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Post subject: Bugera 6262 into Mustang 4x12 stereo cab
Posted: Tue Jan 06, 2015 8:58 pm
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I've done my best to find the answer to this in various forums and have come close but no definitive answer. Here is my issue: I have the stereo 4x12 cab that came with my Mustang V head. I also have a Bugera 6262 tube head that I use with my Mustang cab. The inputs on the back of the cab say "stereo at 8 ohms each" or "mono at 4 ohms - use either jack". I have two speaker outs on the Bugera head that read "120 watts min 4 ohms speaker impedance / jacks paralleled". There is also a switch that allows either 4, 8, or 16 ohms. http://www.bugera-amps.com/images/lightboxphotos/6262%20INFINIUM_P0AAH_Back_XXL.png


I have blown a wiring harness (melted it) twice by plugging into one of the inputs on the back of the cab and setting the switch on the amp to 4ohms. This is assuming that the text saying "4 ohms either jack" means that the cab needs 4ohms from the amp.

I'm wondering if I should plug into both inputs of the cab (which says 8 ohms for left and 8 ohms for right) and switch the amp to 8 ohms output. Shrug. I dunno. Could be that I'm trying to use a cheap Bugera head that is unreliable in the first place.

Can anyone help me??!!! I like the sound I get with the combination but after a few hours of loud playing, I melt the wiring harness.

Thanks in advance.

Pickle


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Post subject: Re: Bugera 6262 into Mustang 4x12 stereo cab
Posted: Wed Jan 07, 2015 1:26 am
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assuming that the text saying "4 ohms either jack" means that the cab needs 4ohms from the amp

Not quite. It's saying that the cab will present a 4 ohm load to the amp.

But, superficially, what you're doing sounds the right thing: set your amp to 4 ohms (ie you're telling the amp that you're connecting it to a 4 ohm cab), and connect just one of the amp outputs to just one of the cab inputs.

(From what you say about the Mustang cabinet, it seems as though if you use just one of the cab inputs, you get all four speakers in a 4x12 mono configuration, with an overall 4 ohm load; if you use both cab inputs, you get two completely independent 2x12 8-ohm "cabs" in a single box).

Because the amp outputs are connected in parallel, you could also connect both the amp outputs, one to each of the cab inputs. Leave the amp setting on 4 ohms (each half of the cab is 8 ohms, which in parallel gives you 4 ohms total).

What you shouldn't do is connect both amp outputs to both cab inputs with the amp setting on 8 (or 16) ohms. That's the only configuration I can think of that would overload anything (if all the equipment is working properly). So:

Quote:
I'm wondering if I should plug into both inputs of the cab (which says 8 ohms for left and 8 ohms for right) and switch the amp to 8 ohms output

No. As above, in your setup (taking the Bugera documentation at face value that the two amp outputs are connected in parallel) this will give you 4 ohms.

If you've done all the above and you're still melting the cab wiring, and you're 100% certain everything is connected properly, with no short circuits or impedance mis-matches etc etc, then yes it does start to sound like faulty equipment. Although it would have to be a big fault to melt wires. The Bugera is rated at 120w; the cab can cope with 200w in normal operation, which suggests it would be able to withstand somewhat more than that before catastrophic failure. It seems unlikely your 120w amp is outputting more than double its rated power?

If you have suitable test equipment, it might be interesting to measure the AC voltage and current being output from your amp, while it's connected to the cab and you're playing at typical volumes. Both peak and averages over a few seconds. For a 120w amp on mid volume into a 4 ohm load, you should expect to see about 12-to-16 volts and 3-to-4 amps.

If the current is any more than a quarter of the voltage, stop and turn off immediately - there is a short circuit somewhere. If the current is significantly less than a quarter of the voltage, then it isn't a 4 ohm load, it's something more. If the voltage is more than about 20 volts, and/or the current is more than about 5 amps, again stop and turn off immediately - that would indicate you're sending too much power into the (4 ohm) load. That may not in itself be a major issue and may even be a valid "maxed-out" setup, but you should understand what's going on and why before continuing with such a setup.


Last edited by scott-uk on Wed Jan 07, 2015 3:16 am, edited 1 time in total.

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Post subject: Re: Bugera 6262 into Mustang 4x12 stereo cab
Posted: Wed Jan 07, 2015 2:34 am
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I have blown a wiring harness (melted it) twice

A further thought... when you say "wiring harness" which wiring specifically do you mean? I was initially assuming you meant wiring inside the cab.

But do you actually mean the cable you're using to connect the amp to the cab? In which case, could this simply be that the cable you're using isn't a high-enough rated speaker cable? For example, (and sorry if this is an obvious question but worth checking), you aren't using a guitar/instrument cable, are you?


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Post subject: Re: Bugera 6262 into Mustang 4x12 stereo cab
Posted: Wed Jan 07, 2015 1:35 pm
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Thanks very much for the detailed response. This helps a lot. By the "wiring harness" I mean it's a harness inside the body of the amp that leads to one of the power supplies (big heavy silver blocks). It has about 5 wires into the harness and I noticed some blackening on the while plastic so I replaced the harness, cleaned up the contacts, and all was good until the end of the next jam. Curiously, the amp stopped working while the power was on, but in standby. Huh? I've since sold the Mustang V head as it was a squeal machine at higher volumes and I may use a solid state Marshall 100 watt that I have sitting around. I assume the SS head won't have to worry about the impedance much?.


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Post subject: Re: Bugera 6262 into Mustang 4x12 stereo cab
Posted: Wed Jan 07, 2015 10:12 pm
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Quote:
the "wiring harness" I mean it's a harness inside the body of the amp

Oh, ok. Different to what I originally thought. This is definitely starting to sound like a problem with the Bugera amp. I'd suggest you look on the 'net for others having similar problems with the same amp head, and see if they were able to solve them - I don't think this is related to your Mustang cab. Also obviously raise it with the retailer to see if it's covered by warranty etc.

(Not this particular model, but I have seen enough reports of Bugera amps with fried internals to make me think you're probably not alone; some of the Bugera amps do sound fantastic and are well-designed from that point of view, but sadly it seems they aren't always built to a high enough quality, which is a great shame).


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