Wiring Up A Rack Case w/ External Spkr. Jacks

Steve Feldman · Post by **Steve Feldman** » 10 Mar 2002 5:06 am

I'm going to wire up my rack with external jacks that will connect to the 1/4 speaker outs on my power amp. With the existing setup, I run 14 gauge speaker wire direct from amp to speakers, but the question is:

1) For the short internal rack connection run(amp to rack jacks), can I use any old decent 2-strand speaker wire, or do I need to go out and get the same kind of 14 gauge speaker cord.

I'm also rigging an external power jack to run a computer-type power cord from box to outlet. 2) Same deal with the short run of AC power cord on the inside of the rack, or should I just chop off and shorten the end of the power cord that comes with my power conditioner unit?

Any other thoughts for minimizing hum, etc.?

Thanks much.
Steve (no electronic whiz-bang) Feldman[This message was edited by Steve Feldman on 10 March 2002 at 05:21 AM.]

John Flewellen · Post by **John Flewellen** » 10 Mar 2002 5:48 am

For the safety of the rack, I would use the same type of speaker cord that you would use without the rack jack. Make sure there is a speaker load on it so you don't fry your amp. I would not "chop off" the power cord to the power conditioner. If you ever want to sell it later, it would be a hard sell. Wrap it with those wiring harness ties. If you are sure you are going to keep it, and never sell it, go ahead. Make sure it's a grounded plug that you put back on. For other noise, isolate the gear in the rack with plastic 'shoulder' washers or 'Humfrees'. Have one, but only one ground going on, so you don't have a ground loop happening. There is an Ebtech Hum Eliminator you could try, also. The house wiring where you are playing makes a big difference as well. Ideally, house wiring should be metal sheilded(BX) type. My house has some bad wiring in it, and it causes a lot of hum, picks up radio stations and pretty much acts like a big antenna. If you play out, it's worse. Try things one at a time. Good luck.

Steve Feldman · Post by **Steve Feldman** » 10 Mar 2002 6:07 am

Make sure there is a speaker load on it so you don't fry your amp.

John, could you please explain this? I've got panel mounted 1/4 jacks on the rack (box) and I'll be wiring those to the same 14 gauge speaker cord and then to the 1/4 jacks that plug into the power amp.

You're saying that I shouldn't power up the power amp without already having made the external connection from rack to speakers, right?

And one more thing: Existing power conditioner cord is 14/3 AWG. Can I use a 16/3 cord for the detachable (rack to outlet).

These seem like dumb questions, but I just don't know what makes a difference and what doesn't. Thanks a lot.

[This message was edited by Steve Feldman on 10 March 2002 at 06:14 AM.]

John Flewellen · Post by **John Flewellen** » 10 Mar 2002 8:06 am

Steve, yes don't power up the power amp without a speaker load on it. Although, if you don't pass a signal through your system, it probably will not do anything. But I wouldn't chance it. There are a few companies that make speaker load simulators for when/if you want to record direct. As far as the power cord goes: Consider that you most likely have a few hundred dollars (maybe thousands) into this rack. To play "cheap" at the last turn is not something I would not do. I am a great believer in erring on the side of caution. 16/3 wire is what lamp cord is made of. Because of the thin wire and casing, it is also prone to more hum, even if it carries the load. Another thing I forgot to mention before, is the use of ferrite beads or cores. Radio Shack has snap on ferrite cores to cut down on hum and interference. They go for about $5. I have them all over the place (power cords, guitar input cords, outs from power amp to speakers, etc). Are you using a single coil pickup or a humbucker? Do you have a presence of fluorescent or neon lights? Take your time and spend a couple of bucks to get it right. There are so many things to check one by one, that it could be a monument to sheilding and grounding before you are done. I did it a few times, so I know how it can be. But now it's not a problem.

John Flewellen · Post by **John Flewellen** » 10 Mar 2002 8:43 am

Steve, it just occurred to me ask you this. Is this external jack arrangement to provide strain relief on the cords? What I mean is that if somebody trips over the speaker cords behind your rack the worst they could do is tear out the jack and not the amp outputs. What I hope you are not going to do is leave the back cover on your rack. Power amps, depending on size and whether it's a tube amp or solid state, give off heat to a considerable degree. If you leave the back cover on, there is no way for the heat to leave the rack. I would leave the back cover off. Just looking out for your best interest.

Steve Feldman · Post by **Steve Feldman** » 10 Mar 2002 11:53 am

John - It's actually a cush-type case w/ 3 doors. The top will come off and although the bottom stays on, there's a 3rd door on the bottom that opens and will remain open when the amp is on.

I'm also splitting the components into 2 racks because of weight. The amp is a VHT 2/90/2 and weighs a ton. It will be paired with the power conditioner and maybe the preamp. The other 2 effects will be in a separate 3-space rack.

BTW - I got hold of some 12 ga. speaker cable today for the inside of the box. I guess that should work fine with the 14 ga. that will come out of the box and go to the speakers, eh? I'm going to have to look into these ferrite beads - never heard of them.

Thanks much for your help.

[This message was edited by Steve Feldman on 10 March 2002 at 11:54 AM.]

John Flewellen · Post by **John Flewellen** » 10 Mar 2002 2:28 pm

Steve, the beads are actually for inside a noisy component that picks up interferrance. Unless you know your way around inside a power amp, I'd leave that to a qualified tech. However, ferrite cores are larger and go on cords in the way I previously described. The Shack has them in small varieties, although larger ones can be had, but not from them. In fact, some computer monitors have ferrite cores on the cable that goes from the monitor to the p.c. I have a VHT 2/50/2. It's a good amp. However, if I don't turn it on last, after everything else is powered up, it pops the fuses every time. Sounds great though.

Bobby Lee · Post by **Bobby Lee** » 11 Mar 2002 10:36 am

What's a good mail order source for the jacks?

John Flewellen · Post by **John Flewellen** » 11 Mar 2002 2:11 pm

Bob, I don't know if there is a good mail order source for these jacks for the following reasons: It seems that most of the suppliers are looking for a quantity sale. I prefer Switchcraft and Neutrik brands. Radio shack does not sell these brands as far as I know, but there own brand can be ordered online. Mouser has a catalog that is kind of extensive. One product that Neutrik has is a locking recepticle for speaker cabs. If you have a closed back cab, it's possible for the sound pressure inside the cab to blow the jack right out of the cabinet. Then no speaker load, fried amp. The locking recepticles prevent that from happening. Kinda cool idea. Anyway, Mouser and the Shack, but no preference of one over any other.
[This message was edited by John Flewellen on 11 March 2002 at 03:09 PM.]

Steve Feldman · Post by **Steve Feldman** » 11 Mar 2002 3:15 pm

http://www.jameco.com

http://www.partsexpress.com

These are a couple of pretty good companies with 'readable' catalogues (less than 500 pages with lots of pics!). They also have small minimum orders (~$20.00 or so). [This message was edited by Steve Feldman on 11 March 2002 at 03:16 PM.]