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Power Attenuators

>if it has 4 power tubes, pull two out (outside or inside pair), OR,

>Aim the speaker cabinet at the wall (really) OR use YellowJackets tube convertors

[todo: add postings from my PA FAQ thread at amp and fx ng's and uk guitar ng. (think in terms of watts per speaker).]

Tubes: Mechanics & Mystique - Reprinted from Guitar Player (June 1983) - In the case of a tube amp, preamp and power amp tubes have different distortion characteristics due to the difference in both their tubes and their circuit design. For example, relying on a master volume distortion circuit by itself will yield less sensitivity to variations in a player's touch than if the amp is attenuated (has its volume limited) after its power stage (that is, with a power attenuator). This is due to the contribution of the output transformer to the sound of the amp and also to the difference in sonic qualities between different power tubes compared to preamp tubes. Leaving some of the distortion to the power amp section rather than relying mainly on the preamp section gives a broader range of sensitivity. In addition, the nature of the tube allows the player to vary his touch, producing different tonal responses from the amp according to the manner in which he plays.

xxx - mentions Pete Cornish Dummy Load Box 8 ohm used by Dave Gilmour for easing the talkbox.

power attenuator to ease talkbox - "I was talking to my buddy, Jerry, about talkboxes recently, and we both agreed that the use of a Power Soak, Hot Plate, Marshall PowerBrake, Altair Power Attenuator, or similar product would be a good way to save your talkbox driver if you use it with a really large amp. Besides, if you own one of the aforementioned devices, you probably don't use it aside from recording and the occasional low volume practice session at home. So dust it off and add it to your onstage arsenal when you perform with the talkbox. You'll keep your amp and the talkbox happy."

From: "PM" palletmessinger at email.msn.com
Date: Wed, 7 Jan 1998
Subject: Power Soak etc

Pete Brunelli mentioned the power soak as a way to deal with [blues harp mic squealing] feedback/noise to gain issues . . . I use the Marshall Power soak. I was advised that it's better than the Scholtz unit - but I've never used one so I can't tell you for sure.

I just hook the speaker line to the power soak, then run another short cord back into the amp('65 Super Reverb). It allows you to choose how hot you want to run your tubes, without blasting your ears, and it really seems to help with the noise to gain/feedback issues.

I'm not much of a techie, so I don't know why it works, but a techie-friend(and very fine harp player)George Brooks, could probably explain the electrical reasons. Anyone interested can e-mail him at: gbrooks at plainfield.bypass.com, and I'm sure he'd be happy to give you the details.

I'm pretty sold on it . . . Paul Messinger/Chapel Hill NC

Garply harp forum - I have a Peavy Ultra 410, (60W, 4 10" speakers, 3 separate channels) and I think it's the cat's meow. I tried the following to get more volume and/or the ability to turn up the controls to overdrive the amp without earsplitting volume:

Power Attenuator: I really liked this (I had an old one) and was getting some good overdrive but when I cranked the amp to FULL POWER I blew a fuse (the amp was only a day or so old and I nearly died). I have been told that power attenuators will push your tubes and they will burn out faster I can deal with that if the tone is worth it. More importantly I have been told that damage caused by using one is not covered under the warrenty, and some people have said that they will burn out your amp. A dealer I was talking to said that this should not be the case. Another dealer said that it probably was because the attenuator I had was an older model and that the new model he had for sale for about $150 would not do that. Who knows? (if you do please post). Anyway now I am very nervous about trying one again: It sure was great sound when I used it, and I would like to use it again--if I knew I wouldn't blow up my amp.

Garply harp bbs

What it is man, Power Soak
joy_top at juno.com
Tue, 20 Oct 1998

A power soak is a load that plugs into a speaker jack on an amp. It will have an output jack for a speaker. This is the basic box. Mine has an input, switch for 4 or 8 ohm resistance, multi-position volume switch, and 2 speaker jacks. There are some which probably have a line out also.

