#1
Among many other things I want to do to my champ, this is currently at the top of my list.

"4) had my bass player construct my "magic box" attenuator/headphone adapter using a schematic that Gerald Weber of Kendrick gave me for a starting point to build with. The "magic box" is an "L-pad", 15 watts, with a volume control, and the metal box with the "L-pad" inside accepts headphones or can be used as an attenuator to connect to another speaker or cab. The SF Champ wants to see about 4 ohms, and what works best is to connect a speaker load of 8 ohms to the magic box, which works to help the Champ accept the 8 ohm load. The "magic box" plugs into the speaker out of the SF Champ, and I either plug in headphones or an 8 ohm load, with a speaker cable of course. For my gig-rig I use a `72 Marshall 2 x 12 cab, 30 watt Celestions, 16 ohms each, cab wired for 8 ohms. Or, I have gone from the "magic box" attenuator to the 12" Celestion speaker, 8 ohms, in my Matchless Lightning 15 combo. THIS combination sounds killer, the open back Matchless cab with the box and SF Champ, but I hate to drag the Matchless around bars and clubs. So my second best cab is the Marshall 2 x 12 cab, it's a real close second, sounds really good. You won't believe how big this SF Champ sounds with a better speaker, or with a cab! It really opens this amp up. I play the SF Champ at a volume setting of between "7" and "8", and I'll put this tone up against most any amp/combo I've heard recently. It roars, growls, sings, has really edgey raw tone with sustain, I love it." from here

The part I consider relevant is bolded.
With the exception of the attenuator/headphone out part, could I use this to allow my 3.8 ohm champ use an 8 ohm cab?
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#2
No. An L-pad lets you control the output level of speakers without changing the impedance seen by the amplifier.

It uses resistors to keep a constant load on the amp. It won't make a 8ohm cab 4ohm.
#3
Quote by Matt420740
No. An L-pad lets you control the output level of speakers without changing the impedance seen by the amplifier.

It uses resistors to keep a constant load on the amp. It won't make a 8ohm cab 4ohm.



"The SF Champ wants to see about 4 ohms, and what works best is to connect a speaker load of 8 ohms to the magic box, which works to help the Champ accept the 8 ohm load."

then what does he mean by that? I don't necessarily want to turn 8 into 4, but I want to be able to use my 4 ohm champ with a larger cab and I've heard of multiple people doing stuff like this with an L-pad.
Winner of the 2011 Virginia Guitar Festival

Protools HD
Lynx Aurora 16/HD192
Mojave, Sennheiser, AKG, EV etc mics
Focusrite ISA828 pres
Waves Mercury
Random Rack Gear

65 Deluxe Reverb
PRS CE 22
American Standard Strat
Taylor 712
#4
Quote by Artemis Entreri
"The SF Champ wants to see about 4 ohms, and what works best is to connect a speaker load of 8 ohms to the magic box, which works to help the Champ accept the 8 ohm load."

then what does he mean by that? I don't necessarily want to turn 8 into 4, but I want to be able to use my 4 ohm champ with a larger cab and I've heard of multiple people doing stuff like this with an L-pad.


I have no idea what he means by that, and it doesn't sound like he knows either

As I said before it allows you to adjust the level of signal the speaker is getting WITHOUT changing the load on the amp. So you will still be putting an 8ohm load on a amp designed for 4ohm.

Go here to learn more about how an L-pad works. - http://www.bcae1.com/lpad.htm
Last edited by Matt420740 at Nov 19, 2009,
#5
Quote by Matt420740
As I said before it allows you to adjust the level of signal the speaker is getting WITHOUT changing the load on the amp. So you will still be putting an 8ohm load on a amp designed for 4ohm.

Go here to learn more about how an L-pad works. - http://www.bcae1.com/lpad.htm



I've been reading these things for the past 2 weeks, I came here to see if someone could explain it to me in a different way. I didn't come here first, I read all of this stuff first and had trouble processing it, so I came here.

EDIT:

Ah, I saw your edit, is there anyway I can help ease the strain on my amplifier? I really don't want to spend 300+ to get a new cab when I have a decent, 8ohm one sitting around collecting dust.
Winner of the 2011 Virginia Guitar Festival

Protools HD
Lynx Aurora 16/HD192
Mojave, Sennheiser, AKG, EV etc mics
Focusrite ISA828 pres
Waves Mercury
Random Rack Gear

65 Deluxe Reverb
PRS CE 22
American Standard Strat
Taylor 712
Last edited by Artemis Entreri at Nov 19, 2009,
#6
Quote by Artemis Entreri


Ah, I saw your edit, is there anyway I can help ease the strain on my amplifier? I really don't want to spend 300+ to get a new cab when I have a decent, 8ohm one sitting around collecting dust.



If your cab has 2 8ohm speakers inside you can re-wire them in parallel to get 4ohms.

If they are 16ohm, already in parallel then there isn't much you can do.
Last edited by Matt420740 at Nov 19, 2009,
#7
Quote by Matt420740
If your cab has 2 8ohm speakers inside you can re-wire them in parallel to get 4ohms.

If they are 16ohm, already in parallel then there isn't much you can do.



Yeah, they are two 16's in parallel. I've tried to combine other speakers in my house but I can't get them down haha.
Winner of the 2011 Virginia Guitar Festival

Protools HD
Lynx Aurora 16/HD192
Mojave, Sennheiser, AKG, EV etc mics
Focusrite ISA828 pres
Waves Mercury
Random Rack Gear

65 Deluxe Reverb
PRS CE 22
American Standard Strat
Taylor 712
#8
Quote by Artemis Entreri
Yeah, they are two 16's in parallel. I've tried to combine other speakers in my house but I can't get them down haha.


Only advice I can give then is to get a 4ohm cab, OR get another 8ohm cab, and run the two together to get 4ohm.