How to brighten up Champ

[eddy4753]

Hi, all
I have put together a 5F1 clone from a BBQ kit and all works fine except, my Tele sounds like a LP and my Strat sounds like it's tone pot is rolled way back.
Do any of you guys have any tricks that will help me get some brightness out of this thing? The amp has JJ tubes and a Hammond 125cse OT, otherwise stock. I know that this amp will sound dark (if thats the correct term) when dimed & driven hard but at sane levels its still to dull.

Thanks in advance,
Eddy

[Freight Twang]

You can add a 47pf capacitor to the volume pot lugs and be able to brighten the amp up. If a 47 is to much go to a lower value, or if it needs more treble, go higher. A Fender twin bright switch is 120pf.

[emu!]

The 5F1 just has a volume knob and no tone knob, right?

If that's the case, you could add a tone knob. Look at the 5F2 schematic for the wiring. Or, you can change the cathode by-pass cap on the pre-amp tube to a smaller value. Maybe even put a 3-way switch to change by-pass caps on the fly. Either way, there will be some soldering involved.

[zook]

Originally Posted by Freight Twang

You can add a 47pf capacitor to the volume pot lugs and be able to brighten the amp up. If a 47 is to much go to a lower value, or if it needs more treble, go higher. A Fender twin bright switch is 120pf.

I'd try a 150pf or even a 250 pf cap. put it between the sweep (center pin) and pin one, the one coneected to the circuit board. Pin 3 is grounded.

Winnie

[TexGoneNW]

ThunderTweak "tweaks" page:
http://www.sonicdeli.com/ThunderTweakWeb/tweaks.htm

There's a good article in the current Vintage Guitar mag about tweaking your amp, too.

[PRNDL]

5F1 is such a simple amp that there's a lot of simple mods.

The easiest is to try some different tubes. You'll be surprised how much that changes the tone.

You might also try changing the coupling caps. A lower value will reduce the bass, which increases the treble. I'm a huge fan of paper-in-oil caps. I think they do something special with the high end.

You could also try some caps over the 1.5K cathode resistor. The .68µF cap is common Marshall amps that increases mids and highs.

[Kbibs]

Try a different 12ax7. I replace the JJ with a Sovtek 12ax7LPS in my STF Supercharged Champ (5F1 with Tone and MV and parallel 6v6s) and it gave it a more Fenderesque tone. The JJ was much darker. I later replaced the Sovtek with a new Tungsol 12ax7 with very little difference in tone.

[jjmantele]

I also had dark tone when I scrapped together my 5F1. I had made some errors and it still could be just a hair brighter. I tried the bypass cap on the volume and it works but only at lower volume settings. When you approach maxing the control the contribution from the bypass cap approaches nil.

I added a 0.1u cap to the cathode of the 1st stage which increased highs and “gain.”

[Alamo]

What about the speaker?

I had a Jensen Mod 8 in my '79 SF Champ but I went back to the stock Oxford.
It has more of this brittling hight to mid-range twang. I was missing that on the Mod speaker.

[zook]

You could also try .22uf bypass caps on both cathodes of the 12AX7. Wire them in parallel like a blackface circuit.

Winnie

[Gee]

Originally Posted by eddy4753

I have put together a 5F1 clone from a BBQ kit and all works fine except, my Tele sounds like a LP and my Strat sounds like it's tone pot is rolled way back.
Do any of you guys have any tricks that will help me get some brightness out of this thing? The amp has JJ tubes and a Hammond 125cse OT, otherwise stock. I know that this amp will sound dark (if thats the correct term) when dimed & driven hard but at sane levels its still to dull.Eddy

A 5F1 shouldn't sound the way that you describe if everything is correct and the speaker is known to be balanced, i.e. not too dark. Have you tried it with another speaker?
I would keep checking the input (s) over and over. E.g. maybe the High I/P is wired as a Low etc. Are the 0.022uF caps the correct value and not 0.22uF?

[CIM]

Originally Posted by Alamo

What about the speaker?

I had a Jensen Mod 8 in my '79 SF Champ but I went back to the stock Oxford.
It has more of this brittling hight to mid-range twang. I was missing that on the Mod speaker.

Same experience here.

Do you have an alnico speaker? If not, that will probably get you where you want to go.

[Hoodster]

The most obvious thing is again to use an alnico speaker, if you are not already. I would recommend the Weber Signature Series alnico 10S, 12S, 8S--depending on your size.

[JohnnyCrash]

Originally Posted by PRNDL

5F1 is such a simple amp that there's a lot of simple mods.

The easiest is to try some different tubes. You'll be surprised how much that changes the tone.

You might also try changing the coupling caps. A lower value will reduce the bass, which increases the treble. I'm a huge fan of paper-in-oil caps. I think they do something special with the high end.

You could also try some caps over the 1.5K cathode resistor. The .68µF cap is common Marshall amps that increases mids and highs.

Sorry, I'm a little late...

The above advice is great.

I routinely drop my coupling caps down from 0.022uF to 0.01uF as well as increase the cathode resistors to 2.7k and bypass caps to 0.68uF (both a la Marshall style amps).

With humbuckers its great. With single coils it may or may not get fizzy/buzzy depending on how many of these steps you take or what values you go down to... so you may want to put in a switch to get you back to some of the old values if you use a single coil guitar.

Also, you may want to drop those input grid resistors down from 68k to maybe 47k, or even lower (I tend to just go with one input at 22k, myself).