noises going to ground still drops a tiny voltage as it finds its way to the earth, and usually the output of a source is less sensitive to those tiny voltages than is the input of the next device, because the source impedance is much lower.

Thank you, Paul.  That clears up a lot.  I like the antenna analogy. 

 

[Bern1]

Yes, I do 2 hot 2 ground, wiring the braided shield to the RCA connector that is the source (preamp if going preamp to amp, CD player if CD player to preamp). 

I use 2 colors of heatshrink to make left/right pairs of cables, then I use a 1/4" cut of the opposite color of heatshrink to mark the end with the shield connection.  I can post a photo of that if it helps

Hi all, thanks for the great info.

Sorry if this sounds dense, but in this case are you doubling up the connectors in the cable for a single path?  So you still wind up with two completely separate cables, each using the 2 hots, 2 negatives and the shield, one cable each for  L & R?

This is what it sounds like, just want to make sure, thanks!