Amp ICs -- What are they? (1 Viewer)

[Bill Kane]

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!

 

[Mark Austin]

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..

 

[Bill Kane]

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...

 

[Rob Roth]

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.

 

[brucek]

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

 

[Mark Austin]

And that my friends, is why silver sounds so much different than copper.

 

[Bob McElfresh]

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.

 

[Bill Kane]

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?

 

[brucek]

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

 

[Scott-C]

brucek,
Very impressive; thanks. When do we get the "Interconnect 201" course? I want to complete my graduate studies.

 

[Mark Austin]

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.

 

[Michael D]

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??

 

[Mark Austin]

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.

And by the way, how do you know the measurements on the Kimber Kable page are indeed accurate, can you say advertising and hype??

Well, I don't know the measuerments to be true, as I have not measured them myself, but I do know Ray Kimber, and I doubt he would flasify those numbers. It's just not the type of person he is. His reputation is far more valuable than to falsify them. Most cable manufacturers doen't even publish them, and he would not publish them if they were not correct. It leaves too much liability.

 

[Scott-C]

...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.

Mark,

I'm not disputing any of your opinions (or anyone else's for that matter), but for me at least, the simple fact remains that Bruce's email was very detailed and a good source of information. He pointed out some "scientific" (for lack of a better term) aspects of cables that I had not considered before. It doesn't automatically change my perspective on cable differences based on my own experiences (I do in some cases hear a difference), but I always want to hear every side of the discussion and this thread brings into play the scientific side, which I believe is what the original poster was requesting.

I do respect your opinion and you raise some good points.

Take care,

 

[Ken Shiring]

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 . 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.

Quote:

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 .
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 .

 

[Mark Austin]

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.

Everyone has their own standard for quality.

I don't see it as a standard for quality, as much as a standard of the performance in scientific terms.
No need for a flame suit at all. In fact, I want to thank you for allowing me to see some of the errors in my posting, and giving me the opportunity to clarify some points. I truly appreciate it. This place is for learning, and I think it is important to raise issues of disagreement like you have done. I just wish I had been as eloquent as you when I first addressed the issue.

 

[Jay Mitchosky]

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.

 

[Scott-C]

Hi Mark,
Thanks for clarifying. I think I better understand your perspective now.
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.

 

[Mark Austin]

Scott,
I was probably a little worked up since all I own are braided interconnect cabling.:frowning: I agree though, there was some very informative information.
I'm glad my latter statement made SOME sense.

 

[Ken Shiring]

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 .
One thing that surprised me was the passage you wrote here:

Making a judgement on the value, is not a scientific consideration. The science doesn't tell him that. And another quote: "This, I'm afraid to say is a bit of a marketing gimmick." See, it's the use of scientifically factual data mixed in with personal unproven opinion at the end, that I think is a bit disengenuous.

This brings up a point which I never even considered until you mentioned it : it is possible for people with technical backgounds to deliberatly mislead those who don't have such understanding. However, it should be clearly noted that brucek is not attempting any such thing, because as an EE I can confirm that every representation he makes is correct. The notion of taking advantage of others without the same background as you makes me mad, because I like the idea of sharing my understanding with others. It should be noted that most objectivists will argue that this is exactly what boutique cable companies do, using terms not relevant to the electrical audio world. Myself, I am not convinced that this entirely true, given that there are many cases where measurement techniques fail to identify sonic differences.
The crux of this whole debate is really this (IMHO) : we need to come up with accurate and repeatable causal relationships for all the things which our ears tell us and the oscilloscope does not. I refuse to believe that the science of sound is so beyond our mastery as to make it a trial-and-error affair. The fact that we are still debating this subject right now proves that we have far to go yet in this effort .
In particular, the community at DIYaudio grapples with this very question. One of the fist challenges faced by the amp designer is how to reconcile the very mathematical nature of circuit design with the elusive nature of a great sounding amp. There are countless crappy sounding amps out there with 0.5% THD. Food for thought .