Author Topic: Tech help with power amp? (Read 160 times)

jagerphan84 · « **on:** May 31, 2004, 12:25:01 PM »

Hi everyone,

I am in the process of putting together my first decent bass rig, and in my frenzy of eBaying I picked up an Ampeg SVR 212, a Crown XLS-602 and an Alembic F-1X. I plan on supplementing these components with a tuner, power conditioner, and possibly a compressor/limiter, but not until after my bank account heals from these last buys.
Anyways, the cabinet and power amp have arrived, and now I see that this power amp features XLR inputs, and outputs that I wouldn't know what to call. Looks to me like the red and black connectors on those old speakers in my parents' attic! Two pair of red and black knobs that unscrew to open little wire-sized ports in the sides, and screw shut to secure them. What will my best bet be in terms of hooking this rig up? Should I just use the XLR output on the F-1X to the input on the power amp? Then how is the power amp connected to the cab? Will I be doing some splicing, or are there good cables available with the proper connections already?
Forgive my lack of knowledge, but it corresponds pretty well to my lack of experience.

Adam

edwin · « **Reply #1 on:** May 31, 2004, 01:05:57 PM »

You can run the XLR from the F1X, but usually that is used for the PA system. Be sure to run it in post mode if you do it this way.

As far as speaker cables go, it sounds like you need banana to 1/4 or if your amplifier has it (which I think it does judging from the Crown site) Speakon to 1/4, which is preferable for a number of reasons. If your local music store doesn't have it, then any pro audio source would have cables that would fit this situation. Just make sure you get at least 14ga or lower wire.

Edwin

David Houck · « **Reply #2 on:** May 31, 2004, 01:40:13 PM »

The red and black connectors are binding posts and accept banana plugs. Banana plugs are generally considered a better connection than standard quarter inch plugs for speaker cables, so this is a good thing. And yes, most good cables are available with banana plugs. Apparently, later XLS-602's have Speakon connectors as well, which generally are considered an even better connection. What connections does the SVR-212 have?

I don't see any reason why you can't use the XLR Out on the F-1X to run to the XLR In on the Crown. You'll want to set the output switch on the F-1X to Post. Another alternative would be to use a quarter inch to XLR transformer (example: http://www.midi-classics.com/c/c4283.htm); then you can use the full range quarter inch output on the rear of the F-1X and save your XLR Out for running direct to the PA.

There is a manual for the XLS here:
http://www.crownaudio.com/pdf/amps/133465.pdf
Looking at the manual, it does not look like you can run a cabinet off each output with only one input in use; the only choices are stereo and bridged mono. I suppose you could use a Y adaptor out of the F-1X full range output into two quarter inch / XLR transformers and then into the two XLR inputs on the Crown. Then you would have both channels available without having to use the bridge mode.

jagerphan84 · « **Reply #3 on:** June 04, 2004, 02:09:33 PM »

Edwin, Dave, thanks for the help.

Looks like my XLS is not one of the newer models sporting the speakon connections, but if banana plugs will do the trick, that's what I will go for. The SVR-212 has a standard 1/4 input, so looks like I will be running as follows:
(I like to keep things confusing...so components are in parenthesis, connectors are in brackets)

(Distillate)-[standard 1/4]-(Alembic F-1X)-[standard 1/4]-[1/4 to XLR adapter]-(Crown XLS602)-[Banana to 1/4]-(SVR-212)

Does this look like it makes sense? I hope so.

I thought being a bass player was tricky enough, I didn't realize we are electrical engineers to boot! Well worth the effort, though...

As long as I am posting, I'll throw in a related question. Anyone want to thoroughly explain the importance of ohms when selecting cabinets? I currently plan on using just the SVR-212 (4 ohms), but not for too long. I'm gonna pick up some more cabs as soon as I know what to buy, but to quote another club member, I know just enough to blow everything up.

Thanks again,
Adam

David Houck · « **Reply #4 on:** June 04, 2004, 02:53:21 PM »

Looks like it makes sense to me.

There are a number of people in this group that can answer the ohm question better than I; but, as a generalization I think it is the case that a 4 ohm cabinet makes more efficient use of your amp's power than an 8 ohm version of the same cabinet. Your amp's power rating is 370 watts per channel into an 8 ohm load, but 600 watts per channel into a 4 ohm load. So the 4 ohm cabinet is getting a lot more power than the 8 ohm cabinet. The main disadvantage of the 4 ohm cabinet is the situation where you are wanting to use multiple cabinets. Say for purposes of saving weight all of your cabinets are 210's; and there are certain gigs where you use 4 of these 210 cabs. With two cabs on each side in parallel, if they are 4 ohm cabs you're coming close to 2 ohm loads; which is something most amps don't really want to do. So in such a case the 8 ohm cabs work out better since in parallel they approach 4 ohms. This is why monitors tend to be 8 ohm cabs since they are often strung together in parallel. My cabs are all 4 ohm and I have not yet run more than one cab off each side of the amp.