Attenuators question for the amp pros.

bluesypicky

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With a topic derived from the members music section, I am coming here in an attempt to scrape off some of the dirt covering the area of my brain that's supposed to be dedicated to technical understanding. :?
I own a Fender Prosonic described here http://en.wikipedia.org/wiki/Fender_Prosonic, and face the challenge to capture the broken signal from it (for recording purposes), at levels suitable for neighbors and local authorities. In a feedback exchange, jcwu (and I thank him again for that) suggested the use of an attenuator. He is using a Weber himself on a Peavey amp.
My specific question relates to the attenuator power / amp power ratio. As you saw in the prosonic description, it's unique feature is the rear-mounted RECTIFIER/BIAS switch lets the user select from the following three options:

1. Solid-state rectification with fixed bias (marked "S.S. AB2"). Listed at 60 Watts R.M.S.
2. Tube rectification with fixed bias (marked "AB2"). Listed at 50 Watts R.M.S.
3. Tube rectification with cathode bias (marked "A"). Listed at 30 Watts R.M.S.

Based on this info, and the fact that I would like being able to use the attenuator for more than an hour before seeing flames shooting from the tubes, what attenuator power and type would you suggest I use and on which rectifier position?
Since there is a big difference between the 30 and 60 watts ratings from the "SS AB2" position to the "A", and since it doesn't take much to get me confused, I am confused..... :roll:
Thanks!
Oh, and in case you need it, here's jcwu's link to the weber attenuators, pointing out the importance to select the right type and power attenuator for the given amp....
http://www.tedweber.com/atten.htm
 

bluesypicky

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dapmdave said:
An alternative: http://www.rivera.com/products/silentsi ... sister.php
You gotta wonder how hard it would be to build your own.
Dave :D
First thing I thought about! I remember looking at it with you upon my last visit....
But what I really like though, is the idea (confirmed by jcwu's experience) to get the tubes "pushed" by the attenuator and giving this nice sweet broken but tamed signal...
And actually, looking deeper into the weber line, I see that they have various powers on the same attenuator, which partly answers my question above, just not sure which one to go with yet.
Ah the world of recording equipment!!! It's a bit like when you buy a house... never ending story!
(BTW Dave, I'm done with the kitchen cabinets.. looking good, I'll PM you a pic :) )
And do you get good low volume sound with your Rivera?
 

cjd-player

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I use a Weber 100 on my 50 watt tube amp and like it very much. If I remember correctly, they recommend using an attenuator with a power rating twice that of your amp if you are going to dime the volume. Something about when in tube distortion, the amp can actually put out more power than what it's rated at. So based on that I think you want a 100 Watt attenuator.

Here's the Weber web site on attenuators: http://www.tedweber.com/atten.htm
 

dapmdave

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bluesypicky said:
dapmdave said:
An alternative: http://www.rivera.com/products/silentsi ... sister.php
You gotta wonder how hard it would be to build your own.
Dave :D
First thing I thought about! I remember looking at it with you upon my last visit....
But what I really like though, is the idea (confirmed by jcwu's experience) to get the tubes "pushed" by the attenuator and giving this nice sweet broken but tamed signal...
And actually, looking deeper into the weber line, I see that they have various powers on the same attenuator, which partly answers my question above, just not sure which one to go with yet.
Ah the world of recording equipment!!! It's a bit like when you buy a house... never ending story!
(BTW Dave, I'm done with the kitchen cabinets.. looking good, I'll PM you a pic :) )
And do you get good low volume sound with your Rivera?

I would like to see how the cabinets turned out. From the video you posted recently, the new place looks nice. But I miss the mirror and the GM bottle. :lol:

The Rivera does sound pretty good at lower volumes, but best cranked up a bit. But I imagine that cranked on the little Rivera is a long way from the volume you are using on the Prosonic. It also has a direct out, so I guess it could go straight in. But I haven't had much time to play with it, yet. I tend to pick up an acoustic when I feel like playing.

Dave :D
 

Default

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cjd-player said:
Something about when in tube distortion, the amp can actually put out more power than what it's rated at. So based on that I think you want a 100 Watt attenuator.



