What is a "power attenuator" and how is it used?

  • Thread starter Thread starter 64Firebird
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I have been using a 100 watt L Pad. The imported one I have cost around 5 bucks I thnk at partsexpress.com. I have one in my Hot Rod Deville4x10, and 1 on a heavily modded Peavey Bravo 25 watt tube amp. It's the same principle as the expensive things. It looks like a big potentiometer, but it has 2 resistive elements, 1 that is in series, 1 in parallel - keeps the load at 8 ohms. I have mine mounted in the back of both combos, with a jack and an output lead so I can easily disconnect it if I want. they work well and are cheap. If you turn them down too low, the sound will suffer, but that's probably somewhat caused by the fact that the speakers don't work well below a certain threshold. I would guess that it takes the level of a 50 watt amp down to around the level of a 5-10 watt or so (or anything inbetween), and sounds great. I think it would work well for you, sounds like your tone is comparable to mine, I leave the clean channel on around 5 or 6, just at the point where the 6L6's are starting to sweat a little. If you try one, mount it so that it receives adequate ventilation, it will produce a fair amount of heat. I don't think I would recommend it for someone runnning a saturated/distorted, boosted signal with the amp dimed.
 
Major Tom said:
I have been using a 100 watt L Pad. The imported one I have cost around 5 bucks I thnk at partsexpress.com. I have one in my Hot Rod Deville4x10, and 1 on a heavily modded Peavey Bravo 25 watt tube amp. It's the same principle as the expensive things. It looks like a big potentiometer, but it has 2 resistive elements, 1 that is in series, 1 in parallel - keeps the load at 8 ohms. I have mine mounted in the back of both combos, with a jack and an output lead so I can easily disconnect it if I want. they work well and are cheap. If you turn them down too low, the sound will suffer, but that's probably somewhat caused by the fact that the speakers don't work well below a certain threshold. I would guess that it takes the level of a 50 watt amp down to around the level of a 5-10 watt or so (or anything inbetween), and sounds great. I think it would work well for you, sounds like your tone is comparable to mine, I leave the clean channel on around 5 or 6, just at the point where the 6L6's are starting to sweat a little. If you try one, mount it so that it receives adequate ventilation, it will produce a fair amount of heat. I don't think I would recommend it for someone runnning a saturated/distorted, boosted signal with the amp dimed.
Click to expand...

Only $5.00!!! Now that's what I'm talking about! Many thanks.
 
I remember Paul Gilbert once said he used to use an old toaster. He said that the "Top Brown" setting was 16ohms.

That could be a myth though....
 
I just checked - the 100 watt mono L pad is $5.90 at partsexpress.com. They probably have a wiring diagram in the box, if not you can do a web search like "L pad wiring" or something to find it. Some wiring schemes will be for multiple-speaker apps like a woofer/mid/tweeter system, you want one that is just for a single speaker. Otherwise send me a PM, I think I have a file I could send you.
 
Major Tom said:
I just checked - the 100 watt mono L pad is $5.90 at partsexpress.com. They probably have a wiring diagram in the box, if not you can do a web search like "L pad wiring" or something to find it. Some wiring schemes will be for multiple-speaker apps like a woofer/mid/tweeter system, you want one that is just for a single speaker. Otherwise send me a PM, I think I have a file I could send you.
Click to expand...

Consider yourself PMed.
 
Firebird - when yer ready to go I'll be there, glad to give you any help you need. If I had a digital cam, I'd take a couple pics to send ya...

By the way, the L pads come in different impedances, 8 ohm is the most common, you have to use one that is the same value as your speaker system. If your 2x12 cab is 4 ohms, you would need a 4 ohm L Pad (or a stereo 8 ohm, 1 wired to each 8 ohm speaker...)

The reason the big commercial units are expensive is they have multiple sets of large fixed wirewound resistors, inductors or combination thereof; one set for each of the several attenuation settings, not to mention a cooling fan, fuse block, jacks, metal box, etc. Instead of several sets of fixed, an L Pad is 1 set of 2 wirewound variable resistors, controlled together. I knew what L Pads were from my electronic background, but was too dense to think about using one with a guitar amp, until I happened to stumble across a mention of using an L Pad for an amp somewhere on the web, and a huge light came on in my head, I happened to have 2 of these things in a junk box in my basement! Don't know why I never thought of it before.

By the way, that is a sweet rig you've got. I used to have a blackface Bassman head that I used to gig with for years, sold it in the late seventies while I was out of the performance thing for a while. Wish I had it back!
 
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