Amp ICs -- What are they?

Discussion in 'Archived Threads 2001-2004' started by Bill Kane, Jan 28, 2002.

  1. Bill Kane

    Bill Kane Screenwriter

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    Let me be perfectly clear: I need to see thru the cable hype. What EXACTLY are amp-preamp (pre/pro) connections? 75 ohn coax cable; audio analog wire (like RS Gold, say), or what.

    I mean, what's the BASIC electrical construction here?

    I am asking because I have always had receivers. Now, I'm getting plenty of input about silver this, silver that cables, like $200. I need to know the "Home Depot 12 gauge" version for separate-to-pre/pro wires!
     
  2. Mark Austin

    Mark Austin Supporting Actor

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    Any 50ohm regular audio cable will work. I prefer the silver interconnects, but that's with my system. If you want the "Home Depot version", I'm sure you could find them at either Home Depot, Radio Shack, Best Buy, Circuit City, etc..
     
  3. Bill Kane

    Bill Kane Screenwriter

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    Sigh....ok, I am not perfectly clear. I am not asking what to buy, rather an Electical Connections 101 question.

    Anyway thanks, mark. I guess "regular 50ohm audio cable" is my answer. I actually have some Cats and Silver Serpents comin' in the mail...
     
  4. Rob Roth

    Rob Roth Stunt Coordinator

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    The signal coming from a pre/pro to the amplifier is analog- that's exactly what the pre/pro does (convert digital sources to analog). Thus you will be sending a full range of analog waveforms; following the general rule that sound only degrades at each stage, I'd suggest good quality cables be at least auditioned. Since the cables are intended to move analog info, it MAY take some time to break in the cables. This has something to do with the orientation of the atoms in a conductor in response to current flow.
     
  5. brucek

    brucek Second Unit

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    Bill,

    You are interested in the preamp to amplifier analog interface. I will give you the interconnect 101 course.

    This is considered a line level, high impedance connection where the input impedance of the power amp will be in the order of 50Kohms with the output impedance of the preamp being in the order of 100 ohms. This is a voltage bridge type high impedance connection where the preamp acts as a voltage source and almost no current is drawn. We are not interested in power transfer in this interface.

    We want to present a relatively low voltage to the amplifier input with as low a noise floor as possible. So generally the main concern is noise. A properly shielded cable is important. Coaxial cable fits this bill. Wouldn't matter if it was 50ohms or 200 ohms. The characteristic impedance of an audio cable is of little concern here. In fact the characteristic impedance of a piece of coax is only valid at higher frequencies - audio doesn't qualify, believe me.

    We do care about capacitance in long runs for interconnects. The parallel reactance can become a factor in relation to the input impedance of your power amp. The result would be a slight rolling off of higher frequencies. So, if you can get a cable with as low a capacitance per foot, that would be wise - but it's really only a concern in long runs.

    We don't care about inductance on this interface. The series reactance caused by the inductance created at audio frequencies with relation to input impedances is not worth talking about.

    Avoid unshielded twisted wire cables, they usually have fairly high capacitance figures which tends to roll off the upper frequencies. They act like a low pass filter. To make an unshielded pair of wires usable on this interface, companies have to incorporate an interweaving technique of the insulated conductors. This usually works to reduce noise and can be almost as effective as a shielded coax but the technique also causes the capacitance per foot to rise. The parallel reactance resulting from the cables high capacitance starts to become a player in your impedance equation. Why bother.

    Avoid cables that add networks to their cables to create an admitted low pass filter.

    There is no such thing as directivity in interconnects, so don't get too fussed by that claim.

    As far as silver cables are concerned, well, silver as a conductor is only slightly better than copper, but that's about the only measurable quality other than it's oxidative product has the same conductivity as the pure metal. With proper connections this isn't an issue.

    Silvers resistivity compared to copper is 0.94. This is hardly significant enough to justify the rather large cost difference for silver cables compared to copper. Silver as a conductor will exhibit the same inductance and capacitance per foot because this is a generally a function of geometry.

    Simple resistance is a very small issue when considering interconnects. As I said this is a voltage bridge type high impedance connection where the preamp acts as a voltage source and almost no current is drawn. So unlike a speaker connection, with an interconnect, resistance becomes inconsequential. Silver gains no advantage, and also no disadvantage. This, I'm afraid to say is a bit of a marketing gimmick.

    What this means is that the important features of an interconnect is that it be solidly constructed using well shielded coaxial type cable and have well made terminations at each end.

    Certainly any well made 75 ohm cable will do. Most RG-6 or RG59 cables terminated in RCA connectors will do well. You mentioned the Radio Shack Gold cables - these are very good cables and will serve you well also.

    The purpose of an interconnect is to degrade the signal as little as possible before the signal reaches its destination. Most coax cable does an adequate job of this. Terminate it with some mechanically sound connectors and your good.

    brucek
     
  6. Mark Austin

    Mark Austin Supporting Actor

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    And that my friends, is why silver sounds so much different than copper.[​IMG]
     
  7. Bob McElfresh

    Bob McElfresh Producer

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    Wow! Bruce, you nailed that one very nicely. I admire the way you brought up the issues and dismissed the ones that dont apply for short-run interconnects. Nicely done.
     
  8. Bill Kane

    Bill Kane Screenwriter

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    bruce, I'm just checking back, and, again, wow!

    this is what I was trying to understand: that short-run ICs in this application are NOT boutique dependent. Even RG-6, huh? thanks. the emperor wears no clothes.

    still, I see you use Bryston cables with Brystom amps. just to balance-match, yes? is this XLR here?
     
