I am wondering if an unbalanced interconnect using BJ Cables LC-1 Audio Cable Design Notes -- Blue Jeans Cable of 11 feet/3.4 meters would present a problem? Source is a Cary SLP-98 and the amplifiers are DIY 2A3 Radiotron monoblocks. The capacitance of the cable is 12.2pf/foot. Is there a better cable for unbalanced use in this application?
TIA and all that.
Dave
TIA and all that.
Dave
> 11 feet
> Cary SLP-98
> 12.2pf/foot.
11 feet at 12.2pF/ft is135pFd. There must be some pFd in your amp's input, so pencil 200pFd.
The SLP claims 440 ohms output impedance. (But what will it *drive*??)
440 Ohms driving 200pFd is -3dB at 1,809,496Hz.
> Is there a better cable
Personally, for a mere 11 feet I'd use $0.50/foot cable and use the $100+ saved to buy better tweeters.
> Cary SLP-98
> 12.2pf/foot.
11 feet at 12.2pF/ft is135pFd. There must be some pFd in your amp's input, so pencil 200pFd.
The SLP claims 440 ohms output impedance. (But what will it *drive*??)
440 Ohms driving 200pFd is -3dB at 1,809,496Hz.
> Is there a better cable
Personally, for a mere 11 feet I'd use $0.50/foot cable and use the $100+ saved to buy better tweeters.
If you're worried about high frequency attenuation here are the numbers...
The Cary SLP-98 lists an output impedance of 440 ohms. The DIY 2A3 Radiotron monoblocks almost certainly have an input impedance of at least 10 kohms or more, which give a total nodal impedance of about 420 ohms or more, up to the 440 ohms of the Cary at maximum. The coax you listed at 11 ft. would have around 150pF of total capacitance. With those numbers the math says your Fc is around 2.5 MHz, so nothing to worry about.
Mike
The Cary SLP-98 lists an output impedance of 440 ohms. The DIY 2A3 Radiotron monoblocks almost certainly have an input impedance of at least 10 kohms or more, which give a total nodal impedance of about 420 ohms or more, up to the 440 ohms of the Cary at maximum. The coax you listed at 11 ft. would have around 150pF of total capacitance. With those numbers the math says your Fc is around 2.5 MHz, so nothing to worry about.
Mike
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I was primary concerned about performance. Is this an appropriate cable for 11 feet of unbalanced design? The cost of the BJ stuff is low enough for me at this point. They have done some research, have the appropriate connectors and the equipment to swage them on. They also offer a 30 day return if you don't like them.
If you have other specific suggestions , I'd welcome that..
I was primary concerned about performance. Is this an appropriate cable for 11 feet of unbalanced design? The cost of the BJ stuff is low enough for me at this point. They have done some research, have the appropriate connectors and the equipment to swage them on. They also offer a 30 day return if you don't like them.
If you have other specific suggestions , I'd welcome that..
I have a 20' cable run between preamp and power amp, and the key issue is shielding, not HF roll off, in my experience. The Blue Jeans cables are well shielded, and with some work to eliminate ground loops I have a quiet system. I certainly can't detect any loss of high frequencies (but I'm using compression tweeters, which roll off at about 16K anyway).
tim
Thanks TimB. I too have compression drivers and my ears roll off before that anyways. My continued question regarding unbalanced interconnect wire is that I believe that both conductors should be of similar construction for best performance. A coaxial assembly obviously does not meet that criteria. Thoughts?
You don't get the same common mode noise advantages from single ended relative to balanced, which is why twisted pair performs "better" in balanced. It's fine for single ended and lets you do things like a telescoped shield, but LC-1 is a quality and fine sounding product. At DIYaudio you won't find much support for differences in sound quality in cables, for a variety of reasons, they'll generally recc the cheapest decent option with good basic design. LC-1 is well-designed, with good materials and shielding, is very durable and will last a lifetime of even rough use (as if that should be an issue, but I've seen people destroy equipment by yanking on cables so hard). If money isn't too terribly dear it's a great option.
When Ive built interconnects using shielded twisted pair I've used one conductor for the center pin. The other conductor to the outer solder lug and the shield connected to the same lug at one end only. I'm not claiming I used ANY electrical smarts about doing that but it seemed to work OK.
The wire closely resembled this:
Attachments
No, there is no requirement for similar construction for the two wires of an unbalanced connection; maybe you are thinking of a balanced connection?WntrMute2 said:
For unbalanced the signal wire can be as thin as you like; the return/shield should be as thick as you can get, and coax construction is best.
Shielded twisted pair is popular for unbalanced too. I am not sure why. It will work fine when one end (typically the source) is electrically floating e.g. MM cartridge. When both ends are grounded, as for a typical interconnect, then you really need a low resistance return conductor - which a shielded TP does not give you. Fortunately audio is uncritical about such things so the wrong cable will often work sufficiently well for some people to proclaim that it is better than the right cable.
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Wouldn't noise in the shield be coupled to the "hot/flow" of the twisted pair?
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