What are the pitfalls of using long IC runs?

[synsei]

My power amp (Quad 306) sits more or less centrally between my speakers and I currently utilise a 2.4m run of Belkin PureAV Silver IC's running from my pre, which sits in the rack with the rest of my equipment on a side wall (the power amp and speakers are located on the front wall of the property). Soon I will be experimenting with other cables to see if there are any gains to be had in SQ. 2.4 metres is a tad short therefore the cables are left dangling approximately an inch and a half off the floor. Even though the Belkins are quite lightweight, it worries me a little that this state of affairs may exert undue stress on the RCA sockets on the equipment over time. I have two options: The tidy approach would be to run 4m length IC's along the side and front walls to the 306, negotiating a corner on the way. The second option would be to reduce this length by 1m and run the IC's across the carpet, cutting out the corner, as I do just now. Although the DR5 has balanced outputs, the Quad has no balanced inputs therefore I am forced to use unbalanced IC's. The simple upshot of this is, will the extra metre of cable I would need to keep things looking tidy unduly upset the apple-cart?

[The Grand Wazoo]

It should be fine Dave - 3 or 4 metres isn't long.
I have 7m pairs between a reel to reel and my preamp. Pre to power runs are only about 2m pairs at the moment but I've had well over 12 metres in previous arrangements.

[Barry]

Dave, 4m long interconnects (or longer) will be perfectly OK, as long as the capacitance per unit length is not too high. Most coaxial interconnects have a capacitance of ~ 100pF/m which is fine.

[synsei]

Cheers guys :)

My next question is this then: I have a budget of around £100, which isn't much granted but that's all I have available. I have compiled a short list of my own, however I would welcome other members IC recommendations up to my budget please. Most of the usual suspects are on my list, Van Damme, Gotham etc, etc, however perhaps somebody has come across a seller who makes decent sounding IC's in his/her spare time and who sells them for a song? ;)

[NRG]

Dave, 4m long interconnects (or longer) will be perfectly OK, as long as the capacitance per unit length is not too high. Most coaxial interconnects have a capacitance of ~ 100pF/m which is fine.

But the input impedance will also have an effect, the cable capacitance forming a low pass filter in conjunction with the impedance...so it may not be OK....

[NRG]

As an example if the 4m cable run is 400pf input into 10k the -3db roll off point is 40khz ish

20k is -3db at 20khz which will be audible

If 100k then -3db is at 4khz, in this case the cable capacitance will have to Drop substantially for it not to be audible.


Edit: the quad 306 is 20k so you need to choose a low capacitance cable No more than 250pf / M. IMHO

[Barry]

But the input impedance will also have an effect, the cable capacitance forming a low pass filter in conjunction with the impedance...so it may not be OK....

A low-pass filter is formed by the cable capacitance and the output impedance of the pre-amp. In most cases the power amplifier input impedance is sufficiently high, that it can be neglected with respect to the low output impedance of the pre-amp. Under these conditions the high frequency roll off (-3dB point) occurs at 1/(2*pi*C*R), where R is the output impedance of the pre-amp and C is the total capacitance.

If we set the roll off frequency to be 20kHz, then even with a pre-amp output impedance as high as 5KOhm, the interconnects could be as long as 14m, if the cable capacitance is no greater than 100pF/m.

[Audio Al]

As an example if the 4m cable run is 400pf input into 10k the -3db roll off point is 40khz ish

20k is -3db at 20khz which will be audible

If 100k then -3db is at 4khz, in this case the cable capacitance will have to Drop substantially for it not to be audible.

:hmm::hmm::hmm:

I just read this 3 times and it means nothing to me :scratch: ,

I wish I was clever like you lot :D

[synsei]

:hmm::hmm::hmm:

I just read this 3 times and it means nothing to me :scratch: ,

I wish I was clever like you lot :D

I don't understand the tech-speak either Al but if Barry is correct (and he knows his stuff so I don't doubt that he is) then 4 metres is looking good ;)

[Barry]

Trust me Dave, 4m will cause you no trouble at all.

[Mike g]

There's a guy on eBay who does custom lengths on van damme. Very good workmanship (I have rca to din between phononstage and pre) and he will do a range of different types of van damme.

[synsei]

I have a 3m set of modified Van Damme Black IC's fitted with Neutrik Rean plugs sitting in my wish list just now Mike at £28.99, IIRC a 4m set were £32.99. A 4m pair of Fisual Rio's are sitting in the list too ;)

http://i.ebayimg.com/t/Fisual-Rio-Stereo-Phono-RCA-Cable-4m-/00/s/NDg3WDU0MA==/$(KGrHqRHJEIE88cr4FWiBPWgJEifbg~~60_12.JPG

[NRG]

Quite right Barry, I blame the heat and beer...

[Barry]

Quite right Barry, I blame the heat and beer...

No worries Neil! What with the heat and, in my case, a chilled bottle of Pinot Grigot - I was having doubts myself. :scratch: Just checked the maths and yes, we are in agreement.

Regards

[Reffc]

Just picked up on this. Barry is basically correct. Whether long ICs make a sonic difference wrt capacitance is a function of both the output impedance of the pre AND the input impedance of the power. As Barry says, most power amps input impedance is 10 times or (far) more the output impedance of the pre, but ideally, 15 to 20 times means you wont have any audible effects due to capacitance of a coax IC for the lengths considered (and you can get away with much longer runs).

