Film-Tech Forum ARCHIVE: amplifier connections

This is topic amplifier connections in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Scott Norwood (Member # 30) on 08-31-2010, 12:37 PM:

As we know, most amplifiers have inputs on both terminal strips and some sort of connector (XLR or 1/4" TRS, usually). When installing a cinema sound system (or any other permanent or semi-permanent installation), do you connect the crossover box or processor to the amplifier using the terminal strip or the connector? Why?

Similarly, do you prefer to use Speakon connectors or twist-type connectors (for spades or bare wires) on amplifier outputs?

I could see arguments either way: connectors add a point of failure and can easily become disconnected (particularly 1/4" connector); on the other hand, they make an amplifer swap easier (assuming that the replacement uses the same type of connector and wiring).

I have seen both methods used in various installations, but am curious about the preferred approach. Do the manufacturers (QSC, Crown, etc.) have recommendations on this?

Posted by Gordon McLeod (Member # 33) on 08-31-2010, 12:41 PM:

I have always preffered to use spade connectors and screw terminals
all connectors like tip sing sleave xlr and speakon relay on just wipping contact area and that will get corroded sooner or lator

Posted by Monte L Fullmer (Member # 2797) on 09-01-2010, 12:36 AM:

..along with doing spade connectors, I also fill it with solder after the crimp is done.

Posted by Tony Bandiera Jr (Member # 2365) on 09-02-2010, 01:29 PM:

quote: Monte L Fullmer
..along with doing spade connectors, I also fill it with solder after the crimp is done.

Great minds think alike..same here. I do not trust a crimp to keep a solid connection for years on end especially at locations by the coast here in Cali. Never had one fail in over 20 years of installs.

And Gordon is right..XLR and 1/4" connections rely on the wiping action of mating/unmating to keep the contact surfaces from corroding and going high resistance.

Any cinema that has such connections, you should once or twice a year unplug and re-plug all such connections (ONE at a time so you don't mix them up), especially if you have a history of noise or intermittent sound problems. With the 1/4" connections, give it a twist as you unplug/re-plug too.

Posted by Dave Macaulay (Member # 813) on 09-03-2010, 05:38 PM:

I prefer to use XLR or TRS phone plugs and speakons. This makes it much less hassle when replacing or re-arranging amplifiers. When a centre channel amp dies on Friday afternoon it's nice to swap in the rear surround amp and keep the show on for the weekend.
The QSC system setup with the monitor/crossover is very nice for this assuming you use all 2 or all 4 channel amps. This doesn't work so well when you must have higher power 2 channel amps for the main channels but if you keep a spare of each amp type, changeouts are easier when you don't have to mess with terminal strips. Sometimes the operator or manager can even handle this!

Posted by Tony Bandiera Jr (Member # 2365) on 09-03-2010, 06:23 PM:

Sorry Dave, but I am gonna respectfully say that the use of 1/4" or XLR (and to a lesser extent, Speakons) has no business in a fixed installation for the reasons I outlined in my post above.

As for the swap out issue, it is NOT that much harder to unscrew the terminals from the inputs to make an amp change. Anyone who cannot understand that simple connection method has no business touching the inner workings of a sound rack in the first place.

Time will tell if the current DataPort connections like QSC uses suffers from the issues that 1/4" and XLR have when left undisturbed over a long period of time.

A bigger beef I have is the excessive use of cable ties making it a manner of lost time cutting ties to be able to swap out an amp. (And I am as guilty as the next guy as my early installs I went for the beauty of wire bundling without thinking ahead to how many ties would have to be cut to swap an amp.)

Posted by Steve Guttag (Member # 268) on 09-03-2010, 09:23 PM:

I have no problem with the XLR connector on "permanent" installations...I've NEVER had one go bad/noisy...now I tend to use the good ones.

TRS...that is another story...they suck even when new (Regardless of brand)

The argument against XLRs in cinema racks (unless that is THE input method) is the extra time and materials needed to make them versus a spade or phoenix type connector.

Somewhere around here are pictures of how we have wired racks (I think it had to do with active crossovers and the racks came along for the ride).

found it!

Steve

Posted by Rick Raskin (Member # 1561) on 09-04-2010, 08:15 AM:

My beef with cable ties is when the installer does not cut the tab flush with the base. This leaves a protruding edge that is likely to cut someone in the future.

Posted by Monte L Fullmer (Member # 2797) on 09-04-2010, 12:10 PM:

..at least that rack in the pict that Steve loaded in here isn't full of "spider webs" like some of the rack jobs that I've seen ... Excellent job on that, by the way!

Posted by Eric Robinson (Member # 2966) on 09-07-2010, 10:31 PM:

quote: Tony Bandiera Jr
A bigger beef I have is the excessive use of cable ties making it a manner of lost time cutting ties to be able to swap out an amp.

So true, I spend more time cutting all the ties than swapping the amp.

Posted by Steve Guttag (Member # 268) on 09-07-2010, 11:09 PM:

If you look at our racks on the linked page, you will see one can properly dress a rack with wire ties and yet not go overboard as well as provide adequate service loops to allow for changes. To change one of those amps, only a single tie would need to be cut (and likely not replaced as the cables will have taken a "set" by the time the amp is changed).

-Steve