Bottlehead Forum
General Category => General Discussion => Topic started by: Laudanum on July 20, 2011, 02:05:22 AM
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... not specific brands but rather cable types for rca interconnects. What are your preferences? Coaxial, UTP, Braided?
Need to make some RCA interconnects in the near future, just looking for what seems to be the cable type preference these days.
Thanks
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For the lowest signal level in my system I have a Incognito/Cardas/Rega replacement cable from my cartridge clips to the input of my Seduction. My phono cables, Seduction to Foreplay, are shielded coaxial. Same for Foreplay to Creek OBH-10 (remote volume control for lazy guys like me). The rest are unshielded twisted pair (sources to FP, OBH-10 to Paramours).
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So Grainger, sounds like your approach is coax for most noise pickup sensitive connections and UTP for the rest. Where does cable capacitance come into play of turntables. Is it from the turntable to the phono stange only? Or is it phono stage to pre-amp or amp? Or is it both? Coax is geneally lower capacitance than twisted pair, is it not?
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And I answered before really understanding your question...
Cable capacitance is in parallel with the destination resistance. It rolls off the high frequencies, "shunting" them to ground. The variables have to do with the source impedance and the total capacitance and resistance "seen" by that source. It is the simple first order high pass formula.
Fo=1/2*Pi*R*C
Fo is the 3dB down point, Fo*10 is flat, no roll off.
Pi=1.414
R=destination (phono stage for cartridges, input resistance for line stages) resistance
C=total capacitance of the cable and the destination device
I can't help with the source requirements, Eros or Seduction (should be the same) but PJ is good at taking all that into consideration.
Some cartridges want to have a given capacitive load. It is good to try to get there, but changing the capacitance at the load resistor and listening is the best way to see if you like it.
This is applicable to all source destination situations. The Seduction and Eros both say, "Output impedance is 4K ohms (a preamp of at least 15K input impedance and interconnect cables of 1 meter or less are recommended," that from the Eros page. The Seduction says something similar. Cabling is rated in pF per foot or meter. I don't know about twisted pair vs. coax but again PJ is a great source.
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Twisted pair rules over coax in my book. The ability to control which piece of gear the shield is attached to is critical to keeping the noise floor down.
We have been cooking up a few different cables over the past few years. My favorite recipe these days is a strand of 22 and a strand of 20 twisted together, with 22 being signal + and 20 being signal -. Both are Teflon insulated and they are slipped into Belden braided shield tubing that is connected to the RCA shell only at the source end. That gets techflex over it because the shield braids can make a lot of noise if they rub together. We use Neutrik Pro Fi RCA plugs.
Capacitance with this design has not been a problem when used with tape heads or phono cartridges.
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Thanks Doc and Grainger. I dont think Ill get that selective but I do have some twisted pair cable that has a drain that can easily be wired as suggested as well as some full braided twisted pair in which I solder the braid at only end. In fact, there is some that has been in the main system for years.
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We have been cooking up a few different cables over the past few years. My favorite recipe these days is a strand of 22 and a strand of 20 twisted together, with 22 being signal + and 20 being signal -. Both are Teflon insulated and they are slipped into Belden braided shield tubing that is connected to the RCA shell only at the source end. That gets techflex over it because the shield braids can make a lot of noise if they rub together. We use Neutrik Pro Fi RCA plugs.
Could you give us more info related to the braided shield tubing? Pardon my ignorance. I didn't know such thing existed. I've been using CAT5 cables for years (teflon insulated) and I like them a lot. They are very relaxed and detailed at the same time (I guess no one will understand that!). I mostly use Pro Fi plugs. But I could definitely use some shielding. At least it wouldn't hurt.
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I know that you can buy the braided shield alone. Try a search for braided shield tubing or check cableorganizer, I know that they used to sell it. There a few other places I have seen that sell it online. Ive never used it so I dont know the specifics or where best to buy it or what types may be best.
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Your CAT5 should have a foil shield and so I don't think adding the braid would do much. Belden braided sleeving is what we use. They make several sizes. Newark carries it and I think it runs about $2.50 per foot in the size we use.
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Thanks I'll look for it. I'm using individual pairs of CAT5 so no shielding in them.
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I make my own interconnects from homegrownaudio wire. I use both silver and copper. More copper than silver these days though as the price of silver wire has quadupled over what I paid 10 years ago! Back then I could get 100' of their 22awg silver/teflon wire for under $200.
Their copper wire is just as good and is still a decent bargain. It's very easy to strip and bend and work with. I use it for my other projects as well. For instance I used a lot of it for my latest creation: A highly modified clone of the Dynaco ST35.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi576.photobucket.com%2Falbums%2Fss207%2Fcorndog642%2FDynaco%2520ST35%2Fd5d68d7c.jpg&hash=dfe1ccd5c21c730701011a3980687745f38c8da2)
I've also used the cotton-insulated silver wire for the outputs of my Sex amp to good effect.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi576.photobucket.com%2Falbums%2Fss207%2Fcorndog642%2FBottlehead%2520Sex%2520Amp%2F95d035f6.jpg&hash=f45eca0a7d9537437bd447ca8061a0be919014a5)
...and for 3-wire braided interconnects.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi576.photobucket.com%2Falbums%2Fss207%2Fcorndog642%2FMisc%2520Audio%2FIMG_2535.jpg&hash=818b853903fc97f6cfc6ca9286a06c58428214f1)
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Xavier,
Look for "ground braid" I have bought mine from surplus sales of nebraska for cheap -- tinned copper. I typically buy it in rolls of 100 feet as well.
HTH,
Jim
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Links to where to purchase pre-made cables of the sorts mentioned in this thread?
I recently switched out some cheap RCA cables with (also cheap, but, I guess, better) cables and it reduced the hum coming from my TT. Wondering if I should switch out all my cables...?
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I bought some shielded twisted pair wire at my local surplus store. When I got home and examined the wire closely I noticed it had one silver colored wire and one copper. I tested the resistance of the silver colored wire and determined it has to be stainless steel or titanium. Does anyone have any idea what this is good for? The insulator is blue for the copper and red for the steel.
Thanks
Michael
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It might be thermocouple wire...John
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John,
Yes, that's what I think too.
-- Jim