Silverface Champ to 12 inch Cannabis Rex..extremely low output

[rog951]

Hey, the Champ wants a 4 ohm load if I'm remembering right - I doubt the C. Rex is 4 ohms, right? If so, you might be losing a little volume with the bigger load, but I wouldn't think enough to merit it being down so much as you're making it seem. Is your 10-ft cable a speaker cable or a guitar cable? Speaker cable has fat conductors for both + and - current paths, guitar/co-ax cable generally uses very light gauge wire for its signal conductor which can be problematic. Also, you have the potential for high-impedance connections at the adapters. So, yeah...I guess I didn't really narrow it down much for you, huh?

I will say that a dimed Champ should be able to make a very loud noise with a properly hooked-up 4 ohm 12" speaker, even one that's not terribly efficient. If you're getting almost no sound or very quiet sound, be careful and make sure your output transformer isn't overheating!

[Pchicago]

Hey Rog,

The cable Im using for the majority of the run to the 12" speaker is for sure a guitar cable. I'm pretty sure im ok with going from the champ expecting 4ohm load to a speaker rated for 8ohms. I asked around a bit before trying this.

Im pretty sure im in a cable/adapter jumble. Im in the middle of nowhere wondering where i can find a speaker cable with 1/4" terminations on it??

[norton]

The can Rex is a very efficient speaker....should be plenty loud. Why not solder up your own cable?

I love my can Rex speakers.....super smooth. Should be great with a champ.

[stafs]

Use speaker cable, not guitar.

[rog951]

Originally Posted by Pchicago

Hey Rog,

The cable Im using for the majority of the run to the 12" speaker is for sure a guitar cable. I'm pretty sure im ok with going from the champ expecting 4ohm load to a speaker rated for 8ohms. I asked around a bit before trying this.

Im pretty sure im in a cable/adapter jumble. Im in the middle of nowhere wondering where i can find a speaker cable with 1/4" terminations on it??

I use these CBI 12 ga cables in the 3' length. But Radio Shack has one in their system if you need something quick locally...it's like 15' though and almost $20...overpriced IMO. You can use almost anything as long as it is two conductor, and both conductors are something like 18ga or larger (smaller number). I think if you switch to a good speaker cable, your problem will go away.

Also, I'd say that you're generally correct that output transformers on the old Fender amps are pretty tolerant of an impedance mismatch, but when you use a guitar cable in place of the speaker cable, it's kinda hard to ascertain exactly what the transformer is seeing. It's trying to drive a lot of current into a tiny wire and the impedance it sees is going to be higher because of it. What you think is only 8 ohms might be something more like 20-30 or more ohms at certain frequencies. Always safest to use a speaker cable and stick pretty close to the correct impedance speaker IMO.

[Pchicago]

Was able to locate a Radio Shack 30 miles from here so i drove to get some parts..so i thought.

That Radio Shack is some cheap stuff. After eyeballing the structure of the parts, solder points etc., I opted out on parts and bought a ready made male RCA x 1/4 male..had a female adapter to get to the necessary female to accept my the 1/4 male on the speakers feed.

Thought it wasn't working again but then realized I had a Jack mismatch..one of those 1/4 inchers that you have to "pull out" just a hair to make the connection, tape..Woof!!

Everything's working fine, just need to get to an actual city so i can get some decent parts.

Damn..the C-rex is very efficient..loud, nice, having fun..My Champ is sounding quite a bit different, incredible. Especially with P90's on my old Reverend.."amazing balls on the witness, your honor".

I also have a little 1966 Thomas Organ Vox 7watt Pathfinder, the tube version..holy shit. This thing is just mind boggling through a 12" speaker..wow, Im speechless on this one. This amp STAYS surprisingly clean until the very end of the dial and then it grows beards.

Both of these results were worth the 60 mile round trip for parts..feel kind of guilty as modern energy conscious person doing this, but let it be said.. Rock can most times trump sensible behavior.

Thanks gentlemos, appreciated. Right on!!

[rog951]

Glad you got it going! Little amps like the Champ and that Pathfinder can really open up when paired with a bigger speaker.

I've got a Musicmaster Bass amp that has a 12" speaker and the chassis is supposedly identical in size to a Champ. It's currently on the blink and I'm starting to think about grafting one of my Vibro-Champs in there! :D

[rog951]

Oh yeah, be careful with that 1/4" TRS plug you're using. If you left it plugged in all the way (no sound) with the amp powered up for an extended time, it could mess up the OT...if I'm thinking right, the OT would be seeing an open in that condition (more or less infinite impedance) and that's a definite no-no in the tube amp world. I'd replace it with a standard TS plug ASAP (or just solder the tip and ring conductors together).

[Pchicago]

Rog,

Thats the thing on this 1/4 male coming off of the 12 inch speaker, it's not TRS its just a regular old Mono 1/4 right angle the plugs into the amp it lives in.

I think the mismatch is in the femaleXfemale 1/4 barrel connector/coupling. It's something i snagged from guitar center on the way out of town..live wire-maybe Hosa. Seen this before and drives me nuts.

Thanks for that info though, good to know.