Making your own amp to cab speaker cables

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  • Danny1969Danny1969 Frets: 10357
    It pains me that guitar amps use the jack for speaker connections ..... I can't think of any other device which would let the end user plug something in wrong cos all ins and outs use the same connection type ... and destroy the output stage

    I mean you can plug a push to make footswitch into the speaker output socket ... I saw a guy do that with a solidstate Fender amp. Insane really ! The amp used those TDAxxxx IC's for the output stage .... short circuit protected apparently according to the data sheet :)  ...Not !

    The jack isn't a safe connector for higher wattage higher impedance cabs either, being easy to touch. You could get a tiny belt from a 100 watt 16 Ohm connection  
     
    www.2020studios.co.uk 
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  • dannyboy82dannyboy82 Frets: 147
    Anyone have an idea if it’s safe to use the cable in the pic?
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  • ICBMICBM Frets: 71963
    Anyone have an idea if it’s safe to use the cable in the pic?
    I don't see any reason it shouldn't be. It looks well made.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • dannyboy82dannyboy82 Frets: 147

    Thanks ICBM, it is very well made and as I mentioned the service was excellent. I’d just never seen multi strand cable used in this application before. 
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  • ICBMICBM Frets: 71963

    Thanks ICBM, it is very well made and as I mentioned the service was excellent. I’d just never seen multi strand cable used in this application before. 
    The type of cable doesn’t matter, it’s the quality of the fittings and how well they’re fitted which does.

    From an electrical point of view anything thicker than bell wire is all the same at these currents.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • DJH83004DJH83004 Frets: 196
    This is the cable I use in the workshop to make up speaker leads and the only reason I use this rather than ordinary mains flex is that it is red and black, which I think looks better inside the cab. As IC says the important thing is the quality of the plugs and the termination that counts.   
    https://www.ebay.co.uk/itm/2-CORE-ROUND-TWIN-12V-RED-BLACK-ELECTRICAL-AUTO-CAR-AUTOMOTIVE-MARINE-CABLE-WIRE/182948804313?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
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  • ecc83ecc83 Frets: 1592
    Danny1969 said:
    It pains me that guitar amps use the jack for speaker connections ..... I can't think of any other device which would let the end user plug something in wrong cos all ins and outs use the same connection type ... and destroy the output stage

    I mean you can plug a push to make footswitch into the speaker output socket ... I saw a guy do that with a solidstate Fender amp. Insane really ! The amp used those TDAxxxx IC's for the output stage .... short circuit protected apparently according to the data sheet :)  ...Not !

    The jack isn't a safe connector for higher wattage higher impedance cabs either, being easy to touch. You could get a tiny belt from a 100 watt 16 Ohm connection  
     


    The voltage is around 100V pk to pk but in practice there is no shock hazard. People were playing ducks and drakes with 100V line speaker systems in muddy fields for close to 100 years and I have never heard of anyone being injured other than a guy who got a tickle and fell off a ladder!

    No, the 1/4" jack is not a good connector for much about a few watts of 'lecktric but you would have a hard time replacing them on guitar kit. In practice again though, has anyone here had any speaker jack in otherwise good condition get hot?  Amps are not kettles, you don't pull 100watts continuously.

    I WILL concede that we should not switch speakers with them other than sub about 5watts but the fact is the CARRYING capacity of a switch contact is many times its SWITCHING capacity which is why perhaps I personally never had trouble with them in cabs (plus they were all spanking clean and new!)

    Dave.

