BF Champ Clone - Some Guidance Please

[Lonely Raven]

I built a Champ clone completely from scratch...well, I didn't wind the transformers or bend the chassis, but you get my point. It's going to be an Xmas gift for my fiance.

Electronically it's to early BF Champ specs taken from a 63 or 64 Champ. The transformers are rescued from a 63 or 64 Champ I found being parted out on eBay. The cabinet is Champ sized, but built for a 10" speaker. I'm currently using a Jenson 10" alnico (forgot the model).

The amp sounds great until you dime it. Then it farts out on the bass.

How can I tame this? And is this typical of the Champ and I need to maybe dial it in with some component changes, or is there something I should be checking to make sure I've not made a mistake.

[LeftyStrat]

What value cathode resistor are you using on the power tube? If you can 500 in there, you can raise this value to take away some of the flub, try 820.

You can also play with the value of the cathode cap, smaller values will reduce bass content. But I'd try a high cathode resistor first.

[Lonely Raven]

So basically changing the bias to reduce flub? Cool. Sounds like an option as I'm almost positive I used a 500k 3W in that position.

I doubt my fiance would dime it much, but I don't want to give it to her till I'd be happy with it myself....then I know it's good enough.

I fired it up the other night...and it was so dead quiet I thought something was wrong with it...then I turned up the volume on the guitar.

[Johnhenry]

F@nder amp's usually got to much bass for me, I alway's drop the value of the cathode cap on my preamp tube's and and hold the Value of my coupling cap's down, also read where upping the MF of the Bais cap will tighten the bass up, Just a few more idea's for you !
Johnhenry

[Lonely Raven]

Ahh, got ya. I'll have to look into that. Thanks.

[v00d00blues79]

If that doesn't help it may be the power supply caps not putting out enough steady DC... I haven't looked that the BF Champ schem in a while, but I do know that to be a place that can cause farty bass when driven hard.


Andy

[RedRock]

You might try changing the .1 mfd. tone stack cap to
.047.

[Lonely Raven]

Thank you. I'll keep that in mind when I get back to this project....work sux!