Average capacitance for a coax (single core) depending on dielectrics used and diameter of positive conductor is between 70 to 100pF/m. The better (quality) designed coax cables imho are closer to 65 to 75pF and this is primarily a function of their geometry and the fact that better cables use insulation with lower dielectric constants.

There's more to it than meets the eye though. Whether you notice any difference ALSO depends upon the electrical environment you use them and the type of shielding employed. No shielding is generally a bad thing so we'll ignore that one. Cheaper cables tend to be spiral wound (cheaper to manufacture and more flexible) whilst the better quality cables tend to use braided outer shields. I favour the use of braided shields because repeated bends or small radius bends are less prone to opening up gaps in the shield which allow EMI noise to be induced in the conductor. As mentioned, it depends upon the environment they're used. The rule of thumb though is that it pays to use a better quality cable if you are considering longer runs, whilst less expensively manufactured cables are usually fine for shorter runs. Just my tuppenceworth.

[synsei]

Cheers for your input Paul. The IC's will be running from a Classé Audio DR5 pre into a QUAD 306 and ideally I'd need a 4m run (although I could get away with only 3m at a pinch). Currently the frontrunners in my list are the Atratus IC's which seem to have garnered a lot of respect from users and reviewers alike. One fly in the ointment however is that the longest run available would seem to be 2m :eyebrows:

[hifi_dave]

RFC does a range of great incons and will tailor make to suit your situation.

[Andrew B]

I found Klotz LaGrange (the stuff they use in Rega Couple) to be excellent over long runs. It was marketed as ultra low capacitance, but I'm not a techie, so it may or may not be.

It IS good cable though. The only thing that is a viable alternative to Sound Cord IMO. I've had some £100plus cables but never went higher up the chain than that.

Now my memory prevents me from recalling the full details, but I'm sure it's no longer called LaGrange. I think the modern equivalent has a model number instead of a name, but I'm sure someone on here will know. I had some long lengths made up from this cable and I compared them to standard lengths of Rega Couple. They were every bit as good and a fair bit cheaper. I used decent locking plugs, but not Profis.
I'm not massively experienced with interconnects, but LaGrange was embarrassingly superior to the more expensive Atlas cables, a few Van Den Huls, Nordost and Chord Chameleon Sliver Plus. I figured that was enough to tell me it was a good cable. I used 3.5 metre lengths.

[synsei]

I am looking for the best bang for my buck under a hundred quid and a product which will significantly outperform the Belkin's I am currently using, which are no slouches themselves. Quite a tall order but I'm confident of success ;)

[Oldpinkman]

I daren't comment on the which cable, except why not try one for a tenner first and see what you think of it. I am using a very inexpensive interconnect off ebay for all except the AV input (sitting on the desk - not got round to it). I have a knot tied in my hanky to try a flash one from the Dac to the Pip one day, but the Pip has bloody DIN sockets so it involves me searing the flesh off my fingers with a soldering iron.:doh:

I know you'll despair of that advice - but it reminds me I still have that bloody hum problem with the Arcam on that input. They are 4m or 5m interconnects of unknown provenance I found at the back of the shed, and they run alongside mains cables (although I have tried to improve the routing so there is no longer 4m along 4m of mains cable. But just to warn you that one consequence of long ic routings, if near mains, is increased hum risk.

[synsei]

I daren't comment on the which cable, except why not try one for a tenner first and see what you think of it. I am using a very inexpensive interconnect off ebay for all except the AV input (sitting on the desk - not got round to it). I have a knot tied in my hanky to try a flash one from the Dac to the Pip one day, but the Pip has bloody DIN sockets so it involves me searing the flesh off my fingers with a soldering iron.:doh:

I know you'll despair of that advice - but it reminds me I still have that bloody hum problem with the Arcam on that input. They are 4m or 5m interconnects of unknown provenance I found at the back of the shed, and they run alongside mains cables (although I have tried to improve the routing so there is no longer 4m along 4m of mains cable. But just to warn you that one consequence of long ic routings, if near mains, is increased hum risk.

Cable routing is not an issue Richard as they will be routed a fair distance from any mains sockets and leads (at least until it reaches the 306 anyway) ;)

[synsei]

Well, I have come to a decision. The IC's which will be replacing my Belkins will be an all Furutech affair comprising two 3m lengths of Furutech FP61 75ohm coaxial cable terminated with FP126 RCA connectors. I'd like to say more about the kind gent who is making them for me however I have been sworn to secrecy so my lips are sealed. Needless to say I am eagerly anticipating installing these into my system and if all goes well this should be happening either late next week or early the following week. I will be paying a little over my budget for them however they are excellent value considering the quality of the components and workmanship which will go into making them. I'm eager to hear the results of his labours... :D

[synsei]

After a quick chat via PM's with Paul Coupe from Reffc I can reveal that it is he who will be making these IC's for me this weekend. I look forward to receiving them Paul and thanks for all your help dude. Guys, Paul is an absolute gentleman and a joy to do business with so purchase with confidence. Once I have lived with these cables for a couple of weeks I will post up a progress report and review. Watch this space ;)

[synsei]

Well, the cables arrived from Paul@Reffc this morning and I wasted no time installing them into the system and.... they are very different. I will report back in more detail on my gallery thread (http://theartofsound.net/forum/showthread.php?10732-The-Long-Way-Home) a little later however first impressions are that they are very good indeed... :D