What just happened?

V-Spot

V-Spot

New member
It's been a long, long time since I've posted here, and nothing has changed. Great!

Anyways, here's my story. Last night I purchased a new rig for playing out. I got a Blackstar HT Studio 20, and then as if a lightning bolt of fate hit me, I found an old Ampeg 4x10 bass cabinet. After trying it out in the store for about ten minutes I was completely sold.

So I'm plugging and getting ready to go once I'm home. I start with the clean channel; it sounds good, nothing exciting. I move on to the overdrive channel and start foolin' around. It sounds effing fantastic, I'm nailing all the classic stoner rock tones from Kyuss, Sleep, etc. I'm feeling high as hell off the tone I'm getting from this sucker, so I decide to crank the master.. then something happens.

After I had the master at about 3 o'clock (volume on the overdrive channel was set at noon), I heard a pop/click/noise of some sort, then all of a sudden all the BALLS went away. My rig now sounded a midrangey Mexican buzzsaw. I turned the amp off, disconnected all the cables, waited a couple minutes, then reconnected everything, and still the same midrangey crap.

What happened? Did I eff the cab, blow a tube, a speaker possibly? This is a brand new rig (well, besides the cab) and I was definitely not expecting this to happen. Any ideas?

Any help is greatly appreciated;
V-Spot
 
Re: What just happened?

Cab - 500W RMS, 4 Ohms
Head - Puts out 20W max, has 1x8 Ohm out, and 2x16 Ohm out.
 
Re: What just happened?

The cab is fine, but the head has at best a blown tube in it. You were running it hard with at best a 4 ohm mismatch with the cab if not a 12 ohm mismatch. Not a good idea for longevity.

You can potentially blow the output tranny doing that, so I really wouldn't recommend it. It also stresses the tubes out bigtime. Running it hard like that almost certainly ruined your output tubes. You are still getting sound, so the output tranny must still be ok thankfully. You need to rewire the cabinet to be either 8 or 16 ohms to match the amp and you need to do it before you run that cab with that head again.

Once they match properly, you can run it hard and the tubes will wear out in six months to two years time depending on the tubes and their condition. I've had output tubes that died in less than six seconds just because they were poorly made.
 
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Re: What just happened?

Well it sounds like that's what it's gonna have to be. I'm going to stop by the store when I got a spare moment to see if they'll swap the head for me (warranty, anyone?) just to be on the safe side, and just rent a cab for now.

How would I go about re-wiring the cab? If I wanted to change from 4ohms to 8ohms, would I need all new drivers and the like? What it boils down to, how costly and time-consuming is this?

Thank you for your help, BTW.
 
Re: What just happened?

V-Spot said:
Well it sounds like that's what it's gonna have to be. I'm going to stop by the store when I got a spare moment to see if they'll swap the head for me (warranty, anyone?) just to be on the safe side, and just rent a cab for now.

How would I go about re-wiring the cab? If I wanted to change from 4ohms to 8ohms, would I need all new drivers and the like? What it boils down to, how costly and time-consuming is this?

Thank you for your help, BTW.
Click to expand...

The warranty won't likely cover the tubes. Technically speaking, you mis-used the amp and blew the tubes as a result. If they take that amp back, it will be a miracle for you and sheer stupidity for them. You are probably going to have to spring for new tubes. Luckily for you, the amp is self biased. This means that it will take whatever EL34 tubes you plug into it and it won't require that you take it to a tech to bias the amp.

You will need to open the back of the cab and look at the speakers to see what their individual ohm rating is. They will either be 4 ohms or 16 ohms each. Once we figure that out, I can suggest a wiring scheme to help you achieve the correct ohm rating for the cab to match the head properly.

One thing I must inform you about. This will likely change the sound a touch when completed. You may not have the sludgy stoner rock tones you want once everything matches properly. You may be able to dial down the highs a bit and still get the sound you want though. Can't say anything for sure until you've tried it out again.

Good luck to ya man. Hope you can get everything worked out suitably.
 
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