Amp to cab cable question

[Richard R]

I have been given a very early Asdown ABM C300-100 combo, with a 15" extension cab. I need a cable to go between the amp and the extension cab. 

A quick email to Ashtons provided a full set of specs, drawings and a manual, and a recommendation of a cable rated to 200W. The rating was given as 200W, but not a current rating.

 

It's jack plugs at either end, and my question is this:   I have high quality jack plugs, and flexible 13A mains cable. Is there any reason I can't make up my own lead? 

 

 

[chyc]

26 minutes ago, Richard R said:

It's jack plugs at either end, and my question is this:   I have high quality jack plugs, and flexible 13A mains cable. Is there any reason I can't make up my own lead?

On a practical level, mains cable will not be as flexible as dedicated speaker cable but if treated right I would happily use repurposed mains cable (and I have done, albeit internal to a cabinet). It's not going to be melting the wire. For reference, a 13A mains cable will happily take multiple kW of power.

 

Using the cable as a guitar lead will not work out so well as the cable will be unshielded so you'll get a lot of unwanted interference added to your signal so bear that in mind if you want the cable for double duty.

[jezzaboy]

You can buy a decent speaker cable for £15 or so, I wouldn`t be faffing about with a mains cable. Better off with the right thing?

[Richard R]

It's not flat twin-and-earth, it's mains cable from an appliance- should be flexible enough.

 

The amps rating is relevant - 200W at 20V is 10A. That would melt a 3A cable which at 250V would handle well over 500W.

[Richard R]

1 minute ago, jezzaboy said:

You can buy a decent speaker cable for £15 or so, I wouldn`t be faffing about with a mains cable. Better off with the right thing?

 

True, but I have the cable and connectors sat in the garage.

 

[tauzero]

8 ohm cab? Power = I^2 * R, substituting known values 200 = I^2 * 8 (assuming it's an 8 ohm cab) so I^2 = 12.5, so the current is about 3.5A.

[tauzero]

And all my jack-jack speaker cables are 2-core flexible mains cable.

[chyc]

3 minutes ago, Richard R said:

The amps rating is relevant - 200W at 20V is 10A. That would melt a 3A cable which at 250V would handle well over 500W.

The voltage drop you need to worry about is from one end of the cable to the other. Tauzero's power equation is what you need, and you need to measure the resistence of the wire but trust me 13A is plenty, the resistence of the wire will be tiny, orders of magnitude lower than the resistence of the cabinet.

[Downunderwonder]

13A mains cable is way more than required. You could run a space heater at 5m on it.

 

Your biggest hassle is going to he soldering the big wire onto your plugs, and hoping the strain relief holds.

[Richard R]

I had worried about the size of the wires onto the terminals.

I may have some 5A wire somewhere.  I shall have a look and report back.

[Richard R]

9 hours ago, tauzero said:

8 ohm cab? Power = I^2 * R, substituting known values 200 = I^2 * 8 (assuming it's an 8 ohm cab) so I^2 = 12.5, so the current is about 3.5A.

 

👍

I had forgotten that I had the resistance of the cab as another known quantity and so the current could be calculated.

 

I wondered why anyone would quote a cable rating in W not A, but I guess it's easier to read the amp specs which quote power into a given speaker and buy a cable to match the power.

Which is of course @jezzaboy's very sensible suggestion 😀

 

[Bill Fitzmaurice]

3 hours ago, Richard R said:

I wondered why anyone would quote a cable rating in W not A 

 

Because both amp and speaker ratings are written by marketing departments, not engineering departments. Watts sell gear, amperes and volts don't. Wire capacity ratings come from engineering departments. 

[BassmanPaul]

In my mind the biggie here is to be certain that there is no possibility of a short between the conductors. That would not bode well for the health of a solid state amplifier.

[Bill Fitzmaurice]

That's where the voltage and amperage ratings come in. Most wire is rated at 600V. A 1kV amp into a 4 ohm load is 63v. 14 gauge wire is rated at 15A. Said 1kV into 4 ohms is 16A. However, those ratings are for constant full voltage and current. Amps never run at constant full voltage and current. Even 50% duty cycle would be unusual. 

[Richard R]

After all that I've just been given a spare Designacable speaker lead, so no need to solder my own after all. 

[Stub Mandrel]

In the days before Speakon, I used to make my own speaker leads using (orange) twin-core 13A mains cable. I used high quality metal body jacks with internal plastic insulation over the tip connection and I fitted heat shrink over the metal body and strain relief to minimise the risk of any shorts.