What they do is allow you to control the volume after the amp and before the speaker(s). What this means for me is that, I can run any combination of drive, gain, master and control the volume without sacrificing overdrive. It will adjust to parlor sitting room conditions on a large stack and still get that SOUND minus speaker breakup.

My blues deluxe amp just puts out to much volume for me to really drive the tubes, let alone feedback. So thats where the soak comes in. And I get controllable serious over drive then. When I've used large amps I aways have trouble getting that sound and saving my hearing. I'm going to have to work at that because I've already lost 55 to 60 db in the high range of hearing. (3kHz to 6kHz)

-- Denis Aldrich

Garply harp bbs

From: RussGrayNY at aol.com
Date: Sat, 9 Jan 1999
Subject: Re: Loud Crunch at lower volume

The attenuator is hooked up between the amp and the speakers. In effect it puts a dummy load on the amp (the amp thinks its driving a lot more speakers than it really is). which allows you to overdrive the amp at a lower volume eliminating some feedback, I think, because you are only hearing the speakers that are actually hooked up, not the dummy load.

Normally I can't run my [blues harp] mic full throttle with my amp opened up. One of them has to be turned down. With the attenuator you can run everything opened up without huge volume and consequently overdrive your amp without megafeedback.

The local music store let me play with an old Altair with the attenuation marked off in decibels and it seemed to work well. I made the mistake of turning the attenuator to a real high decibel level and cranking the amp all the way. This resulted in a blown fuse and scared me half to death as it was a new amp and people had been telling me that attenuators can destroy your amp. So be careful how much attenuation you use. He said he'd sell it to me for 50 bucks, which I think is the going rate. Its on my wish list after I buy some tubes.

If anyone has any info on the Altair Power Attenuators I would appreciate hearing about them.

From: George Brooks gbrooks at together.net
Date: Sat, 09 Jan 1999
Subject: Loud Crunch at lower volume

Ken Ficara wrote:

>Can anyone explain how using an attenuator after the mic is different from turning the volume down on your mic and up on the amp?

The kind of attenuator I am talking about is inserted between the amplifier's output and the speaker. The amp can then be run hard, at a level that without the attenuator would be very loud and prone to [squealing harp mic] feedback, but the "final volume,"as I call it, can then be turned down at the attenuator. This allows the player to use all of the amp's distortion characteristics, including output stage distortion (the kind that I believe is most pleasing for amplified harmonica, as opposed to pre-amp stage distortion).

Turning down at the mike and up at the amp simply will not drive the amp hard. The volume knob on the amp may be at 11, but if you have turned the mic volume down to the point that the amp is only being fed a tiny signal, you will not be driving the amplifier into the zone where the distortion that many of us find pleasing is produced.

Attenuators will not result in the speaker being driven hard, an additional component of distortion. To push the speaker hard, you have to put it in an isolation box (these are commercially available; used for practice and recording) or another room (a big isolation box), or live with ringing ears.


From: George Brooks gbrooks at together.net
Date: Sat, 09 Jan 1999 15:50:16 -0500
Subject: Loud crunch at lower volume

Tim Norris wrote:

>I typically use small amps, 10 watts or under. I count myself fortunate in that it seems the amps I use crunch at low volume settings. I assume devices such as the "power soak" are primarily for large amps? Has anyone used such devices on amps under 20 watts? For those of you using them...Are you using them in addition to the typical harp amp tube subs?

Attenuators are primarily for larger amps. I have not used them in conjunction with tube substitutions, but there is no reason not to. Attenuators, I believe, inevitable mess to some degree with tone. The less attenuation you have to use, the better, and the right tube substitutions could reduce the degree of attenuation needed.

I have not used an attenuator with a small amp. None of the really small amps I have tried would, in my opinion, benefit from the use of an attenuator except in very quiet practice or acoustic jam settings. At reasonable volumes, small are already working hard enough produce an overdriven sound. But 20 watts is a lot. Again, I am not well grounded in the technical details, but according to my understanding, 20 watts is not a whole lot less loud than 50 watts. It's not a linear relationship. A 20 watt amp will drive an efficient speaker cabinet quite loud. Such a set-up might well benefit from the use of an attenuator.


