The Steel Guitar Forum

Say fellows, I have 684 Peavey power amp which i use for our PA. Can you use the mains side for a 2 amp set of speakers for a short time or never? Need to know! Thanks Dave Frye

So sorry guys, i said two amps on my power amp, i should have said ohms! Sorry again guys, please forgive me, i,m old!!!!!!!!!!!! Dave Frye

Hello Dave,
this is what Peavey writes in their manual of XR 684 (didn´t find others):

PARALLELLEFT/RIGHT SPEAKER OUTPUTS: ........ Two cabinets
can be connected to each channel, as long as the combined impedance
of the cabinets is not less than 4 ohms. (i.e., two 8 ohms cabinets in
parallel = 4 ohms, four 16 ohms speakers in parallel = 4 ohms, etc.).

If you connect two 4-Ohm Speakers hooled up in parallel to one Amp-side,(is this your plan?)
you won´t blow the amp right away, but if you then crank up the volume, the current going through the amp will get too high, thus frying the powertrasistors inside.
BE CAREFUL....

pit

If the manual says not to run either side at less than 4 ohms, you should not run it at less than 4 ohms, period. Unless you happen to like replacing power transistors. The issue is not how long you run them, but how much power you try to force the transistors to put out. If you exceed their current limit, they can burn up very quickly. The lower impedance limit on the load is to keep the current below that limit.

For example, if you have two 4-ohm mains speakers run in parallel, the combined impedance is 2 ohms. You should not hook up 2 ohms to any amp that specifies "don't run into less than 4-ohm load".

But if your mains speakers are 8 ohms (which is pretty typical for PA speakers), there is no problem running both of them in parallel in such an amp.

You should measure the resistance of the speaker cabs using an ohmmeter. Just put the speaker cable into the speaker cab jack, and measure resistance across the tip and sleeve on the other end. 8 ohms impedance typically measures around 6.5-7 ohms DC resistance or so, 4 ohms impedance typically measures around 3.2-3.5 ohms or so. If they're 8 ohms, no problem. If they're 4 ohms, don't do it.

My opinion, of course.

Ok guys, thanks for helping me save my amp! Kinda thought that was right, but now i know! Again thanks a lot! Dave Frye