Sunday 29 March 2015

On cables and sound

I posted just a little while back about my project to build some new amplifiers for my stereo.   I had a little problem with the power supply for one of the amps - it gave off a spark when switched on.  I sent it back to Hypex, who told me that they couldn't reproduce the problem, but they sent me a new one anyway.  So I installed it, fired up the amps, and they worked fine.  So now they form part of my stereo.  Here's a picture - the new amps are the two side-by-side silver boxes halfway up.



One of the things that I noticed is that they new amps have a bit more top end that I'm used to - they're a bit trebly.   I don't know if that's because the amps have to be run in - that's a common enough phenomenon.   But as it happens I have a set of very fine audio interconnect cables that I have used on systems in the past, that tame a slightly wild top end, and I swapped them into the system. Perfect.

Now, I know that audio signals fall into the lower end of the frequency spectrum that cables might have to deal with, and that measurable effects on cable performance only start to come in at radio frequencies.  I have debated with friends of mine about whether or not  choice of cables can impact the sound of a stereo.  The only proof is by demonstration, and I have shown puzzled scientific friends that two different types of cable, both of which should be perfectly adequate for audio, give very different results.  And they then sit and debate what might be happening.  As far as I'm aware, right now, no-one really knows.

As a listener to music, I really don't care what's happening, as long as I like the result.  As a scientist, I'd like to know.  And the trouble with no-one knowing, is that there tend to be forwarded all sorts of nonsensical explanations, most of which relate sound quality to the price of the cable.

Never mind.  Enjoy the music.

7 comments:

James Higham said...

I have debated with friends of mine about whether or not choice of cables can impact the sound of a stereo. The only proof is by demonstration, and I have shown puzzled scientific friends that two different types of cable, both of which should be perfectly adequate for audio, give very different results. And they then sit and debate what might be happening. As far as I'm aware, right now, no-one really knows.

You'd say it's very much a factor though?

ivan said...

Humm, It sounds as if you are all digital in which case cable resistance and inductance come into play with the cables. You can also get into cable length v wave length - very akin to radio - this didn't apply as much when we used analog signals.

Mark In Mayenne said...

James: Yes, very important especially at the top end of hi-fi. Poor choice of cables can negate the sonic benefits of a small fortune in other kit. If you're setting up a system it's worth borrowing various different cables from the shop to see (hear) what works well. If you can't then the silver litz - braided cables you can get on eBay for not-silly money are a very good start. They are what I have been using up till now.

Mark In Mayenne said...

Hi Ivan, the only interconnect carrying digital signals is the optical link between the PC and DAC; all the rest are carrying audio.

ivan said...

Mark, audio signals can be digital or analog.

In your system I would imagine the only analog signals are those between the power amps and speakers, all the others would be digital.

The way to check what is going on is to get out the oscilloscope and a good signal generator. Feed the output from the signal generator and compare it with the output of the various cables - that may require a breakout box if you can't connect the oscilloscope probes in the equipment. By feeding a square wave into the system it is very easy to see any clipping and/or distortion caused by the cables - you can also check how well the power amps deal with the signal and see any clipping and/or distortion they add.

Mark In Mayenne said...

Hi Ivan,
My signal source is a PC, that outputs SPDIF optical to a Logitech Transporter that I use as a DAC and volume control. The analogue output from this goes to two places: one is the analogue inputs of the class D amps (Hypex) that drive the wideband cones and tweeters, and the other goes to the input of the Amcron (also marketed as Crown) DC300A MkII, analogue class A/B DC-coupled amp, via a digital crossover used as a low-pass filter, to drive the bass bins.

The only digital interconnect is the optical.
Regards
Mark

ivan said...

Hi Mark,

The part of me that used to be an audio design engineer for the film and TV industry in the 70s would love to attach some of my test equipment to your installation just to see what is going on.

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