Will using a Marshall Power Brake, break my non-Marshall amp?

January 31, 2007 2:14 PM

Will using a Marshall Power Brake, break my non-Marshall amp?

I have been using a Marshall Power Brake with my 5 year old JCM 800 2203 with pretty good results. It produces a nice warm, crunch and slightly (thought not too) overdriven tone. I have used the brake consistently for 5 years, and have not noticed any degradation at all in the tubes in my 800. I was told that using it would shorten the lives of my tubes, but so far so, good.

Recently, I purchased a brand new VHT Deliverance 120, and while I love its tone, it's just too damn loud to play at volume in the home studio. Will adding the Brake to the setup damage the amp in any way.

Long story short, I did use the Brake on Soldano Lucky 13, and it quickly blew a fuse on the amp. Lesson learned: never again... at least not without checking it out first.

Any advice?

posted by psmealey to sports, hobbies, & recreation (5 answers total)

The brake works by varying the current going into the amp. A great way to work with tube amps. Solid State, not so.

While I can't say for SURE, what I can say is that if the VHT is solid state, its a for sure NO.

Sorry if this is a totally obvious response.
posted by emptyinside at 2:42 PM on January 31, 2007

No, it will not hurt your amp, and it does not have anything to do with whether or not the amp is solid state or tube - that's sort of a red herring.

The Power Brake works by pretending to be a speaker - it's an inductive load of the right approximate impedance. It has it's load in series with the speaker output and essentially the more power you sink into the load (via the dial on the front) the less gets to the speakers. It present a constant load to the amp though. It does not vary the current going into the amp. I think you are thinking of something like power scaling, which limits the current that the output tubes consume.

The power break also did not blow the fuse on your soldano. It just allowed you to turn the output of your soldano way up without making the output at the speakers exceptionally loud. Likely, the same thing would have happened without the power brake, except it would have been really loud.

The power brake does expect a specific output impedance from the amp, I think it's switchable between 8ohms and 16ohms. I have used the power brake with a 4ohm load (all tube) and it didn't really harm anything. It's probably not advisable. This is something that tube outputs are worse at, they really do expect and desire the right output impedance - with transistor amps usually you just experience a loss of power and sometimes some frequency-dependant signal loss.

Also, the power brake does not burn your tubes out faster - that is, it doesn't burn them out any faster than running your tube at a high volume into normal speakers does. However, you may get less life out of your tubes than if you had the amp turned way down and didn't use the power brake. This is a useless comparison because you'd laos get a lot more life out of your tubes if you never turned the amp on - so what? The point is to get the sound you desire at the volume you're comfortable with.

Just remember that the power brake is entirely external from your amp, think of it as just being a speaker with a volume control. It has been postulated that the quality of the output is not exactly the same, because frequency response of the power brake is not exactly the same as a speaker, and this is probably true, but also probably somewhat irrelevant. It sounds good enough and works good enough for most people, myself included.


A quick note: there are some other solutions that big names have undertaken. Eddie Van Halen reputedly runs the outputs of his amps into regular speakers that are contained in a soundproof box. Say you had 8 speakers in series, with 7 inside of the soundproof box and 1 outside. You'd hear 1/8th of the total output of the amp. This is as close to getting the real sound as you can get - there are still caveats since each indivudual speaker gets less than the total wattage output of the amp - when the wattage a speaker gets drops below a certain point it does not produce some desirable characteristics such as speaker smoothing. Typically we are talking about sub-1-watt here though.

I've built several isolation cabinets over the years, and it's a nice solution for recording. Basically it's a sound proof box you put around the cabinet, and you position mics inside the soundproof box, and take the output of the mics and run it to headphones or speakers, but at much lower volumes, or run it into the mixing board, etc, etc. This is the absolute best way to get cranked-amp-tone at apartment levels. It's also a total pain in the ass.

I use a 5-watt tube amp for recording and I'm currently building a 1/2 watt tube amp (single ended 6K6 based). 1/2 watts is pretty loud, for bedroom use. 5w at full bore is deafening, I use ear protection. At a live venue it's not so much (although often enough, I have run 2 5w heads into 2 cabinets with decent results)

I've devoted a lot of time and effort into producing cranked tone at low levels, I'd be happy to talk about it off-metafilter if you're interested.
posted by RustyBrooks at 4:14 PM on January 31, 2007 [6 favorites]

Holy crap, what a good answer. Thanks so much, RustyBrooks.
posted by psmealey at 4:20 PM on January 31, 2007

You happened to hit upon one of my passions. I own a power brake, a hot plate, and I even made my own custom thingy which in the end sucked without a lot of post-eq and even then it was not great.

You wouldn't believe one of my projects... I want to put a cabinet in the attic and mic it from there, but I don't want to go up and down all the time to adjust mics so I'm working on a remote mic positioner. It's about 5th on my project list though. Probably it would be easier and cheaper to hire an assistant.
posted by RustyBrooks at 4:53 PM on January 31, 2007

Thanks again, RustyBrooks. EQ'ing the signal both before and after the distortion stages is also something I had considered, but it makes a lot of sense.

I had not tried any low wattage amps, but I might be inclined to check them out. Mostly I have a fondness for "vintage" sounding amps (Vox AC30, Matchless C30, Marshall JTM45 or JCM 800, Mesa Boogie Maverick (Class A), Trem-o-verb, Fender Twin Reverb, Soldano SLO). Some of the modern incarnations of these amps have master volume knobs (or low power switches), but they invariably end up sounding a bit sterile. You also lose a bit of the harmonic textures when generating feedback, and you don't get that great warmth when you are pushing the speakers in the cabinet a bit, when you crank the volume way down.

Since I'm not really a pedal person, I usually crank the amps as normal, and try to isolate the amp sound in the corner of the studio, and either wear ear protection, or just limit my durations to being around volumes of those levels. It has worked pretty well with my current fleet of amps, but the VHT is something again a little different. It sounds terrible at low volumes (like ice picks), but great when it's opened up, but it is painfully loud. I'll give the Power Brake a shot today, and see what I can do.

Thanks again, you've given me ideas for at least three fun new projects!
posted by psmealey at 5:28 AM on February 1, 2007