  9. brucek

    brucek Second Unit

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    Bill,

    Yep, when I purchased my SP1 I needed 6 XLR balanced cables. Bryston makes some very reasonably priced XLR cables with the features I mentioned. The terminators are well made, standard Neutrik XLR's. The wire is a flexible, well made microphone cable suitable for a balanced interface with relatively low capacitance per foot. The price is not a great deal more than if I made them myself (and I'm getting lazy). No boutique here - not that it would make anything worse - just no better. Most of the rest of the cables in my system I make myself. RG-6 works great for all single ended cabling (video, audio, digital, subs). I like to color code mine to its usage so I'm able to identify a cable in the morase of wire behind my system.

    RG6 can be a little difficult to terminate, so if you just want to purchase, I would recommend the RS Gold type - very reasonable.

    Thanks, Bob. I appreciate that from someone like yourself, who gives so much time to helping people and handing out good advice on this forum.

    I know the engineering realities of some equipment issues aren't very popular - particularily when it comes to cabling, but I think if both sides of the argument are represented, then people can make up their own minds.

    brucek
     
  10. Scott-C

    Scott-C Supporting Actor

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    brucek,
    Very impressive; thanks. When do we get the "Interconnect 201" course? I want to complete my graduate studies. [​IMG]
     
  11. Mark Austin

    Mark Austin Supporting Actor

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    I really don't understand all this WOW stuff. Nothing that has been posted carries any amount of weight. but theoretical. There has been no stated proof, nothing, just a bunch of commentary from a textbook. The fact still remains that science is still not able to measure acurately the way we hear things. One can spout all the science classes they like, but it has no bearing on the reality that different cables sound different. If our resident science professor would like to visit www.kimber.com he can see that his previous statements don't hold true, at least in the measurements provided therein about silver vs. copper. The theories can flow as the day is long, but it doesn't really amount to crap.
     
  12. Michael D

    Michael D Stunt Coordinator

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    Mark,

    I think most of us that frequent this board appreciate your opinions and if you can hear the difference, that is great. I think what Ken is trying to say is that you don't necessarily need to spend a lot of money on cable to get a good sounding system. And by the way, how do you know the measurements on the Kimber Kable page are indeed accurate, can you say advertising and hype??
     
  13. Mark Austin

    Mark Austin Supporting Actor

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    I appreciate your comments Michael. My comments weren't necessarily directed towards Ken, but more towards the people that tend to think that because someone can give some psuedo-scientific explantion for something that can't be explained by scientific means, that there is some WOW factor that lends some credence to that particular point of view. The fact is is that there have been very eloquent psuedo scientific explanations given with a large degree of un-scientific "believe me", "you just have to trust me" type comments. To me, it just smacks of someone trying to poo poo different audio points of view with less than credible science. At least as offered here.

    I agree that one does not have to spend a lot of money to have good sounding cables. That isn't my issue at all.

     
  14. Scott-C

    Scott-C Supporting Actor

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  15. Ken Shiring

    Ken Shiring Agent

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    Mark,
    Given the amount of anti-objectivism in your post, I fee that this thread needs some counter argument to make any attempt at balance. I have been lurking on this forum for some time now, so I think I am going to try jumping into a heated debate for a change of pace [​IMG] . Please don't misunderstand the fact that I am not directing these criticisms to you personally, or that subjectivism in audio is wrong. I personally am a believer in both philosophies.
    I'm going to have to disagree with you there. Regardless of the respect in which you hold Mr. Kimber, I take issue with the problem of liability. Since the audio community can't even agree on a common standard by which to judge cable, liability is all but nonexistant. How is someone liable if you can't prove, using an agreed upon standard, if something is substandard? It's a little like ISO9000 certification. You can do anything you like as long as you document a methodology and follow it. Everyone has their own standard for quality. It's a little hard to prove liability when there's no common standard to be held to [​IMG] .
    Again I need to clarify that my implication is not that Kimber is bad. Based on the experiences of others, I am certain that Kimber cable is top notch, and I am certain that his company would not be where it is today if their cable was irrelevant as brucek's post implies.
    Now that I have that off my chest, I had better get my flamesuit [​IMG] .
     
  16. Mark Austin

    Mark Austin Supporting Actor

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    Ken,
    That was a very well thought out, and very well written post.
    I think you do point out some things in which I mis-spoke, or was incorrect.
     
  17. Jay Mitchosky

    Jay Mitchosky Producer

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    Guys

    This discussion is going really well, considering the subject matter. Good spirited debate from alternative perspectives. The only reason I'm writing anything is to give forewarning to anyone who wants to turn this into a slugfest, as very often happens with The Great Wire Debate. If that happens offenders will be removed and/or the thread will be closed.
     
  18. Scott-C

    Scott-C Supporting Actor

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    Hi Mark,
    Thanks for clarifying. I think I better understand your perspective now. [​IMG]
    This is an interesting thread. As Jay said, nice to see a mature, spirited debate on cables without inflammatory remarks. Thanks to all those who have posted; I feel I learned some things from this thread, which after all, is one of the goals of this BBS as someone else said.
     
  19. Mark Austin

    Mark Austin Supporting Actor

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    Scott,
    I was probably a little worked up since all I own are braided interconnect cabling.[​IMG] I agree though, there was some very informative information.
    I'm glad my latter statement made SOME sense. [​IMG]
     
  20. Ken Shiring

    Ken Shiring Agent

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    Mark, I am very glad that we clarified these things. It is so rare when people on these forums concentrate on supporting their arguments without relying on criticisms of personal taste. It is only when disuccions of this quality happen do people actually develop respect for opposing opinions [​IMG] .
    One thing that surprised me was the passage you wrote here:
     

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