Correct Carl! A tube amp can put out twice the wattage at full roar.
At the Cheap Trick concert, Rick Neilson had two Marshall stacks, two Vox AC30's and some wacky trapezoidal stack that I'm thinking was some kind of Doctor Z?
That assortment was putting out probably close to 700 watts, pointing directly at me, plus the pa. It was brutally loud and I'm glad we had earplugs with us!
 

bluesypicky

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dapmdave said:
I would like to see how the cabinets turned out. From the video you posted recently, the new place looks nice. But I miss the mirror and the GM bottle. :lol:
Dave :D

E-mail sent!
 

bluesypicky

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Thanks Carl and Default!
I think I'm going to go with the one that does 50 and 100 watts.
My amp is rated 30 watts in class A, think I might get away with a 50 watts attenuator?
Then I always have the 100 watts position for use in the "AB2" rectifier position, with a rating of 50 watts... Getting closer! :D
 

capnjuan

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Hi Pascal; I don't think the switching power supply / rated output of the Prosonic is anything to be concerned about. The attenuator only sees what's downstream of the output transformer ... it's indifferent to exactly how the signal got to be 30, 50, or 60 watts. The only time I think it might have been an issue is if it were possible to have too little watts out for the power handling of the attenuator but this risk isn't mentioned at all by the Webers.

With respect to power handling, they do say: "You should select an attenuator that can handle at least as much power as your amp puts out ... If you are going to dime a 50 watt amp, you should choose a 100 watt attenuator."

I guess it's hard to know in advance where you'll find the sweet spot but the Weber 100 watt Mass ought to do it. Good luck! J
 

jcwu

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There isn't really anything left that I can contribute that everyone else hasn't already said. That being said - we hear the praises for tube amps all the time, but rarely are able to really push the amp to the point where they hit their sweet spot. It's like getting a sports car and occasionally taking it out for a grocery run, you know? You're just not getting all the bang for your buck.

The attenuator lets you push the amp, scratch its belly, make it growl in the way that it was meant to growl. With my Peavey Classic 50, that beast is loud enough as it is, so I was always playing with the volume at around 1.5. Once, though, I had the beast set up in a large-ish hall with the attenuator in place, and I pushed the clean channel (yes, the clean channel, not the overdrive channel), and I was getting beautiful tones that I'd never heard from the amp before. It was like heaven!

But that's about where my expertise ends. All I know is, I've used one, and I really really like it. :) Oh, and I'm running the 50 watt amp through a 100 watt Weber Mass, in case anyone's curious.
 

cjd-player

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jcwu said:
... I pushed the clean channel (yes, the clean channel, not the overdrive channel), and I was getting beautiful tones that I'd never heard from the amp before. It was like heaven!
Oh man, I know exactly what you mean.
I love to dime the volume and push the clean channel on my 50-watt Traynor.
EL34 heaven, indeed.
The way overdrive was meant to be ... not the preamp overdrive buzz.
 

bluesypicky

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You got it guys.... that's exactly what I want to be able to capture: The clean chl to the point where it breaks. I'm on the ball now, thanks all for your help and guidance! :D
 

jcwu

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bluesypicky said:
You got it guys.... that's exactly what I want to be able to capture: The clean chl to the point where it breaks. I'm on the ball now, thanks all for your help and guidance! :D

I know it's an old thread, but thought I'd chime in here: the amp I had been using with an attenuator was starting to have problems, blowing fuses right after turning on the unit. After taking it in for diagnostics, turns out a tube had gone bad, but not just that, but a trace on the PCB had burned out. I guess the tube died and took something out with it.

The tech explained that using an attenuator is sure-fire way of tubes dying prematurely, since you're pushing them much harder. And I wasn't even gigging with this amp regularly - just played it with the attenuator a few times for practice, and then during a live set that lasted about an hour. Then it went into storage, and the next time I powered it up about a year later, the tube failed.

So.. just a word of caution. Could be my tube died from lack of use, but nevertheless..
 

bluesypicky

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Thanks jcwu, and for the very reason you bring up here (read too many similar catastrophic scenarios where the damage hadn't stopped at the tubes...) I chose to go another route and got me a "pre-amp simulator" with multiple settings that has been working wonders so far, and safely. :wink:
 

bluzman

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To me the best attenuators out there are the Dr. Z Air Brake (Ken Fischer design) good for up to 100 Watts and the the Dr. Z Brake Lite food for up to 45 watts. The Brake Lite can mount inside a combo or speaker cabinet and they have a stand alone model. The all work with 4,8 or 16 ohms. There is a bypass and 4 steps of about -3db each.

Here's one I installed in a small 1x10 cab.

Z281x10back.jpg


http://www.drzamps.com/products/brake_lite_sa.html
 
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