Can I hurt my amp by putting an L-pad resistor before the speaker?

[johnnylighton]

Hey All, I have a Fender SuperChamp XD that I play at low volumes. I read on the Telecaster forum that people have had success putting an L-pad resistor between the amp output and the speaker, like this one:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-262

They report that you can turn the amp up to 7 and get lots of tube sound at very low volumes. The pot is almost at the "infinity" setting when using it this way. Could using this shorten the life of my amp or hurt it in any way? And if it's so easy, why do people pay big $$$ for other attenuators?

Note: my amp needs an 8 ohm speaker; one user review of this L-pad resistor says that the impedance varies between 8 and 12 ohms.

Many thanks. :)

[donnyjaguar]

It certainly looks worthy of consideration. There aren't that many details on the site though so can't say for sure.

[ked]

There are a couple of threads over at 18watt.com that cover this topic well.

http://www.18watt.com/modules.php?name=Forums&file=viewtopic&t=6936#63637

http://www.18watt.com/modules.php?name=Forums&file=viewtopic&t=16712

[Cosmik de Bris]

It won't hurt, it will just dissipate some of the power and get warm. I used a bank of 20W resistors to do the same thing.

[doctorx]

That will work with your amp. I have built several attenuators using those, check them out:

Ampwell House (http://www.regiscoyne.com/ampwell/)

Havanatone (http://www.regiscoyne.com/havanatone/)

Coppertone (http://www.regiscoyne.com/coppertone/)

You might have to install an attenuator insert, the speaker is probably hard wired in your amp.

I'm building a 16 ohm one right now for my AC30CC.

It won't hurt your amp as long as you choose the correct impedance. I've been using them for years with no issues.

[Reincaster]

I'm not entirely sure, but attenuators have something else going on, like a tone circuit to try to adjust the sound after it runs through the l-pad.

What is an attenuator insert, if I may ask?

[doctorx]

I'm not entirely sure, but attenuators have something else going on, like a tone circuit to try to adjust the sound after it runs through the l-pad.

What is an attenuator insert, if I may ask?

My DIY attenuators have a cap added to the circuit to add back in some high end that is lost when the attenuator is dialed down low. Some commercial attenuators have inductors and other circuits that adjust the low end response as well.

The attenuator goes between the amp and speaker. If your amp is a combo and is hardwired to the speaker you have to have a means to insert it, hence the attenuator insert.

Here is a webpage I did on how to add an attenuator insert. (http://www.regiscoyne.com/tech/atten_insert/)

good luck,

Regis

[johnnylighton]

Thanks very much to everyone who responded!

ked, unfortunately the 18watt.com site restricts the viewing of its forum content. I registered a few days ago but have not yet received approval so I can view those posts.

doctorx, your work - and your companion, informative web pages - are awesome!

[doctorx]

doctorx, your work - and your companion, informative web pages - are awesome!

Your welcome, pm me if you have any more questions

[Reincaster]

Excellent! One more question, I notice on your pages, that while an lpad can be rated at 100watts, you don't recommend any more than 22 watts or similar for your coffee can attenuator. How can one increase the handling wattage?

[doctorx]

Excellent! One more question, I notice on your pages, that while an lpad can be rated at 100watts, you don't recommend any more than 22 watts or similar for your coffee can attenuator. How can one increase the handling wattage?

The 22 watts was the amp I was planning to use it with at the time. If it is fan cooled it can be used with amps up to 30 watts or so rms.

The wattage cannot be increased, that is what it is.