Hooking up a mixer, amp and EQ

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The Wizard Of OZ

Well-Known DJ
Dec 13, 2007
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Tampa Bay Area
I now have a small 8 channel mixer with all 1/4" inputs and outputs. Someone gave me an old Radio Shack Optimus amplifier that says 250 watts on the front in red. The amp is pretty big and it's real heavy. On the back of the amp there are red and black knobs for (2) pairs of speakers, channel A and channel B.

I'm going from my laptop into two of the four mono mic channels on the mixer into 1/4" jacks. I'm going from the mixer main output L into the amp 1/4" to 1/4" and the mixer is panned to L on any used channels.

From the amp I have two small 8ohm speakers hooked to one single speaker output jack so I'm running a 4ohm load. The amp stays cool and the clip light on the amp only flashes from time to time if I REALLY push the volume hard. When that happens I just back off the gain on the two input channels or lower the main volume level on the mixer. I'm running the amp attenuated all the way on the one channel that the speakers are hooked to. I believe I'm running in mono which is what I want. With this little rig I just want the two speakers on one channel and one or two microphones+the laptop connected to the mixer.

So here is my question: I have a single EQ or a dual 31 band EQ to choose from that I want to add in to this combination. Where in this chain of components do I hook the EQ up and what cables do I use and where do I plug the EQ into the mixer?

Eventually, SOON, I'm going to get a much more powerful amp and a crossover. Then I'll be using my EV Zx1s and my Sb122 subs. That will be my main system. At that point I'll need to have a rack with the mixer, an EQ, a crossover and the amp all together. I'll probably need a cart for that setup.
 
The Wizard Of OZ said:
So I guess that when I get my crossover it goes after the amp, before the speakers?
Click to expand...

No, it goes mixer --> eq --> crossover --> amp. By the way the RS anchor can get hot when running hard on 4 Ohm loads.
 
I'll try to get some pictures of this stuff. What amazed me about the amp is the amount of sound I can get with it and a couple of 10" speakers running off of half of one speaker channel. I figured a 250 watt amp was puny and I had no idea if it even worked at all when I got it. I'm going to try hooking 2 more speakers off the other channel and see what happens. So far with just the two little speakers off one channel the amp runs cool without even a hint of warmth.

Here's the story. I saw an ad a couple of months ago on craig's list for a pair of Yamaha S115V speakers for very little money. (I bought a pair of the monitor version about a year ago and they sounded great, but they were way too heavy for me to tote around or to put up on stands so I sold them to a friend of mine who has a company that provides sound for small concerts, events etc. He loves them, they're great monitors.) Anyways, I called about the Yamahas and the guy said one of the woofers was not working, but he had a dual 31 band EQ for $70 and he had some other stuff he would just give to me, some old equipment from a church that had been sitting in storage collecting dust for a long time.

So I went to pick up the EQ and he has a stack of stuff waiting for me. (1) 12" Community speaker, (1) 15" Community speaker, a single 31 band EQ, an old Radio Shack Optimus 250 watt amp, some old AKG headphones and an old, HUGE Tascam mixer.

The amp works perfect. I haven't even tried the dual 31 band EQ yet, but it was new in the box and had never been used. Tomorrow I'll try the single 31 band EQ and I'm sure it's fine. It's made by Audio Centron. It has both 1/4" and XLR jacks on the back. The guy gave me way more stuff than what I bought from him.

What's really strange is that he called me today to tell me he still had the Yamahas and that I could have them for $100. I just need to check the internal connections and if the woofer is bad I can have it reconed or just replace it. Most likely I'll just replace it. Reconing is kind of expensive. Hopefully I can find a good quality replacement 15" woofer for a reasonable price that's roughly comparable to the Yamaha woofer. After that I'll have enough speakers to do a small concert.
 
Yup, the electronic or active crossover is patched before the amp(s). Don't patch anything between the crossover output and the amp channel inputs.

Here's a typical frontend system patching chain:

Mixer
EQ
Compressor/Limiter
Electronic crossover
Amp channels

If memory serves, the RS amp is made by GemSound and will handle a 4 ohm load without issues. The model you have may be bridgeable ~ RS released a version of this amp that could be bridged. Again, (if I recollect correctly) the bridgeable model had a cooling fan. I had a pair of those old school RS amps in the early years. :)

I know you didn't ask but I'd like to pass along a money-saving option for you: When you get a more powerful amp and decide to bi-amp with the crossover, use the RS amp for your mid-highs and the big amp for your bass bins.

Also, you can bi-amp with a single two-channel amp. Patch the mid-highs to channel one and the lows to channel two. It'll be mono but it will work. :)
 
That's fine Fred, I prefer to run in mono anyways. I want everyone no matter where they are in the room to hear the same thing. I don't believe stereo is optimal for large rooms or concerts anyways.

