Champ 5F1 with vibrato

[dinkotom]

Hi all,
I am building a 5F1 Champ for my nephew and he'd like to have a vibrato in it. Could I just add a new 12AX7, wire up a vibrato section as on Vibro Champ and connect it at the same spot (pin 8 on first 12AX7), or should I look for another vibrato circuit? Please let me know if it's possible, I see that 5F1 and Vibro Champ have their cathodes and NFB wired a bit different.
Thanks,
Dinko

[txstrat]

I'd go for the vibro champ circuit from the wiper of the vol pot on.
That way you could leave everything before the volume pot just like in a 5F1 and hence get the tone from it's preamp.

[dinkotom]

Thanks for reply.
If I understand correctly, you mean there's another Champ vibrato circuit apart from BF Vibro Champ? Do I just connect the wiper of the volume pot to the input lug of intensity pot?
I am still a bit of a noob, so I don't quite get it, so please could you give me more detailed explanation?
Thanks.

[txstrat]

The 5F1 has two preamp triodes (one tube = two triodes).
The vol pots wiper leads to the second triodes grid.
Same applies to the vibro champ circuit (AA764).
Before the vol pot you use the circuit of the 5f1. After the vol pot you use the circuit of the AA764. That should work out fine.

Hope this helps

Matt

[dinkotom]

OK, thanks, I think I get it now.

[tubeswell]

If you are making a 5F1 with tremolo, why not make a 5F2A with a BF vibro-champ style tremolo (for the price of another pot and two caps)? That way you will have some way of adjusting the tone, which might be affected by the tremolo when you hit the trem footswitch.

[txstrat]

If you are making a 5F1 with tremolo, why not make a 5F2A with a BF vibro-champ style tremolo (for the price of another pot and two caps)? That way you will have some way of adjusting the tone, which might be affected by the tremolo when you hit the trem footswitch.

Good advice TW

[tubeswell]

Having thought about this a bit further, for the price of a DPDT switch , you can have a 5F2A or a 5F1 pre-amp (if you also spend the dosh on a pot and two caps (and a knob)). See my sketch for where to put the 'tone-out' switch

[dinkotom]

Thanks, I'll try to talk my nephew into it. We made the chassis ourselves yesterday, it's about the size of a Deluxe one, so there is enough space for an additional pot.

[tubeswell]

Thanks, I'll try to talk my nephew into it. We made the chassis ourselves yesterday, it's about the size of a Deluxe one, so there is enough space for an additional pot.

Cool! I made a 5F2A last year with a tweed deluxe size chassis that I made. Plenty of room for that circuit plus a few extra pots and switches etc.

[txstrat]

You know what guys, we're all suffering the same disease.
And it's great, ain't it?

[dinkotom]

...disease continues: We'll use only one input jack, is one 33K resistor a correct value to use (instead of two 68K)?
Also, filter caps - any recommendations for cheaper (Illinois, TAD) or should we go for Sprague Atoms?

[txstrat]

33k would be the nr.1 input (high) on a regular fender amp. 68k wozuld be the nr. 2 (low) input.
The better the filter caps the better. I've used TAD caps. They're OK.

[Resonator Guy]

Filter caps

I was having problems with a little Beltone (Teisco made) that I had recapped with Illinois filter caps. I got Spragues and put them in and there was a noticeable difference in tone and volume, all for the better.
The price difference wasn't that much but the sound really did improve!!

[dinkotom]

OK, I ordered TADs...

...and, I have a bit of a problem - where to put OT: I know there's some kind of a rule that OT should be far from guitar input (though there are amps that have OT mounted near guitar input- Marshalls for one). I did the headphone test for the least hum, and found that the sweet spot is the farthest from PT, right at the guitar input. If I move it closer to PT, I get the loud hum. Any help?