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  • ICBMICBM Frets: 71963
    ecc83 said:

    In practice again though, has anyone here had any speaker jack in otherwise good condition get hot?
    Yes, on a fairly high-powered bass amp. I forget what type exactly, but probably about 300W into 4 ohms.

    ecc83 said:

    I WILL concede that we should not switch speakers with them other than sub about 5watts but the fact is the CARRYING capacity of a switch contact is many times its SWITCHING capacity
    Exactly, and this is why things like extension speaker jacks and headphone jacks should not be used to switch the speaker off in a combo. You can simply have the speaker plugged in with a standard 1/4" jack, and unplug it if you don't want to use it.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • ecc83ecc83 Frets: 1592
    ICBM said:
    ecc83 said:

    In practice again though, has anyone here had any speaker jack in otherwise good condition get hot?
    Yes, on a fairly high-powered bass amp. I forget what type exactly, but probably about 300W into 4 ohms.

    ecc83 said:

    I WILL concede that we should not switch speakers with them other than sub about 5watts but the fact is the CARRYING capacity of a switch contact is many times its SWITCHING capacity
    Exactly, and this is why things like extension speaker jacks and headphone jacks should not be used to switch the speaker off in a combo. You can simply have the speaker plugged in with a standard 1/4" jack, and unplug it if you don't want to use it.


    Not quite my point IC. The fact is, jacks do carry currents way above the switch rating (and in the case of the 300W >4R bass rig, way above the connector rating!) and 99.9% of the time "we" get away with it. Indeed, until the advent of the Speakon there was no alternative* .

    The guitar industry as a whole AND especially its customer is rabidly conservative (small c) and cost conscious. It would be a brave amp maker that fitted switching Speakons to their amps and cabs!  The better connectors are some 3-4 times the price of jacks and I doubt will ever have the same economies of scale nor be as common.  There are some very, very expensive 'booteek' amps around, still fit jacks.

    All this is "practical" engineering.  Any major modern car's power train will do 100,000 miles without being touched bar oil and filters (and Mercs use synthetics that get changed at 75,000m intervals!) with reasonable sane driving. Put the same car round the Top Gear track a few times and you will knock out the clutch PD bloody Q!

    We get what we are prepared to pay for and WANT convenience, i.e.  you can almost always blag a jack lead from someone! Personally I would like 'better engineering' but we all has to eat!

    I wonder what the rating of the old GPO jack switches was? These had 'stacked' bifurcated contacts. Mind you, plugging a standard "type A" plug into a GPO (small tit) jack buggered it instantly!

    Dave.

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  • ICBMICBM Frets: 71963
    ecc83 said:

    Not quite my point IC. The fact is, jacks do carry currents way above the switch rating (and in the case of the 300W >4R bass rig, way above the connector rating!) and 99.9% of the time "we" get away with it. Indeed, until the advent of the Speakon there was no alternative* .
    I assume you meant to add (*XLR) :).

    As you probably remember these were commonly used on bass amps, especially in the 1980s by Trace Elliot, for speaker connections. 

    Although there is the problem that like a 1/4" speaker cable being substituted with an instrument cable, you can sub a microphone cable for an XLR speaker cable, at least the connectors are rated higher (15A, from memory) - and a lot of mic cable is surprisingly robust, you probably remember the old RS stuff with the fully-braided shield and hefty cores, which I think is rated for something like 10A! I keep a couple of spare cables made with this in my 'gig kit', one XLR and one 1/4", because they can be used for anything the plugs fit...

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • ecc83ecc83 Frets: 1592

    I deliberately did not include the XLR IC for a number of reasons.

    One, as you say is the risk to microphones! The other is that we are primarily talking about the very convenient switches on jacks (shorting inputs just for one) The XLR cannot do this (although I guess the "combo" now ubiquitous to AIs could be wired that way?)  For a long time, CONTINENTAL gear was the reverse of UK XLR sense (and US no doubt) i.e. line INPUTS were MALE!

    XLRs are also again more expensive than jacks, are bigger and 'clunckier' . They are also rarely seen outside microphone cables.

    When I was involved with AV work many years ago 100V line speakers were rigged by twisting the wires! If you were lucky you got a bit of black fabric lekkie's tape. We decided upon XLR4 for 100V line but retained 1/4" jack for 'low Z'.

    Dave.

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  • DJH83004DJH83004 Frets: 196
    Although not switchable, I have worked on quite a lot of old ‘60s PA equipment that used two pin Bulgins for speaker outputs, certainly up to the job current wise.
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