Power Brake not functioning as an attenuator..?

[Star87]

Hi all, I bought a 2nd hand power brake to tame the JCM800, although I think it's not functioning correctly, although it's reducing volume, it's like it's barely even attempting to work as an attenuator and it doesn't even get warm. The amp is loud but I'd like to think on the lowest attenuated setting it would quieten it down a bit before even reaching 1/10 on the master volume. Although I've noticed at times when I do twiddle with the attenuator volume, it can cut out entirely and be a bit scratchy until I twist it back and forth and it works, though I'd have no idea how to even begin to fix that.(Excuse dodgy phone audio which equalises and quick playing so I dont disturb neighbours!)

 

[JohnH]

I had a look at the instructions for the PB, which you can find online. It says that it's lowest attenuated setting is -30dB, which is a reduction in power of x 1/1000. That's enough to go from unbearably loud, down to reasonably quiet. Or from a medium home volume down to 'can hardly hear it'

With my attenuator (see Workbench forum) I made some tests going from max attenuation up to full volume, uding a looped riff. These are in accurate and equal steps of -3.5dB, and the quietest is -31.5dB. So it's covering very much the same range as a PowerBrake and maybe the relative volumes that you can hear as follows could help relate to what the PB should be doing:

 

[V-man]

Not sure what amp you are demoing since no 800 came in a JMP headshell (JMP? Master Volume Mk 2 clone kit?)

That aside, I am not a fan of the sound quality of attenuated MV Marshalls… if one is trying to push volume to cook the power tubes (and invest in attenuation) for power amp distortion, they should have bought/used a NMV Marshall, not the MV.

Regarding the PB, I have never used one but unless bought for a bargain, I don’t see the wisdom in buying beyond collecting. There are far better-updated alternatives in the same price ballpark, some of them new with warranty.

The one thing I can say IME is that (with input gain past 6-7) the 2203 pretty much begins to level out at 4 on the master anyway, meaning there might be a little more “physical” volume, but it’s not much/any more perceptibly louder at 7 or 9… it just gets more saturated and/or flubby as volume gets pushed out of the 5-6 range.

 

[Tatzmann]

It's probably just the rotary-switch that needs a good shot of electronics-contact-cleaner.

 

[Matthews Guitars]

You'd have to be going pretty insane to get a power brake to get substantially warm with a 100 watt amp. The power it soaks is used to drive its own cooling fan and the duty cycle of a guitar signal is pretty low.

 

[Star87]

I had a look at the instructions for the PB, which you can find online. It says that it's lowest attenuated setting is -30dB, which is a reduction in power of x 1/1000. That's enough to go from unbearably loud, down to reasonably quiet. Or from a medium home volume down to 'can hardly hear it'

With my attenuator (see Workbench forum) I made some tests going from max attenuation up to full volume, uding a looped riff. These are in accurate and equal steps of -3.5dB, and the quietest is -31.5dB. So it's covering very much the same range as a PowerBrake and maybe the relative volumes that you can hear as follows could help relate to what the PB should be doing:

Thanks, yes I did the see the instructions too. Looks like yours is working correctly! I get no attenuation from mine

Not sure what amp you are demoing since no 800 came in a JMP headshell (JMP? Master Volume Mk 2 clone kit?)

That aside, I am not a fan of the sound quality of attenuated MV Marshalls… if one is trying to push volume to cook the power tubes (and invest in attenuation) for power amp distortion, they should have bought/used a NMV Marshall, not the MV.

Regarding the PB, I have never used one but unless bought for a bargain, I don’t see the wisdom in buying beyond collecting. There are far better-updated alternatives in the same price ballpark, some of them new with warranty.

The one thing I can say IME is that (with input gain past 6-7) the 2203 pretty much begins to level out at 4 on the master anyway, meaning there might be a little more “physical” volume, but it’s not much/any more perceptibly louder at 7 or 9… it just gets more saturated and/or flubby as volume gets pushed out of the 5-6 range.

Hi, it's a Ceriatone JCM800 clone. It's an absolute monster of an amp and sounds incredible pushed, even on stage I'll max put it on 3 on the master volume, but obviously at home I can't do that. You can search a million threads for and against all sorts of attenuators and saw this for a good price and bought it, but it doesn't feel it's it's even attenuating anything at all. It's basically the same as if I don't have it in.

It's probably just the rotary-switch that needs a good shot of electronics-contact-cleaner.

Thanks, though I'm a bit hesitant opening the thing up.

You'd have to be going pretty insane to get a power brake to get substantially warm with a 100 watt amp. The power it soaks is used to drive its own cooling fan and the duty cycle of a guitar signal is pretty low.

I mean it in the sense that it doesn't even feel like it's generating any signal to heat, I don't want to whack the master volume up to anything more than 4 but I'd like it to actually attenuate.

 

[Tatzmann]

Thanks, though I'm a bit hesitant opening the thing up.

Unfortunately it won't fix itself, so someone has to open it, either you or someone who is more experienced.

If you cant dial the cranked up amp down to acceptable home volume then something isn't working right and it may even potentially bring harm to your amp if further used in a state of disrepair.

 

[Star87]

Unfortunately it won't fix itself, so someone has to open it, either you or someone who is more experienced.

If you cant dial the cranked up amp down to acceptable home volume then something isn't working right and it may even potentially bring harm to your amp if further used in a state of disrepair.

You're correct, I'd hate to damage the amp. I'm quite fussy when it comes to touching electronics, especially amplifiers as there may be residual charge. (No idea if that can happen with an attenuator). So will try and find someone who knows what is going on with it.

 

[playloud]

Unfortunately it won't fix itself, so someone has to open it, either you or someone who is more experienced.

If you cant dial the cranked up amp down to acceptable home volume then something isn't working right and it may even potentially bring harm to your amp if further used in a state of disrepair.

Yes, this is very important. It sounds like a component (or two) might be open in the load circuit, or maybe a wire or solder joint is broken. In particular, make sure you don't use the min (load box) setting until you've been inside and diagnosed the problem.

There's a schematic here:

The PB is a well-designed unit (better than many more expensive, currently-available alternatives) so worth paying to get fixed professionally if you aren't confident.

You'd have to be going pretty insane to get a power brake to get substantially warm with a 100 watt amp. The power it soaks is used to drive its own cooling fan and the duty cycle of a guitar signal is pretty low.

I must be going insane then. When I play a dimed 100W through mine, the fan wails with every chord and pinch harmonic, and the cat perches on it once it warms up.