IMO stereo is for your living room or in a car where you can sit a few feet away and get the stereo effect. In a bar, a restaurant or a wedding banquet hall with a couple hundred people I can't see how stereo could be useful or desirable, but that's a debate that will rage forever.

Stereo is an artificial separation IMO. If you sit in an audience in front of a band without a PA, what are you hearing? It ain't stereo. You're hearing all the instruments and all the vocals all at the same time, together. Why should sound re enforcement be any different? Recordings should be made in mono IMO.

eezee, I just spent the last 20-30 minutes searching ebay for a replacement speaker just in case I might need it for the Yamaha. When the right deal comes along I'll snag it.

I'm also thinking about experimenting with building an 18" sub somewhere down the line and I saw some speakers on ebay that looked promising. For right now I'm set, but for my own personal knowledge and experience I want to give it a try one day. This is all a big adventure for me.
 
and using 250 watts from Radio Shack will provide incredible concert hall sound. thanks guys for helping this newbie out hes certainly on his way and completely DELICIOUS! Congrats Rob your almost there!!
 
Thanks, Jon. :)

The RS PA amp isn't touring grade, I concur. But Wiz has it already and it works. It'll do for mid-tops until he can get a more pro grade amp to replace it.

The thing with bi-amping, mids and highs require very little amp power. 250 (and I'm presuming this is a total spec) isn't much for lows but it would serve for horns.

I hope Wiz has better luck with his RS amp than I did. Both of mine were trouble, off and on right out of the box. With one, one channel kept cutting out. The other developed an intermittent power supply short and had to be shut off during a show. Thankfully they didn't crap out at the same time, lol. I had to repair the things myself because RS' so-called factory service wouldn't or couldn't fix 'em. I'd get them back from repair and they still had the same issues as before.

Once I got 'em fixed up right they performed flawlessly for years. The power to weight ratio wasn't too impressive but they worked. When I got my DCM amps I gave one of the RS units to Shirl's son who still uses it for his home stereo to this day. The other I moved on eBay.
 
That RS amp is for my practice/rehearsal system at home. For gigs I'll be using my Yamaha EMX512 powered mixer until I get a more powerful amp from Ben. The RS amp was FREE and it works great. Puts out a very good amount of sound to my surprise. I hooked speakers to both A and B channels today and that darn thing cranks. It sounds fine and there is absolutely no reason I couldn't use it for small professional gigs other than the fact that it's heavy as heck and I don't have a rack.

I hooked up the FREE single band EQ today and played with it for a while. I seems to work fine. It's going to take some time to fiddle with it a few times and it takes some real keen listening to set each frequency band. I may not even use it if I can't hear a significant improvement in sound quality. I can hear a lot more change at higher volume levels when I switch from bypass to EQ on. I'll have to try it with some of my EV speakers to see what kind of tweaking I can do and if it's worth carrying around. It has a HPF and I set it at around 50hz which seems to be the sweet spot. Anyways, thanks to those who offered help, I appreciate it.
 
Rob do you have a testing area as big as the typical venue as I thought of something else. Your quality of sound will be much different at a venue than your living room or garage.
 
The really nice thing about a 2/3 octave EQ, they are especially useful for shaping your tone and trimming harshness. You can get your speakers to sound the way you want them to and cut frequencies they aren't able to reproduce. For example, if a given cabinet rolls off above 50 Hz, you can cut the frequency bands below 50 to keep your sound from getting muddy.

A three-band, mixer-mounted EQ can't do this alone, sorry. You've got to have that narrow band control over your sound.

Also, the 2/3 EQ is your best weapon against mic feedback. By lowering or cutting the ring frequencies slightly you can eliminate feedback honks and ringing without adversely affecting your tone.

Folks, I've seen a lot of PA rigs in my time. In practically every case, the ones with mic ring and/or harshness had no professional EQ in the processing. If they did, it wasn't set up right. :)
 
The single band EQ that I used says on the front "1/3 Octave Equalizer". What's a 2/3 Octave EQ?
I have the bands below 50hz pulled all the way down and the HPF knob set right at 50hz.

I don't usually get feedback even when standing right in front of the speaker(s) unless I have the mic cranked way up or/and when I have the vocal effects turned way up. Just when I have my voice sounding huge and really powerful, that's when I start getting ringing and feedback. SOOOO, how do I know what frequencies to back off? There are no lights on any of the bands on this old EQ.

With my Yamaha I can crank the mic way up before I get feedback, but I don't have a whole lot of EQ control, 3 knobs per channel and a small EQ for the mains and a small EQ for the monitors. If I crank up the vocal effects I start getting the ringing and some feedback if I'm anywhere near the speakers. If I move too far away then I can't hear myself and the music properly to be able to follow along and keep with the music and stay on key etc.
 
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