From: "Don D." mdestefano at snet.net
Date: Sat, 09 Jan 1999 17:24:15 -0800
Subject: Re: Crunch at low volumes

Power soaks, attenuators, etc., whatever you call them, work great but there are some things you should be aware of. They cause your power tubes to wear out quicker. I've heard some amp techs recommend against using them for other reasons but I don't know why, nor do I necessarily agree with them, but just passing it along here on the list. I think some say they can also cause problems with your amps output transformer. Also remember, them things get hot, keep that in mind where you place it during your stage set up.

I use a what I think IMHO is a better idea and that is a small amp slaved through a larger amp. Most will agree that for that fat, creamy, overdriven harp sound, nothing really sounds better than them little 5 watt, single ended class A wonders such as Fender Champs, tweed Princetons, Premier Twin 8s, Silvertones, Kalamazoos, etc. (the list could go on and on) cranked out to the max. The only problem is they don't have the volume or projection to cut it in a full blown band situation. By using a slave box or a similar circuit internally wired in your little amp, you can get the full sound and tone of both the pre-amp and power amp sections of your class A amp but padded down to an instrument level signal for injection into a larger slave amp. If your slave amp happens to be another tube amp, say a Super Reverb or Bassman, your now running that signal through whole 'nother set of tubes and getting their tone enhancement added.

Some other advantages of the slave box set-up vs. a power soak is, that a power soak can only power soak, at around $300 new, the power soak is just as expensive as buying a second smaller class A amp. And a small amp isn't that much more to lug to a gig then a power soak. You know have a great little practice/backup/recording amp, when if you purchase a power soak it can only, like I stated, is soak up excess speaker volume. If your at a gig for example with a Champ slaved through a Bassman, if for some reason the Bassman has trouble, you now got the Champ that can now either be miked or slaved through the PA. I'm not trying to deride the guys who use power soaks, I'm just suggesting another alternative. Try it, a small amp slaved through a large amp, has got some of the nicest, fattest, crunchiest harp tone you'll ever hear. A slave box can be made for about $10 at Radio Shack and about 1/2 hour with some hand tools and a soldering iron. Interested in a schematic, contact me off-list.

Don D.

Try using a single low-wattage speaker rather than four 70-watt spks at 10 mW. This pushes one speaker toward smoothing rather than underpowering four speakers.

song "power soak" - at johnny_beane

cascading tube amps and dummy loads - Joe uses an 80's Fender Vibroluxe that's very near stock along with his Acoushall. He has an Altair Power Attenuator, which he'll use with one or the other of those amps, and then run a line out of there to the other amp.

The idea of using great sounding small amps has always appealed to me. That way, you can get a good sound at low volume--always a challenge--and if you need to be louder just use that small amp to preamp a 50- or 100-watter. So for that reason I wanted to build something fairly small for my first full-blown amp. After a lot of reading and looking at lots of schematics, and with everybody jumping up and down about the '59 Bassman and the Marshall Plexi, I thought, "Why not make a low-wattage version of that basic design?" So combining the Marshall Plexi preamp with the power amp from a 60's Marshall that used two EL84's looked like the thing to do. I took this hilariously atrocious little EL84 thing called the Gregory Apollo 500 that I got for $35, stripped it down to chassis, transformer, tube sockets and terminal board, and built my "Baby Marshall" hybrid into it. The result was about the best-sounding amplifier I've ever heard, especially once I got rid of some hum problems.

[get my edit from pa FAQ thread in remarq.]

[se-ii] hc se-ii groove tubes user reviews - link. cover se-ii and se100. read h-c for all power attenuators, systematically. [se100] hc se-ii groove tubes user reviews - link. cover se-ii and se100. read h-c for all power attenuators, systematically.

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