[casapete]

7 hours ago, Stub Mandrel said:

In the days before Speakon, I used to make my own speaker leads using (orange) twin-core 13A mains cable. I used high quality metal body jacks with internal plastic insulation over the tip connection and I fitted heat shrink over the metal body and strain relief to minimise the risk of any shorts.

I did the same, still got a couple. Used one last week between my Hartke amp and old 4x10. 

The orange cable was easy to find in a bag of leads too.

[BassmanPaul]

I've always made my own speaker cables. I use two core black rubber insulated power cable, IIRC 12 gauge. I've never had a problem with any of them. For storage I lust loop them end to end until I get three or four feet length and just then tie each of them in a knot. They then go into a milk crate with others of their ilk. 

 

In my mind concern about speaker cables is much ado about nothing! 

 

Edited June 18 by BassmanPaul

[Rosie C]

18 hours ago, Stub Mandrel said:

In the days before Speakon, I used to make my own speaker leads using (orange) twin-core 13A mains cable.

 

Despite these days of Speakon, I still use orange twin-core mains cable to make my speaker cables, just I use Speakon plugs now  

 

[Chienmortbb]

I hope this does not turn into a rant, but... here goes:

 

In general, the main difference between mains cable and speaker cable is that the speaker cable is more flexible and generally has more strands. The good brands are also virtually oxygen free. You will not really notice the difference sound wise, just the lack of flexibility.  So why use speaker cable? It's more flexible, less power is absorbed in the cable, and it is generally no more expensive than cut cable. 

 

Many sites sell Van Damme Studio (blue). This is a rigid (in comparison to tour grade cable), cable designed for Studio Installations where they do not move. They do a tour grade speaker cable, but it seems to be quite rare. I use Sommer Meridien, for my speaker cables it has even more cores than the others (120+ Vs 80+) on the market and coils beautifully. The best speakers cables won't make you play like a pro, but they are designed for the job.

 

The same is true of many instrument cables, although there the benefits can be huge and the reliability of cheaper cables is suspect. As I make cables for people, I often get sent, or given, faulty cables. It may sound strange, but I learn a lot from them. The first thing is that the name brands often don't make good cables. It is often style over substance, with a posh tweed covered cable attached to a poor riveted plug moulded inside a rubberised or PVC boot.

 

Similarly, speaker cables with Speakons can only be recommended if the speakon is from a reputable manufacturer. Neutrik, of course, but REAN (Neutrik subsidiary), Cliff and Amphenol all make good speakons to the relevant standards. A £15 cable eBay/Amazon will not usually have "legal" speakons. One look at the cost, even in bulk, of a decent speakon is close to £5. A decent 2.5mm cable would probably be £4/metre. So there is little left for profit and postage on a £15 cable. 

 

Anyone that has bought cables from me will know I am happy to chat about cables, I have made speaker cables instrument cables and wireless cables (to connect instruments to wireless backpacks) as well as unusual cables, so I now have years of experience. Despite SWMBO* moaning about the amount of stock, I am almost as happy to lose a sale rather than sell something that is either wrong, or where a viable version is available from elsewhere. 

 

*She who must be obeyed does not moan and has the patience of a saint really.

 

 

 

[Rosie C]

2 hours ago, Chienmortbb said:

I hope this does not turn into a rant, but... here goes:

...

 

Interesting. I'd not realised the difference in flexibility. I must admit my main reason to buy orange lawnmower flex was it being hi-vis for teenage boys running amok at our community band break time... though I'm sure the pro cable comes in bright colours too. I always use Neutrik connectors though.

 

Edited 4 hours ago by Rosie C

[Stub Mandrel]

I think the arguments for specialist speaker cable are weaker than for instrument level cables. For bass stacks cables are so short any losses are negligible. For long PA runs maybe. 

 

The speaker cables I made in the distant past used cable designed for repeated coiling and flexing and I've never had a failure. 

 

I do use branded off-the-shelf speaker cables now because I greatly prefer speakon.

 

Instrument wise, I use decent cables and prefer my Van Damme/Neutrik ones for reliability and 'limpness', although I have many others.

[NancyJohnson]

Aah, in the decades I've been playing I've used everything from hotwired bell-wire through to my current @obbm Speakons.  Never suffered damage, any (noticable) loss in sound, no explosions etc. 

 

Maybe I've just been lucky, or maybe we were too stupid to know better.