How many watt VR being attenuater in 5w tube amp

[kldguitar]

A 5w tube guitar amp need add one attenuater, We use L-pad attenuater, But we don't know how many watt does the Variable resistor need?We found commonly the attenuater was larger power variable resistor ..such as 20w tube amp, 100w attenuater used. Why people use so larger power.
Thanks

[d95err]

The power rating of an amp is measured at maximum clean output. The reason to use an attenuator is probably to be able to overdrive it. When cranked, the amp will put out a lot more power than its power rating.

Another factor is that even if the attenuator can handle the power, the heat has to go somewhere. I tried a 100W variable L-pad with my Peavey Classic 30, and it got so hot the insulation on the cables to the L-Pad started to melt after playing a while...

So, the L-Pad needs to be able to handle at least twice the power rating of the amp, preferably more. You should also try to heatsink the L-Pad somehow to make sure the heat dissipates well.

For a 5W tube amp you should be able to do fine with 10W resistors (for a fixed L-Pad). A 15W variable L-Pad should work as well.

[kldguitar]

Thank you for your advices

The power rating of an amp is measured at maximum clean output. The reason to use an attenuator is probably to be able to overdrive it. When cranked, the amp will put out a lot more power than its power rating.

Another factor is that even if the attenuator can handle the power, the heat has to go somewhere. I tried a 100W variable L-pad with my Peavey Classic 30, and it got so hot the insulation on the cables to the L-Pad started to melt after playing a while...

So, the L-Pad needs to be able to handle at least twice the power rating of the amp, preferably more. You should also try to heatsink the L-Pad somehow to make sure the heat dissipates well.

For a 5W tube amp you should be able to do fine with 10W resistors (for a fixed L-Pad). A 15W variable L-Pad should work as well.

I think it is better fix heatsink on attenuater, It will lower the overheat risk.
Do you agree with me?

[Bruce / Mission Amps]

What is kldguitar all about?

??
http://www.kldguitar.com/

I don't quite get it so I don't reply or contribute to any of threads yet

You'd think they would know most of this stuff by now....

[kldguitar]

I don't know what your means

??
http://www.kldguitar.com/

I don't quite get it so I don't reply or contribute to any of threads yet

You'd think they would know most of this stuff by now....

I don't know what your means?

[mooreamps]

What I think Bruce means is ; most engineers should already be able to calculate the answer to this type of a question. If you really are a design engineer for the company you work for, this should be an easy one.

-g

[kldguitar]

what I call you

Alright, I've had it with this guy. I don't know what kind of reputation I have around, here, I value this forum and most everyone in it, and I don't wish to devalue what little rep I have, but...

I think this guy should be banned. He violates all the understood civilities we at this forum follow. He doesn't care to be a part of the community and as far as I'm concerned he is just a goddamn chinese bastard that wants to bleed America of jobs, money, prestige, and information and give nothing in return. You notice he doesn't reply to any of my comments or questions, and don't believe for a minute that it's because of a language barrier. Arrgh... It just pisses me off. As far as I am concerned, he can just fuck off. I strongly recommend that everyone ignore his posts and refrain from replying to anything he asks in any thread he creates.

Do not disturb me by your stupid comments. You can stop watch my messge.I did not ask you watch. bastard. shut up.
I only want dicuss with people about problem.
I don't want distube by you a bastard.if you know my question, you tell me. Thanks,If you don't know , go away.Are you better engineer? You still ask simple question, why you don't let other people saids.Are you Nazi?

[kldguitar]

We tested our annetuater

What I think Bruce means is ; most engineers should already be able to calculate the answer to this type of a question. If you really are a design engineer for the company you work for, this should be an easy one.

-g

The calculate is enogh, It is more than 3 times than real output power of amp, We tested the Temp of anntenuater by let it working two hours.
But we are afraid of that it is not enough,becuase other people use larger power resistor.
Thanks

[bbartilson]

Why people use so larger power.

There's smoke inside most electronic components. Some components even have fire inside of them. As they are electronic, it is not good to use water on these devices to keep the smoke and fire inside.

Also the smoke is poisonous and has magical qualities. If you let even a little of the smoke out, the magic is gone and the device will not operate properly.

We tend to use larger components because they have more smoke inside of them. That, and we tend to overcompensate for smaller genitals by making other things bigger. Guitars, motorcycles, trucks. It all applies.

As for L-Pads, we know they haven't been useful in a guitar amp since the 60's. If you truly want to use L-Pads with a 5w guitar amp, you'll need to cascade them, and you'll need to add peak right to circuit. Peak right should no be on wrong time. If peak right on wrong time magic smoke escape and ruin L-Pad. Use at least three, and turn down only 'til 9PM. Then go to bed.

Make sure to always never insert batteries backwards. If using AC for power, always to never force into plug. Keep one hand in pocket.

Instead of L-Pad try, Iridium Q-36 Space Modulator, available at Digi-Key and other common parts sources. This a 2KV part, so observer correct polarity.

http://search.digikey.com/scripts/Dk...?name=P9627-ND

This should solve your problem.

Or, just plug into the external speaker jack on a Bassman while leaving the normal speaker output unused. This works at least as well as an L-Pad, and is less expensive than the Modulator circuit. It worked for Eddie.

[mooreamps]

The calculate is enogh, It is more than 3 times than real output power of amp, We tested the Temp of anntenuater by let it working two hours.
But we are afraid of that it is not enough,becuase other people use larger power resistor.
Thanks

Well, some other builders, big and small, do use the resistive and/or resistive - inductive power attenuators. I am not knowing the exact values because we do not use them in our equipment. We prefer electronic power scaling instead.

-g