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Amp-Cab Mismatch Query


Si600
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We were in a practice room for the first time last night *bounce, bounce* :) and there is a Peavey stack in it. A Mark VI XP head and two cabs, a single 15 and what looked like it may have been a 2x10.

I took my GK MB500 Fusion head with me, just so that I could use it more than anything else, and used that with the Peavey cabs. The cabs are instrument cable connected and when I was only using the 15 I had to wind the head up, almost to the three quarter mark to get a sensible level. I then plugged the other cab in and brought it back down to below halfway.

I've got two queries regarding this, was it louder because I was using both cabs so the head was producing it's stated 500w or was it louder because it was moving more air with three speakers instead of one? Or both!

I've got a GK 212 at home, but I didn't bring it, but I'm now worried that it wouldn't be able to cope on it's own and I should look at getting another cab. Is running the head with the dial almost all the way 'round going to be normal when we use our own kit to gig or is it going to be a mismatch between my head and the Peavey cabs? I'll leave it at home next time and use the one in the room I think to save the magic smoke.

TBH, I'm a bit surprised that I had to take it up so far which is why I'm worried. It's not a huge room though and maybe our drummer is a bit of a thug and we didn't realise...

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I think if everything was as it should be and you wound your 500 Fusion up that far then it would be ear-splittingly loud to the point of pain, so something's not right at all. I'm in a rock band and my Fusion master is generally at around 9 o'clock which is very bloody loud. Instrument cables are not suitable for connecting cabs - they can't properly handle the output current of an amp, so you are likely getting some kind of anomaly resistance-wise which could be the problem. You need to use proper speaker cables.

Edited by discreet
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It didn't feel right, and from what you're saying it isn't right so I'll either stick with the Peavey head or if I can be bothered next time I'll take my full rig along.

I've got a proper speaker cable, but the Peavey units don't have a speakon connection. I think if I used the amp with the 212 as it's set up now then the house would fall down!

Cheers :)

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Yep, the GK MB Fusion is incredibly loud. Never needed the volume on more than 3 (Gain on about 7) for rehearsals, in a (fairly loud) punk band. I`d try out the Fusion as quickly as possible with the GK212, just to make sure it`s not the amp that has an issue. Set it all up at home, take the volume down to about 2 or 3 and play. It should be ridiculously loud in a home setting. If it`s not, then there may be a problem with the amp.

Re the 212 - providing the amp is fine, there shouldn`t be any problems at all using a single 212 for gigging. Even if an 8ohm 212 - so "only" getting 300 or so watts that should be more than enough for the majority of bands.

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[quote name='Si600' timestamp='1402649006' post='2475574']
I've got a proper speaker cable, but the Peavey units don't have a speakon connection.
[/quote]

You can get a proper speaker cable with a jack plug fitted (obbm's are v. good), but of course this is yet more expense... :)

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[quote name='SubsonicSimpleton' timestamp='1402652068' post='2475612']
I sincerely hope you mean that you used proper speaker cables with 1/4" jack connectors, and didn't actually use instrument cables to hook up the cabs to your amp.
[/quote]

+1

Just because they are not Speakon connectors it does not mean they are instrument cables. You get both speaker cables and guitar cables with jacks on each end and you should not mix the two. It will tell you along the rubber sheath of the cable whether it is instrument or speaker. You must make sure you are using speaker cables to connect amp to speaker. Tha'ts probably why you are having the issues you are.

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To be really sure you could unscrew a barrel of the jack cable and look at the wires inside. Speaker cable has two unshielded thick wires connected; instrument cable has a much thinner inner core connected to the tip, and a metal braided sheath connected to the body. The use of an instrument cable as a speaker cable will not only affect the sound, but very often ends in 'magic smoke', as it's not able to handle the much higher current of an amp output.
Of course, the opposite is also true: one should not use speaker jacks for instruments. While destruction is less likely, the hum and noise picked up is a Very Bad Thing. The debate as to why, historically, jack cables were used for speaker at all is now run; they're out there, so one has to be very aware and prudent so as to avoid any possibility of confusion.

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its for this cabling reason i bought myself a speakon to jack cable so handy when you turn up to a gig using another bands cab and they only have jack inputs.

it could be down to the 115 not being the greatest cab in the world, doubt you head not being the same brand has alot to do with it.

andy

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Tried it over the weekend into my own cab using the practice room settings... By Crom was that loud! Back to sensible levels and all is well with the world. It sounds better than before, some of the knobs must have been nudged in transit and given a better setting!


[quote name='SubsonicSimpleton' timestamp='1402652068' post='2475612']
I sincerely hope you mean that you used proper speaker cables with 1/4" jack connectors, and didn't actually use instrument cables to hook up the cabs to your amp.
[/quote]

I call them instrument cables because that's what they look like. I've no idea what they are, but as they were in situ on the Peavey rig I'm assuming that they're suitable.

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